Assessment of orientation tuning in mouse primary visual cortex with intrinsic signal optical imaging.

Intrinsic signal optical imaging is becoming a popular tool to measure hemodynamic response reflecting activity of local neurons and is commonly used to map cortical function in rodents. We used this method to characterise orientation sensitivity in the mouse primary visual cortex. Accumulating body of research performed on different species including humans has shown a cardinal bias for preference of spatially oriented targets, indicating greater neuronal responses in the visual cortex for horizontal or vertical contours in opposite to oblique ones. Our aim was to verify the hypothesis whether a cardinal bias is also present in the mouse primary visual cortex. The experiments were performed on young wild anaesthetised mice. Intrinsic signals were recorded using CCD camera set above the visual cortex. Images were collected for responses to visual stimuli, square-wave black-and-white gratings of four orientations: 0, 45, 90, 135 deg, drifting in two directions, back and forth, presented in random order with uniform grey images. Imaging was performed under the control of Imager 3001 system. We successfully mapped cortical responses to visual stimuli of different orientations. Collected images showed the strongest responses for horizontally and vertically oriented gratings. Thus our results support the hypothesis of the cardinal bias in the mouse visual cortex.

Supported by grant Symfonia 1 from the National Science Centre (2013/08/W/NZ4/00691)

Authors: Ida Raciborska, Katarzyna Kordecka, Anna Posłuszny, Wioletta J. Waleszczyk