Color modulation of motion aftereffect on optomotor response in zebrafish larvae

Visual aftereffects are perceptual distortions that occur after prolonged exposure to a visual stimulus. We examined zebrafish larval behaviors in response to unidirectional or bidirectional grating movement in red, green, and blue during adaptation and test phases. At the end of the test, larvae were collected to assess cone photoreceptor expression Unidirectional motion adaptation induced robust, color-dependent MAEs, with the strongest effect under red stimuli, followed by green and blue. In contrast, bidirectional adaptation abolished MAEs across all colors. General locomotor activity decreased during test phases, with unidirectional adaptation maintaining higher activity than bidirectional, particularly under red stimuli. Importantly, qRT-PCR and immunostaining revealed no changes in cone photoreceptor markers, indicating that the observed behavioral modulation occurred independently of photoreceptor expression. Together, these findings demonstrate that color selectively modulates motion perception in zebrafish larvae, with red stimuli producing the strongest motion adaptation effects, while general locomotor activity and photoreceptor expression remain largely unaffected. These behavioral patterns may arise from higher-order neural processing rather than from changes at the level of photoreceptor composition.