Slow potential changes from cat cortex and classical aversive conditioning

1. 1. The present study was designed to investigate variations in the amplitude of slow electrical potential changes (SPCs) recorded from motor and somato-sensory cortex of cats undergoing classical leg flexion conditioning. Eleven cats (the “learning group”) reached the behavioral criterion of 90% CRs. Eight cats who failed to reach conditioning criterion in 300 trials formed a “non-learning” comparison group. 2. 2. In the learning group negative SPCs from all cortical areas sampled showed decreasing amplitudes during habituation and extinction. All areas, with the exception of the motor cortex ipsilateral to the left hind leg of the animal (the leg receiving the UCS), showed similar decreases in amplitude during overlearning. Slow potential changes from the non-learning group showed consistent decreases only during extinction trials. In the learning group, negative SPCs recorded from contralateral motor and somato-sensory areas during conditioning showed greater mean amplitude than those recorded from the respective ipsilateral areas. In the non-learning group no significant differences appeared between contralateral and ipsilateral areas during CS-UCS pairings. 3. 3. No relation between SPCs and eye movement could be established. 4. 4. It was concluded that the SPC reflects two processes representing the activity of two or more subcortical systems. The equal bilateral changes in SPC amplitude seen in both the learning and non-learning groups were attributed to a diffuse activation via a system such as the midbrain reticular formation. The enhancement of negative SPCs restricted to the contralateral motor and somato-sensory cortices in the learning group, during acquisition, was attributed to a “localized” activation system. This could involve the nucleus ventralis lateralis and nucleus ventralis anterior of the thalamus. The diffuse system may be involved in the maintenance of general levels of “arousal”, or “activation”, a view commonly held. The localized system may be necessary for the elaboration and development of conditioned responding, but does not appear to be necessary for the maintenance of such behavioral activity. 1. 1. Cette étude a pour but de rechercher les modifications de l'amplitude des variations lentes de potentiel électrique (SPCs) enregistrées au niveau du cortex moteur et somato-sensoriel de chats sous conditionnement classique de flexion de la jambe. Onze chats (“groupe bien entraîné”) ont atteint le critère comportemental de 90%