Direction selectivity of excitatory and inhibitory neurons in ferret visual cortex

Direction selectivity is a characteristic feature of neurons in the visual cortex of higher mammals. Excitatory and inhibitory cortical neurons receiv e different patterns of synaptic connections resulting in different recepti ve field properties. We have analyzed the direction tuning of excitatory an d inhibitory neurons of ferret visual cortex using single unit recordings. Direction tuning was constant among neurons in a vertical column. The major ity (>80%) of excitatory (regular spiking) neurons were direction tuned or direction biased. Fast spiking (inhibitory) neurons were orientation. but o nly weakly or not direction tuned. This indicates that excitatory and inhib itory neurons have different functions in visual processing and their diffe rent integration in thalamocortical and intracortical circuits results in a diversification of receptive field properties. NeuroReport 12:2293-2296 (C ) 2001 Lippincott Williams & Wilkins.