Late consequences of cryogenic brain lesion in rat; an electrophysiological study.

The left somatosensory cortex of PVG/C rats was subjected to a transcranial cold lesion, spontaneous and evoked cortical activity was studied 2-3 weeks after the lesion. The spontaneous activity underwent a depression at the focus of the lesion. Close to the epicentre of the lesion, the amplitude of the potentials evoked by electrical stimulation of the contralateral whisker pad was considerably smaller than in the controls and an almost complete reduction of the initial positive phase was found. Perifocally, 3-4 mm from the epicentre, evoked potentials with enhanced amplitudes were recorded in all experiments. It seems that considerable damage took place at the epicentre of the lesion, while perifocally an excitatory (and/or inhibitory?) mechanism was activated.