Macaque V1 responses to 2nd-order contrast-modulated stimuli and the possible subcortical and cortical contributions. (October 2022)

• Record Type: Journal Article
• Authors: Ju, Nian-Sheng; Guan, Shu-Chen; Tang, Shi-Ming; Yu, Cong
• Is Part Of: Progress in neurobiology. Volume 217(2022)
• Publication Date: 2022-10
• Subjects: CM Contrast modulated -- LM Luminance modulated -- SF Spatial frequency -- FOV Field of view; Second-order stimuli -- Orientation tuning -- Primary visual cortex (V1) -- Macaque -- Two-photon imaging; Neurobiology -- Periodicals; Neurology -- Periodicals; Neurology -- Periodicals; Neurobiologie -- Périodiques; 612.8
• DOI: 10.1016/j.pneurobio.2022.102315
• Languages: English
• ISSNs: 0301-0082

Abstract

Abstract: Natural images comprise contours and boundaries defined by 1st-order luminance-modulated (LM) cues that are readily encoded by V1 neurons, and 2nd-order contrast-modulated (CM) cues that carry local, but not over-the-space, luminance changes. The neurophysiological foundations for CM processing remain unsolved. Here we used two-photon calcium imaging to demonstrate that V1 superficial-layer neurons respond to both LM and CM gratings in awake, fixating, macaques, with overall LM responses stronger than CM responses. Furthermore, adaptation experiments revealed that LM responses were similarly suppressed by LM and CM adaptation, with moderately larger effects by iso-orientation adaptation than by orthogonal adaptation, suggesting that LM and CM orientation responses likely share a strong orientation-non-selective subcortical origin. In contrast, CM responses were substantially more suppressed by iso-orientation than by orthogonal LM and CM adaptation, likely suggesting stronger orientation-specific intracortical influences for CM responses than for LM responses, besides shared orientation-non-selective subcortical influences. These results thus may indicate a subcortical-to-V1 filter-rectify-filter mechanism for CM processing: Local luminance changes in CM stimuli are initially encoded by orientation-non-selective subcortical neurons, and the outputs are half-wave rectified, and then summed by V1 neurons to signal CM orientation, which may be further substantially refined by intracortical influences. Highlights: Two-photon calcium imaging is used to study neuronal responses to contrast-modulated (CM) 2nd-order stimuli in macaque V1. Many V1 neurons are selective to the orientation of contrast-modulated stimuli. Adaptation reveals subcortical and cortical contributions to CM orientation tuning, suggesting a LGN-to-V1 filter-rectify-filter model.