My research focuses on the brain circuits underlying visual perception. Specifically, I am most interested in the functions of different cortical layers in the primary visual cortex (V1). V1 is organized in six layers of neurons that have different physiologies/morphologies and serve different functions. However, the functional transformation from one layer to another remains unclear. By simultaneously recording from multiple neurons in different macaque V1 layers, we found that receptive fields mapped with different stimulus ensembles were similar for the input layer-4c neurons but were very different for the output layer-2/3 neurons. Many layer 2/3 cells have receptive fields with multiple elongated subregions when mapped with briefly flashed gratings, but their spatial maps collapse to only a single, less-elongated subregion when mapped with sparse noise. These results challenge the concept of a stimulus-invariant receptive field that has dominated the field of Visual Neuroscience for decades (ref. 1). Another focus of my research is on the neural basis of visual perception of brightness and darkness. Humans tend to have higher sensitivity to texts and objects that are negative contrast (black on white background) than to those that are positive contrast (white on black background). However, it remains unclear which part of the visual pathway is responsible for the substantial black-over-white bias. By studying response properties of neurons in different macaque V1 layers, we found that the majority of layer-2/3 neurons were black-preferring (~85%), but the numbers of black- and white-preferring neurons were nearly equal in layer 4c. The predominance of black-preferring neurons in layers 2/3 of V1, which provide information to higher visual areas, may serve as the neural basis for the substantial black-over-white bias in visual perception (refs 2-4). My laboratory combines electrophysiological, behavioral, psychophysical, and computational approaches to uncover the functional significances of cortical layers in visual areas. In addition, I maintain active collaborations with several PIs, including Professors. Chen-Ying Huang, Shih-Wei Wu, and Yu-Cheng Pei, on projects related to the neural basis of decision making and multisensory integration..