Reading Point-Light Walkers and Amorphous-A TMS Study

Objective: (a) Evaluate if human actions with and without pictorial information result in comparable motor facilitation; and (b) verify if the isolated features of movement and human shape increase motor excitability. Method: Motor evoked potentials (MEPs) of M1 were recorded from 18 healthy subject...

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Bibliographic Details
Published in:Psychology & Neuroscience Vol. 15; no. 2; pp. 198 - 209
Main Authors: Lapenta, Olivia M., Valasek, Cláudia A., Vieira, Sofia M. G., Boggio, Paulo S.
Format: Journal Article
Language:English
Published: Rio de Janeiro Educational Publishing Foundation 01-06-2022
American Psychological Association
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Summary:Objective: (a) Evaluate if human actions with and without pictorial information result in comparable motor facilitation; and (b) verify if the isolated features of movement and human shape increase motor excitability. Method: Motor evoked potentials (MEPs) of M1 were recorded from 18 healthy subjects using transcranial magnetic stimulation (TMS) during presentation of full-body video clips of everyday human actions either with (real movement, RM) or without (biological point-light, PLbio) pictorial information, non-biological/scrambled moving point-lights (PLnb), and static point-lights arranged in a human shape (PLs). All videos were approximately 1,000 ms long. Peak-to-peak MEP amplitude was individually averaged for each condition. Results: repeated measures analysis of variance (rmANOVA) considering MEP as dependent variable and stimuli as within-subject factor revealed an effect for Stimuli (F 1,17 = 6.53; p < .001; η p 2 = .227). Such effect was due to lower MEP amplitude in PLs when compared to RM (p = .002), PLbio (p = .002) and PLnb (p = .005). Conclusion: The similar corticospinal excitability (CE) increase during PLbio and RM observation corroborates the use of human PL in motor resonance/action observation studies. Noteworthy, PLnb also engaged the motor network, which could be due to kinematic aspects of human velocity profile or anthropomorphism of non-biological agents. Observation of PLs resulted in significantly smaller MEPs. Therefore, M1 activation seems restrict to movement perception but might not be strictly dependent on human form. Thus, planning the control stimuli and task context is crucial when using PL displays in the study of human action perception and the action observation network (AON). Public Significance Statement Our study demonstrated that observing real and point-light human actions activates motor brain areas in a similar fashion. Furthermore, observing moving point-light deprived of human shape also increased motor activation whereas static human shaped point-lights didn't. Thus, either movement feature suffice to engage motor areas or most likely, humans anthropomorphized the scrambled dots in an attempt to attribute meaning to the observed movement.
ISBN:1433895838
9781433895838
ISSN:1984-3054
1983-3288
DOI:10.1037/pne0000273