Sheng Li

Department of Psychology
Peking University
sli@pku.edu.cn

Abstract

We combined psychophysics and multi-modal brain imaging techniques, aiming to understand the spatiotemporal dynamics of perceptual decision and learning processes. We generated two types of perceptual decision tasks. That is, the task based on signal detection and the task based on criterion comparison. We trained separate groups of human subject on the two tasks and recorded simultaneous EEG-fMRI signals before and after the training. We found that the learning effects for the two tasks correspond to different cortical networks. Particularly, in the task based on signal detection, the learning effect is correlated with the neural activities at both the early stage perceptual processing. Therefore, the learning shapes feedforward interactions across brain areas. On the other hand, in the task based on criterion comparison, the learning effect is correlated only with the late stage activities, indicating that learning acts on a feedback-based circuit. We also varied the task uncertainty for both tasks. In the task based on signal detection, task difficulty modulates brain activities in higher visual cortex related to information accumulation. In the task based on criterion comparison, such modulation happens in frontal areas that are thought to be responsible for rule retrieval. Our findings demonstrate that the neural systems represent the task-related perceptual information with a flexible and adaptive strategy.

Short Bio

Sheng Li is a professor (tenure-track, Bairen Project) at the Department of Psychology, Peking University, China. He received his B.Eng degree from Beijing University of Posts and Telecommunications, China, in 1998 and D.Phil degree from the University of Sussex, UK, in 2006. From 2006 to 2009, he was a postdoctoral research fellow at the School of Psychology, University of Birmingham, UK. His research focused on three topics related to the human perception, decision, and learning: (1) the neural mechanisms of human categorical and perceptual learning, (2) the neural mechanism of human perceptual decision, and (3) the modulatory effects of reward signal on learning and memory. He combined psychophysics, multi-modal functional brain imaging (fMRI, EEG, and EEG- fMRI simultaneous recording), and computational modeling in his research. His research findings have been published at journals including Neuron, Journal of Neuroscience, Cerebral Cortex, European Journal of Neuroscience, and IEEE Transactions on Neural Networks.