ISSN 1671-3710
CN 11-4766/R

Advances in Psychological Science ›› 2019, Vol. 27 ›› Issue (suppl.): 154-154.

### Offline transcranial direct current stimulation (tDCS) can improve the ability to perceive crowded targets

Guanpeng Chena,b,c,d, Ziyun Zhua,b,c,d, Fang Fanga,b,c,d

1. aSchool of Psychological and Cognitive Sciences and Beijing Key Laboratory of Behavior and Mental Health, Peking University, Beijing, China, 100871;
bPeking-Tsinghua Center for Life Sciences, Peking University, Beijing, China, 100871;
cKey Laboratory of Machine Perception (Ministry of Education), Peking University, Beijing, China, 100871;
dPKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing, China, 100871
• Online:2019-08-26 Published:2022-03-21

Abstract: PURPOSE: Visual crowding refers to the deleterious effect of nearby flankers on target identification. Studying visual crowding can advance our understanding of the mechanisms of visual awareness and object recognition. Transcranial direct current stimulation (tDCS) provides a promising way to alter human visual functions because of its capacity to modulate cortical excitability. Here, we performed three experiments to investigate whether tDCS could alleviate visual crowding at different visual eccentricities and with different visual stimuli.
METHODS: Subjects were asked to perform an orientation discrimination task or a letter recognition task with the isolated and crowded targets in the periphery, before and after applying 20 minutes of 2 mA anodal tDCS to the visual cortex (P1 or P2) of the hemisphere contralateral or ipsilateral to the visual stimuli.
RESULTS: We first found that, electrical stimulation of the hemisphere contralateral to the visual stimuli could significantly reduce the crowding effect in the orientation discrimination task. This reduction was absent after the sham stimulation and could not be explained by the performance improvement with the isolated target. Then, using the same behavioral task and the same tDCS protocol, we found that the contralateral DC stimulation remained effective in alleviating crowding at a smaller eccentricity. Finally, we adopted a letter recognition task and found that the alleviation of the letter crowding effect still existed after tDCS. In all the three experiments, no reduction was observed when tDCS was applied to the hemisphere ipsilateral to the visual stimuli.
CONCLUSIONS: Taken together, we concluded that offline tDCS was effective in alleviating visual crowding across different visual eccentricities and perceptual tasks, which shed new light on the mechanisms of visual crowding and possible practical applications.