Suppression at high spatial frequencies in the lateral geniculate nucleus of the cat

The spatial weighting functions of both retinal and lateral geniculate nucleus (LGN) X-cell receptive fields have been viewed as the difference of two Gaussians (DOG). We focus on a particular shortcoming of the DOG model, that is, suppression of responses of LGN cells at spatial frequencies above those to which the classical receptive field surround is responsive. By simultaneously recording one of the retinal ganglion cell (RGC) inputs (S-potentials) to an LGN cell, we find that half of this suppression at high spatial frequencies arises from the retinal input and that suppression in LGN cells is greater than that in RGCs, regardless of spatial frequency. We also inactivated the ipsilateral visual cortex and show that one quarter of the suppression at high spatial frequencies arises from corticothalamic feedback. We show that this suppression at high spatial frequencies is colocalized with the classical surround, is not dependent on the relative orientation of the center and surround stimuli, and that the cortical component of this suppression is divisive. We propose that the role of this suppression at high spatial frequencies is to restrict the response to large stimuli composed of high spatial frequencies.