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Depth and scalp recordings of the N4 and P3 cognitive evoked potential components
S55 SHORT TIALS.
LATENCY
H. Hafner, J.F. Soustiel (Rambam
Medical
TRIGEMINAL
EVOKED
POTEN-
Center,
Haifa,
Israel)
msec to T7: 7.2 msec). Normative data was obtained from 25 healthy volunteers. The impact of the stimulus rate and intensity on the response was studied in each subject. These results were then compared to those obtained in 18 patients suffering from posterior fossa lesions. The STEP was consistently abnormal whenever the involved side was stimulated. In the patients whose lesions were obviously peripheral in the trigeminal system, T2 latency was markedly prolonged, creating an enlarged Tl-T2 interpeak interval while T2-T3 remained unchanged. On the other hand, STEPS recorded in patients with evidence of brain-stem lesion or compression demonstrated a T3 markedly delayed and of decreased amplitude. T2-T3 time in this group was most often obviously prolonged, Tl-T2, however, was normal. The STEP proved to be a reliable method for evaluating the trigeminal system in its peripheral and central pathways. The STEP may thus serve as an additional parameter in studying brain-stem functions.
IMAGING OF HAEMODYNAMIC CHANGES IN PATIENTS WITH FOCAL AND PRIMARY GENERALIZED EPILEPSY USING 99m Tc-HM-PA0 AND SPECT. S. Hajnfek, 2. ZivEec and M. Bajc of Zagreb,
more precise
and M. Feinsod
A very short latency trigeminal evoked potential (STEP) to electrical stimulation of the upper lip was recorded from over the scalp. This potential consists of 5 distinct peaks within the 12 msec range, named accordingly to their latencies (Tl: 0.8
(University
tional cerebral disorders, as well as for enabling localization of epileptogenic foci.
Zagreb,
Yugoslavia)
Cerebral distribution of the new liposoluble radiopharmaceutical 99m Tc-HM-PA0 was investigated using single photon emission computerized tomography (SPECT) in 13 patients with partial epilepsy (with either simple or complex symptomatology, with or without secondary generalization) and in 34 patients with primary generalized epilepsy (with grand-ma] attacks, absences or their combination). These findings were compared with those from a control group which included 5 healthy individuals. In 11 patients with focal epilepsy decreased accumulation of 99m Tc-HM-PA0 was found, one patient had increased accumulation, and the others showed normal distribution of activity. Changes of cerebral perfusion in patients with primary generalized epilepsy were investigated regarding the accumulation of the radiopharmaceutical in the cortical region, in the region of the basal ganglia, and in both regions simultaneously. These results suggest that this method has significant diagnostic potential (95% sensitivity) for the verification of func-
DEPTH AND SCALP RECORDINGS OF THE N4 AND P3 COGNITIVE EVOKED POTENTIAL COMPONENTS. E. Halgren, M.E. Smith, J. Stapleton, Baudens, C. Liegeois and P. Chauvel (Brain
Research
Institute
UCLA,
V.I. Nenov.
Los Angeles,
G. Heit. P.
CA, USA)
Scalp recordings across psychological tasks indicate that the N4 (or N400) and P3 (or P300) embody successive stages in the integration of a meaningful stimulus with the cognitive context. Depth recordings have begun to identify the neural generators of the N4 and P3. The largest P3s within the brain are recorded in the hippocampus, where they have negative polarity, and are sometimes accompanied by parallel changes in unit activity. The P3 is smaller and positive in sites medial, lateral, and superior to the hippocampus. Large P3s are recorded in medial and dorsolateral frontal association cortices, where they are occasionally found to invert polarity. The P3s in parietal association cortex, while sometimes large (70 pV), are always positive but may change amplitude rapidly. The parietal and frontal P3s have a characteristic triphasic waveform (apparently corresponding to N2/P3/SW), and slightly precede the scalp-P3 in latency. In contrast, the hippocampal P3 is primarily monophasic, long-lasting, and slightly later than the scalp P3. Large-amplitude polarity-inverting N4s are also recorded in the left and right medial temporal lobes, inferior to the hippocampus. The left angular gyrus may be involved in the N4 evoked by words, inasmuch as the angular gyrus is metabolically activated by novel words (which evoke a large N4) but not by repeated words (which do not), and this increased metabolism is correlated with the size of the N4 across subjects. Together with lesion data. this evidence implies multiple generators for the N4 and P3.
MOTOR ATAXIA.
CONTROL
MECHANISMS
IN CEREBELLAR
M. Hall&t (NINDS,
Bethesda,
MD, USA)
Recent physiological data support the clinical view that the cerebellum helps with coordination of movement. Ballistic movements in patients with cerebellar deficits show the normal triphasic pattern of EMG activity, but the duration of the first agonist burst is prolonged. This correlates with prolonged acceleration time, and hypermetria would be the expected resultant movement error unless there is compensation. Slow, visual tracking movements are abnormal because of the irregularity of the movement, possibly due to problems in handling of visual feedback.
LATENCY
H. Hafner, J.F. Soustiel (Rambam
Medical
TRIGEMINAL
EVOKED
POTEN-
Center,
Haifa,
Israel)
msec to T7: 7.2 msec). Normative data was obtained from 25 healthy volunteers. The impact of the stimulus rate and intensity on the response was studied in each subject. These results were then compared to those obtained in 18 patients suffering from posterior fossa lesions. The STEP was consistently abnormal whenever the involved side was stimulated. In the patients whose lesions were obviously peripheral in the trigeminal system, T2 latency was markedly prolonged, creating an enlarged Tl-T2 interpeak interval while T2-T3 remained unchanged. On the other hand, STEPS recorded in patients with evidence of brain-stem lesion or compression demonstrated a T3 markedly delayed and of decreased amplitude. T2-T3 time in this group was most often obviously prolonged, Tl-T2, however, was normal. The STEP proved to be a reliable method for evaluating the trigeminal system in its peripheral and central pathways. The STEP may thus serve as an additional parameter in studying brain-stem functions.
IMAGING OF HAEMODYNAMIC CHANGES IN PATIENTS WITH FOCAL AND PRIMARY GENERALIZED EPILEPSY USING 99m Tc-HM-PA0 AND SPECT. S. Hajnfek, 2. ZivEec and M. Bajc of Zagreb,
more precise
and M. Feinsod
A very short latency trigeminal evoked potential (STEP) to electrical stimulation of the upper lip was recorded from over the scalp. This potential consists of 5 distinct peaks within the 12 msec range, named accordingly to their latencies (Tl: 0.8
(University
tional cerebral disorders, as well as for enabling localization of epileptogenic foci.
Zagreb,
Yugoslavia)
Cerebral distribution of the new liposoluble radiopharmaceutical 99m Tc-HM-PA0 was investigated using single photon emission computerized tomography (SPECT) in 13 patients with partial epilepsy (with either simple or complex symptomatology, with or without secondary generalization) and in 34 patients with primary generalized epilepsy (with grand-ma] attacks, absences or their combination). These findings were compared with those from a control group which included 5 healthy individuals. In 11 patients with focal epilepsy decreased accumulation of 99m Tc-HM-PA0 was found, one patient had increased accumulation, and the others showed normal distribution of activity. Changes of cerebral perfusion in patients with primary generalized epilepsy were investigated regarding the accumulation of the radiopharmaceutical in the cortical region, in the region of the basal ganglia, and in both regions simultaneously. These results suggest that this method has significant diagnostic potential (95% sensitivity) for the verification of func-
DEPTH AND SCALP RECORDINGS OF THE N4 AND P3 COGNITIVE EVOKED POTENTIAL COMPONENTS. E. Halgren, M.E. Smith, J. Stapleton, Baudens, C. Liegeois and P. Chauvel (Brain
Research
Institute
UCLA,
V.I. Nenov.
Los Angeles,
G. Heit. P.
CA, USA)
Scalp recordings across psychological tasks indicate that the N4 (or N400) and P3 (or P300) embody successive stages in the integration of a meaningful stimulus with the cognitive context. Depth recordings have begun to identify the neural generators of the N4 and P3. The largest P3s within the brain are recorded in the hippocampus, where they have negative polarity, and are sometimes accompanied by parallel changes in unit activity. The P3 is smaller and positive in sites medial, lateral, and superior to the hippocampus. Large P3s are recorded in medial and dorsolateral frontal association cortices, where they are occasionally found to invert polarity. The P3s in parietal association cortex, while sometimes large (70 pV), are always positive but may change amplitude rapidly. The parietal and frontal P3s have a characteristic triphasic waveform (apparently corresponding to N2/P3/SW), and slightly precede the scalp-P3 in latency. In contrast, the hippocampal P3 is primarily monophasic, long-lasting, and slightly later than the scalp P3. Large-amplitude polarity-inverting N4s are also recorded in the left and right medial temporal lobes, inferior to the hippocampus. The left angular gyrus may be involved in the N4 evoked by words, inasmuch as the angular gyrus is metabolically activated by novel words (which evoke a large N4) but not by repeated words (which do not), and this increased metabolism is correlated with the size of the N4 across subjects. Together with lesion data. this evidence implies multiple generators for the N4 and P3.
MOTOR ATAXIA.
CONTROL
MECHANISMS
IN CEREBELLAR
M. Hall&t (NINDS,
Bethesda,
MD, USA)
Recent physiological data support the clinical view that the cerebellum helps with coordination of movement. Ballistic movements in patients with cerebellar deficits show the normal triphasic pattern of EMG activity, but the duration of the first agonist burst is prolonged. This correlates with prolonged acceleration time, and hypermetria would be the expected resultant movement error unless there is compensation. Slow, visual tracking movements are abnormal because of the irregularity of the movement, possibly due to problems in handling of visual feedback.