Effects of Locomotion on Visual Responses in the Mouse Superior Colliculus

Visual responses are extensively shaped by internal factors. This effect is drastic in the primary visual cortex (VI), where locomotion profoundly increases visually-evoked responses. Here we investigate whether a similar effect exists in another major visual structure, the superior colliculus (SC). By performing two-photon calcium imaging of head-fixed male and female mice running on a treadmill, we find that only a minority of neurons in the most superficial lamina of the SC display significant changes during locomotion. This modulation includes both increase and decrease in response amplitude and is similar between excitatory and inhibitory neurons. The overall change in the SC is small, whereas VI responses almost double during locomotion. Additionally, SC neurons display lower response variability and less spontaneous activity than VI neurons. Together, these experiments indicate that locomotion-dependent modulation is not a widespread phenomenon in the early visual system and that the SC and VI use different strategies to encode visual information.