Repetition-induced decreases in BOLD fMRI signal for recognition of ‘communicative’ (intransitive) and tool use (transitive) gestures G Kroliczak |
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Institute of Psychology, Adam Mickiewicz University, Poland
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| Neuroimaging activation studies of intransitive and transitive gesture recognition converge on the idea of largely overlapping neural substrates (e.g. Villarreal et al 2008, pointing merely to greater engagement of the left inferior frontal gyrus for intransitive actions). Here, repetition-induced changes in BOLD-fMRI signal were studied to look for differential processing of the two gesture categories. Event-related data were acquired from twelve right-handed adults during four experimental runs. Two back-to-back videos depicting for 2.5 s either the same or different actions (12 from each category) were separated by a 1.5s delay interval (and after short variable ISIs followed by imitation of the second movie). On repetition trials, the gestures were always shown from different perspectives to avoid signal adaptation due to watching identical low-level perceptual attributes. Repeated observation of intransitive gestures resulted in significant signal decreases, bilaterally at the border of the caudal middle temporal and occipital cortices, and in ventro-medial prefrontal cortices. Much weaker activity suppression was observed for repeated transitive gestures. Direct between-category contrasts of the adaptation trials revealed significantly greater decrease in the posterior cingulate gyrus for intransitive gestures. These effects are consistent with the idea of different patterns of signal modulation within a common network. |
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