Abstracts

RATIONALE: To characterize the functional connections between anterior thalamic nuclei (ANT), mesial temporal structures (MTS), and other regoins of the brain, in humans using Evoked Responce Methodology.
METHODS: We studied three subjects with intractable epilepsy who were not candidates for conventional surgery. All had depth electrodes stereotaxically placed into MTS, orbito-frontal (OF) regions and ANT bilaterally. Signals were recorded using averaging techniques and the following parameters: Filters: 0.5 Hz - 3 KHz; stimulus rate: 0.7 Hz; pw: 0.2 usec; intensity: 5.1 mA. Stimuli were delivered independently to each ANT and responses monitored simultaneously from structures in both hemispheres; additionally, EP were recorded from ANT following MST Mode instead of mean or median latencies are reported.
RESULTS: Reproducible responses from all subjects were evoked bilaterally with unilateral ANT stimulation and with similar peak latencies (in msec.):
N 20 (range: N13-N30); P30 (range: 10-30); N37 (17-43).
Waves with similar latencies were recorded from ANT following MST and OF stimulation.
CONCLUSIONS: These results suggest that in humans, ANT has reciprocal connections with MST and OF regions. Interestingly, mode peak latencies are comparable to those obtained with median n. SSEPs. Given the close proximity, between these central structures, compared to those involved in the generation of far-fields potentials, the latencies reported in this study suggest the connections between ANT and MTS and OF regions are multi-synaptic and that intense processing may take place at each level.
Support: Flint Hills Scientific, L.L.C.