Figure 1. Orientation and direction tuning of visual cortex neurons in 8–10 month-old WT mice.

(a) Experimental arrangement for in vivo two-photon calcium imaging of stimulation-evoked neuronal activity. Left panel, in vivo two-photon image of cortical layer 2/3 of the primary visual cortex stained in vivo with the fluorescent calcium indicator dye Oregon Green BAPTA-1 (green) and the glial marker Sulforhodamine 101 (yellow). Right panel, visual stimuli (drifting gratings) were projected on a screen placed 30 cm away from the contralateral eye of the mouse. (b) Left panel, in vivo two-photon image of layer 2/3 neurons in the visual cortex of a WT mouse (8-months). Right panel, stimulus-evoked calcium transients recorded from the orientation selective neuron indicated in the left panel by a white dotted circle. Grey regions indicate periods of visual stimulation with drifting gratings schematized by oriented arrows on the bottom of each panel. Four single trials are represented on top and the average of six trials is shown below. Scale bar, 10 μm. (c) Polar plot showing the neuron's response function to oriented drifting gratings. The responses to each of the eight directions tested were normalized with respect to the maximal response. Then, the function was constructed by connecting the eight values. (d) Distribution of the orientation (OSI) and direction (DSI) selectivity indices of all responsive neurons (n=131 neurons) recorded in the visual cortices of 13 WT mice.