Neuronal dysfunction at the border of focal lesions in cat visual cortex.

Traditional concepts assume that traumatic or ischemic brain lesions are surrounded by regions with depressed neuronal function. More recently hyperactivity gained increasing attention as excitotoxic mechanisms become effective at certain stages of neuronal injury. Single cell recordings in the surrounding of small focal lesions in the cat visual cortex revealed both types of functional pathology 1-30 days after lesioning. A rim of suppressed neurons surrounded a completely silent core. Cells further away from the lesion showed bursts and long lasting hyperactivity with extremely high discharge rates. Consequently, the volume of disturbed tissue was considerably larger than the region of initial cell death. This halo of dysfunction may be important for neurological symptoms evoked by cortical lesions.