Objective: To investigate the rate and precision of co-speech gestures produced by people with Parkinson’s as they describe self-produced actions.

Background: Motor and cognitive impairments in Parkinson’s disease can substantially impact language and communication, with some evidence of a specific impairment in action-related semantics. Co-speech gestures embody a link between action and language and may thus be particularly affected in Parkinson’s. Previous studies have shown no significant reductions in gesture rate in mild-to-moderate Parkinson’s [1-3], but gestures depicting actions may be less precise [1], more likely to be produced from a third-person perspective [2,3], and less likely to include manners of motion, while paths of motion may be spared [3]. This previous work largely examined how Parkinson’s affects gestures while describing the actions of others, but little is known about gestures describing one’s own previous actions.

Method: 37 people with mild-to-moderate Parkinson’s [12 female; M(SD) age = 65.0 (7.3)] and 34 [20 female; 65.9 (6.1)] controls were video recorded as they explained the Tower of Hanoi task, which they had physically performed a few minutes earlier, to an unfamiliar addressee. Both groups were screened for cognitive impairment. We examined gestures that referred to objects (e.g., shape/size of the discs) and actions (e.g., moving discs between pegs).

Results: The Parkinson’s group produced significantly fewer gestures per 100 words (Mdn = 11.6) than controls (14.92; p = .023), and their gestures depicting graspable objects were significantly less precise (p = .003). However, this reduction in precision was not observed for action gestures (p = .767).

Conclusion: In a departure from previous studies of co-speech gestures in mild-to-moderate Parkinson’s [1-3], the small but significant decrease in gesture rate here may reflect an increase in gestures by healthy controls when describing self-produced actions in a highly communicative situation. This may suggest an upper limit to co-speech gesture use in Parkinson’s. That the precision of action gestures was not reduced may indicate that people with Parkinson’s may still gesture successfully about highly salient aspects of actions.

References: [1] Cleary RA, Poliakoff E, Galpin A, Dick JPR, Holler J (2011) An investigation of co-speech gesture production during action description in Parkinson’s Disease. Parkinsonism and Related Disorders, 17, 753-756. [2] Humphries S, Holler J, Crawford T.J., Herrera E, Poliakoff E (2016) A third-person perspective on co-speech action gestures in Parkinson’s disease. Cortex, 78, 44-54. [3] Humphries S, Holler J, Crawford TJ, Poliakoff E (2021) Co-speech gestures are a window into the effects of Parkinson’s disease on action representations. Journal of Experimental Psychology: General. https://doi.org/10.1037/xge0001002

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MDS Abstracts - https://www.mdsabstracts.org/abstract/speaking-with-your-hands-in-parkinsons-investigating-the-rate-and-precision-of-co-speech-gestures/