Mixing of Chromatic and Luminance Retinal Signals in Primate Area V1

Abstract

Vision emerges from activation of chromatic and achromatic retinal channels whose interaction in visual cortex is still poorly understood. To investigate this interaction, we recorded neuronal activity from retinal ganglion cells and V1 cortical cells in macaques and measured their visual responses to grating stimuli that had either luminance contrast (luminance grating), chromatic contrast (chromatic grating), or a combination of the two (compound grating). As with parvocellular or koniocellular retinal ganglion cells, some V1 cells responded mostly to the chromatic contrast of the compound grating. As with magnocellular retinal ganglion cells, other V1 cells responded mostly to the luminance contrast and generated a frequency-doubled response to equiluminant chromatic gratings. Unlike magnocellular and parvocellular retinal ganglion cells, V1 cells formed a unimodal distribution for luminance/color preference with a 2- to 4-fold bias toward luminance. V1 cells associated with positive local field potentials in deep layers showed the strongest combined responses to color and luminance and, as a population, V1 cells encoded a diverse combination of luminance/color edges that matched edge distributions of natural scenes. Taken together, these results suggest that the primary visual cortex combines magnocellular and parvocellular retinal inputs to increase cortical receptive field diversity and to optimize visual processing of our natural environment.

Brightness–Color Interactions in Human Early Visual Cortex

“…Evidence that the cVEP reflects V1 activity is as follows. Prior work on VEPs as we recorded them, over occipital cortex along the midline, indicates that the signals recorded come from V1 cortex (Onofrj et al, 1995;Nakamura et al, 2000;Kulikowski et al, 2002). The cVEP does not vary with attention, a result that strongly suggests it is evoked early in cortical visual processing (Highsmith and Crognale, 2010).…”

“…V1 neurons can be categorized into three groups (Johnson et al, 2001). One group of neurons are only interested in luminance contrast (Lum-Neuron); another group of neurons are only interested in pure color difference (Color-Neuron); the third group of neurons are interested in both color and luminance contrast (Color-Lum-Neuron) (Johnson et al, 2001;Li et al, 2014). Generally, Color neurons are the minority in the V1 population, and they respond best at low spatial frequency (Johnson et al, 2001;Schluppeck and Engel, 2002;Conway and Livingstone, 2006).…”

“…The perceptual importance of neuronal activity near the edges of targets (Krauskopf, 1963;Faul et al, 2008) is illustrated in Figure 1A (top) by the reduced perceived color saturation of targets on equiluminant surrounds when the targets have thin black bands drawn around them. We found analogous reductions of cVEPs when observers viewed colormodulated targets that had black bands around them (Fig.…”

Multiple-target tracking in human and machine vision

“…It is worth noting that the brain chooses an efficient strategy to track multiple targets considering its physical and cognitive limitations; these limitations are mostly related to the physiological properties and functions of neurons, which are tuned to specific features of visual scenes, visual spatial mapping, and varied emotional and intrinsic brain states [13][14][15][16][17]. Computers do not have similar computational limitations.…”

The selectivity of responses to red‐green colour and achromatic contrast in the human visual cortex: an fMRI adaptation study

“…Subsequent evidence, however, tended to favour the merging and interaction of colour and achromatic (Ach) contrast into mixed, shape-processing pathways (Sincich & Horton, 2005;Economides et al, 2011). In V1, colour-luminance neurons, tuned to orientation and spatial frequency, potentially provide a common form-processing pathway, with only a minority of lowpass, nonoriented (isotropic) neurons exclusively sensitive to colour (Thorell et al, 1984;Lennie et al, 1990;Leventhal et al, 1995;Schluppeck & Engel, 2002;Friedman et al, 2003;Johnson et al, 2008;Shapley & Hawken, 2011;Li et al, 2015). In V4, neurophysiological evidence suggests multiple functional organizations, including colourselective neurons that process shape (Bushnell et al, 2011;Bushnell & Pasupathy, 2012), segregated pathways with colour contrast or luminance contrast preferences, and colour-luminance shape-processing regions (Tanigawa et al, 2010).…”