RECENT studies have demonstrated that small cryogenic lesions made in cortex of rabbit, cat, or monkey1-3 will produce epileptogenic foci. The epileptogenic discharge does not remain restricted to the primary site but is transmitted to the area homotopic to the freeze, and an independent epileptic (mirror) focus may develop in a region which has not been disturbed during the original experimental procedure.3
In the present study we wished to determine whether cryogenic lesions made in subcortical nuclei of varying cellular architectonics would produce epileptogenic foci and whether the epileptogenic activity would spread to other synaptically related areas which would in turn develop independent epileptogenic activity.
Under aseptic conditions 22 cats and 7 rabbits were chronically implanted using standard stereotaxic techniques. Bipolar depth electrodes consisted of side-by-side pairs of 250μ stainless steel wires insulated to within 0.5 mm of their tips with tip separation of 1 mm.