Neural Correlates of Perceptual Grouping in Brain

Humans are proficient in detecting even subtle regularities in their sensory inputs. In the specific context of vision, one manifestation of this ability is the perception of structures embedded in noisy backgrounds. Here we use electrophysiology to explore the neural correlates of this proficiency. Observers underwent EEG recordings while being presented with random-dot displays. A few dots in some of the displays were arranged in a line. The results reveal that the two kinds of displays, those with and without the embedded lines, though identical in low-level attributes such as mean luminance and spatial frequency distribution, elicit markedly different neural responses. We find that the first divergence in the ERPs corresponding to these two stimulus classes occurs around 100 milliseconds. These differences are evident in occipital sensors suggesting that the perceptual distinction between structured and non-structured stimuli is accomplished in the very early cortical stages of visual processing. The short latency and early locus of the ERP divergence point to a largely feedforward computation underlying this feat of perceptual organization. The functional connectivity for difference between the two events also supports the ERP findings and thus, exhibits relation between synchrony time-course and ERP dynamics.