In this study, we investigated

the development of orientation and direction selectivity in the mouse primary visual cortex by using in vivo two-photon calcium imaging (Stosiek et al., 2003 and Rochefort et al., 2009). We characterized the responses of layer 2/3 neurons to oriented drifting gratings with single-cell resolution at different developmental stages, from eye opening until adulthood, Volasertib research buy in normally reared mice as well as in mice reared in darkness for a month. We first compared neuronal calcium signals evoked by drifting gratings in the monocular region of the primary visual cortex of normally reared and dark-reared juvenile mice (P26–P30). For this purpose, we presented drifting gratings to the contralateral eye while performing two-photon calcium imaging recordings of layer 2/3 neurons stained with the fluorescent calcium indicator dye OGB1-AM (Rochefort et al., 2009). Figure 1A illustrates selleck inhibitor such recordings obtained in a normally reared juvenile mouse (P27). In the field of view (left panel of Figure 1A), neuron 1 displayed large calcium transients during the presentation of a specific orientation and direction of the drifting gratings (middle panel,

direction of 0°, red calcium transients), but no significant responses for all the other directions. A quantitative analysis of the stimulus-evoked responses showed that the neuron had an orientation-selectivity index (OSI) of 0.98 and a direction-selectivity index (DSI) of 0.78. Thus, this neuron was defined as a highly tuned orientation- and direction-selective neuron (Niell and Stryker, 2008). In the same field of view, neuron 2 displayed

Phosphoprotein phosphatase large calcium transients for one orientation of the drifting gratings, but not for a specific direction of motion (right panel, responses for both directions of 135° and 315°). Thus, this neuron was identified as a highly tuned orientation-selective, but not direction-selective, neuron (OSI, 1.0; DSI, 0.2). Surprisingly, both orientation- and direction-selective neurons were also found in the visual cortex of dark-reared mice. Figure 1B illustrates an example of a direction-selective (middle panel) and of an orientation-selective neuron (right panel) in a juvenile dark-reared mouse (P30). An analysis of all recorded neurons in normally reared and dark-reared mice showed that the percentage of neurons responding to drifting gratings was not significantly different in the two groups (Figure 1C). Furthermore, the tuning level of the responsive neurons was also remarkably similar (Figure 1D and Figure S1, available online). The quantitative estimation of orientation and direction tuning showed no significant differences between the cumulative distributions of both OSIs and DSIs (Mann-Whitney test: OSI, p = 0.50; DSI, p = 0.15) (Figure 1D). In addition, we explored whether the visual stimulation itself modified the level of orientation and direction selectivity in dark-reared mice.