Encoding of Component and Pattern Motion in Awake Mouse Visual Cortex and Superior Colliculus

The encoding of motion features by the visual system is critical for an animal’s survival in a dynamic environment. As one of the important features, the detection of motion direction varies to some degree in different species and brain areas. In mice, orientation (or motion axis) selective cells are consistently reported in the primary visual cortex (V1), whereas a large proportion of cells in the superficial layer of the Superior Colliculus (SC) are direction selective. However, little is known about how exactly these two structures respond to complex motion in awake mice. To address this question, we presented the animals with drifting gratings and moving plaids which are formed by superimposing two sinusoidal gratings. We used two-photon calcium imaging to record neuronal responses in layer II/III of V1 and superficial SC. We found that the majority of V1 neurons are sensitive to two opposite directions of the gratings with a narrow tuning curve, while superficial SC neurons are tuned specifically to a range of directions with a broader curve. Next, we identified a group of V1 neurons sensitive to the component directions of the plaid. These component motion-selective neurons display tuning curves with four peaks, each of which indicates the preferred direction of the elemental drifting grating of plaids. On the contrary, most SC neurons are selective for pattern motion such that they prefer the global direction of the plaid. In general, our results suggest that the mouse V1 is essential for encoding elemental motion whereas the SC is important for global motion, indicating different roles of V1 and SC in processing visual motion.