The Representation of S-Cone Signals in Primary Visual Cortex

Abstract

Recent studies of middle-wavelength-sensitive and long-wavelength-sensitive cone responses in primate primary visual cortex (V1) have challenged the view that color and form are represented by distinct neuronal populations. Individual V1 neurons exhibit hallmarks of both color and form processing (cone opponency and orientation selectivity), and many display cone interactions that do not fit classic chromatic/achromatic classifications. Comparable analysis of short-wavelength-sensitive (S) cone responses has yet to be achieved and is of considerable interest because S-cones are the basis for the primordial mammalian chromatic pathway. Using intrinsic and twophoton imaging techniques in the tree shrew, we assessed the properties of V1 layer 2/3 neurons responsive to S-cone stimulation. These responses were orientation selective, exhibited distinct spatiotemporal properties, and reflected integration of S-cone inputs via opponent, summing, and intermediate configurations. Our observations support a common framework for the representation of cone signals in V1, one that endows orientation-selective neurons with a range of chromatic, achromatic, and mixed response properties.

Processing of the S-cone signals in the early visual cortex of primates

“…This hypothesis is further supported by fMRI studies that directly compared the activity in human LGN and V1 in response to cone-specific stimuli (Mullen et al, 2010; D’Souza et al, 2011). It is also consistent with imaging studies on marmosets (Buzas et al, 2008) and tree shrews (Johnson et al, 2010) that found widespread activation in V1 in response to S-cone stimulation. Finally, an EEG study on human V1 found strong S-cone inputs to the mechanism underlying surround suppression (Xiao & Wade, 2010), although this mechanism was found to receive predominantly achromatic inputs in a study of single neurons in monkey V1 (Solomon et al, 2004).…”

Thalamocortical processing in vision

“…Ferret: (Baker, Thompson et al 1998). Tree shrew : (Johnson, Van Hooser et al 2010). Marmoset : (Forte, Hashemi-Nezhad et al 2005).…”

Advances in Color Science: From Retina to Behavior

“…A growing body of evidence shows that many double-opponent neurons are orientation-selective for both color and achromatic patterns, regardless of the constitution of cone input (Thorell et al, 1984; Conway, 2001; Johnson et al, 2001; Conway et al, 2002; Heimel et al, 2005; Conway and Livingstone, 2006; Horwitz et al, 2007; Johnson et al, 2008; Johnson et al, 2010). This transformation means that these cells respond to cues for form, such as boundaries and edges, and may take signals from color or black and white as needed.…”

“…The neural basis of color has been reviewed previously from a range of perspectives (Gegenfurtner, 2003; Gegenfurtner and Kiper, 2003; Lennie and Movshon, 2005; Sincich and Horton, 2005; Solomon and Lennie, 2007; Conway, 2009; Dobkins, 2009; Jacobs and Nathans, 2009; Stockman and Brainard, 2010). Here we focus on advances and pressing questions regarding the mechanisms of color in retina, striate cortex and extrastriate cortex of non-human primates, although we note that other species are emerging as excellent model systems of color processing (Lotto and Chittka, 2005; Van Hooser and Nelson, 2006; Osorio and Vorobyev, 2008; Borst, 2009; Johnson et al, 2010; Srinivasan, 2010). …”