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Abstract:
In communication, speech is often accompanied by co-speech gestures, which embody a link between language and action. Language impairments in Parkinson’s disease (PD) are particularly pronounced for action-related words in comparison to nouns. People with PD produce fewer gestures from a first-person perspective when they describe others’ actions (Humphries et al., 2016), which may reflect a difficulty in simulation. We extended this to investigate the gestural depiction of other types of action information such as “manner” (how an action is performed) and “path” (the trajectory of a moving figure in space). We also explored whether the level of motion required to perform an action influences the way that people with PD use gestures to depict those actions.
37 people with PD and 35 age-matched controls viewed a cartoon which included low motion actions (e.g. hiding, knocking) and high motion actions (e.g. running, climbing), and described it to an addressee. We analysed the co-speech gestures they spontaneously produced while doing so. Overall gesture rate was similar in both groups, but people with PD produced action-gestures at a significantly lower rate than controls in both motion conditions. Also, people with PD produced significantly fewer manner and first-person action gestures than controls in the high motion condition (but not the low motion condition).
Our findings suggest that motor impairments in PD contribute to the way in which actions, especially high motion actions, are depicted gesturally. Thus, people with Parkinson’s may have particular difficulty cognitively representing high motion actions
