Spatiotemporal Tuning and Contrast Adaptation in Mouse Primary Visual Cortex
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Mice have emerged as a popular model of cortical visual processing due to their genetic manipulability. Compared to traditional animal models of visual processing there is less research describing the visual system of mice. Before we can use the genetic techniques available in mice, we must examine the similarity between their visual processing, and that of common animal models used in vision research. One useful method to characterize the way information about form and motion is processed is to examine the interaction between selectivity for spatial and temporal frequency of sine-wave gratings in a given visual area. In experiment 1, we investigated spatiotemporal tuning in neurons of mouse primary visual cortex (V1). Tuning for stimulus speed can readily be extracted from the spatiotemporal profile of a neuron, and we were interested in whether recently described differences in the degree of speed tuning in mouse V1 and macaque V1 were due to methodology. We confirm that speed tuning is rare in mouse V1, demonstrating a difference between motion processing in the striate cortex of mice and macaques. In experiment 2, we examined the spatiotemporal dependence of contrast adaptation in mouse V1 neurons. Little is known about the underlying cellular mechanisms of contrast adaptation, so the mouse provides an attractive model in which to study this phenomenon. We characterized the spatial and temporal frequency dependence of contrast adaptation in mouse V1 neurons simultaneously using a dynamic contrast ramp. We found that for most mouse V1 neurons there was often a difference between the grating that elicited maximal firing, and the grating where adaptation was most pronounced, such that adaptation was usually stronger at higher spatial frequencies.