Neuronal activity of the amygdala in patients with psychomotor epilepsy

Abstract

Microelectrodes were stereotaxically introduced, through a previously implanted cannula, into the amygdala of patients with psychomotor epilepsy. Under laboratory conditions and without anesthesia, recordings of extracellular action potentials and gross waves were obtained during interictal periods. Epileptiform waves were seen in all regions of the amygdala. The neuronal activity consisted, most frequently, of clusters of actions potentials, occasionally associated with trains of waves. During one recording session, a clinical seizure occurred fortuitously and it was possible to follow the electrical events during the preceding minutes. It was found that, as the seizure was approaching, the clustering of neuronal action potentials became progressively more marked, more regularly periodic, and more frequently associated, in time and in phase, with the gross waves, as the latter increased in amplitude and in duration. These progressive changes in the patterns of neuronal activity, in the characteristics of the gross waves, and in their association, were similar to those which have been found to occur in the progressive “hypersynchronization” leading to convulsive states, induced in animals by means of pharmacological agents, and assumed to be related to changes in interactions between groups of neurons in neuronal networks. It is suggested that a similar mechanism may be involved in the development of electrical events preceding the convulsive seizure in the human. Should it become possible to continually detect and monitor such changes in neuronal activity and gross waves, characteristic of an impending seizure, therapeutic measures might be taken in time to prevent it.