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Gravity matters for the neural representations of action semantics
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Poster A15 in Poster Session A, Tuesday, October 24, 10:15 am - 12:00 pm CEST, Espace Vieux-Port
Ziyi Xiong1, Yu Tian2,3, Xiaosha Wang1, Kunlin Wei3, Yanchao Bi1,4; 1Beijing Normal University, 2China Astronaut Research and Training Center, 3Peking University, 4Chinese Institute for Brain Research
How plastic are semantic neural representations? Are common word meanings that have been already acquired still constantly updated as a result of our constant experiential streams? Here, we took advantage of an unusual setting that introduces intriguing sensorimotor experience alterations (microgravity training) to address this question. As a ground-based homolog for microgravity, the head-down tilt bed rest (HDBR) procedure asked participants to remain in the 6° head-down tilt position all the time for 15 days, during which the lower-limb actions were practically absent, whereas manual actions were unrestricted. This allows us to examine whether such a pattern of motor experience alteration specifically affects how the brain represents the meanings of lower-limb action verbs. Neural responses on verbs of two upper-limb actions (“to scratch”, “to pinch”) and two lower-limb actions (“to stomp”, “to kick”) were collected via functional magnetic resonance imaging (fMRI) before and after HDBR. Intriguingly, an experience-effector-specific (lower vs. upper limb) modulation was observed in subcortical motor region (peaking at the right subthalamic nuclei) and the left temporal region (peaking at the left dorsal anterior temporal lobe), and not within the canonical effector-specific verb semantic regions (including the left lateral posterior temporal cortex, the left dorsal premotor cortex, the supplementary motor area, and the left posterior intraparietal sulcus) or hand/foot-effector-specific primary sensorimotor regions. The results showed fine separation between neural structures supporting experience-independent knowledge representation and those whose neural semantic representation induced dynamically by sensorimotor experiences, which does not fully align with the effector-specific representation structures. These findings highlight the multidimensional and dynamic nature of semantic neural representations and the intriguing effects of gravity on cognition in a broader way.
Topic Areas: Meaning: Lexical Semantics,