Context Modulates the ERP Signature of Contour Integration

Abstract

We investigated how the electrophysiological signature of contour integration is changed by the context in which a contour is embedded. Specifically, we manipulated the orientations of Gabor elements surrounding an embedded shape outline. The amplitudes of early visual components over posterior scalp regions were changed by the presence of a contour, and by the orientation of elements surrounding the contour. Differences in context type had an effect on the early P1 and N1 components, but not on the later P2 component. The presence of a contour had an effect on the N1 and P2 components, but not on the earlier P1 component. A modulatory effect of context on contour integration was observed on the N1 component. These results highlight the importance of the context in which contour integration takes place.

The time course of pattern discrimination in the human brain

“…Executing of this task suggests activation of mechanisms of visual integration by grouping spatially integrated elements into a global structure rather than discrimination of the local features as in the Collinearity task. A similar increase in the negative wave of ERP in this time window was observed when a global Gabor contour was embedded in an array of randomly oriented Gabor patches (Butler et al, 2013;Machilsen, Novitskiy, Vancleef, & Wagemans, 2011;Shpaner, Molholm, Forde, & Foxe, 2013). An increase in the N1-amplitude peaking $100-170 ms after stimulus onset is also often found when participants observe an illusory contour such as a Kanizsa square which is associated with the emergence of a global shape (Herrmann & Bosch, 2001;Murray et al, 2002;Proverbio & Zani, 2002).…”

Early Spatial Frequency Processing of Natural Images: An ERP Study

“…Additionally, these components are sensitive to grouping and closure phenomena [7], [8], [28], [34]–[36], and the P2 has been observed to be modulated by perceptual implicit memory [37]. Taking these findings together, the P2 appears to index an intermediate processing stage that is closely bound to perceptual processes such as segmentation or grouping and higher-level processes such as categorization.…”

A temporo-spatial analysis of the neural correlates of extrinsic perceptual grouping in vision

“…Grouping by proximity was associated with a positive component over occipital electrodes that peaked between 100 and 120 ms after sensory stimulation. Similarly, contour integration by collinearity emerges from 130 ms after stimulus onset, as evidenced by the results from Machilsen et al (2011). In contrast, grouping by similarity (in shape or colour) was linked to a negativity over occipito-temporal scalp regions occurring much later, around 300 ms (Han, 2004;Han and Humphreys, 2007;Han et al, 2001Han et al, , 2002Han et al, , 2005aMao et al, 2004).…”