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Bianca van Kemenade, Neil Muggleton, Vincent Walsh, Ayse Pinar Saygin; The Effects of TMS over STS and Premotor Cortex on the Perception of Biological Motion. Journal of Vision 2010;10(7):785. doi: 10.1167/10.7.785.
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© ARVO (1962-2015); The Authors (2016-present)
Multiple brain areas have been identified as important for biological motion processing in neuroimaging and neuropsychological studies. Here, we investigated the role of two areas implicated in biological motion, the posterior superior temporal sulcus (STS) and the premotor cortex, using offline transcranial magnetic stimulation (TMS). Stimuli were noise masked point light displays (PLDs) of human figures performing various actions, and scrambled versions of the same stimuli. Subjects had to determine whether a moving person was present in each trial. Noise levels were determined individually based on each subject's 75% accuracy threshold estimated adaptively prior to the session. After three baseline runs of 40 trials each, theta burst TMS was delivered over left premotor cortex (near the inferior frontal sulcus, IFS), left STS, or vertex in different sessions. The coordinates of stimulation were based on our previous lesion-mapping study (Saygin, 2007, Brain). Subjects then completed three post-TMS runs. A non-biological motion task (detecting PLDs of translating polygons) served as a further control. Accuracy decreased significantly after TMS of the IFS, while reaction times shortened significantly after TMS of the STS. Using signal detection analysis, we observed that d′ and criterion values were significantly decreased after TMS of the IFS, (but not STS), which was due to subjects making significantly more false alarms post-TMS. None of these TMS effects were found for the non-biological control task, indicating some specificity to biological motion. Our findings constitute important steps towards understanding the neural systems subserving biological motion perception, but future work is needed to clarify the precise functional roles of these two areas in biological motion perception. We hypothesize that during biological motion perception, premotor cortex provides a modulatory influence to help refine the computations of posterior areas. Alternatively, premotor cortex might be important for decision making regarding biological motion.
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