题 目 (TITLE) : Using two-photon calcium imaging to study macaque visual cortex
讲座人 (SPEAKER): 余聪，教授，北京大学心理与认知科学学院
主持人（CHAIR） : 蒋田仔，研究员，中国科学院自动化研究所
时 间 (TIME) : 2023年4月25日，下午2:30-3:30
地 点 (VENUE) : 智能化大厦三层第三会议室
Two-photon calcium imaging allows simultaneous recording of thousands of neurons at cellular resolution. I will present three 2-p studies on macaque visual cortex, and discuss this technology from the perspective of a psychophysicist.
(1) Orientation, OD, and SF functional maps. In FOVs about the size of a hypercolumn, V1 superficiallayer neurons are clustered in orientation and OD preferences, but much less so in SF preferences that only cover a limited portion (2-3 octaves) of the visible SF range. The three maps do not intersect orthogonally or in parallel. Thus, hypercolumns may represent full ranges of orientation and OD, but not SF, preferences, and with no tight geometric restrictions.
(2) Plaid detectors. Psychophysicists have long speculated that V1 neurons can detect two-dimensional plaid patterns as textons, but neuronal responses to plaids are typically suppressed (cross-orientation suppression). Still, 2-p imaging revealed a subgroup of V1 neurons that prefer plaid patterns to Gabor gratings, with plaid orientation preferences. These plaid detectors are likely overlooked by electrode recordings that use gratings/lines to map RFs.
(3) Texture segregation. For texture-based figure-ground segregation, whether V1 can detect the figure, or only the figure-ground texture border, remains debated, while V4 is agreed to play a major role. We applied PCA to reduce the dimension of V1 and V4 responses to figure-ground texture stimuli, and then used linear SVMs to calculate the decoding accuracies for border detection and figure-ground segregation.