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1. chinaXiv:201605.01805 [pdf]

Attention-Dependent Early Cortical Suppression Contributes to Crowding

Chen, Juan; He, Yingchen; Zhu, Ziyun; Peng, Yujia; Zhang, Xilin; Fang, Fang; Chen, Juan; He, Yingchen; Zhu, Ziyun; Peng, Yujia; Zhang, Xilin; Fang, Fang; Fang, Fang; Fang, Fang; Zhou, Tiangang
Subjects: Biology >> Biophysics >> Neurosciences

Crowding, the identification difficulty for a target in the presence of nearby flankers, is ubiquitous in spatial vision and is considered a bottleneck of object recognition and visual awareness. Despite its significance, the neural mechanisms of crowding are still unclear. Here, we performed event-related potential and fMRI experiments to measure the cortical interaction between the target and flankers in human subjects. We found that the magnitude of the crowding effect was closely associated with an early suppressive cortical interaction. The cortical suppression was reflected in the earliest event-related potential component (C1), which originated in V1, and in the BOLD signal in V1, but not other higher cortical areas. Intriguingly, spatial attention played a critical role in the manifestation of the suppression. These findings provide direct and converging evidence that attention-dependent V1 suppression contributes to crowding at a very early stage of visual processing.

submitted time 2016-05-18 Hits3454Downloads1881 Comment 0

2. chinaXiv:201605.01366 [pdf]

Sharpened cortical tuning and enhanced cortico-cortical communication contribute to the long-term neural mechanisms of visual motion perceptual learning

Chen, Nihong; Li, Sheng; Fang, Fang; Chen, Nihong; Li, Sheng; Fang, Fang; Chen, Nihong; Li, Sheng; Fang, Fang; Chen, Nihong; Fang, Fang; Bi, Taiyong; Bi, Taiyong; Zhou, Tiangang; Liu, Zili
Subjects: Biology >> Biophysics >> Neurosciences

Much has been debated about whether the neural plasticity mediating perceptual learning takes place at the sensory or decision-making stage in the brain. To investigate this, we trained human subjects in a visual motion direction discrimination task. Behavioral performance and BOLD signals were measured before, immediately after, and two weeks after training. Parallel to subjects' long-lasting behavioral improvement, the neural selectivity in V3A and the effective connectivity from V3A to IPS (intraparietal sulcus, a motion decisionmaking area) exhibited a persistent increase for the trained direction. Moreover, the improvement was well explained by a linear combination of the selectivity and connectivity increases. These findings suggest that the long-term neural mechanisms of motion perceptual learning are implemented by sharpening cortical tuning to trained stimuli at the sensory processing stage, as well as by optimizing the connections between sensory and decision-making areas in the brain. (C) 2015 Elsevier Inc. All rights reserved.

submitted time 2016-05-12 Hits2907Downloads1442 Comment 0

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