Co-fluctuations of neural activity define intra-V1 networks related to perceptual organization

Abstract

Using functional resonance imaging (fMRI), we studied the relationship between perceptual organization and network topology within the primary visual cortex (V1). Twenty-six humans (male and female) were recorded during active observation of two Global and Local Navon letters. Correlations between fMRI fluctuations from different V1 sites were measured (after removing stimulus-evoked signals) in windows specific to each condition. Intra-V1, like brain-wide networks, presented an overall decrease of correlations during stimulation compared to baseline but with increased statistical dimensionality. Massive edgewise testing and network based-statistics (both corrected by FDR) identified differences in connection strengths between stimuli that were mapped to the visual field. Global letters elicited long links mainly connecting V1 sites mapping the lower left/right visual quadrants. Shorter links were associated with local letters, primarily mapped within the lower-left visual quadrant. These connections were not observed in the time-locked (feedforward) responses shared across participants, and their lengths exceeded V1 population receptive field sizes. Thus, these networks reflect activity idiosyncratic to each participant, possibly generated by interactions within or feedback to V1. Perception would sculpt V1 connectivity, with specific increases in link strengths (in a background of decreases). These findings could help shed light on V1 as a "cognitive blackboard".

Intra-V1 functional networks predict observed stimuli

“…These missing values could have been due to noise or BOLD signal dropout at specific cortical vertices. However, they were few and concentrated in restricted areas of the visual field (see Figure 10 in Valdes-Sosa et al, 2022).…”

“…To our knowledge, only two studies have attempted to address this directly, both focusing on the perceptual organization of visual scenes. These works (Nasr et al, 2021;Valdes-Sosa et al, 2022) found that fMRI cofluctuations in V1 change over a large spatial scale as the perceptual organization of observed . CC-BY-NC-ND 4.0 International license perpetuity.…”

“…To our knowledge, only two studies have attempted to address this directly, both focusing on the perceptual organization of visual scenes. These works (Nasr et al, 2021;Valdes-Sosa et al, 2022) found that fMRI cofluctuations in V1 change over a large spatial scale as the perceptual organization of observed V1 networks predict observed stimuli 4 stimuli varies. Previous work on intra-V1 connectivity with resting-state fMRI had focused on structural (task-invariant) factors as the geodesic distance between cortical sites (Dawson et al, 2016).…”

“…In one case (Nasr et al, 2021), a small number of V1 ROIs were selected. In the other study (Valdes-Sosa et al, 2022), massive edgewise tests or network-based statistics were employed (followed by multiple-comparisons corrections). It would be interesting to examine if multivariate characterizations of V1 network topology also vary with, or are even more sensitive to, the effects of perceptual organization.…”

“…To sum up, here we re-analyzed data from our previous work (Valdes-Sosa et al 2022) to answer the following questions: 1) Is it possible to train inter-subject classifiers based on V1 correlation matrices to accurately predict in new subjects the hierarchical level and shape of observed Navon letters? 2) Is it possible to perform accurate intra-subject cross-classification of observed letter shapes tolerant to changes in level and presented levels tolerant to changes in letter shape?…”