Representing actions in co-speech gestures in Parkinson's Disease

Humphries, S., Holler, J., Crawford, T., & Poliakoff, E. (2014). Representing actions in co-speech gestures in Parkinson's Disease. Poster presented at the 6th International Society for Gesture Studies Congress, San Diego, California, USA.
Parkinson’s disease (PD) is a progressive, neurological dis- order caused by the loss of dopaminergic cells in the basal ganglia, which is involved in motor control. This leads to the cardinal motor symptoms of PD: tremor, bradykinesia (slow- ness of movement), rigidity and postural instability. PD also leads to general cognitive impairment (executive function, memory, visuospatial abilities), and language impairments; PD patients perform worse at language tasks such as provid- ing word definitions and naming objects, generating lists of verbs, and naming actions. Thus, there seems to be a par- ticular impairment for action-language. Despite the fact that action and language are both impaired in PD, little research has explored if and how co-speech gestures, which embody a link between these two domains, are affected. The Ges- ture as Simulated Action hypothesis argues that gestures arise from cognitive representations or simulations of actions. It has been argued that people with PD may be less able to cog- nitively represent, simulate and imagine actions, which could account for their action-language impairment and may also mean that gestures are affected. Recently, it has been shown that while there is not a straightforward reduction in gesture use in PD, patients’ gestures which described actions are less precise/informative than those of controls. However, partici- pants only described two actions, and to a knowing addressee (so the task was not communicative). The present study extended this by asking participants to describe a wide range of actions in an apparently commu- nicative task, and compared viewpoint as well as precision between the two groups. Gesture viewpoint was examined in order to provide a window into the cognitive representa- tions underlying gesture, by demonstrating whether or not the speaker has placed themselves as the agent within the ac- tion (character viewpoint), requiring a cognitive simulation of the action. Overall, studying gestures in PD has clinical relevance, and will provide insight into the cognitive basis of gestures in healthy people. 25 PD patients and 25 age-matched controls viewed 10 pictures and 10 videos depicting a range of actions and de- scribed them to help an addressee identify the correct stimu- lus. No difference in the rate of gesture production between the two groups was found. However, the precision of ges- tures describing actions was found to be significantly lower in the PD group. Furthermore, the proportion of gestures produced from character viewpoint was found to differ be- tween the groups, with PD patients producing significantly less C-VPT gestures. This suggests that the cognitive repre- sentations underlying the gestures have changed in PD, and that people with PD are less able to imagine themselves as the agent of the action. This supports the GSA hypothesis by demonstrating that gesture production changes when the abil- ity to perform and to cognitively simulate actions is impaired. Our next study will assess the relationships between cognitive factors affected in PD and gesture, and motor imagery ability and gesture. The study will also examine gestures produced by people with PD when describing a wide range of semantic content in various communicative situations.
Publication type
Poster
Publication date
2014

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