The response properties of neurons to sensory stimuli have been used to identify their receptive fields and functionally map sensory systems. In primary visual cortex, most neurons are selective to a particular orientation and spatial frequency of the visual stimulus. Using two-photon calcium imaging of neuronal populations from the primary visual cortex of mice, we have characterized the response properties of neurons to various orientations and spatial frequencies. Surprisingly, we found that the orientation selectivity of neurons actually depends on the spatial frequency of the stimulus. This dependence can be easily explained if one assumed spatially asymmetric Gabor-type receptive fields. We propose that receptive fields of neurons in layer 2/3 of visual cortex are indeed spatially asymmetric, and that this asymmetry could be used effectively by the visual system to encode natural scenes.
Significance Statement In this manuscript we show that the orientation selectivity of neurons in primary visual cortex of mouse is highly dependent on the stimulus spatial frequency (SF). This dependence is demonstrated quantitatively by a decrease in the selectivity strength of cells in non-optimum SF, and more importantly, it is also demonstrated qualitatively by a shift in the preferred orientation of cells in non-optimum SF. We show that a receptive-field model of a 2D asymmetric Gabor, rather than a symmetric one, can explain this surprising observation. Therefore, we propose that the receptive fields of neurons in layer 2/3 of mouse visual cortex are spatially asymmetric and this asymmetry could be used effectively by the visual system to encode natural scenes.
Authors report no conflict of interest
Marie Curie IOF; Canadian Institutes of Health Research; NEI DP1EY024503; R01EY011787; DARPA SIMPLEX N66001-15-C-4032
Orientation selectivity is dependent on spatial frequency.
Asymmetric Gabor model can explain this dependence.