Available online 3 September 2022
Highlights•TMS over the left supramarginal gyrus (SMG) interferes with pantomime of tool use.
•Studies suggest a direct link between an object and the respective pantomime.
•A novel task assessed the recognition and comprehension of object-use pantomimes’ meaning.
•Online TMS over left SMG revealed that SMG supports both facets of pantomime.
AbstractBackgroundA key question in apraxia research is which specific cognitive processes in pantomiming the parietal cortex supports. The manipulation-based hypothesis and the technical-reasoning hypothesis ascribe different roles to the inferior parietal lobule (IPL).
ObjectiveWe elucidated the role of the left supramarginal gyrus (SMG, i.e., part of IPL) during the processing of different aspects of object-use pantomime.
MethodsThirty-one healthy participants matched pantomimes with the corresponding object (PO) or the corresponding situation (PS) during online transcranial magnetic stimulation (TMS) interference applied to left SMG, compared to a control stimulation (vertex). Notably, the object corresponding to a given pantomime was explicitly not shown in the PS task, excluding the possibility to analyse a physical object. Matching an object to the corresponding situation (OS) served as a control task.
ResultsTMS interference with left SMG significantly affected response times for both investigated pantomime tasks (PO and PS); the effect in the PO task significantly correlated with the PS task. As expected, no TMS effect was observed in the control task (OS).
ConclusionLeft SMG does not only establish a link between pantomime and a manipulable object but is also involved in pantomime recognition and comprehension. That TMS interfered with both pantomime tasks supports the manipulation-based hypothesis, assuming that the IPL recruits stored gesture engrams whenever pantomimes are processed.
Keywordsapraxia
manipulation knowledge
action knowledge
parietal cortex
transcranial magnetic stimulation (TMS)
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