Different patterns of visual processing for shapes in V1 of mouse and monkey

Recently, mice became a popular research model for the visual system including objects processing. However, while primates use their fovea to inspect objects at high resolution, mice have low visual acuity and lack a foveal region. Thus, how objects are encoded in the visual cortex of mice and whether monkeys and mice use similar neural mechanisms to discriminate between shapes, is unknown. Using voltage sensitive dye imaging, we investigated spatio-temporal patterns of population response in the primary visual cortex (V1) of mice and monkeys to shape contours. Neural responses in mice showed blurred spatial patterns, low correlation to the original stimuli and only subtle spatial differences between the shapes. In contrast, the neural responses in monkeys V1 fovea, showed prominent differences between the shapes at sub-degree resolution with high resemblance to the original shapes, in agreement with a topographic code. Furthermore, the spatial patterns of neural synchronization in monkeys V1 suggested contour binding by synchrony, but not in mice V1. Finally, monkeys V1 responses at larger eccentricities, resembled more to those in mice. These results may suggest that to discriminate between shapes, mice rely on neural processing of low-level cues, whereas monkeys rely more on a topographic code.