Color Naming and Categorization Depend on Distinct Functional Brain Networks

Abstract

Naming a color can be understood as an act of categorization, that is, identifying it as a member of a category of colors that are referred to by the same name. But are naming and categorization equivalent cognitive processes and consequently rely on same neural substrates? Here, we used task and resting-state functional magnetic resonance imaging as well as behavioral measures to identify functional brain networks that modulated naming and categorization of colors. We first identified three bilateral color-sensitive regions in the ventro-occipital cortex. We then showed that, across participants, color naming and categorization response times (RTs) were correlated with different resting state connectivity networks seeded from the color-sensitive regions. Color naming RTs correlated with the connectivity between the left posterior color region, the left middle temporal gyrus, and the left angular gyrus. In contrast, color categorization RTs correlated with the connectivity between the bilateral posterior color regions, and left frontal, right temporal and bilateral parietal areas. The networks supporting naming and categorization had a minimal overlap, indicating that the 2 processes rely on different neural mechanisms.

Temporal dynamics of the neural representation of hue and luminance polarity

“…The time course for decoding hue (peak 123 ms; Figure 3 ) is comparable to that for decoding shape-independent object category 83 and face identity 84 , operations that probably reflect activity in area LO and the fusiform face area (FFA). The decoding time course for hue is therefore consistent with the hypothesis that hue is computed at about the same distance along the visual processing hierarchy as LO and the FFA, which implicates the posterior color-biased region of the ventral visual pathway, part of the V4 Complex 77, 85–87 . Within this region there are compartments comprising neurons that are spatially organized according to hue, and whose hue selectivity is tolerant to changes in luminance contrast 88–90 , showing that these neurons are capable of representing hue tolerant to changes in luminance contrast.…”

“…The time course for decoding hue (peak 123 ms; Figure 3) is comparable to that for decoding shape-independent object category (Kaiser et al, 2016) and face identity (Dobs et al, 2019), operations that probably reflect activity in area LO and the fusiform face area (FFA). The decoding time course for hue is therefore consistent with the hypothesis that hue is computed at about the same distance along the visual processing hierarchy as LO and the FFA, which implicates the posterior color-biased region of the ventral visual pathway, part of the V4 Complex(Lafer-Sousa and Conway, 2013;Lafer-Sousa et al, 2016;Bannert and Bartels, 2018;Siuda-Krzywicka et al, 2020).…”

Color Compensation in Anomalous Trichromats Assessed with fMRI

“…There have been few direct tests of compensation by measuring neural activity 20 and, to our knowledge, none using fMRI to assess color processing in anomalous trichromats, a technique that has been shown to be an effective measure of color and contrast coding throughout cortex. [21][22][23][24][25][26][27][28][29][30] Multiple colorselective areas have been identified along the ventral pathway, [31][32][33] each with potentially different functions and representations of chromatic information. We focused on characterizing the strength of the responses to chromatic contrast in early cortical areas.…”

Color compensation in anomalous trichromats assessed with fMRI

“…There have been few direct tests of compensation by measuring neural activity [20], and to our knowledge none using functional MRI to assess color processing in anomalous trichromats, a technique that has been shown to be an effective measure of color and contrast coding throughout cortex [21-26] [27-30]. Multiple color-selective areas have been identified along the ventral pathway [31-33], each with potentially different functions and representations of chromatic information. We focused on characterizing the strength of the responses to chromatic contrast in early cortical areas.…”