Kindling in the posterior cingulate cortex: electrographic and behavioral characteristics.

Ictal, postictal and interictal electrical activities were recorded in the posterior cingulate cortex and hippocampus in the rat following kindling stimulations in the cingulate cortex. The afterdischarges (ADs) consisted of fast spikes and slow spike-and-wave of 2-5 Hz. Initial motor signs typically consisted of extension of the forelimbs and head, followed by clonic fore- and/or hind limb movements; there was no consistent laterality in any of the motor signs. Electrodes at or near the cingulum or corpus callosum ('white matter' group) gave kindling rates faster than other sites in the 'grey matter' of cingulate cortex (area 29); 2 of 7 animals had first-trial generalized motor seizures. The 'white matter' group averaged 4.6 ADs to reach the first 'bilateral forelimb clonus,' as compared to 17.8 ADs for the 'grey matter' group. The frequency and morphology of sharp EEG spikes in the cingulate cortex remained largely unchanged during the course of kindling. Cingulate interictal spikes were infrequent. The intimate connections of the cingulate cortex to motor and limbic structures rather than its intrinsic circuitry may be important for its fast kindling rates.