A New Method of Isolating the Cerebral Cortex

A new surgical technique is described which permits section of all nervous connections of the posterior third of the cerebral mantle of the rabbit without impairing the blood supply. This method is easy to perform and avoids the artefacts of the ‘isolated-cortex’ preparations described previously. The spontaneous electrical activity of the isolated cortex is normal, and no spontaneous epileptic activity was observed. On the other hand, the epileptic threshold i.v. epileptogenic substances is somewhat lowered. With such an ‘isolated cortex’ preparation, we have confirmed the epileptogenic nature of four substances in particular: lidocain, amylocain, cyclain and dioxone. These are highly epileptogenic by intravenous injection but not at all by direct application to the cortex. The isolated cortex reacts to their administration in the same way as the intact cortex. We reiterate our hypothesis that the blood-brain barrier is the site of this epileptogenic action (phragmatic epilepsy).