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Neuronal oscillations in auditory evoked potentials
55 NEURONAL POTENTIALS
OSCILLATIONS
IN AUDITORY
EVOKED
Ch. Madler, D. Schwender and E. Piippel ’ Institut fir Anaesthesiologie, ’ Institut fiir medizinische chologie, LMU Miinchen. F.R.G.
Psy-
The concept of neuronal oscillations has played an important role in theorizing about the neuronal mechanisms underlying the organization of brain activity. Such oscillation:, with a period of approximately 30 ms have been suggested on the basis of several different psychophysical paradigms. Some time ago it has been observed that the mid-latency response of the auditory evoked potential shows oscillations in the same frequency domain. and recently oscillations have been described in single cell activity. Possibly. all these phenomena reflect one basic mechanism of central nervous activity, which is essential for sensory information processing and cognitive control. We therefore anticipated that a suppression of these oscillations results in a state of general anaesthesia. It was observed that for one class of anaesthetic agents the oacillatory component in the mid-latency response of the auditory evoked potential disappears: this physiological state is correlated with controlled anaesthesia.
AUDITORY DISCRIMINATION TASK AND EVOKED POTENTIAL RECORDED DURING MOVEMENT ALONG THE EXTRALEMNISCAL PATHWAY OF THE CAT M. Maitte Lille I University.
Lille. France
The present experiment was undertaken to examine whether modulations of cutaneous afferents take place during movement triggered by a tone in an auditory discrimination task. Three cats were trained to press down a pedal to a tone S+ and to stay still after another tone S -. Electrical stimulation was delivered to the forelimb after Sand when the cat pressed the lever. During movement triggered by S + , somesthetic evoked potentials (SEPs) ipsi- and contralateral to the moving limb were recorded over the suprasylvian gyrus (SSG), the bulbar nucleus gigantocellularis (NGC) and the centrum medianum (CM) of the thalamus and expressed in percent of the SEPs recorded after S -. Medians of percentage of variation of the SEPs at the three sites were calculated by pooling the sessions when the discrimination was inferior at 50% (Myl) or superior at 70% (Mg2). Ipsilaterally, significant differences are found in the NGC (Mgl = +44.5. Mg2 = +O.YS), in the CM (+47.79, - 16.66) and a contralaterally significant difference is observed over the SSG (0. ~ 28.63l.The discrimination of auditory signals is accompanied during movement by reduction of cutaneous afferents in the extra lemniscal pathways.
COMPARISON OF VEP MORPHOLOGY AND THRESHOLD STIMULI
TO
BRIGHT
Natalia E. Maksimova and Igor 0. Aleksandrov Institute of Psychology. AS U.S.S.R.. Moscow. U.S.S.R. VEPs to bright light flash (0.3 _I) (BF). and near-threshold light flash (IO-’ nits) (ThF) were recorded in two experimental series in the same Ss at central and occipital electrodes locations. Ss were instructed to press the button after the flash presentation. The EOG, and EMG of mm. thenar were recorded also. VEP to BF consisted of P50. N6S. PIOO, NI40. P300 components, and for ThF - of P220. N3lS. P5XO. Onset of EMG in BF situation was in close relation with PlOO; in ThF situation - with P220. The strong correspondence of PlOO and P220 with EMG onset reveals the functional similarity of these positive waves in comparing situations. Thus. in the BF situation we can identify PI, Nl. P2, N3. P3 components, whereas in the ThF situation only P2. N2 and P3; early components Pl and Nl are not represented. Comparison of the waveform of VEPs and cortical unit activity in freely moving rabbits after BF (Shevchenko. 1980). and after ThF (Aleksandrov, 1984) indicates that disappearance of early components of VEP corresponds to a decreasing number of units activated at the EMG latency interval (approximately up to 30% of its number in BF situation). Thus. alteration ot VEP morphology in ThF situation can be explained not by dramatic latency increasing of early components hut by a decreasing number of activated units resulting in the disappearance of early components.
ACCULTURATION TION OF AFRICAN
STRESS VENDAS
AMONGST
A
POPULA-
N.T. Malan. P.J. Pretorius, F.C. Eloff. H.W. Huisman. J.S. vd Merwe. P.J. Laubscher and F.A.J. de Klerk Dept. Physiology. Potchefstroom University. Potchefstroom. South Africa Acculturation as a result of increasing urbanization is an ongoing process amongst various cultural groups in South Africa. Accompanying this process is an increase in psychological stress and the development of so-called Western-type diseases like hypertension. coronary heart disease and diabetes. The aim of this study was to investigate the physiology of acute stress in three groups of subjects. viz unacculturated Vendas (UV) living in a traditional rural setup, acculturated Vendas (AV) living and working in a Western economy and a group of whites (W). These groups were subjected to a passive coping streasor (cold pressor) and an active coping htressor (Crawford dexterity test) while blood samples Were taken after each stressor and blood pressure was continuously montored by means of a non-invasive method. The AV group showed significantly higher reactivity for prolactin, cortisol and growth hormone values perhaps indicating a higher base-
OSCILLATIONS
IN AUDITORY
EVOKED
Ch. Madler, D. Schwender and E. Piippel ’ Institut fir Anaesthesiologie, ’ Institut fiir medizinische chologie, LMU Miinchen. F.R.G.
Psy-
The concept of neuronal oscillations has played an important role in theorizing about the neuronal mechanisms underlying the organization of brain activity. Such oscillation:, with a period of approximately 30 ms have been suggested on the basis of several different psychophysical paradigms. Some time ago it has been observed that the mid-latency response of the auditory evoked potential shows oscillations in the same frequency domain. and recently oscillations have been described in single cell activity. Possibly. all these phenomena reflect one basic mechanism of central nervous activity, which is essential for sensory information processing and cognitive control. We therefore anticipated that a suppression of these oscillations results in a state of general anaesthesia. It was observed that for one class of anaesthetic agents the oacillatory component in the mid-latency response of the auditory evoked potential disappears: this physiological state is correlated with controlled anaesthesia.
AUDITORY DISCRIMINATION TASK AND EVOKED POTENTIAL RECORDED DURING MOVEMENT ALONG THE EXTRALEMNISCAL PATHWAY OF THE CAT M. Maitte Lille I University.
Lille. France
The present experiment was undertaken to examine whether modulations of cutaneous afferents take place during movement triggered by a tone in an auditory discrimination task. Three cats were trained to press down a pedal to a tone S+ and to stay still after another tone S -. Electrical stimulation was delivered to the forelimb after Sand when the cat pressed the lever. During movement triggered by S + , somesthetic evoked potentials (SEPs) ipsi- and contralateral to the moving limb were recorded over the suprasylvian gyrus (SSG), the bulbar nucleus gigantocellularis (NGC) and the centrum medianum (CM) of the thalamus and expressed in percent of the SEPs recorded after S -. Medians of percentage of variation of the SEPs at the three sites were calculated by pooling the sessions when the discrimination was inferior at 50% (Myl) or superior at 70% (Mg2). Ipsilaterally, significant differences are found in the NGC (Mgl = +44.5. Mg2 = +O.YS), in the CM (+47.79, - 16.66) and a contralaterally significant difference is observed over the SSG (0. ~ 28.63l.The discrimination of auditory signals is accompanied during movement by reduction of cutaneous afferents in the extra lemniscal pathways.
COMPARISON OF VEP MORPHOLOGY AND THRESHOLD STIMULI
TO
BRIGHT
Natalia E. Maksimova and Igor 0. Aleksandrov Institute of Psychology. AS U.S.S.R.. Moscow. U.S.S.R. VEPs to bright light flash (0.3 _I) (BF). and near-threshold light flash (IO-’ nits) (ThF) were recorded in two experimental series in the same Ss at central and occipital electrodes locations. Ss were instructed to press the button after the flash presentation. The EOG, and EMG of mm. thenar were recorded also. VEP to BF consisted of P50. N6S. PIOO, NI40. P300 components, and for ThF - of P220. N3lS. P5XO. Onset of EMG in BF situation was in close relation with PlOO; in ThF situation - with P220. The strong correspondence of PlOO and P220 with EMG onset reveals the functional similarity of these positive waves in comparing situations. Thus. in the BF situation we can identify PI, Nl. P2, N3. P3 components, whereas in the ThF situation only P2. N2 and P3; early components Pl and Nl are not represented. Comparison of the waveform of VEPs and cortical unit activity in freely moving rabbits after BF (Shevchenko. 1980). and after ThF (Aleksandrov, 1984) indicates that disappearance of early components of VEP corresponds to a decreasing number of units activated at the EMG latency interval (approximately up to 30% of its number in BF situation). Thus. alteration ot VEP morphology in ThF situation can be explained not by dramatic latency increasing of early components hut by a decreasing number of activated units resulting in the disappearance of early components.
ACCULTURATION TION OF AFRICAN
STRESS VENDAS
AMONGST
A
POPULA-
N.T. Malan. P.J. Pretorius, F.C. Eloff. H.W. Huisman. J.S. vd Merwe. P.J. Laubscher and F.A.J. de Klerk Dept. Physiology. Potchefstroom University. Potchefstroom. South Africa Acculturation as a result of increasing urbanization is an ongoing process amongst various cultural groups in South Africa. Accompanying this process is an increase in psychological stress and the development of so-called Western-type diseases like hypertension. coronary heart disease and diabetes. The aim of this study was to investigate the physiology of acute stress in three groups of subjects. viz unacculturated Vendas (UV) living in a traditional rural setup, acculturated Vendas (AV) living and working in a Western economy and a group of whites (W). These groups were subjected to a passive coping streasor (cold pressor) and an active coping htressor (Crawford dexterity test) while blood samples Were taken after each stressor and blood pressure was continuously montored by means of a non-invasive method. The AV group showed significantly higher reactivity for prolactin, cortisol and growth hormone values perhaps indicating a higher base-