Electrophysiological signatures of crowding are similar in foveal and peripheral vision

Flankers can strongly deteriorate performance on a visual target (crowding). For example, vernier offset discrimination strongly deteriorates when neighbouring flankers are presented. Interestingly, performance for longer and shorter flankers is better than performance for flankers of the same length as the vernier. Based on these findings, we proposed that crowding is strongest when the vernier and the flankers group (same length flankers) and weaker when the vernier ungroups from the flankers (shorter or longer flankers). These effects were observed both in foveal and peripheral vision. Here, using high-density EEG, we show that electrophysiological signatures of crowding are also similar in foveal and peripheral vision. In both foveal and peripheral (3.9°) vision, the N1 wave correlated well with performance levels and, hence, with crowding. Amplitudes were highest for the long flankers, intermediate for the short flankers and lowest for the equal length flankers. This effect was observed neither at earlier stages of processing, nor in control conditions matched for stimulus energy. Effects are more pronounced in the fovea than in the periphery. These similarities are evidence for a common mechanism of crowding in both foveal and peripheral vision.