The Effect of Low-Level Visual Stimulation Features on Inter-Subject Human Brain Hemodynamics Synchronization during Naturalistic Viewing

• Main Authors: Tai-Yu Lu, 盧泰宇
• Other Authors: 鍾孝文
• Format: Others
• Language: en_US
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/8z3pf7

碩士 === 國立臺灣大學 === 生醫電子與資訊學研究所 === 107 === Measuring synchronized hemodynamic responses across subjects has been widely used to detect active human brain areas under naturalistic and complex stimuli. Using this analysis, higher order areas are typically less synchronized than sensory and association areas. Considering the hierarchical processing of sensory stimuli, synchronized brain activity can occur at brain areas dynamically processing either low-level or high-level features. To isolate the latter for which cognitive studies are mainly interested in, it is important to suppress the synchronized brain activity due to the former causes. Here we proposed an experiment by controlling the effect due to low-level visual stimulation. We prepared montage movie clips of the same session of a video game but from four different perspectives. The subjects were instructed to project themselves into the players in the movie, including imagining cooperative and competitive behaviors with others. We first identified brain areas where the correlated fMRI signals between two subjects during viewing the movie but from two distinct perspectives related to the similarity between two perspectives. The similarity between two distinct perspectives was measured by the degree of overlapped field-of-view (FOV) of video frames. These brain areas were hypothesized to be related to low-level processing. The characteristic time courses at these areas were then found by clustering analysis. Inter-subject correlation (ISC) was subsequently calculated after removing these characteristic time courses by regression. The synchronization of brain activity between subjects showed significantly reduced at visual and lateral occipital cortex, but significantly increased at cingulate cortex, frontal cortex and insula. The result suggested the feasibility of using the overlapped field-of-FOV to quantify low-level visual related features during naturalistic viewing between subjects.