Subacute Electrical Stimulation of the Human Hippocampus: I. Hippocampal Evoked Potentials and Recovery Cycles.
Abstract number :
2.153
Submission category :
Year :
2000
Submission ID :
1241
Source :
www.aesnet.org
Presentation date :
12/2/2000 12:00:00 AM
Published date :
Dec 1, 2000, 06:00 AM
Authors :
Marcos Velaco, Fransisco Velasco, Ana Luisa Velasco, Irma Marquez, National Medical Ctr IMSS, Mexico City, Mexico; National Medical Ctr, Mexico City, Mexico.
RATIONALE: We recently showed that subacute electrical stimulation of the hippocampus (SAHCS) blocks clinical and EEG untreatable temporal lobe epileptogenesis with no additional damage of the stimultaed tissue. Present work attempts to demonstrate that SAHCS produces its antiepileptic effect by a physiological inhibition of the stimulated tissue. METHODS: For this purpose we studied the threshold, amplitude and recovery cycles of the hippocampal and amygdaloid responses evoked by single shock stimulation of the amygdala and hippocampus, respectivelly. RESULTS: Before SAHCS, both hippocampal (electronegative) and amygdaloid (electropositive) responses showed low threshold (100-250 uA), long peak latency (10-20 ms) and large amplitude (200-280 uV). Recovery cycles studied by paired pulses of identical intensity and decreasing intervals between te first (conditioning) and the second (test) stimuli showed a progressive amplitude reduction of the test responses from 100% to 0% from 80-100 ms to 10-20 ms intervals. After SAHCS, hippocampal responses increased threshold, decreased amplitude and showed a flattened down of their recovery cycles without change in latency and polarity; while amygdaloid responses remained the same as before SAHCS. CONCLUSIONS: Present results reveal an inhibitory effect of SAHCS on the epileptogenic hippocampal neurons.