A critical epileptic area in the cat's cortex and its relation to the cortical columns

The critical size of active penicillin foci in cat's parietal cortex was determined in two different ways: (a) by gradually enlarging the area of drug application from 0.78 mm² to 3.14 mm²; (b) by reducing the area of the active penicillin focus, using subpial incisions. Results indicate that a critical area of 0.7 mm² is necessary. The possibility that in the parietal cortex a single functional column may be the basic generator unit for inter-ictal spikes is discussed. It is concluded that: (a) the size of the critical area is related to the cross-sectional area of a single functional column. This column is not yet determined by parallel anatomical findings; (b) inactivation of a given epileptic focus in the cat's cortex may be achieved by cutting layer III of the focus.