The Generalized Convulsive Seizure State Induced by Daily Electrical Stimulation of the Amygdala in Split Brain Cats

Abstract

Daily unilateral electrical stimulation of amygdala in forebrain bisected cats provoked the development of the final stage of the kindled convulsion with remarkable rapidity regardless of presence or absence of anterior commissure. The chronological and spatial pattern of propagation of afterdischarge, interictal spike discharge, and clinical manifestations strongly suggest the significant role played by the midbrain reticular formation and possibly other brainstem structures in the progressive electroclinical seizure development. This assumption was supported by the results of a lesion study in which placement of a destructive lesion in the ipsilateral midbrain reticular formation markedly increased the generalized seizure triggering threshold, lateralized the afterdischarge to the stimulated hemisphere when induced with increased intensity stimulation, fragmented clinical seizure manifestations, and failed to produce progression of clinical and electrographic events with prolonged daily stimulation. This is in contrast to the insignificant effect produced by a peduncular lesion. Our findings suggest that vertical (limbic-brainstem), but not horizontal (transhemispheric interlimbic) connection is critically involved in the amygdaloid seizure development while the forebrain commissures may play a role in the development of bisynchronous and bisymmetrical ictal and interictal electrographic and clinical manifestations. Finally, possible differential effect of forebrain bisection depending on developing in contrast with a established (cerebral) hemispheric epileptogenic process is postulated to explain the "facilitatory" effect observed in our series in contrast to the beneficial effects reported on some intractable seizure patients.

Effect of Anterior Callosotomy on Bilaterally Synchronous Spike and Wave and Other EEG Discharges

“…Four patients with type 1 EEG patterns had disruption of GSW with newly developed or increased discharges in the previously less involved hemisphere. The corpus callosum is reported to play both a facilitatory and an inhibitory role on interhemispheric spread of seizures (Spencer et al, 1984); this finding may be due to reduction of the inhibitory effects of the corpus callosum (Wada and Sato, 1975). It may also indicate that before callosotomy the epileptic area in the less involved hemisphere discharged only under the effect of an epileptic pacemaker located in the contralateral hemisphere, resulting in GSW.…”

Interference effects within the kindling paradigm

“…The "kindling effect" has been investigated in a number of laboratories as a model of learning, a model of epilepsy, or as an example of behavioral change of interest in its own right (e.g., Gaito & Gaito, 1974;Goddard, Mcintyre, & Leech, 1969;Racine, 1972;Wada & Sato, 1975). Repeated lowlevel electrical stimulation of any of a number of brain regions induces progressive changes which culminate in clonic convulsions; as stimulation trials proceed, the animal's behavior changes in a gradual and predictable way from an initial stage of exploratory behavior (Stage 1), to behavioral automatisms usually involving facial contractions, chewing movements, eye closure, and salivation (Stage 2), and, finally, to a motor seizure (Stage 3).…”

Limbic Kindling in the Forebrain‐Bisected Photosensitive Baboon, Papio papio

“…Baboons with an intact AC showed AD propagation into the contralateral AM and HIPP, yet their seizures remained largely lateralized, while asymmetrical generalization occurred leading to hemiconvulsion showed evidence of a significant delay in the intrahemispheric ictal processes in all the animals. This finding suggests a facilitatory role played by the comrnissural system in Papio pupio, a role which is entirely opposite to that in cats (Wada and Sato, 1975) and rhesus mon- , 1981), in which the CC appears to mediate a suppressive effect on various aspects of seizure development and developed seizures. It is possible that dysfunction of the commissural system is involved in the predisposed seizure susceptibility of Pupio pupio.…”