Epileptic activity and anatomical characteristics of different lesions in cat cortex. Ultrastructural study.

Three different types of lesions have been studied in the cortex of the cat, by means of electroencephalography and electron microscopy. These three types of lesions can be listed in order of increasing magnitude according to their capacity to induce abnormal electrical activity: 1. incision of the cortex gives paroxymal activity, 2. intracortical insertion of a resin pellet generates weak epileptic activity, 3. intracortical insertion of a colbalt resin pellet produces epileptic activity. A parallel can be drawn between electrophysiological and anatomical data: there seems to be a quantitative relationship between the degree of epileptic activity and the extent of perilesional tissue. Furthermore, in this perilesional tissue, oedema is observed, the intensity of which varies according to the type of lesion. Thus, the epileptic activity of a lesion seems to be proportional not only to the volume of the perilesional tissue but also to the development of the oedema.