VISION

Kim, I., Hong, S.W., Shevell, S.K., & Shim, W.M. (2019). Neural representations of perceptual color experience in the human visual pathway. PNAS. Link

Perceptual color experience vs. Physical light

We aim to understand how subjective perceptual experiences (color percept) that are distinct from retinal stimulation are represented across the visual hierarchy. By linking the population-level, color-selective responses in a series of hierarchically organized cortical regions and moment-to-moment color experiences in each subject under interocular switch rivalry, this research provides insights into how the neural representation that corresponds to conscious perception evolves across the visual processing hierarchy.

Neural representations of color in LGN

Perception of color emerges from hierarchical neural processing from the retina via lateral geniculate nucleus (LGN) to visual cortex. Despite its commonly known functional role as a relay station, neural representation of color in human LGN remains elusive. Using fMRI in conjunction with encoding methods, we investigate the characteristics of color representation in human LGN. Our results suggest that color representation in LGN is more complicated than previously considered, which inherits representative characteristics of color processing from both the retina and primary visual cortex elucidating LGN’s functional role as an intermediate transition step in a multi-stage color processing stream.

Tark, K-. J., Kang, M-, S., Chong, S. C., & Shim, W. M. (2021). Neural representations of ensemble coding in the occipital and parietal cortices. NeuroImage. Link

Summary Statistics

The human visual system is able to extract summary statistics from sets of similar items, but the underlying neural mechanism remains poorly understood. Using fMRI and an encoding model, we examine how the neural representation of ensemble coding is constructed. We found a gradual increase in orientation-selective responses to the mean orientation of multiple stimuli along the visual hierarchy only when these orientations were task-relevant. Our findings suggest that the neural representation of the ensemble percept is formed by pooling signals at multiple levels of the visual processing stream.