Rats with neocortical and hippocampal lesions, as well as normal animals, were trained in a visual discrimination task. The periods of stimulus presentation indicating the "correct lever" were separated by 10-sec intertrial intervals. Both lesion groups were impaired in the acquisition of the problem, but only the animals with hippocampal damage evidenced significantly higher response rates during the intertrial intervals.

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SUMMARY The interaction between KCl‐induced cortical spreading depression and penicillin‐induced cortical epileptiform activity was studied in the rat brain. In one experimental procedure, a primary epileptiform focus was initiated with penicillin in one hemisphere, and at various subsequent time intervals KCl was applied and spreading depression produced. In the second procedure, spreading depression was induced in one hemisphere and a seizure focus later established in the other. Electrophysiological correlates of the chemical manipulations were monitored throughout. The effects of spreading depression on the developing and established primary and secondary foci were studied. Results indicated an antagonism between spreading depression and penicillin‐induced cortical seizure foci. Possible mechanisms underlying the observed interactions are discussed. RESUME On a étudié sur le cerveau du rat l'interaction de la ←spreading depression→ corticale induite par KCl et l'activitéépileptique corticale produite par la pénicilline. Dans une première série d'expériences, on a d'abord crée avec la pénicilline un foyer épileptiforme primaire sur un hémisphère et successivement à intervalle variable, on appliqué le KCl et produit la ←spreading depression→. Dans une seconde série d'expériences, on a induit la ←spreading depression→ sur un hémisphère et un foyer épileptique sur l'autre. On a contrôlé tout au long des expériences les variations électrophysiologiques correspondant aux manipulations chimiques. De même, on a étudié l'effet de la ←spreading depression→ sur le développement et l'établissement du foyer primaire et du foyer secondaire. Les résultats indiquent qu'il y a un antagonisme entre la ←spreading depression→ et les foyers corticaux épileptiques induits par la pénicilline. On a discuté les mécanismes possibles responsables des interactions observées.