Temporal dynamics of spatial frequency tuning in mouse visual cortex

Recent extracellular electrophysiological recordings in mouse primary visual cortex have shown that, despite a much lower visual acuity, spatial frequency tuning is similar to that of cats and monkeys, with mice possessing band-pass filtering units with almost equal bandwidths compared to macaque monkeys (Niell and Stryker, 2008; Van den Bergh et al., 2010). Here, we wanted to assess whether these similarities of spatial frequency tuning have their roots in analogous neural mechanisms as in primates. We therefore studied the dynamics of spatial frequency tuning in mouse V1 using a reverse correlation technique that has been previously used in monkey V1 (Bredfeldt and Ringach, 2002). As stimulus, we used a sequence of rapidly changing sinusoidal gratings of varying spatial frequencies and spatial phases but fixed orientation, interleaved with blank images of uniform luminance to obtain the cells'baseline response and to assess response suppression. We found that many individual cells responded robustly and selectively to this stimulus, enabling us to analyze the dynamics of spatial frequency tuning. As in monkeys, many cells showed a shift over time of the preferred spatial frequency from low to higher frequencies, while at the same time tuning became more selective over the course of the response. Nevertheless, selectivity of the mean response was lower than in monkeys, probably because of the larger number of low-pass filtering units. As in monkeys, the time-dependent increase in selectivity was predominantly due to a change in the response to low spatial frequencies, as demonstrated by an increased steepness of the lower limb of the tuning curve over time. We conclude from our results that notwithstanding the absence of a columnar organization and a different visual scale, the basic mechanisms of spatial frequency tuning in mouse are similar to higher visual mammals.status: publishe