calcium-imaging-in-mouse-superior-colliculus

Calcium Imaging in Mouse Superior Colliculus

The superior colliculus (SC), an evolutionarily conserved midbrain structure in all vertebrates, is the most sophisticated visual center before the ...

Chinese Institute for Brain Research

Motion vision is important in guiding animal behavior. Both the retina and the visual cortex process object motion in largely unbiased fashion: all directions are represented at all locations in the visual field. We investigate motion processing in the superior colliculus of the awake mouse by optically recording neural responses across both hemispheres. Within the retinotopic map, one finds large regions of ∼500 μm size where neurons prefer the same direction of motion. This preference is maintained in depth to ∼350 μm. The scale of these patches, ∼30 degrees of visual angle, is much coarser than the animal's visual resolution (∼2 degrees). A global map of motion direction shows approximate symmetry between the left and right hemispheres and a net bias for upward-nasal motion in the upper visual field.

Functional Architecture of Motion Direction in the Mouse Superior Colliculus.

The superior colliculus (SC) represents a major visual processing station in the mammalian brain that receives input from many types of retinal ganglion cells (RGCs). How many parallel channels exist in the SC, and what information does each encode? Here, we recorded from mouse superficial SC neurons under a battery of visual stimuli including those used for classification of RGCs. An unsupervised clustering algorithm identified 24 functional types based on their visual responses. They fall into two groups: one that responds similarly to RGCs and another with more diverse and specialized stimulus selectivity. The second group is dominant at greater depths, consistent with a vertical progression of signal processing in the SC. Cells of the same functional type tend to cluster near each other in anatomical space. Compared to the retina, the visual representation in the SC has lower dimensionality, consistent with a sifting process along the visual pathway.

Ya-tang Li

Chinese Institute for Brain Research

Calcium Imaging in Mouse Superior Colliculus