Objective: To develop a paradigm to test whether the perception of mouth movements is improved when movements occur at a predictable point in time. In the long-run this paradigm will enable us to investigate the role of spatiotemporal predictions in expression recognition in people with Parkinson’s Disease (PwP).

Background: Parkinson’s is associated with differences in internal timing mechanisms and in facial expression recognition. We hypothesise that differences in these two processes are related because recognising facial expressions relies on accurate timing. The current study comprised the first step in the development of a paradigm for investigating spatiotemporal predictions in expression recognition. We tested whether perception of mouth movements is improved when movements occur at a predictable, versus unpredictable, time.

Method: On each trial participants were presented with an image of a human avatar and the mouth moved to one of 20 positions varying between 100% up-turned and 100% down-turned. Participants were required to manipulate a slider to recreate the mouth position from memory. In ‘predictable blocks’ (20 trials per block) the mouth movement was cued by the image of the avatar’s eyes opening. The cue predictably preceded the mouth movement by 1 second.  In ‘unpredictable blocks’, the time between eyes opening and mouth moving was 0.5-1.5 seconds. Accuracy was calculated as the difference between the position of the observed and recreated mouth. We predicted higher accuracy for predictable trials and a correlation between accuracy and the difference between expected (1 second) and actual time of stimulus presentation in unpredictable trials.

Results: 19 healthy adult participants successfully completed the task. A paired t-test showed that there was no significant difference in accuracy between predictable (M=18.4, SD=0.465) and unpredictable (M=18.4, SD=0.418) blocks (t(18)=0.22, p>.05). A Spearman’s correlation found no significant relationship between accuracy and the difference between expected and actual time of stimulus presentation (t(18) = 0.067, p>.05).

Conclusion: Results failed to support our predictions. High mean scores for both predictable and unpredictable blocks suggest that increasing task difficulty may be necessary to see a wider distribution of scores. Our future work will build on this to optimise a paradigm for investigating the role of spatiotemporal predictions in expression recognition.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/expression-perception-and-timing-in-people-with-parkinsons-disease/