Unaltered emotional experience in Parkinson’s disease: Pupillometry and behavioral evidence

ABSTRACT

Introduction: Recognizing emotions in others is a pivotal part of socioemotional functioning and plays a central role in social interactions. It has been shown that individuals suffering from Parkinson’s disease (PD) are less accurate at identifying basic emotions such as fear, sadness, and happiness; however, previous studies have predominantly assessed emotion processing using unimodal stimuli (e.g., pictures) that do not reflect the complexity of real-world processing demands. Dynamic, naturalistic stimuli (e.g., movies) have been shown to elicit stronger subjective emotional experiences than unimodal stimuli and can facilitate emotion recognition.

Method: In this experiment, pupil measurements of PD patients and matched healthy controls (HC) were recorded while they watched short film clips. Participants’ task was to identify the emotion elicited by each clip and rate the intensity of their emotional response. We explored (a) how PD affects subjective emotional experience in response to dynamic, ecologically valid film stimuli, and (b) whether there are PD-related changes in pupillary response, which may contribute to the differences in emotion processing reported in the literature.

Results: Behavioral results showed that identification of the felt emotion as well as perceived intensity varies by emotion, but no significant group effect was found. Pupil measurements revealed differences in dilation depending on the emotion evoked by the film clips (happy, tender, sadness, fear, and neutral) for both groups.

Conclusions: Our results suggest that differences in emotional response may be negligible when PD patients and healthy controls are presented with dynamic, ecologically valid emotional stimuli. Given the limited data available on pupil response in PD, this study provides new evidence to suggest that the PD-related deficits in emotion processing reported in the literature may not translate to real-world differences in physiological or subjective emotion processing in early-stage PD patients.

KEYWORDS:

• Ecological validity
• emotion
• dynamic stimuli
• emotional intensity
• Parkinson’s disease
• pupillometry
• video clip.

Acknowledgments

The authors would like to thank the participants who took part in the study, as well as Karyn Fish for her help with multiple aspects of stimuli development, and Patrick van Wagenen, Joanna Liu, and Lila Weintraub for help with data analysis. Thank you to Fatemeh Mollaei, Lesley Fellows, Christine Dery, and the Cummings Centre for help with participant recruitment. Thank you to Alexandre Schaefer and Pierre Mahau for patiently answering questions about how best to recreate emotion elicitation stimuli for an English-speaking audience. We would also like to thank Nathanaël Lécaudé for help in programming the slider, as well as Moritz Dannhauer and Joanna Liu for proofreading.

Disclosure statement

No potential conflict of interest was reported by the authors.

Notes

1. An LME model rerun on the accuracy and intensity ratings, restricted to the subgroup of participants for the pupillometry analysis, confirmed that there were no significant group differences or emotion effects for either measure.

Additional information

Funding

This research was funded by operating grants from the Canadian Institutes of Health Research and Parkinson Society Canada (to M.D.P. and S.A.K.); and awards from the Fonds de la recherché en santé du Québec (postdoctoral fellowship to K.R., Chercheur-boursier Senior award to M.D.P.).