Primary visual cortex and behavioral responses to reverse-phi motion in mice.

Abstract

When the contrast of a moving random dot pattern is flipped periodically, the direction of motion appears reversed. This phenomenon is called reverse-phi motion. In this study we tested whether mice are susceptible to this effect. We measured neural activity in primary visual cortex (V1) and optomotor reflex behavior in response to reverse-phi motion. Our visual stimuli consisted of randomly positioned black and white dots that we moved using a single-step dot lifetime paradigm. The luminance contrast of the dots was constant ('phi motion') or inverted each step ('reverse-phi motion'). We used two-photon calcium imaging to measure the neural responses of layer 2/3 V1 neurons of awake mice that passively viewed the moving dots on a screen. In the behavioral experiments, we projected the moving dots on the inside of a dome that covered the entire visual field. We measured the spontaneous optomotor reflexes that this motion elicited in head-fixed mice that ran on a spherical treadmill. We found that direction-tuned V1 neurons systematically reversed their tuning to phi and reverse-phi motion. The behavioral tests show that running mice turned in response to our stimuli in a manner consistent with the phi and reverse-phi motion percepts. Our findings suggest that mice perceive reverse-phi motion and that this is reflected in neural responses at the level of V1.

Meeting abstract presented at VSS 2016