Visual Crowding in V1

Abstract

In peripheral vision, objects in clutter are difficult to identify. The exact cause of this "crowding" effect is unclear. To perceive coherent shapes in clutter, the visual system must integrate certain local features across receptive fields while preventing others from being combined. It is believed that this selective feature integration-segmentation process is impaired in peripheral vision, leading to crowding. We used functional magnetic resonance imaging (fMRI) to investigate the neural origin of crowding. We found that crowding was associated with suppressed fMRI signal as early as V1, regardless of whether attention was directed toward or away from a target stimulus. This suppression in early visual cortex was greatest for stimuli that produced the strongest crowding. In contrast, the pattern of activity was mixed in higher level visual areas, such as the lateral occipital cortex. These results support the view that the deficiency in feature integration and segmentation in peripheral vision is present at the earliest stages of cortical processing.

Targets but not flankers are suppressed in crowding as revealed by EEG frequency tagging

“…However, there must be also a general kind of mutual suppression, which occurs in passive-viewing conditions when the element is not a target, as has been observed in several EEG and fMRI studies (e.g., Fuchs et al, 2008;Millin et al, 2014). We previously found that even when subjects performed a task on the whole stimulus, instead of the central vernier target, ERP amplitudes were lower in the grouped than in ungrouped condition (Chicherov et al, 2014).…”

Uncorking the bottleneck of crowding: a fresh look at object recognition

“…Current models propose that features are not simply pooled but merged in textural representations by summary statistics [7,8,9 ]. Interactions in Bouma's window are usually thought to be mainly mediated by low-level features because crowding is strong if target and flankers have the same color, and much reduced for different colors [10,11 ], in line with current EEG and fMRI studies showing feature-specific suppression in the early visual areas [12][13][14].…”

The neural origins of visual crowding as revealed by event-related potentials and oscillatory dynamics

“…A C C E P T E D ACCEPTED MANUSCRIPT 4 Donner, & Heeger, 2011;Kwon, Bao, Millin, & Tjan, 2014;Millin, Arman, Chung, & Tjan, 2014). Results from these studies are far from being exhaustive, suggesting either a lowlevel or a high-level (Anderson et al, 2012) locus for crowding.…”