INSENSITIVITY OF V1 COMPLEX CELL RESPONSES TO SMALL SHIFTS IN THE RETINAL IMAGE OF COMPLEX PATTERNS

An important role for neurons in the early visual system is to convey information about the structure of visual stimuli. However, neuronal r esponses show substantial variation across presentations of the same s timulus. In awake monkeys, it has been assumed that a great deal of th is variation is related to the scatter in eye position (inducing scatt er in the retinal position of the stimulus). Here we investigate the i mplied consequence of this assumption, i.e., that the scatter variatio n in eye position degrades the decodability of the neural response. We recorded from 50 complex cells in primary visual cortex of fixating m onkeys while different complex stimuli were presented. Three types of retinal shifts were considered: natural scatter in the fixation, syste matic fixation point shift, and systematic stimulus position shift. Th e stimulus pattern accounts for >50% of the response variance, always six times that accounted for by the scatter in eye position during fix ation. The retinal location of a stimulus had to be shifted by 10-12 m in of are, an amount almost two times larger than the smallest picture element, before the responses changed systematically. Nonetheless, ch anges of the stimulus at the single pixel level often gave rise to dis criminable responses. Thus complex cells convey information about the spatial structure of a stimulus, independent of rigid stimulus displac ements on the order of the receptive field size or smaller.