The gamma response to colour hue in humans: Evidence from MEG

Abstract

It has recently been demonstrated through invasive electrophysiology that visual stimulation with extended patches of uniform colour generates pronounced gamma oscillations in the visual cortex of both macaques and humans. In this study we sought to discover if this oscillatory response to colour can be measured non-invasively in humans using magnetoencephalography. We were able to demonstrate increased gamma (40–70 Hz) power in response to full-screen stimulation with four different colour hues and found that the gamma response is particularly strong for long wavelength (i.e. red) stimulation, as was found in previous studies. However, we also found that gamma power in response to colour was generally weaker than the response to an identically sized luminance-defined grating. We also observed two additional responses in the gamma frequency: a lower frequency response around 25–35 Hz that showed fewer clear differences between conditions than the gamma response, and a higher frequency response around 70–100 Hz that was present for red stimulation but not for other colours. In a second experiment we sought to test whether differences in the gamma response between colour hues could be explained by their chromatic separation from the preceding display. We presented stimuli that alternated between each of the three pairings of the three primary colours (red, green, blue) at two levels of chromatic separation defined in the CIELUV colour space. We observed that the gamma response was significantly greater to high relative to low chromatic separation, but that at each level of separation the response was greater for both red-blue and red-green than for blue-green stimulation. Our findings suggest that the stronger gamma response to red stimulation cannot be wholly explained by the chromatic separation of the stimuli.

Orientation and color tuning of the human visual gamma rhythm

“…blue) (18). We recently replicated this NBG color tuning via invasive recordings in human visual cortex (2), with similar findings subsequently shown via noninvasive measurements (35). Similar to orientation, this color tuning of NBG is consistent with prior neuroimaging reports of an end-spectral bias in population responses within human early visual cortex, particularly V1 (30).…”

“…red / orange) (18). Recently, we reported that this color tuning of NBG can also be observed in human visual cortex (2), which was later replicated with non-invasive measurements (35). It is therefore of interest to understand how these biases in orientation and color interact to modulate population responses, in particular NBG activity.…”

Human visual gamma for color stimuli: When LGN drive is equalized, red is not special

“…Oscillatory neuronal responses to full-screen colored stimuli have also been reported in MEG recordings from 20 participants (Perry et al, 2020). When full-screen red, green, purple, and blue colors were shown after a gray background or in alteration, red stimuli induced the strongest power in several oscillatory bands above 30 Hz.…”

“…Large homogenous patches of color have also been shown to induce strong gamma oscillations, both in the early visual cortex of macaques (Brunet et al, 2015;Peter et al, 2019;Rols et al, 2001;Shirhatti and Ray, 2018) and humans (Bartoli et al, 2019;Li et al, 2021;Perry et al, 2020). Interestingly, red stimuli have been reported to induce especially strong gamma-band responses in several of these reports (Bartoli et al, 2019;Perry et al, 2020;Rols et al, 2001;Shirhatti and Ray, 2018).…”

“…Large homogenous patches of color have also been shown to induce strong gamma oscillations, both in the early visual cortex of macaques (Brunet et al, 2015;Peter et al, 2019;Rols et al, 2001;Shirhatti and Ray, 2018) and humans (Bartoli et al, 2019;Li et al, 2021;Perry et al, 2020). Interestingly, red stimuli have been reported to induce especially strong gamma-band responses in several of these reports (Bartoli et al, 2019;Perry et al, 2020;Rols et al, 2001;Shirhatti and Ray, 2018). It has been speculated that this might be due to a higher ecological relevance of the color red in natural environments (Bartoli et al, 2020), and it was recently related to potentially faster adaptation of the M-cone pathway (Peter et al, 2019).…”