Compound stimuli promote architectural reorganization in cat striate cortex

Abstract

Striate cortical organization can be modeled either as static or as dynamically modifiable by complex stimuli. To study this issue we performed intrinsic optical imaging on cats anesthetized with N2O and Propofol and paralyzed with Pavulon. The influence of complex stimuli on orientation maps was examined by superimposing sinusoidal gratings. Four single gratings presented at 45 deg intervals and 56% contrast were used as control stimuli. These stimuli were then combined with a spatially congruent “mask” grating oriented at 30 deg and the mask was also presented alone. All presentations were interleaved to reduce motion artifact. After compensating for the presence of the mask, we constructed single condition maps (SCM) using cocktail blanks for each stimulus. These SCMs were compared with the controls to determine mask-induced changes in activation patterns. For orientations within ± 45 deg of the mask, there was less activation in the compensated maps than in the controls and activation patterns were shifted. For orientations greater than 45 deg from the mask, the activation patterns of the control and compensated maps were similar, but there was less contrast in the compensated maps. An orientation preference map was created using the compensated SCMs and compared to the control orientation preference map. The mask caused shifts in regions of constant orientation, but these were confined to orientations within ± 45 deg of the mask orientation. Iso-orientation domains were shifted away from the mask orientation. We found both creation and annihilation of pinwheel centers in the experimental map, but the loci of the orientation pinwheels that weren′t annihilated by the mask did not change. Our results suggest that the spatial organization of striate cortex can be dynamically modified by complex stimuli, which has impact on physiological models of visual function.