- Email: [email protected]
sec wave and spike in the cat
ELECTROENCEPHALOGRAPHYAND CLINICAL NEUROPHYSiOLOGY
57
MICRO-ELECTRODE STUDIES OF EXPERIMENTAL 3/SEC W A V E A N D SPIKE IN THE CAT DANIELA. POLLEN,M.DY, I~ENNETHH. RUD, M.S. AND PHANORPEROT,M.D., PH.D. Department of Neurology and Neurosurgery, Montreal Neurological Institute and MeOili University, Montreal (Canada) (A~:epted for publication: September 30, 1963)
twelve exl~riments the sciatic nerve was exposed for direct bipolar stimulation. Jasper and Droogleever-Fortuyn (1947) found Stainless steel concentric electrodes were used that stimulation of the intralaminar system of to stimulate the midiine thalamus. Electrode rethe thalamus sometimes resulted in the producsistances, as measured in brain tissue, ranged from tion of cortical 3/see wave and spike complexes. 100-150 kfL Thresholds for minimal recruiting This pattern can regularly be observed a~eter inat 6/see under moderate barbiturate anesthesia tralaminar thalamic stimulation at a critical level ranged from 3=4 V, and 4-6 V was required for of arousal in cat~ waking from carefully conwell developed 6/see responses. An additional trolled light pentobarbital anesthesia (Pollen el 1-2 V was generally required to evoke sustained al. 1963). At this level of anesthesia, recruiting recruiting responses (gRs) at 3/see under moderresponse (the "spike") was followed by a long ate anesthesia. During the critical stage for obduration (generally 150--250 msec), surface negaserving the 3/see "wave and spike" pattern, the tive wave of 350-700 pV amplitude. voltage necessary to evoke g g s at 3/see increased The slow wave of the typical pattern of by 1-3 V (Pollen et al. 1963). Furthermore, the "petit real" epilepsy as well as other long durathreshold for observing the long duration surface tion surface negative waves in clinical EEG have negative wave (SNW) was usually I-2 V higher been suspected of being associated with inhibithan for observing the RR (Perot 1963). Henc~ tory events (.rung and TOnnies 1950; Jasper ! 955; voltages used for 3/see intralaminar stimulation Gastaut and Fischer.Williams 1959). Animal at the time that SNWs were present, usually experiments in which wave and spike patterns ranged from 8-12 V (occasio|mlly up to 15 V). were evoked by pharmacological means have Glass micro-pipettes (Ling and Gerard 1949) tended to confirm this view as have studies of the drawn to 1-2/~ in diameter were used for recordlong duration surface negative wave that some- ing extracellular unit responses. A short chloridtimes follows the direct cortical response (see ed silver wire connected the micro-electrode to Discussion). the grid of the cathode follower which was The primary aim of this study was to analyze firmly mounted to the micro-manipulator. In the relationship between cortical unit activity early experiments the micro-pipettes were filled and the gross electrographic events composing with 3 M KCI, later on with 4 M NaCI. Surface the "wave and spike" response. activity was recorded through a silver ball electrode placed close to the micro-electrode. Either METHODS a midline occipital point or the frame of the Twenty cats weighing between 2 and_ 3 kg Horsley-Clarke instrument was used as reference were used. Details of the method for reproduc- for both surface and micro-electrode recordings. tion of the "wave and spike" response have The cortex was covered with paraffin oil at 37°C. been described elsewhere (Pollen et al. 1963). In Surface and micro-electrode potentials were led through condenser-coupled Tektronix 122 Present address : National Institute of Neurological Diseases and Blindness, National Institutes of Health, pre-amplifiers to a 2-beam Dumont cathode ray oscilloscope. Micro-electrode activity was also Bethesda 14, Md. INTRODUCTION
EleetroenceDh. clin. Neurophysiol.. ~964. 17:57-67
D.A. POLLEN et al.
58
monitor~.d on a loudspeaker. A 1 sec time constant for surface activity and either a 2 msec or 1 sec time constant for micro-electrode recording were used. CRO tracings were photographed with a Grass camera using moving film. A negative deflection is represented as upgoing in all records except in Fig. 4. In many experiments the primary cortical projection area of the contralateral sciatic nerve was chosen while at other times gross and unitary responses were studied in anterior sigmoid gyrus and anterior portions of the lateral gyrus. The site of the stimulus was marked by dectrolytic deposit of iron. The points were then checked histologically by serial sections with both cell at~d fibtr stains. RESULTS
I. Surface potentials Each stimulus during 3/see intralaminar stim. elation can evoke five well-defined surface slow potential events (Fig. !), Component I, an in-
A
¢
Fig. I Schematicrepresentationof responsesto 3/see intralaminar stimulationunder differentconditions, A: Response under moderate ~ntobarbital anesthesia. Component IV absent. B: Next stage, as anesthesia lightenscomponent IV increases in amplitudebut spindle interaction is prominent. C: Later stage, when "rectangular" wave results from lessprominentspindlesinteractionwithcom. ponentIV. Wave after V in A, B and C is also part of the spindle. D: "Smooth domed" wave when spindle interaction is minimalor absent. Calibrations: 250/iV and 50 msec. constant, small amplitude initial positivity was observed in the original studies of Morison and Dempsey (1942) and Dempsey and Morison 0942). This initial positivity is minimal or absent at threshold stimulation for recruiting from midline intralaminar sites, but it appears with
supra-threshold stimulation. Unlike the initial positivity, component II, the surface negative recruiting response, is independent from the specific nuclear system (Hart-" bery and Jasper 1953). The recruiting after-positivity corresponds to component HI. Component IV, the long duration surface negative wave (SNW) at times appeared to begin immediately after the positive peak of IH; at other times, an inflection point on the early rising phase of the negative wave suggested an overlap of events. The duration of component IV generally ranged between 150-250 msec and could be as long as 320 msec. Component(s) V include the delayed spindle wave(s). These may follow with a latency of 150-250 msec either single shock or low frequency repetitive intralaminar stimulation. Triggering of a spindle would depend upon both the strength of the stimulus and the arousal level of the animal. As the barbiturate wore off the intralaminar stimulus would no longer evoke a spindle, and component IV assumed a "smooth dome" shape, with only minor irregularities on descending limb (Fig. !, D). At earlier stages tripped spindle waves interacted with component IV resulting in marked irregularities on its descending limb (Fig. I, B). In intermediate stages component IV sometimes had a "rectangular shape" (Fig. I, C and 3, B) caused by an evoked spindle wave which seemed to bring it to a sharp termination.
2. Selection and type of units Many units were found "spontaneously" active, often showing higher rates offiringduring bursts of rhythmical slow surface potentials. Units were "typed" according to whether their firing pattern was influenced by low frequency (3--6 sec) midline thalamic stimulation. When somatosensory cortex was studied with contralateral sciatic nerve stimulation, units were also typed by their response to such stimulation. Most of these units were silent or fired sporadically in the absence of such stimulation. At times low frequency intralaminar stimulation was carried out during the search for units. Cells found to "respond" during recruiting responses were generally cells which otherwise fired spontaneously at 3-20/see. Electroenceph. din. Neurophysiol., 1964, 17:5%67
UNIT ACTIVITYAND 3/SEC WAVEAND SPIKE Unit responses were exceptionally recorded close to the pial surface and although they were found at all cortical levels below 300 #, most of those studied were from cells in the deeper cortical layers (about 1,000-2,000 /~). These measurements, as well as those mentioned below, are approximate since they were based on micro-manipulator readings in relation to a rigid frame. The activity of 132 units was analyzed. A: Type I units: Units responding with relatively short latency to specific afferent impulses have been termed type ][ units by Li (1955) and Jung (1958). Thirty-two such cells were excited by sciatic nerve stimulation either during the initial positive phase or during the subsequent brief negative phase of the surface response. None of these units preferentially responded during the RR and only one would fire in coincidence with spindle bursts. The spontaneous firing pattern of type I units was not altered during the course of the SNW. However, as mentioned, many of these units were silent or they were firing so slowly that subtle changes could not be easily recognized. Many attempts to determine whether evoked type I unit activity was depressed during component IV proved fruitless. As soon as sciatic stimulation was begun, the SNW decreased in amplitude or disappeared. It also appeared that too frequent repetitive stimulation of the sciatic nerve upset the condition necessary for evoking the SNW, sometimes for minutes after stimulation. The number of type I units observed when the SNW was not greatly disturbed was too small for any conclusions to be drawn. It should be noted that on no occasion were "wave and spike" responses observed as a result of 3/see sciatic stimulation. B: Type II units: The rate of firing of 60 cells tended to increase during bursts of rhythmic slow waves and the units can thus be considered as type II according to Li (1955) and Jung (1958). These ceils were found in every cortical layer below the first (see Li et al. 1956). Fifty-five of these units increased their firing rate during the RR; in five, the firing rate only increased during tripped spindle waves. Eleven units from two experiments were studied when a large amplitude initial positivity
59
preceded each RR. These will be described later. C: Unclassified units: Twenty-nine units were found whose rate of firing was uninfluenced by sciatic nerve stimulation, recruiting responses or spindle waves. The firing pattern of these cells was also not altered during the course of the SNW. 3. Behavior of type H units during 3/sec intralaminar stimulation "Controls"ofunitactivity during 3/see thaJamic stimulation were obtained under slightly deep-
A
Fig. 2 Unit activity in anterior lateral gyrus when a long duration surface negative wave (componentIV) followseach recruitingresponse. Note that probably the spikes of two units are recorded: the largerspikesappear during recruiting response or during recruiting after.positivity and then not again until end of component IV, whereas the smaller one in A also fires about 150msecafter the stimulus. (See text for further discussion of this point). In B note "rectangular" shape of component IV probably due to interaction of two potentials (see Fig. 1). Calibrations: 100/~Vand 25 msec;stim. of region shown in Fig. 3.
Electeoenceph. din. Neurophysiol., 1964, 17:57-67
60
D.A. POLLEN et aL
¢r anesthesia when component IV was minimal or absent. In such cases units increased their rate of firing during the course of the RR (and sometimes also during recruiting after-positivity)and then ceased firing for variable periods ranging from 40-200 reset. This unit behaviour during and following recruiting has been described in different cortical areas by different authors (Li et al. 1956; Akimoto and Creutzfeldt 1958; Jung 1958; and Morillo 1961). When, at the critical stage of anesthesia, a large amplitude SNW became evident, the corresponding depression of unit activity was quite pronounced (Fig. 2). The larger unit in Fig. 2, A and B fired during component I[ or III and again at the end of component IV, The smaller unit occasionally fired as early as 150 msec after the stimulus as in Fig. 2, A, probably indicating that the excitation associated with tripped spindle bursts could "break through" the depression of
unit activity. The midline intra!~rninar site stimulated to evoke the potentials of Fig. 2 is shown in Fig. 3. The responses in Fig. 2 are from association cortex (anterior portions of the lateral gyrus), but similar ones were observed in motor (Fig. 4) and somatosensory cortex. Spontaneous waves, similar in morphology to the evoked SNWs, were sometimes seen during the optimal state and were also associated with the arrest of unit activity. Type II cell fired sporadically during component II but not during component IV. When the latter failed to develop (B) the unit firing was not abolished.
4. Laminar distribution of component IV When recording from a micro-electrode with a longer time constant the progressive changes of component IV in the conical depths could be followed (see Fig. 5). Its amplitude would start ~o decrease at about 200-250 # below the surface. At 600-1000/~ it became isoelectric (while component I[ was in various stages of phase reversal). Below this region, component IV gradually reversed in polarity reaching maximal positive amplitude (up to 500-700/~V) usually by 1.5-1.8 ram, but sometimes at greater depths as in Fig. 5. Unit responses could always be obtained at the depths of maximal inversion. The depth values ~re micro-manipulator measure. ments, and true cortical depths are probably less due to possible obliquity of penetration and cortical dimpUng. Amplitudes of depth potentials were greater than that of the corresponding surface potentials. Recruiting after-positivity corresponded in the depths to a large amplitude negative potential.
5, Testing of the depression of type H unit activity during component IF" In some experiments the depression of unit activity during component IV was tested after a brief (1-2 sec) burst of repetitive stimulation of the mesencephalic reticular formation applied a few seconds prior to intralaminar stimulation. Fig. 3 This is shown in Fig. 6 while recording from the Fiber stain showing localization of stimulating electrode cortical depth (components II, II[, IV and V inwhich evoked the activity shown in Fig. 2. Placement (arrow) is midline at crossing of the internal medullary verted), Though the very rapid firing of this unit lamina from each half of the thalamus at about FI0, L0, may indicate injury as well as a reticular formaHI.5. tion effect, the "braking" of unit activity during Electroenceph.olin. NeurophysioL,1964, 17:5%67
UNIT ACTIVITY AND 3/SEC WAVE AND SPIKE
61
Fig. il "Wave and spike" responsesfrom right anterior sigmoidcortex. Positivity upgoing in unit channel. Same unit in A and B but activityseparated by 5 min. A: Arrest of unit activity during both spontaneous and evoked long duration surface negativewaves. Unit activityarrested during evokedSNW even though not activated during previous RR. B. In second complex unit fired randomly in postrecruiting interval in the absence of component IV. Calibrations: 150/~V(surface), 10 mV (unit line)and 50 msec; stim. (I 2 V) of NCM. component IV is striking. In A unit firing ceased during and, with the second complex, apparently before the onset of component IV. Depression of unit activity during the course ofcomponent IV is visible in B where after the second stimulus the decrease in frequency and eventual cessation of firing occurred progressively in about 75 msec after the onset of the component. [n each case, unit activity wouldsubsequently "rebound" possibly in relation to excitatory events accompanying the tripped spindle waves. This phenomenon, frequently observed, is most evident in Fig. 6, B. Exceptions to the above described unit behavior were very rare. Only two units, and only in the course of a few complexes, would continue to fire during the first 100 msec of a large amplitude SNW apparently undisturbed by (excitatory?) spindle interactions. In these two units the firing was at a higher frequency than was commonly observed, both in resting conditions and during component IV, and the units may have been injured.
6. Unit activity during recruiting responses preceded by prominent component I In the two experiments in which an initial
positivity was unusually well developed, seven cells were found which selectively fired at its positive peak and in three cases also during component ill (Fig. 7, A and B). Spontaneous firing of these cells was usually arrested by the first stimulus for a period of 150-200 msec though they usually fired with component l of later stimuli (Fig. 7, C). DISCUSSION These studies have demonstrated that a profound depression of type U unit activity occurs during the surface negat,~veslow wave which may follow the RR under special conditions, temponcnt IV corresponds to a deep positive long duration wave and similar positive long duration potentials have been recorded when a large number of neurons arc undergoing hy~rpolarization (Purpura and Cohen 1962; Purpura et al. 1962; Andersen and Eccles 1962). Purpura and coworkers studied rostral thalamic interneurons during thalamic intralaminar stimulation and showed that focal positive potentials in thalamic and perithalamic regions had the same time course as the intracellularly recorded inhibitory post.synaptic potentials (IPSPs). It thus seems
Electroenceph. clin. NeurophysioL, 1964, 17:57-67
LAMINAR ANALYSIS OF 3/sec WAVE AND SPIKE I.iiSl,,-
""iJ ,~ tii' ~ i/"~ I11 tl I tf~ill ~ i}/ if ~'"
,.!~ ~,/~~i1<,.it.i./,,~ ',.,~~.i,, 1~ /',!.,,}l' i,. IV I~ " 17 ii' i+ , ~l ~ " i~ ' i2
,~ ,i'/t I~tk 7°,,??:IX,~7 s~;TDv tD/~)d~,7(,-
$IIM: NCM |/lie
I Ill
FIB, 5 Laminar analysis in riBht posterior sigmoid cortex. Upr~r line shows surface activity, lower llne activity from micro-el~trode at varyinl depths ,~ording to the mlcro-manlpulator readlnRs. Stim. of NCM, lO V.
Fig, 6 Unit ac_~ivitywith slow potentialsin depths of posterior siimoid coMex, A brief burst of tctanic stimulation of the meseneephalic reticular formation preened the intralaminar stimulation by a few seconds. Not© the arrest of firing during the long duration depth positive waves. In A, after second RR, unit activity decreased belore the apparent beginning of component IV. in B, after second RR, the firing stops during the course of component IV and then increases in coincidence with the tripped spindle waves. Calibrations: 250 #iV and 25 msec; stim. of NCM, 8 V.
Electroenceph. clin. Neurophysiol., 1901, 17:57~7
UNIT ACTIVITYAND 3/SEC WAVEAND SPIKE
Fig. 7 Unit activity in posterior sigmoid when initial positivity precededRR./1: Single"triphasic spike and wave"complex with units firing during ~tial and after-positivity (components 1 and Ii) and ceasing to fire during components !1 and IV. B: Same during 6/sec stimulation. C: Unit activity,silent for a brief period prior to stimulus, remainsarrested for long intervalafter first stimulus. Calibrations: 250 ~,V and 10 msec (A, B), 50 msec (C), stim. of nucleusreuniens, 8 V. possible that a local hyperpolarizing response is the primary event correlated with the cessation of unit activity. In a recent intracellular study of unit activity in motor cortex during recruiting, Lux and Klee (1962) found long duration, high voltage hyperpolarizing potentials lasting about 170 msec, beginning after the course of the recruiting potential. Whether their hyperpolarization resulted from spike after-hyperpolarization, an IPSP, or from both will be discussed later. However, it seems extremely probable that the long duration depth positive wave can be accounted for by the summated current flows resulting from hyperpolarization, and we would expect the degree of hyperpolarization to vary directly with the magnitude of the extracellular depth positive wave that may be present. It remains only to be suggested that our component IV represents current flow into superficial cortical structures (presumably apical dendrites) acting as passive sinks for the active current sources in the deeper cortical layers. Curtis (1959) and Eccles et al. (1962) have
63
described cases of hyperpolarization of moteneurons where the cell body serves as an active source of current flow to passive sinks. In these cases the passive sinks were assigned to axons. Purpura et al. (1960) postulated that some surface negative potentials could result from the activity set up by deeper-lying IPSPs. Recently Andersen et aL (1963) in discussing current flows set up during the generation of IPSPs on hippocampal pyramidal cells, considered basilar and apical dendrites as passive sinks for the sources of hyperpolarizing current actively generated at the soma. The long durations of IPSPs observed in the latter study (200-500 msec) are also noteworthy. It would be of interest to know whether the depression of unit firing is caused by a spike after-hyperpolarization, by lPSPs, or by both. Li (1963) and Lux and Klee (1962) have shown that hyperpolarization is observed in the interval beginning immediately after the recruiting response. Li did not draw any conclusion as to the nature of this change. Lux and Klee favored the explanation of an aftet-hyperpolarization rather than that of an IPSP since they could not demonstrate the existence of actively firing inhibitory interneurons during the period of decreased unit activity and since the strength of their hyperpolarizing potential was variable and its latency longer and variable in comparison with that of the sharply defined IPSP observed after stimulation of a specific nucleus. However, IPSPs with long and variable latency 05-40 reset) were described in the above-mentioned study of Purpura and Cohen (1962) in which polysynaptic pathways were very probably involved. If inhibitory effects are mediated through poly.~jnaptic pathways one would expect them to be d~pressed by barbiturate anesthesia. Indeed, component IV becomes fully developed only with careful control of anesthesia and at a critical level of arousal (Pollen et al. 1963). Extracellular recordings cannot prt,'::,~¢ a definite answer to this proole~,, l'hese have shown that cell firing was depressed or totally abolished during the SNW regardless of whether or not the cell had been activated during the previous RR. If the excitation of a cell is dependent upon a closed loop of excitatory interneurons, then the cessation of its firing could be due Electroenceph. c/in. Neurophysiol., 1964, 17:57-67
D. A. POLLEN et al.
to the generation of an IPSP on a cell svmewhere in the loop. In motoneurons, spike after-hyperpolarization occurs only after an action potential has been generated (Coombs et al. 1955). The localization of cell bodies whose axons could provide possible inhibitory synapses remains a major problem. They would not necessexily have to be located in the cortex although there is some indirect evidence that inhibitory mechanisms may be present in pericruciate cortex of cat in relation to recurrent axon collaterals of pyramidal cells (Phillips 1956a and b; Asanuma and Brooks 1963). According to the principle of Dale (1934), all terminals of collaterals of a given axon elaborate the same transmitter substance. If the given transmitter is excitatory at all its synapses, then the collaterals of most pyramidal cells must be expected to be involved in the generation of an lPSP only by prior excitation of inhibitory interneurons. If so, atld if these involve recurrent collatertd endings of pyzamidal cells, one shguld next determine whether pyramidal cells are excited during recruiting. Brookhart and Zanchetti (1956) arid Denney and Brookhart (1962) concluded that relayed pyramidal responses were absent during surface negative recruiting uncontaminated with initittl positivity, many studies having demonstrated relayed responses when initial positivity was present (Arduini ~md Whitlock 1953; Purpura and Housepian 1960). However, axon spikes and gross responses have been reported in the pyramidal tract during surface negative recruiting (Schlag et al. 1960; Purpura and Housepian 1961), and recently in intracellular recordings from antidromically identified pyramidal cells, Purpura et al. (1963) reported significant synaptic drives on those cells during the course of surface negative recruiting. If pyramidal cells are fired during RRs, then their secondary activation of inhibitory interneurons could possibly contribute to the generation of component IV. Subcortical sources of inhibition must also be considered, particularly in view of the fact that stimulation voltages required to evoke compo. nent IV were higher than those for recruiting responses. Fibers from the midline intralaminar system distribute within the system itself and project to other thalamic nuclei (Nauta and
Whitlock 1954), and fibers of passage (not associated with the recruiting system) could well have been stimulated. Hence, inhibitory elements could be located in any or all of these loci as well as in cortex. Purpura and Cohen (1962) have suggested that some of the long latency IPSPs observed in rostral thalamic neurons during recruiting might be explained by involvement of circuits in the reticular formation (see also Scldag and Faidherbe 1961). Perot (1963) suggested that similar mechanisms might be involved in the generation of component IV. Whatever the origin of those fibers providing inhibitory synapses on thalamic neurons during recruiting, it is worth considering whether they send collateral inhibitory branches to cortical cells. The rather long latency of component IV is an unlikely result from an antidromic mechanism; in addition the observation of an "extra wave and spike" outlasting the end of stimulation (Pollen et al. 1963) would indicate that both phenomena involve orthodromic pathways, as antidromic excitation is not known to occur in the absence of electrical stimulation. The arrest of firing of type [l cells during initial positivity in the recruiting response probably corresponds to the short latency hyperpo. larization of cells in posterior cruciate cortex observed by Li (1963) in a similar situation. This mechanism appears unrelated to our present problem since d~pression of cell firing during component IV was noted in the absenceof initial positivity. Long duration surface negative waves induced by other means are known to be associated with the arrest of unit activity, for example the prolonged, negative wave that may follow the direct cortical response (Li 1956). Li and Chou (1962) found that [PSPs could be recorded during the silent period following direct cortical stimulation (see also Creutzfeldt et aL 1956). The prolonged "slow negativity" which follows a direct cortical response was found to become isoelectric 0.7-0.9 mm below the cortical surface in the rabbit before inverting its polarity (O'Leary et al. ]961). That isoclectrie region closely corresponds to that for component IV reported here. The direct cortical response and the subsequent prolonged negative wave also resemble a Electroenceph. din. Neurophysiol., 1964, 17:37-67
UNIT ACTIVITY AND 3/SEC WAVE AND SPIKE
"spike and wave", and perhaps similar mechanisms become operant in the inhibitory period after the direct cortical response, and in the production of the slow negativity of O'Leary and Goldring (1960) and O'Leary et al. (1961), as are involved in the responses described in the present work. Arrest of unit firing during the slow wave of pharmacologically evoked wave and spike patterns has been reported (Li and Jasper 1953; Li 1955; Dunlop et al. 1960). The long duration surface negative wave of the present study is believed to be produced by t he apical dendrites acting as passive sinks for active sources of current in the deeper cortical layers where the hyperpolarizing events are usually more pronounced. This explanation may also apply to some of the other types of above-mentioned long duration surface negative waves. It should be noted that hyperpolariz~tion need not be the only process contributing to the "inhibition" of type 11 cells. Frank and Fuortes (1957) and Eccles (1961) have shown that presynaptic inhibition can occur in certain spinal cord mechanisms. As mentioned in Results, the depression of unit activity sometimes occurred just before, or at the apparent beginning of the long duration depth positive wave. Whereas this might suggest that in such cases the inhibitory events (IPSP, spike after-hyperpolarization, or both) had begun earlier while the extracellular signs of inhibition were masked by still continuing excitatory processes, it is worth considering whether some additional early acting inhibitory mechanism (such as prcsynaptic inhibition) could effectively limit discharge before the full development of synaptic hyperpolarizing events. Such presynaptic inhibition could contribute to the long duration surface negative wave by acting through afferent fibers reaching the most superficial layers, but would not be reflected in intracellular potentials. SUMMARY
1. Unit activity during 3/see intralaminar stimulation at a time when each recruiting response was followed by a long duration surface negative wave has been studied in motor, sensory and association cortex. 2. Type II units which were excited during
65
recruiting negativity and~or after-positivity were depressed during most of the course of the long duration surface negative or corresponding depth positive wave. 3. The depth positive wave can probably be accounted for on the basis of summated current flows set up by intracellular hyperpo!arizing events of similar duration following recruiting responses as reported by others. The corresponding surface negative event could result from the apical dendrites serving as passive sinks for such deep sources. Pc.ocesses that could contribute to the generation of the long duration wave and to the depression of type II unit activity are discussed . . . . The authors acknowledge with gratitude the very helpful suggestions and criticisms of Dr. Herbert Jasper as well as those of Dr. Cos,as Stephanis. REFERENCES AKIMOTO, H. und CREUTZFELDT, O. Reaktionen yon Neuronen des optischen Cortex nach elektrischer Reizung unspczifischer Thalamuskerne. Arch, Psychin,. Nervenkr., 1958, 196: 494-519. AND~nS~N, P. and ECCLF.S,J. Inhibitory phasing of neuronal discharge. Nature, 1962, 196: 645-647. ANDgRSlEN, P., ECCLES, J. C. and LOVNIN(;,Y. Hippocam-
pus of the brain. Recurrent inhibition in the hippocampus with identificationof the inhibitory c¢11and its synapses. Nature, 1963, 198: ~40~542. ARnUINi,A. and WlUTLOCK,D. G. Spike discharges in pyramidal system during recruitment waves. J. Neu. rophysiol., 1953, 16: 430436.
AS^NUM^,H. and Bacx)gs, V. B. Antidromic inhibition in the cat's cerebral cortex. Fed. Prec., 190, 22: 456, BR(X)KHART,J. M. and ZANCltI::rTI,A. The relation between electrocorticalwavesand responsivenessof the corticospinal system, Electroenceph. din. Neurophy,v. iol,, 1956, 8: 427-444. CooMns, J. S., Ecc~.Es,J. C, and F^TT, P. The electrical properties of the motoncuronemembrane. J. Physiol. (Lend.), 1955, 130: 291-325. CREUTZFELDT, O., BAUMOARTNER,G. und SCHOEN, L. Reaktionen ¢inzelner Neurone des senso-motorischen Cortex nach elektrischen Reizcn. 1. Hemmung und Erregung nach direkten und kontralateralen Einzelreizen. Arch. Psychlat. Nervenkr., 1956, 194: 597-619. CURTm, D. R. Pharmacologic investigation upon the inhibition of spinal motoneuroncs. J. PhysioL (Lend.), 1959, 145: 175-192. DALE, H. h Pharmacology and nerve endings. Prec. roy. $oc. Med., 1934, 28: 319-332. D~MPSEY, E. W. and MORISON,R. S. The production of rhythmically recurrent cortical potentials after local-
Eiectroenceph. clin. NeurophysioL, 1964, 17:57-67
66
D. A, POLLEN et aL
ized tha~mic stimulation. Amer. J. Physiol., 1942, 135: 293-300. DENNEY,D. and BROOKHART,J. M. The effects of applied polarization on evoked electro-cortical waves in the cat. ElectrocRceph. din. Neurophysiol., 196Z. 15: 885-897. DUNLOP, C. W., ADEY,W. R., KILt.AM, K. F. and Be.AzmR, M. A. B. Mechanisms of action of thiosemicarbazide and metrazol on cerebellar and cerebral activity in the cat. Amer. J. Physiol., 1960, 198: 399--404. ECCLF~, J. C. Inhibitory pathways to motoneurons. In E. FLOREY (Editor), Nervous inhibition. Pergamon, Oxford, 1961: 47-60. Ecct.Es, J. C., MAGm, F. and WiLLiS, W. D. Depolarization of central terminals of group l afferent fibers from muscle. J. Physiol. (land.), 1962, 160: 62-93. FRANK, K. and FUORTU,M. G. F. Pre-synaptic and postsynapti¢ inhibition on monosynaptic reflexes. Fed. Prec., I~JT, 16: 39-40. G~TAUT, H. and FInCHEs-WiLLIAMS,M. The physiopathology of epileptic seizures. In J. FieLD (Editor), Handbook of physiology. Section i - Neurophysiology. Waverly, Baltimore, 1959: 329-363. HANaeRV, J. and JASPER, H. Independence of diffuse thalamo.cortical projection system shown by specific nuclear destructions. J. Neurophysiol., 1953, 16: 252-271. JASPER, H. H. Electrical signs of epileptic discharge. In T. SHEDLOVSKY(Editor), Electrochemistry in biology aM medicine. Wiley, New York, 1955: 352~359. JASPER, H. H, and DROOC~LEEVER-FORT,'JVN,J. Experimental studies on the functional anatomy of petit real epilepsy. Res, Pabl. Ass. aerv. men,. Dis., 1947, 26: 272~298. JUNCO, R. Coordination of specific and nonspe¢ilic alter. ant impulses at slnBle neurons of the visual cortex, in H, H. JASPER et al. (Editors), Reticular formation of the brain. Little, Brown and Co., Boston, 1958: 423~434. JustJ, R. und TONsils, J. F, Hirnelektrlsche Untersu. ~hunlen 0bar Entstehung und Erhaltung van Krampfentladungen. Die Vorgnnge am Reizort und die Bremsftthigkeit des Gehirns. Arch. Psydelat. Net, cenkr., 19~30,185: 701-735. LG C.-L. Functional properties of cortical neurones with particular reference to strychninization. Eleetroen. ceph. clin. Neurophysiol., 1955, 7" 475--477. Lz, C.-L. The inhibitory effect of stimulation of a thalamic nucleus on neuronal activity in the motor cortex. J. Phy6ol. (Lend.), 1956, 133: 40-53. L,, C.-L. Cortical intracellular synaptic potentials in response to thalamic stimulation. J. cell. camp. Physiol., 1963, 61: 165-179. Lh C.-L. and CHOU, S. N. Cortical intracellular synaptic potentials and direct cortical stimulation. J. cell. comp. PhvsioL, 1962, 60: i-16. L,, C.-L., CULLEN,C. and JASPER,H, H. Laminar microelectrode analysis el' cortical unspecific recruiting re. sponses and spontaneous rhythms. J. Neurophysiol., 1956, 19: 131-143. L[, C.-L. and JAgPER,H. Microelectrode studies of the
electrical activity of the cerebral cortex in the cat. J. Physiol. (Lend.), 1953, 121: 117-140. LING, G. and GERARD, R. W. The normal membrane potential of frog sartorius fibers. J. cell. camp. Physiol., 1949, 34: 383-396. Lax, H. D. und KLEE,M. R. Intracellul~ire Untersuchungen tiber den Einflms remmender Potentiale im motorischen Cortex. I. Die Wirkung elektriseher Reizung unspezifiseher Thalamuskerne. Arch. Psychiat. Nervenkr., 1962, 203: 648-666. MOraL,X3, A. Microelectrode analysis of some functional characteristics and inter-relationships of specific, association and non-specific thalamo-cortical systems. Electroenceph. olin. NeurophysioL, 1961, 13: 9-20. MoRmoN, g. S. and DEMPSEV,E. W. Study of thalamocortical relations. Amer. J. PhysioL, 1942, 135: 281292. NAUTA, W. V. H. and WHtTtX3CK,D. G. An anatomical analysis of the non-specific thalamic projection system. In J. F. DELAFRESNAYE(Editor), Brain mechanisms and consciousness. Blackwell, Oxford, 1954: 81-116. O'LEAaV, J. L. and GOLOmNO, S. Slow cortical potentials. Their origin and contribution to seizure discharge. Epilepsia, 1960, i: 561-574 (4th series). O'LeARY, J. L., GOLOmNO, S. and Coxv., W. S. Experimental evidence relating to the pathogenesis of posttraumatic epilepsy. Epilepsla, 1961, 2: 117-122 (4th series). PEROT, P. Mesencephalic-thalamic relations in the mecha. nlsms of the experimental wave and spike complex it, the cat. Thesis, Dept. of Neurology and Neurosurgery, Montreal Neurological Institute and McOill University, 1963, 220 p. PHILLIPS,C. G. intracellular records from Iktz cells in cat. Quart. J, exp. PhysioL, 1956n, 41: S8o69. PItlLLIPS,C. G. Cortical motor threshold and thresholds and distribution of excited lktz cells in cat, Quart. J. exp. Phy,vloL, 1956b, 41: 70~84. POLLEN,D. A., PI.'.ROT,P, and RE.), K, H. Experimental bilateral wave and spike from thalamic stimulation in relation to level of arousal, £1eetroenceph. ella. Neurophy,ffol., 1963, 15: 1017-1028. PURPURA, D. P. and COHEN, B. lntracellular recruiting from thalamic neurons during recruiting responses. J. Neurophysiol., 1962, 25: 621-635. PUReURA, D. P., COHEN, B. and SHovER,R, Activities of thalamic neurons during evoked EEG synchronization and activation. Thins. Amer. neural. Ass., 1962, 87: 76-80. PURPURA, D. P., GIRADO, M. and GRUNDFEST,H. Components of evoked potentials in cerebral cortex. Electroenceph. olin. Nearoph.rsiol., 1960, 12: 95-110. PU~PURA, D. P. and HOUSEMAN,E. M. Thalamocortical recruiting responses and relayed discharges in pyramidal tract. Fed. Proc., 1960, 19: 291. PURPURA,D. P. and HOUSEMAN,E. M. Alterations in corticospinal neuron activity associated with thalamocortical recruiting responses. Eleetroenceph. din. Newoplo'siol., 1951, 13: 365-381. PURPURA, D. P., SHaPeR, R. J. and MU~eAVE, F. S.
Electroenceph. din. Nearophysiol., 1964, 17" 57-67
67
UNIT ACTIVITY AND 3/SEC WAVE AND SPIKE lntracellular potentials of cortical neurons during augmenting and recruiting responses. Fed. Proc., 1963, 22: 457.
SCHLAG,J., CHAILLET,F. et FAIDHEReE,J. Note sur Fenregistrement des ondes en fuseau et des r6ponses de
recruitment/l partir des fibres pyramidales. Arch int. Physiol., 1960, 68: 793-802.
SCHLAG,J. and Fb,IDHERaE,J. Recruiting responses in the brain stem reticular formation. Arch. ital. Biol., 1961,
99: 135-161.
Reference: POLt.IEN,D. A., REID, K. H. and PEROT,P. Micro-electrode studies of experimental 3/see wave and spike in the cat. Eleetroenceph. clin. Neurophysiol., 1964, 17: 57-67.
ANNOUNCEMENTS THE INTERNATIONAL INSTITUTE OF ADVANCED IN HUMAN ELECTROENCEPHALOGRAPHY
STUDIES
Marseille, 7-19 September, 1964 This Institute will be organized by Prof. H. Gastaut, assisted by Dr. R. Naquet, under the auspices of the World Federation of Neurology and with the financial assistance of N.A,T.O.0 of which it is an Institute of Advanced Studies. These Institutes are non-political and their only aim is the development of science throughout the world. The period 7-12 September will be devoted to discussion of clinical EEG topics by about 40 selected "Lecturers". About 40 "Participants", who will be qualified electroenceph.aJographers, may pose questions to the t.ecturers: a limited number of "Auditors" (student electroencephalographers or specialists in neurology or psychiatry) may attend the sessions. The following Lecturers have agreed to take part: K. Pateisky - Austria; J. Radermecker - Belgium; F . B u e h t h a i - Denmark; W. Cobb, G. Pampiglione, W. Grey Walter- England; G. Arfel, J. Bancaud, J. Cadilhac, H. Cathaia, J. Courjon, M. Dondey, C. Dreyfus-Brisa¢, J. Gaches, G. C. Lair)', R. Lecasble, A. i.¢riqu¢, t,. Loiseau, P. Passouant, R. Rohmer, G. Verdeaux, A. Rgmond - France; O. Creutzfeldt, J. Kugler - Germany; A. Orfanos - Greece; O. Magnus, W. Storm van Leeuwen - Holland; C. Loeb, H. Terzian, R. Vizioli - Italy; B. F u s t e r - South America; L. Oller-Daurella - Spain; L . W i d e n - Sweden; R. Hess - Switzerland; R. G. Bick. ford, M. A. B. Brazier, G. E. Chatrian, F. Gibbs, P. Kellaway, C. Shaghass - United States. The following topics will be discussed:
AMERICAN
I. Problems of methodology. 2. The concept of normality in clinical EEG. 3. Evoked responses recorded transcranially in normal man. 4. EEG and the cerebral mechanisms of behaviour in normal man. 5. EEG and vigilance in normal man. 6. Some EEG aspects of epilepsy. The period from 14--19 September will be reserved for the Participants, who will receive technical and practical instruction, in "French, in clinical EEG from Prof. Gastaut, his collaboratocu~rand some of the Lecturers. Accommodation. So far as possible all Lecturers and Participants will be lodged in the Cit6 Universitaire Saint-Charles. The Secretary will help to find accommodation in Marseille for Auditors. Fees. Participants: 250 francs for lodging and breakfast for 13 days. Auditors: 50 francs, registration only. Noon meals for Participants and Auditors: 10 francs. ,4dmission. Applications should be made as soon as possible because of the limited number of places. Money should not be sent. Those who wish to be Participants should give details of their competence and particular interest in clinical EEG. All correspondence should be addressed to: Mlle. M. Taury, Unit6 de Recherches Neurobiologiques de rlnstitut National d'Hygiene, 300 Bd. de Sainte-Margu~rite, Marseille IX, France.
ASSOCIATION OF ELECI"ROMYOGRAPHY ELECTRODIAGNOSIS
The Annual Meeting of The American Association of Electromyography and Electrodiagnosis will be held on Sunday, August 23, 1964, at the Statler-Hilton Hotel, Boston, Massachusetts.
AND
Please address all communications to Max K. Newman, M.D., 16861 Wyoming Avenue, Detroit, Michigan 48221
Electroenceph. clin. NeurophysioL, 1964, 17:67
57
MICRO-ELECTRODE STUDIES OF EXPERIMENTAL 3/SEC W A V E A N D SPIKE IN THE CAT DANIELA. POLLEN,M.DY, I~ENNETHH. RUD, M.S. AND PHANORPEROT,M.D., PH.D. Department of Neurology and Neurosurgery, Montreal Neurological Institute and MeOili University, Montreal (Canada) (A~:epted for publication: September 30, 1963)
twelve exl~riments the sciatic nerve was exposed for direct bipolar stimulation. Jasper and Droogleever-Fortuyn (1947) found Stainless steel concentric electrodes were used that stimulation of the intralaminar system of to stimulate the midiine thalamus. Electrode rethe thalamus sometimes resulted in the producsistances, as measured in brain tissue, ranged from tion of cortical 3/see wave and spike complexes. 100-150 kfL Thresholds for minimal recruiting This pattern can regularly be observed a~eter inat 6/see under moderate barbiturate anesthesia tralaminar thalamic stimulation at a critical level ranged from 3=4 V, and 4-6 V was required for of arousal in cat~ waking from carefully conwell developed 6/see responses. An additional trolled light pentobarbital anesthesia (Pollen el 1-2 V was generally required to evoke sustained al. 1963). At this level of anesthesia, recruiting recruiting responses (gRs) at 3/see under moderresponse (the "spike") was followed by a long ate anesthesia. During the critical stage for obduration (generally 150--250 msec), surface negaserving the 3/see "wave and spike" pattern, the tive wave of 350-700 pV amplitude. voltage necessary to evoke g g s at 3/see increased The slow wave of the typical pattern of by 1-3 V (Pollen et al. 1963). Furthermore, the "petit real" epilepsy as well as other long durathreshold for observing the long duration surface tion surface negative waves in clinical EEG have negative wave (SNW) was usually I-2 V higher been suspected of being associated with inhibithan for observing the RR (Perot 1963). Henc~ tory events (.rung and TOnnies 1950; Jasper ! 955; voltages used for 3/see intralaminar stimulation Gastaut and Fischer.Williams 1959). Animal at the time that SNWs were present, usually experiments in which wave and spike patterns ranged from 8-12 V (occasio|mlly up to 15 V). were evoked by pharmacological means have Glass micro-pipettes (Ling and Gerard 1949) tended to confirm this view as have studies of the drawn to 1-2/~ in diameter were used for recordlong duration surface negative wave that some- ing extracellular unit responses. A short chloridtimes follows the direct cortical response (see ed silver wire connected the micro-electrode to Discussion). the grid of the cathode follower which was The primary aim of this study was to analyze firmly mounted to the micro-manipulator. In the relationship between cortical unit activity early experiments the micro-pipettes were filled and the gross electrographic events composing with 3 M KCI, later on with 4 M NaCI. Surface the "wave and spike" response. activity was recorded through a silver ball electrode placed close to the micro-electrode. Either METHODS a midline occipital point or the frame of the Twenty cats weighing between 2 and_ 3 kg Horsley-Clarke instrument was used as reference were used. Details of the method for reproduc- for both surface and micro-electrode recordings. tion of the "wave and spike" response have The cortex was covered with paraffin oil at 37°C. been described elsewhere (Pollen et al. 1963). In Surface and micro-electrode potentials were led through condenser-coupled Tektronix 122 Present address : National Institute of Neurological Diseases and Blindness, National Institutes of Health, pre-amplifiers to a 2-beam Dumont cathode ray oscilloscope. Micro-electrode activity was also Bethesda 14, Md. INTRODUCTION
EleetroenceDh. clin. Neurophysiol.. ~964. 17:57-67
D.A. POLLEN et al.
58
monitor~.d on a loudspeaker. A 1 sec time constant for surface activity and either a 2 msec or 1 sec time constant for micro-electrode recording were used. CRO tracings were photographed with a Grass camera using moving film. A negative deflection is represented as upgoing in all records except in Fig. 4. In many experiments the primary cortical projection area of the contralateral sciatic nerve was chosen while at other times gross and unitary responses were studied in anterior sigmoid gyrus and anterior portions of the lateral gyrus. The site of the stimulus was marked by dectrolytic deposit of iron. The points were then checked histologically by serial sections with both cell at~d fibtr stains. RESULTS
I. Surface potentials Each stimulus during 3/see intralaminar stim. elation can evoke five well-defined surface slow potential events (Fig. !), Component I, an in-
A
¢
Fig. I Schematicrepresentationof responsesto 3/see intralaminar stimulationunder differentconditions, A: Response under moderate ~ntobarbital anesthesia. Component IV absent. B: Next stage, as anesthesia lightenscomponent IV increases in amplitudebut spindle interaction is prominent. C: Later stage, when "rectangular" wave results from lessprominentspindlesinteractionwithcom. ponentIV. Wave after V in A, B and C is also part of the spindle. D: "Smooth domed" wave when spindle interaction is minimalor absent. Calibrations: 250/iV and 50 msec. constant, small amplitude initial positivity was observed in the original studies of Morison and Dempsey (1942) and Dempsey and Morison 0942). This initial positivity is minimal or absent at threshold stimulation for recruiting from midline intralaminar sites, but it appears with
supra-threshold stimulation. Unlike the initial positivity, component II, the surface negative recruiting response, is independent from the specific nuclear system (Hart-" bery and Jasper 1953). The recruiting after-positivity corresponds to component HI. Component IV, the long duration surface negative wave (SNW) at times appeared to begin immediately after the positive peak of IH; at other times, an inflection point on the early rising phase of the negative wave suggested an overlap of events. The duration of component IV generally ranged between 150-250 msec and could be as long as 320 msec. Component(s) V include the delayed spindle wave(s). These may follow with a latency of 150-250 msec either single shock or low frequency repetitive intralaminar stimulation. Triggering of a spindle would depend upon both the strength of the stimulus and the arousal level of the animal. As the barbiturate wore off the intralaminar stimulus would no longer evoke a spindle, and component IV assumed a "smooth dome" shape, with only minor irregularities on descending limb (Fig. !, D). At earlier stages tripped spindle waves interacted with component IV resulting in marked irregularities on its descending limb (Fig. I, B). In intermediate stages component IV sometimes had a "rectangular shape" (Fig. I, C and 3, B) caused by an evoked spindle wave which seemed to bring it to a sharp termination.
2. Selection and type of units Many units were found "spontaneously" active, often showing higher rates offiringduring bursts of rhythmical slow surface potentials. Units were "typed" according to whether their firing pattern was influenced by low frequency (3--6 sec) midline thalamic stimulation. When somatosensory cortex was studied with contralateral sciatic nerve stimulation, units were also typed by their response to such stimulation. Most of these units were silent or fired sporadically in the absence of such stimulation. At times low frequency intralaminar stimulation was carried out during the search for units. Cells found to "respond" during recruiting responses were generally cells which otherwise fired spontaneously at 3-20/see. Electroenceph. din. Neurophysiol., 1964, 17:5%67
UNIT ACTIVITYAND 3/SEC WAVEAND SPIKE Unit responses were exceptionally recorded close to the pial surface and although they were found at all cortical levels below 300 #, most of those studied were from cells in the deeper cortical layers (about 1,000-2,000 /~). These measurements, as well as those mentioned below, are approximate since they were based on micro-manipulator readings in relation to a rigid frame. The activity of 132 units was analyzed. A: Type I units: Units responding with relatively short latency to specific afferent impulses have been termed type ][ units by Li (1955) and Jung (1958). Thirty-two such cells were excited by sciatic nerve stimulation either during the initial positive phase or during the subsequent brief negative phase of the surface response. None of these units preferentially responded during the RR and only one would fire in coincidence with spindle bursts. The spontaneous firing pattern of type I units was not altered during the course of the SNW. However, as mentioned, many of these units were silent or they were firing so slowly that subtle changes could not be easily recognized. Many attempts to determine whether evoked type I unit activity was depressed during component IV proved fruitless. As soon as sciatic stimulation was begun, the SNW decreased in amplitude or disappeared. It also appeared that too frequent repetitive stimulation of the sciatic nerve upset the condition necessary for evoking the SNW, sometimes for minutes after stimulation. The number of type I units observed when the SNW was not greatly disturbed was too small for any conclusions to be drawn. It should be noted that on no occasion were "wave and spike" responses observed as a result of 3/see sciatic stimulation. B: Type II units: The rate of firing of 60 cells tended to increase during bursts of rhythmic slow waves and the units can thus be considered as type II according to Li (1955) and Jung (1958). These ceils were found in every cortical layer below the first (see Li et al. 1956). Fifty-five of these units increased their firing rate during the RR; in five, the firing rate only increased during tripped spindle waves. Eleven units from two experiments were studied when a large amplitude initial positivity
59
preceded each RR. These will be described later. C: Unclassified units: Twenty-nine units were found whose rate of firing was uninfluenced by sciatic nerve stimulation, recruiting responses or spindle waves. The firing pattern of these cells was also not altered during the course of the SNW. 3. Behavior of type H units during 3/sec intralaminar stimulation "Controls"ofunitactivity during 3/see thaJamic stimulation were obtained under slightly deep-
A
Fig. 2 Unit activity in anterior lateral gyrus when a long duration surface negative wave (componentIV) followseach recruitingresponse. Note that probably the spikes of two units are recorded: the largerspikesappear during recruiting response or during recruiting after.positivity and then not again until end of component IV, whereas the smaller one in A also fires about 150msecafter the stimulus. (See text for further discussion of this point). In B note "rectangular" shape of component IV probably due to interaction of two potentials (see Fig. 1). Calibrations: 100/~Vand 25 msec;stim. of region shown in Fig. 3.
Electeoenceph. din. Neurophysiol., 1964, 17:57-67
60
D.A. POLLEN et aL
¢r anesthesia when component IV was minimal or absent. In such cases units increased their rate of firing during the course of the RR (and sometimes also during recruiting after-positivity)and then ceased firing for variable periods ranging from 40-200 reset. This unit behaviour during and following recruiting has been described in different cortical areas by different authors (Li et al. 1956; Akimoto and Creutzfeldt 1958; Jung 1958; and Morillo 1961). When, at the critical stage of anesthesia, a large amplitude SNW became evident, the corresponding depression of unit activity was quite pronounced (Fig. 2). The larger unit in Fig. 2, A and B fired during component I[ or III and again at the end of component IV, The smaller unit occasionally fired as early as 150 msec after the stimulus as in Fig. 2, A, probably indicating that the excitation associated with tripped spindle bursts could "break through" the depression of
unit activity. The midline intra!~rninar site stimulated to evoke the potentials of Fig. 2 is shown in Fig. 3. The responses in Fig. 2 are from association cortex (anterior portions of the lateral gyrus), but similar ones were observed in motor (Fig. 4) and somatosensory cortex. Spontaneous waves, similar in morphology to the evoked SNWs, were sometimes seen during the optimal state and were also associated with the arrest of unit activity. Type II cell fired sporadically during component II but not during component IV. When the latter failed to develop (B) the unit firing was not abolished.
4. Laminar distribution of component IV When recording from a micro-electrode with a longer time constant the progressive changes of component IV in the conical depths could be followed (see Fig. 5). Its amplitude would start ~o decrease at about 200-250 # below the surface. At 600-1000/~ it became isoelectric (while component I[ was in various stages of phase reversal). Below this region, component IV gradually reversed in polarity reaching maximal positive amplitude (up to 500-700/~V) usually by 1.5-1.8 ram, but sometimes at greater depths as in Fig. 5. Unit responses could always be obtained at the depths of maximal inversion. The depth values ~re micro-manipulator measure. ments, and true cortical depths are probably less due to possible obliquity of penetration and cortical dimpUng. Amplitudes of depth potentials were greater than that of the corresponding surface potentials. Recruiting after-positivity corresponded in the depths to a large amplitude negative potential.
5, Testing of the depression of type H unit activity during component IF" In some experiments the depression of unit activity during component IV was tested after a brief (1-2 sec) burst of repetitive stimulation of the mesencephalic reticular formation applied a few seconds prior to intralaminar stimulation. Fig. 3 This is shown in Fig. 6 while recording from the Fiber stain showing localization of stimulating electrode cortical depth (components II, II[, IV and V inwhich evoked the activity shown in Fig. 2. Placement (arrow) is midline at crossing of the internal medullary verted), Though the very rapid firing of this unit lamina from each half of the thalamus at about FI0, L0, may indicate injury as well as a reticular formaHI.5. tion effect, the "braking" of unit activity during Electroenceph.olin. NeurophysioL,1964, 17:5%67
UNIT ACTIVITY AND 3/SEC WAVE AND SPIKE
61
Fig. il "Wave and spike" responsesfrom right anterior sigmoidcortex. Positivity upgoing in unit channel. Same unit in A and B but activityseparated by 5 min. A: Arrest of unit activity during both spontaneous and evoked long duration surface negativewaves. Unit activityarrested during evokedSNW even though not activated during previous RR. B. In second complex unit fired randomly in postrecruiting interval in the absence of component IV. Calibrations: 150/~V(surface), 10 mV (unit line)and 50 msec; stim. (I 2 V) of NCM. component IV is striking. In A unit firing ceased during and, with the second complex, apparently before the onset of component IV. Depression of unit activity during the course ofcomponent IV is visible in B where after the second stimulus the decrease in frequency and eventual cessation of firing occurred progressively in about 75 msec after the onset of the component. [n each case, unit activity wouldsubsequently "rebound" possibly in relation to excitatory events accompanying the tripped spindle waves. This phenomenon, frequently observed, is most evident in Fig. 6, B. Exceptions to the above described unit behavior were very rare. Only two units, and only in the course of a few complexes, would continue to fire during the first 100 msec of a large amplitude SNW apparently undisturbed by (excitatory?) spindle interactions. In these two units the firing was at a higher frequency than was commonly observed, both in resting conditions and during component IV, and the units may have been injured.
6. Unit activity during recruiting responses preceded by prominent component I In the two experiments in which an initial
positivity was unusually well developed, seven cells were found which selectively fired at its positive peak and in three cases also during component ill (Fig. 7, A and B). Spontaneous firing of these cells was usually arrested by the first stimulus for a period of 150-200 msec though they usually fired with component l of later stimuli (Fig. 7, C). DISCUSSION These studies have demonstrated that a profound depression of type U unit activity occurs during the surface negat,~veslow wave which may follow the RR under special conditions, temponcnt IV corresponds to a deep positive long duration wave and similar positive long duration potentials have been recorded when a large number of neurons arc undergoing hy~rpolarization (Purpura and Cohen 1962; Purpura et al. 1962; Andersen and Eccles 1962). Purpura and coworkers studied rostral thalamic interneurons during thalamic intralaminar stimulation and showed that focal positive potentials in thalamic and perithalamic regions had the same time course as the intracellularly recorded inhibitory post.synaptic potentials (IPSPs). It thus seems
Electroenceph. clin. NeurophysioL, 1964, 17:57-67
LAMINAR ANALYSIS OF 3/sec WAVE AND SPIKE I.iiSl,,-
""iJ ,~ tii' ~ i/"~ I11 tl I tf~ill ~ i}/ if ~'"
,.!~ ~,/~~i1<,.it.i./,,~ ',.,~~.i,, 1~ /',!.,,}l' i,. IV I~ " 17 ii' i+ , ~l ~ " i~ ' i2
,~ ,i'/t I~tk 7°,,??:IX,~7 s~;TDv tD/~)d~,7(,-
$IIM: NCM |/lie
I Ill
FIB, 5 Laminar analysis in riBht posterior sigmoid cortex. Upr~r line shows surface activity, lower llne activity from micro-el~trode at varyinl depths ,~ording to the mlcro-manlpulator readlnRs. Stim. of NCM, lO V.
Fig, 6 Unit ac_~ivitywith slow potentialsin depths of posterior siimoid coMex, A brief burst of tctanic stimulation of the meseneephalic reticular formation preened the intralaminar stimulation by a few seconds. Not© the arrest of firing during the long duration depth positive waves. In A, after second RR, unit activity decreased belore the apparent beginning of component IV. in B, after second RR, the firing stops during the course of component IV and then increases in coincidence with the tripped spindle waves. Calibrations: 250 #iV and 25 msec; stim. of NCM, 8 V.
Electroenceph. clin. Neurophysiol., 1901, 17:57~7
UNIT ACTIVITYAND 3/SEC WAVEAND SPIKE
Fig. 7 Unit activity in posterior sigmoid when initial positivity precededRR./1: Single"triphasic spike and wave"complex with units firing during ~tial and after-positivity (components 1 and Ii) and ceasing to fire during components !1 and IV. B: Same during 6/sec stimulation. C: Unit activity,silent for a brief period prior to stimulus, remainsarrested for long intervalafter first stimulus. Calibrations: 250 ~,V and 10 msec (A, B), 50 msec (C), stim. of nucleusreuniens, 8 V. possible that a local hyperpolarizing response is the primary event correlated with the cessation of unit activity. In a recent intracellular study of unit activity in motor cortex during recruiting, Lux and Klee (1962) found long duration, high voltage hyperpolarizing potentials lasting about 170 msec, beginning after the course of the recruiting potential. Whether their hyperpolarization resulted from spike after-hyperpolarization, an IPSP, or from both will be discussed later. However, it seems extremely probable that the long duration depth positive wave can be accounted for by the summated current flows resulting from hyperpolarization, and we would expect the degree of hyperpolarization to vary directly with the magnitude of the extracellular depth positive wave that may be present. It remains only to be suggested that our component IV represents current flow into superficial cortical structures (presumably apical dendrites) acting as passive sinks for the active current sources in the deeper cortical layers. Curtis (1959) and Eccles et al. (1962) have
63
described cases of hyperpolarization of moteneurons where the cell body serves as an active source of current flow to passive sinks. In these cases the passive sinks were assigned to axons. Purpura et al. (1960) postulated that some surface negative potentials could result from the activity set up by deeper-lying IPSPs. Recently Andersen et aL (1963) in discussing current flows set up during the generation of IPSPs on hippocampal pyramidal cells, considered basilar and apical dendrites as passive sinks for the sources of hyperpolarizing current actively generated at the soma. The long durations of IPSPs observed in the latter study (200-500 msec) are also noteworthy. It would be of interest to know whether the depression of unit firing is caused by a spike after-hyperpolarization, by lPSPs, or by both. Li (1963) and Lux and Klee (1962) have shown that hyperpolarization is observed in the interval beginning immediately after the recruiting response. Li did not draw any conclusion as to the nature of this change. Lux and Klee favored the explanation of an aftet-hyperpolarization rather than that of an IPSP since they could not demonstrate the existence of actively firing inhibitory interneurons during the period of decreased unit activity and since the strength of their hyperpolarizing potential was variable and its latency longer and variable in comparison with that of the sharply defined IPSP observed after stimulation of a specific nucleus. However, IPSPs with long and variable latency 05-40 reset) were described in the above-mentioned study of Purpura and Cohen (1962) in which polysynaptic pathways were very probably involved. If inhibitory effects are mediated through poly.~jnaptic pathways one would expect them to be d~pressed by barbiturate anesthesia. Indeed, component IV becomes fully developed only with careful control of anesthesia and at a critical level of arousal (Pollen et al. 1963). Extracellular recordings cannot prt,'::,~¢ a definite answer to this proole~,, l'hese have shown that cell firing was depressed or totally abolished during the SNW regardless of whether or not the cell had been activated during the previous RR. If the excitation of a cell is dependent upon a closed loop of excitatory interneurons, then the cessation of its firing could be due Electroenceph. c/in. Neurophysiol., 1964, 17:57-67
D. A. POLLEN et al.
to the generation of an IPSP on a cell svmewhere in the loop. In motoneurons, spike after-hyperpolarization occurs only after an action potential has been generated (Coombs et al. 1955). The localization of cell bodies whose axons could provide possible inhibitory synapses remains a major problem. They would not necessexily have to be located in the cortex although there is some indirect evidence that inhibitory mechanisms may be present in pericruciate cortex of cat in relation to recurrent axon collaterals of pyramidal cells (Phillips 1956a and b; Asanuma and Brooks 1963). According to the principle of Dale (1934), all terminals of collaterals of a given axon elaborate the same transmitter substance. If the given transmitter is excitatory at all its synapses, then the collaterals of most pyramidal cells must be expected to be involved in the generation of an lPSP only by prior excitation of inhibitory interneurons. If so, atld if these involve recurrent collatertd endings of pyzamidal cells, one shguld next determine whether pyramidal cells are excited during recruiting. Brookhart and Zanchetti (1956) arid Denney and Brookhart (1962) concluded that relayed pyramidal responses were absent during surface negative recruiting uncontaminated with initittl positivity, many studies having demonstrated relayed responses when initial positivity was present (Arduini ~md Whitlock 1953; Purpura and Housepian 1960). However, axon spikes and gross responses have been reported in the pyramidal tract during surface negative recruiting (Schlag et al. 1960; Purpura and Housepian 1961), and recently in intracellular recordings from antidromically identified pyramidal cells, Purpura et al. (1963) reported significant synaptic drives on those cells during the course of surface negative recruiting. If pyramidal cells are fired during RRs, then their secondary activation of inhibitory interneurons could possibly contribute to the generation of component IV. Subcortical sources of inhibition must also be considered, particularly in view of the fact that stimulation voltages required to evoke compo. nent IV were higher than those for recruiting responses. Fibers from the midline intralaminar system distribute within the system itself and project to other thalamic nuclei (Nauta and
Whitlock 1954), and fibers of passage (not associated with the recruiting system) could well have been stimulated. Hence, inhibitory elements could be located in any or all of these loci as well as in cortex. Purpura and Cohen (1962) have suggested that some of the long latency IPSPs observed in rostral thalamic neurons during recruiting might be explained by involvement of circuits in the reticular formation (see also Scldag and Faidherbe 1961). Perot (1963) suggested that similar mechanisms might be involved in the generation of component IV. Whatever the origin of those fibers providing inhibitory synapses on thalamic neurons during recruiting, it is worth considering whether they send collateral inhibitory branches to cortical cells. The rather long latency of component IV is an unlikely result from an antidromic mechanism; in addition the observation of an "extra wave and spike" outlasting the end of stimulation (Pollen et al. 1963) would indicate that both phenomena involve orthodromic pathways, as antidromic excitation is not known to occur in the absence of electrical stimulation. The arrest of firing of type [l cells during initial positivity in the recruiting response probably corresponds to the short latency hyperpo. larization of cells in posterior cruciate cortex observed by Li (1963) in a similar situation. This mechanism appears unrelated to our present problem since d~pression of cell firing during component IV was noted in the absenceof initial positivity. Long duration surface negative waves induced by other means are known to be associated with the arrest of unit activity, for example the prolonged, negative wave that may follow the direct cortical response (Li 1956). Li and Chou (1962) found that [PSPs could be recorded during the silent period following direct cortical stimulation (see also Creutzfeldt et aL 1956). The prolonged "slow negativity" which follows a direct cortical response was found to become isoelectric 0.7-0.9 mm below the cortical surface in the rabbit before inverting its polarity (O'Leary et al. ]961). That isoclectrie region closely corresponds to that for component IV reported here. The direct cortical response and the subsequent prolonged negative wave also resemble a Electroenceph. din. Neurophysiol., 1964, 17:37-67
UNIT ACTIVITY AND 3/SEC WAVE AND SPIKE
"spike and wave", and perhaps similar mechanisms become operant in the inhibitory period after the direct cortical response, and in the production of the slow negativity of O'Leary and Goldring (1960) and O'Leary et al. (1961), as are involved in the responses described in the present work. Arrest of unit firing during the slow wave of pharmacologically evoked wave and spike patterns has been reported (Li and Jasper 1953; Li 1955; Dunlop et al. 1960). The long duration surface negative wave of the present study is believed to be produced by t he apical dendrites acting as passive sinks for active sources of current in the deeper cortical layers where the hyperpolarizing events are usually more pronounced. This explanation may also apply to some of the other types of above-mentioned long duration surface negative waves. It should be noted that hyperpolariz~tion need not be the only process contributing to the "inhibition" of type 11 cells. Frank and Fuortes (1957) and Eccles (1961) have shown that presynaptic inhibition can occur in certain spinal cord mechanisms. As mentioned in Results, the depression of unit activity sometimes occurred just before, or at the apparent beginning of the long duration depth positive wave. Whereas this might suggest that in such cases the inhibitory events (IPSP, spike after-hyperpolarization, or both) had begun earlier while the extracellular signs of inhibition were masked by still continuing excitatory processes, it is worth considering whether some additional early acting inhibitory mechanism (such as prcsynaptic inhibition) could effectively limit discharge before the full development of synaptic hyperpolarizing events. Such presynaptic inhibition could contribute to the long duration surface negative wave by acting through afferent fibers reaching the most superficial layers, but would not be reflected in intracellular potentials. SUMMARY
1. Unit activity during 3/see intralaminar stimulation at a time when each recruiting response was followed by a long duration surface negative wave has been studied in motor, sensory and association cortex. 2. Type II units which were excited during
65
recruiting negativity and~or after-positivity were depressed during most of the course of the long duration surface negative or corresponding depth positive wave. 3. The depth positive wave can probably be accounted for on the basis of summated current flows set up by intracellular hyperpo!arizing events of similar duration following recruiting responses as reported by others. The corresponding surface negative event could result from the apical dendrites serving as passive sinks for such deep sources. Pc.ocesses that could contribute to the generation of the long duration wave and to the depression of type II unit activity are discussed . . . . The authors acknowledge with gratitude the very helpful suggestions and criticisms of Dr. Herbert Jasper as well as those of Dr. Cos,as Stephanis. REFERENCES AKIMOTO, H. und CREUTZFELDT, O. Reaktionen yon Neuronen des optischen Cortex nach elektrischer Reizung unspczifischer Thalamuskerne. Arch, Psychin,. Nervenkr., 1958, 196: 494-519. AND~nS~N, P. and ECCLF.S,J. Inhibitory phasing of neuronal discharge. Nature, 1962, 196: 645-647. ANDgRSlEN, P., ECCLES, J. C. and LOVNIN(;,Y. Hippocam-
pus of the brain. Recurrent inhibition in the hippocampus with identificationof the inhibitory c¢11and its synapses. Nature, 1963, 198: ~40~542. ARnUINi,A. and WlUTLOCK,D. G. Spike discharges in pyramidal system during recruitment waves. J. Neu. rophysiol., 1953, 16: 430436.
AS^NUM^,H. and Bacx)gs, V. B. Antidromic inhibition in the cat's cerebral cortex. Fed. Prec., 190, 22: 456, BR(X)KHART,J. M. and ZANCltI::rTI,A. The relation between electrocorticalwavesand responsivenessof the corticospinal system, Electroenceph. din. Neurophy,v. iol,, 1956, 8: 427-444. CooMns, J. S., Ecc~.Es,J. C, and F^TT, P. The electrical properties of the motoncuronemembrane. J. Physiol. (Lend.), 1955, 130: 291-325. CREUTZFELDT, O., BAUMOARTNER,G. und SCHOEN, L. Reaktionen ¢inzelner Neurone des senso-motorischen Cortex nach elektrischen Reizcn. 1. Hemmung und Erregung nach direkten und kontralateralen Einzelreizen. Arch. Psychlat. Nervenkr., 1956, 194: 597-619. CURTm, D. R. Pharmacologic investigation upon the inhibition of spinal motoneuroncs. J. PhysioL (Lend.), 1959, 145: 175-192. DALE, H. h Pharmacology and nerve endings. Prec. roy. $oc. Med., 1934, 28: 319-332. D~MPSEY, E. W. and MORISON,R. S. The production of rhythmically recurrent cortical potentials after local-
Eiectroenceph. clin. NeurophysioL, 1964, 17:57-67
66
D. A, POLLEN et aL
ized tha~mic stimulation. Amer. J. Physiol., 1942, 135: 293-300. DENNEY,D. and BROOKHART,J. M. The effects of applied polarization on evoked electro-cortical waves in the cat. ElectrocRceph. din. Neurophysiol., 196Z. 15: 885-897. DUNLOP, C. W., ADEY,W. R., KILt.AM, K. F. and Be.AzmR, M. A. B. Mechanisms of action of thiosemicarbazide and metrazol on cerebellar and cerebral activity in the cat. Amer. J. Physiol., 1960, 198: 399--404. ECCLF~, J. C. Inhibitory pathways to motoneurons. In E. FLOREY (Editor), Nervous inhibition. Pergamon, Oxford, 1961: 47-60. Ecct.Es, J. C., MAGm, F. and WiLLiS, W. D. Depolarization of central terminals of group l afferent fibers from muscle. J. Physiol. (land.), 1962, 160: 62-93. FRANK, K. and FUORTU,M. G. F. Pre-synaptic and postsynapti¢ inhibition on monosynaptic reflexes. Fed. Prec., I~JT, 16: 39-40. G~TAUT, H. and FInCHEs-WiLLIAMS,M. The physiopathology of epileptic seizures. In J. FieLD (Editor), Handbook of physiology. Section i - Neurophysiology. Waverly, Baltimore, 1959: 329-363. HANaeRV, J. and JASPER, H. Independence of diffuse thalamo.cortical projection system shown by specific nuclear destructions. J. Neurophysiol., 1953, 16: 252-271. JASPER, H. H. Electrical signs of epileptic discharge. In T. SHEDLOVSKY(Editor), Electrochemistry in biology aM medicine. Wiley, New York, 1955: 352~359. JASPER, H. H, and DROOC~LEEVER-FORT,'JVN,J. Experimental studies on the functional anatomy of petit real epilepsy. Res, Pabl. Ass. aerv. men,. Dis., 1947, 26: 272~298. JUNCO, R. Coordination of specific and nonspe¢ilic alter. ant impulses at slnBle neurons of the visual cortex, in H, H. JASPER et al. (Editors), Reticular formation of the brain. Little, Brown and Co., Boston, 1958: 423~434. JustJ, R. und TONsils, J. F, Hirnelektrlsche Untersu. ~hunlen 0bar Entstehung und Erhaltung van Krampfentladungen. Die Vorgnnge am Reizort und die Bremsftthigkeit des Gehirns. Arch. Psydelat. Net, cenkr., 19~30,185: 701-735. LG C.-L. Functional properties of cortical neurones with particular reference to strychninization. Eleetroen. ceph. clin. Neurophysiol., 1955, 7" 475--477. Lz, C.-L. The inhibitory effect of stimulation of a thalamic nucleus on neuronal activity in the motor cortex. J. Phy6ol. (Lend.), 1956, 133: 40-53. L,, C.-L. Cortical intracellular synaptic potentials in response to thalamic stimulation. J. cell. camp. Physiol., 1963, 61: 165-179. Lh C.-L. and CHOU, S. N. Cortical intracellular synaptic potentials and direct cortical stimulation. J. cell. comp. PhvsioL, 1962, 60: i-16. L,, C.-L., CULLEN,C. and JASPER,H, H. Laminar microelectrode analysis el' cortical unspecific recruiting re. sponses and spontaneous rhythms. J. Neurophysiol., 1956, 19: 131-143. L[, C.-L. and JAgPER,H. Microelectrode studies of the
electrical activity of the cerebral cortex in the cat. J. Physiol. (Lend.), 1953, 121: 117-140. LING, G. and GERARD, R. W. The normal membrane potential of frog sartorius fibers. J. cell. camp. Physiol., 1949, 34: 383-396. Lax, H. D. und KLEE,M. R. Intracellul~ire Untersuchungen tiber den Einflms remmender Potentiale im motorischen Cortex. I. Die Wirkung elektriseher Reizung unspezifiseher Thalamuskerne. Arch. Psychiat. Nervenkr., 1962, 203: 648-666. MOraL,X3, A. Microelectrode analysis of some functional characteristics and inter-relationships of specific, association and non-specific thalamo-cortical systems. Electroenceph. olin. NeurophysioL, 1961, 13: 9-20. MoRmoN, g. S. and DEMPSEV,E. W. Study of thalamocortical relations. Amer. J. PhysioL, 1942, 135: 281292. NAUTA, W. V. H. and WHtTtX3CK,D. G. An anatomical analysis of the non-specific thalamic projection system. In J. F. DELAFRESNAYE(Editor), Brain mechanisms and consciousness. Blackwell, Oxford, 1954: 81-116. O'LEAaV, J. L. and GOLOmNO, S. Slow cortical potentials. Their origin and contribution to seizure discharge. Epilepsia, 1960, i: 561-574 (4th series). O'LeARY, J. L., GOLOmNO, S. and Coxv., W. S. Experimental evidence relating to the pathogenesis of posttraumatic epilepsy. Epilepsla, 1961, 2: 117-122 (4th series). PEROT, P. Mesencephalic-thalamic relations in the mecha. nlsms of the experimental wave and spike complex it, the cat. Thesis, Dept. of Neurology and Neurosurgery, Montreal Neurological Institute and McOill University, 1963, 220 p. PHILLIPS,C. G. intracellular records from Iktz cells in cat. Quart. J, exp. PhysioL, 1956n, 41: S8o69. PItlLLIPS,C. G. Cortical motor threshold and thresholds and distribution of excited lktz cells in cat, Quart. J. exp. Phy,vloL, 1956b, 41: 70~84. POLLEN,D. A., PI.'.ROT,P, and RE.), K, H. Experimental bilateral wave and spike from thalamic stimulation in relation to level of arousal, £1eetroenceph. ella. Neurophy,ffol., 1963, 15: 1017-1028. PURPURA, D. P. and COHEN, B. lntracellular recruiting from thalamic neurons during recruiting responses. J. Neurophysiol., 1962, 25: 621-635. PUReURA, D. P., COHEN, B. and SHovER,R, Activities of thalamic neurons during evoked EEG synchronization and activation. Thins. Amer. neural. Ass., 1962, 87: 76-80. PURPURA, D. P., GIRADO, M. and GRUNDFEST,H. Components of evoked potentials in cerebral cortex. Electroenceph. olin. Nearoph.rsiol., 1960, 12: 95-110. PU~PURA, D. P. and HOUSEMAN,E. M. Thalamocortical recruiting responses and relayed discharges in pyramidal tract. Fed. Proc., 1960, 19: 291. PURPURA,D. P. and HOUSEMAN,E. M. Alterations in corticospinal neuron activity associated with thalamocortical recruiting responses. Eleetroenceph. din. Newoplo'siol., 1951, 13: 365-381. PURPURA, D. P., SHaPeR, R. J. and MU~eAVE, F. S.
Electroenceph. din. Nearophysiol., 1964, 17" 57-67
67
UNIT ACTIVITY AND 3/SEC WAVE AND SPIKE lntracellular potentials of cortical neurons during augmenting and recruiting responses. Fed. Proc., 1963, 22: 457.
SCHLAG,J., CHAILLET,F. et FAIDHEReE,J. Note sur Fenregistrement des ondes en fuseau et des r6ponses de
recruitment/l partir des fibres pyramidales. Arch int. Physiol., 1960, 68: 793-802.
SCHLAG,J. and Fb,IDHERaE,J. Recruiting responses in the brain stem reticular formation. Arch. ital. Biol., 1961,
99: 135-161.
Reference: POLt.IEN,D. A., REID, K. H. and PEROT,P. Micro-electrode studies of experimental 3/see wave and spike in the cat. Eleetroenceph. clin. Neurophysiol., 1964, 17: 57-67.
ANNOUNCEMENTS THE INTERNATIONAL INSTITUTE OF ADVANCED IN HUMAN ELECTROENCEPHALOGRAPHY
STUDIES
Marseille, 7-19 September, 1964 This Institute will be organized by Prof. H. Gastaut, assisted by Dr. R. Naquet, under the auspices of the World Federation of Neurology and with the financial assistance of N.A,T.O.0 of which it is an Institute of Advanced Studies. These Institutes are non-political and their only aim is the development of science throughout the world. The period 7-12 September will be devoted to discussion of clinical EEG topics by about 40 selected "Lecturers". About 40 "Participants", who will be qualified electroenceph.aJographers, may pose questions to the t.ecturers: a limited number of "Auditors" (student electroencephalographers or specialists in neurology or psychiatry) may attend the sessions. The following Lecturers have agreed to take part: K. Pateisky - Austria; J. Radermecker - Belgium; F . B u e h t h a i - Denmark; W. Cobb, G. Pampiglione, W. Grey Walter- England; G. Arfel, J. Bancaud, J. Cadilhac, H. Cathaia, J. Courjon, M. Dondey, C. Dreyfus-Brisa¢, J. Gaches, G. C. Lair)', R. Lecasble, A. i.¢riqu¢, t,. Loiseau, P. Passouant, R. Rohmer, G. Verdeaux, A. Rgmond - France; O. Creutzfeldt, J. Kugler - Germany; A. Orfanos - Greece; O. Magnus, W. Storm van Leeuwen - Holland; C. Loeb, H. Terzian, R. Vizioli - Italy; B. F u s t e r - South America; L. Oller-Daurella - Spain; L . W i d e n - Sweden; R. Hess - Switzerland; R. G. Bick. ford, M. A. B. Brazier, G. E. Chatrian, F. Gibbs, P. Kellaway, C. Shaghass - United States. The following topics will be discussed:
AMERICAN
I. Problems of methodology. 2. The concept of normality in clinical EEG. 3. Evoked responses recorded transcranially in normal man. 4. EEG and the cerebral mechanisms of behaviour in normal man. 5. EEG and vigilance in normal man. 6. Some EEG aspects of epilepsy. The period from 14--19 September will be reserved for the Participants, who will receive technical and practical instruction, in "French, in clinical EEG from Prof. Gastaut, his collaboratocu~rand some of the Lecturers. Accommodation. So far as possible all Lecturers and Participants will be lodged in the Cit6 Universitaire Saint-Charles. The Secretary will help to find accommodation in Marseille for Auditors. Fees. Participants: 250 francs for lodging and breakfast for 13 days. Auditors: 50 francs, registration only. Noon meals for Participants and Auditors: 10 francs. ,4dmission. Applications should be made as soon as possible because of the limited number of places. Money should not be sent. Those who wish to be Participants should give details of their competence and particular interest in clinical EEG. All correspondence should be addressed to: Mlle. M. Taury, Unit6 de Recherches Neurobiologiques de rlnstitut National d'Hygiene, 300 Bd. de Sainte-Margu~rite, Marseille IX, France.
ASSOCIATION OF ELECI"ROMYOGRAPHY ELECTRODIAGNOSIS
The Annual Meeting of The American Association of Electromyography and Electrodiagnosis will be held on Sunday, August 23, 1964, at the Statler-Hilton Hotel, Boston, Massachusetts.
AND
Please address all communications to Max K. Newman, M.D., 16861 Wyoming Avenue, Detroit, Michigan 48221
Electroenceph. clin. NeurophysioL, 1964, 17:67