Contrast-Dependence of Temporal Frequency Tuning in Mouse V1.

Daniela Camillo,Mehran Ahmadlou,J Alexander Heimel

doi:10.3389/fnins.2020.00868

Abstract

The perception of speed is influenced by visual contrast. In primary visual cortex (V1), an early stage in the visual perception pathway, the neural tuning to speed is directly related to the neural tuning to temporal frequency of stimulus changes. The influence of contrast on speed perception can be caused by the joint dependency of neural responses in V1 on temporal frequency and contrast. Here, we investigated how tuning to contrast and temporal frequency in V1 of anesthetized mice are related. We found that temporal frequency tuning is contrast-dependent. V1 was more responsive at lower temporal frequencies than the dLGN, consistent with previous work at high contrast. The temporal frequency tuning moves toward higher temporal frequencies with increasing contrast. The low half-maximum temporal frequency does not change with contrast. The Heeger divisive normalization equation provides a good fit to many response characteristics in V1, but does not fit the dependency of temporal frequency and contrast with set of parameters for all temporal frequencies. Different mechanisms for normalization in the visual cortex may predict different relationships between temporal frequency and contrast non-linearity. Our data could help to make a model selection.

Highlights

While the signals that are produced by an image and leave the retina are dependent on the overall level of contrast, the interpretation of an image is largely independent of the overall contrast (Avidan et al, 2002)
While the normalization model with a single saturation constant and exponent can approximately match V1 population responses for all combinations of temporal frequency and contrast, it does not describe the change in temporal frequency tuning with contrast for low and intermediate temporal frequencies
We found that the shape of contrast tuning curves of mouse V1 neurons depended on the temporal frequency of the stimulus and vice versa, the shape of the temporal frequency tuning curve depended on the stimulus contrast

Summary

Introduction

While the signals that are produced by an image and leave the retina are dependent on the overall level of contrast, the interpretation of an image is largely independent of the overall contrast (Avidan et al, 2002). Reducing the contrast makes an image harder to see, but does not change its interpretation. In the primary visual cortex (V1), neurons are responsive to local differences in image contrast, edges in particular (Hubel and Wiesel, 1959). V1 neurons operate as spatiotemporal filters of the image contrast. Most investigations have focused on the interaction of spatial frequency filtering and contrast of grating stimuli. It became clear that spatial frequency tuning and contrast are not completely inseparable in V1 in cat (Skottun et al, 1986), monkey (Sceniak et al, 2002; Priebe et al, 2006), and mouse (Heimel et al, 2010)

Methods

Results

Conclusion