Hierarchical Representation for Chromatic Processing across Macaque V1, V2, and V4

Abstract

Dear Dr. SchriddeWe would like to thank the Editorial team at Neuron for con nuing to assist us in pilo ng NEURON-D--R through the review process with a "minor revision" decision.We were happy to note that reviewer stated that "This already strong paper is much improved", expressing that "I do not want to stand in the way of the dissemina on of this important work". They suggested a new regression model, although they "realized this is a lot to ask". We have nevertheless implemented this to allay their remaining concerns. Reviewer is fully sa sfied with our work, and in the previous round remarked that "This is an outstanding work -both in terms of the techniques combina on and their applica on in alerts monkeys, the high quality data obtained from several visual areas and the important ques ons".It was heartening to see that reviewer recognized that "The work they report is a tour-de-force of several state-of-the-art methods, and I am sure the results will be very useful to anybody inves ga ng the cor cal representa on of color". Of concern to us however, the third referee now provides a novel set of more extensive, purportedly 'fault-finding' commentary. Much of this could and should have been raised in the first review. Several points betray selec ve reading of the manuscript, and are refuted simply by ci ng the exis ng text (and/or exis ng literature). The first round of review judged the logic of our study as predicated on the assump on that color and form are separately encoded in V . We were obliged to add Figure S in the last revision to address this misconcep on. However, the follow-up review gave no jus fica on for this major cri cism. The second round focused on the broad nature of color processing, yet appear agnos c to the unique value of the current study comparing across three successive visual areas of the same prepara on (a point borne out by the strong support obtained from Reviewers and ). We have nonetheless taken all ac onable sugges ons construc vely (for example, adding a new CIELAB analysis into Figures CD and B), and ensured that we carefully disambiguate any text where improvements can be made (please see our reply to the Reviewers appended to this le er).We would like to re-emphasize that we believe there is no precedent in the literature for such a thorough inves ga on of cor cal func onal organiza on along the visual hierarchy of V , V , and V for color representa on. The color vision system progressively removes the V color bias along the visual pathway and achieves spectral uniformity be er reflec ng color percep on. We have implemented whatever improvements we can, to meet the reviews' expecta on for publica on of this manuscript. We would also like to thank you very much for your me and support and are looking forward to hearing from you.

Color Space Geometry Uncovered with Magnetoencephalography

“…The success of the decoding analysis requires that different colors elicit different spatial patterns of response across the brain. The results therefore provide evidence not only of a topographic representation of color in the human brain, as predicted by neurophysiological recordings in monkeys, [38][39][40][41] but also that MEG has the spatial resolution to detect the topography. The spatial patterns of neural responses elicited by different colors were compared using representational similarity analysis.…”

Orientation and color tuning of the human visual gamma rhythm

“…Interestingly, these findings suggest a strong representation of red and blue preferring neurons with strong orientation tuning, providing a potential basis to the stimulus dependence of NBG to both grating and chromatic stimuli (21). As noted above, recent extensions of these findings suggest this strong representation of red/blue is reduced when moving through visual areas V1-V4, such that green becomes more represented and color selective neurons show more spatial clustering (36). Given these joint biases in orientation and color, we would expect interaction effects over NBG modulations when employing stimuli driving both stimulus features.…”

“…How these key features of visual cortex selectivity impact NBG activity patterns are critical for understanding its origin and functional significance. Exploring this interaction is further motivated by recent reports showing large scale organization of single-cell joint orientation and color tuning in early visual cortex (25, 36). Prior to examining how color tuning modulates the orientation tuning documented above, we sought to first replicate recent observations of NBG tuning to uniform color stimuli.…”

“…Overall, color tuning of NBG, and its potential variation across visual area, follows a similar relationship to orientation. While red, green and blue selectivity can be observed in early visual cortex, recent findings in wide field imaging have shown a large predominance of red and blue preferring cells in macaque V1 (25, 36). Again, this predominance at the cellular level links to the population tuning properties exhibited by NBG activity.…”

“…Again, this predominance at the cellular level links to the population tuning properties exhibited by NBG activity. In addition, V1 red/blue predominance changes progressively into downstream visual areas V2-V4, such that the density of green preferring cells increases and that cells sharing the same color preference are more spatially clustered (36). Together these attributes speak to the NBG tuning we observed, which can be considered as a coarse summated sampling of these different populations.…”