Neural representations of ensemble coding in the occipital and parietal cortices
Kyeong-Jin Tark,
Min-Suk Kang,
Sang Chul Chong,
Won Mok Shim
Affiliations
Kyeong-Jin Tark
Center for Neuroscience Imaging Research, Institute for Basic Science (IBS), 2066 Seobu-ro, Jangan-gu, Suwon 16149, South Korea
Min-Suk Kang
Center for Neuroscience Imaging Research, Institute for Basic Science (IBS), 2066 Seobu-ro, Jangan-gu, Suwon 16149, South Korea; Department of Psychology, Sungkyunkwan University, 25-2 Sungkyunkwan-ro, Jongro-gu, Seoul 03063, South Korea
Sang Chul Chong
Graduate Program in Cognitive Science, Yonsei University, 50 Yonsei-ro, Seodaemoon-gu, Seoul 03722, South Korea; Department of Psychology, Yonsei University, 50 Yonsei-ro, Seodaemoon-gu, Seoul 03722, South Korea
Won Mok Shim
Center for Neuroscience Imaging Research, Institute for Basic Science (IBS), 2066 Seobu-ro, Jangan-gu, Suwon 16149, South Korea; Department of Biomedical Engineering, Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon 16149, South Korea; Department of Intelligent Precision Healthcare Convergence, Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon 16149, South Korea; Corresponding author at: Department of Biomedical Engineering, Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon 16149, South Korea.
The human visual system is able to extract summary statistics from sets of similar items, but the underlying neural mechanism remains poorly understood. Using functional magnetic resonance imaging (fMRI) and an encoding model, we examined how the neural representation of ensemble coding is constructed by manipulating the task-relevance of ensemble features. 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. Such responses to the ensemble orientation were present in the extrastriate area, V3, even when the mean orientation was not task-relevant, indicating that the ensemble representation can co-exist with the task-relevant individual feature representation. Ensemble orientations were also represented in frontal regions, but those representations were robust only when each mean orientation was linked to a motor response dimension. Together, our findings suggest that the neural representation of the ensemble percept is formed by pooling signals at multiple levels of the visual processing stream.
