Organization and Origin of Spatial Frequency Maps in Cat Visual Cortex

Abstract

It remains controversial whether and how spatial frequency (SF) is represented tangentially in cat visual cortex. Several models were proposed, but there is no consensus. Worse still, some data indicate that the SF organization previously revealed by optical imaging techniques simply reflects non-stimulus-specific responses. Instead, stimulus-specific responses arise from the homogeneous distribution of geniculo-cortical afferents representing X and Y pathways. To clarify this, we developed a new imaging method allowing rapid stimulation with a wide range of SFs covering more than 6 octaves with only 0.2 octave resolution. A benefit of this method is to avoid error of high-pass filtering methods which systematically under-represent dominant selectivity features near pinwheel centers. We show unequivocally that SF is organized into maps in cat area 17 (A17) and area 18 (A18). The SF organization in each area displays a global anteroposterior SF gradient and local patches. Its layout is constrained to that of the orientation map, and it is suggested that both maps share a common functional architecture. A17 and A18 are bound at the transition zone by another SF gradient involving the geniculocortical and the callosal pathways. A model based on principal component analysis shows that SF maps integrate three different SFdependent channels. Two of these reflect the segregated excitatory input from X and Y geniculate cells to A17 and A18. The third one conveys a specific combination of excitatory and suppressive inputs to the visual cortex. In a manner coherent with anatomical and electrophysiological data, it is interpreted as originating from a subtype of Y geniculate cells.

Modular Representation of Luminance Polarity in the Superficial Layers of Primary Visual Cortex

“…Several studies have suggested that feature maps in the primary visual cortex are spatially arranged in an orthogonal manner to maximize coverage of stimulus space across the visual field (Hubener et al, 1997; Nauhaus et al, 2012; Yu et al, 2005; but also see Ribot et al, 2013). Remarkably, no such relationship appears to exist for polarity and orientation maps, as the intersection angles of the map gradients exhibit a near uniform distribution (Figure 5C–F, WSR: p=0.60).…”

Reorganization of Visual Callosal Connections Following Alterations of Retinal Input and Brain Damage

“…Ribot et al (2013) investigated the spatial frequency organization at the boundary between area 17/18, where callosal axons terminate densely. Using optical imaging techniques, they recorded intrinsic signals at different spatial frequencies, finding that in the transition zone the topographic organization of spatial frequency is dependent similarly on both the geniculo-cortical output and the callosal connections (Ribot et al, 2013). …”

Pinwheel-dipole configuration in cat early visual cortex

“…This requires to precisely locate the PCs, which was done automatically from the OR map, and to determine a typical scale for the PC's vicinity in the SF map. Indeed, our previous results (Ribot et al, 2013) have indicated that cortical regions in the close vicinity from PCs have a high error-of-fit,…”

“…These results fit with the uniform coverage hypothesis (Swindale et al, 2000) according to which all combinations of the attributes should be uniformly represented in the cortex. On the other hand, it was recently argued that these findings might be the result of high-pass filtering methods leading to extreme SF values being over-representation at PC (Ribot et al, 2013). Instead, these new data based on recent intrinsic optical imaging techniques (Kalatsky & Stryker, 2003) have rather suggested that SF gradients were sharp in these cortical locations (Ribot et al, 2013), arguing against uniform coverage hypothesis at PCs.…”