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Tatsuto Takeuchi, Sanae Yoshimoto, Yasuhiro Shimada, Takanori Kochiyama, Hirohito M. Kondo; Individual Differences in Visual Motion Perception and the Associated Excitatory and Inhibitory Neurotransmitter Concentrations in the Brain. Journal of Vision 2016;16(4):42-43. doi: https://doi.org/10.1167/16.4.44.
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© ARVO (1962-2015); The Authors (2016-present)
The interaction of excitatory and inhibitory processes is one of the key principles used to explain various perceptual phenomena. For example perception of directionally ambiguous stimulus is affected by a preceding moving stimulus: prolonged presentation of a preceding stimulus induces motion contrast that might reflect an inhibitory process whereas a briefly presented preceding stimulus induces motion assimilation that might reflect an excitatory process (Takeuchi et al., 2011). Meanwhile, the presentation duration of a preceding moving stimulus at which motion assimilation changes to motion contrast is different across observers. Thus, individual variability exists in the functioning of excitatory/inhibitory processes that induce motion assimilation/contrast. In the present study, we investigated the underlying neural mechanisms of individual variability by measuring the cortical concentrations of neurotransmitters. Using magnetic resonance spectroscopy (Edden et al., 2009), we measured the concentration of γ-aminobutyric acid (GABA), which is a proxy for the inhibitory process, and the concentration of glutamine/glutamate (Glx), which is a proxy for the excitatory process, in the frontal and visual cortical areas. We found that the presentation duration of the preceding moving stimulus at the motion assimilation-contrast transition zone was positively correlated with Glx concentration in the frontal areas, but not with that in the visual areas. Thus, observers who exhibited a higher concentration of Glx had a greater tendency to report motion assimilation. In contrast, no correlation was found between transition dynamics and GABA concentrations in either cortical area. These results suggest that individual variability in the perception of motion assimilation/contrast depends on the excitatory process in the higher cortical areas.
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