Effects of Locomotion on Visual Responses in the Mouse Superior Colliculus

Area of Science:

• Neuroscience
• Visual processing
• Sensory-motor integration

Background:

• Visual responses are influenced by internal states, notably locomotion.
• The primary visual cortex (V1) shows a drastic increase in visually-evoked responses during locomotion.
• The superior colliculus (SC) is another key structure in early visual processing.

Purpose of the Study:

• To investigate if locomotion similarly modulates neural responses in the superior colliculus (SC) as observed in the primary visual cortex (V1).
• To compare the impact of locomotion on neural activity and response characteristics between the SC and V1.

Main Methods:

• Two-photon calcium imaging was performed on head-fixed mice running on a treadmill.
• Neural activity was recorded in the superficial lamina of the SC.
• Responses were analyzed for changes during locomotion, response variability, and spontaneous activity, comparing SC and V1 neurons.

Main Results:

• Only a minority of SC neurons showed significant modulation by locomotion, with varied response amplitude changes.
• Locomotion-induced modulation in the SC was considerably smaller compared to the near doubling of responses in V1.
• SC neurons exhibited lower response variability and less spontaneous activity than V1 neurons.

Conclusions:

• Locomotion-dependent modulation is not a universal feature across the early visual system.
• The SC and V1 employ different strategies for visual information encoding.
• A division of labor exists in visual processing between the SC and V1 pathways.