Neural decoding dissociates perceptual grouping between proximity and similarity in visual perception.

Unlike single grouping principle, cognitive neural mechanism underlying the dissociation across two or more grouping principles is still unclear. In this study, a dimotif lattice paradigm that can adjust the strength of one grouping principle was used to inspect how, when, and where the processing of two grouping principles (proximity and similarity) were carried out in human brain. Our psychophysical findings demonstrated that similarity grouping effect was enhanced with reduced proximity effect when the grouping cues of proximity and similarity were presented simultaneously. Meanwhile, EEG decoding was performed to reveal the specific cognitive patterns involved in each principle by using time-resolved MVPA. More importantly, the onsets of dissociation between 2 grouping principles coincided within 3 time windows: the early-stage proximity-defined local visual element arrangement in middle occipital cortex, the middle-stage processing for feature selection modulating low-level visual cortex such as inferior occipital cortex and fusiform cortex, and the high-level cognitive integration to make decisions for specific grouping preference in the parietal areas. In addition, it was discovered that the brain responses were highly correlated with behavioral grouping. Therefore, our study provides direct evidence for a link between the human perceptual space of grouping decision-making and neural space of brain activation patterns.