Abstract : Orientation-selective neurons shift their preferred orientation after being adapted to a nonpreferred orientation. These shifts of the peaks of tuning curves may be in the attractive or
repulsive direction in relation to the adapter orientation. In anaesthetized cats we recorded evoked electrical responses from the visual cortex in a conventional fashion. The recorded spikes in cortex may present two typical waveforms: regular spikes or fast spikes. However, there is no evidence whether the shapes of spikes are related to the attractive or repulsive shifts of orientation tuning curves of cells. Our results show that after adaptation the recorded cells with both attractive and repulsive shifts display one or the other shape of spike. However, the magnitude of shifts is systematically higher for regular spikes, which is attributed to putative pyramidal cells, while tuning curves for fast spikes have smaller
magnitudes and are evoked by putative interneurons.