LINEARITY OF SUMMATION OF SYNAPTIC POTENTIALS UNDERLYING DIRECTION SELECTIVITY IN SIMPLE CELLS OF THE CAT VISUAL-CORTEX

Intracellular recordings from simple cells of the cat visual cortex we re used to test linear models for the generation of selectivity for th e direction of visual motion. Direction selectivity has been thought t o arise in part from nonlinear processes, as suggested by previous exp eriments that were based on extracellular recordings of action potenti als. In intracellular recordings, however, the fluctuations in membran e potential evoked by moving stimuli were accurately predicted by the linear summation of responses to stationary stimuli. Nonlinear mechani sms were not required.