Evidence map›Paper›PMID 42393353›Full record

ArticleJournal of neural transmission (Vienna, Austria : 1996)2026

Investigating smiling asymmetries in Parkinson's disease through the whistle-smile reflex.

Adriana Martini, Giulia Paparella, Simone Aloisio, Luca Angelini, Anna Sofia Grandolfo, Martina De Riggi, Daniele Birreci, Davide Costa, Luca Marsili, Matteo Bologna

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Article in Journal of neural transmission (Vienna, Austria : 1996), 2026. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Not yet cited in PubMed.

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5 · Who and what money

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10 authors.

Adriana Martini *Department of Human Neurosciences, Sapienza University of Rome, Rome, Italy.
Giulia Paparella *IRCCS Neuromed, Pozzilli (IS), Italy.
Simone AloisioDepartment of Human Neurosciences, Sapienza University of Rome, Rome, Italy.
Luca AngeliniIRCCS Neuromed, Pozzilli (IS), Italy.
Anna Sofia GrandolfoDepartment of Human Neurosciences, Sapienza University of Rome, Rome, Italy.
Martina De RiggiDepartment of Human Neurosciences, Sapienza University of Rome, Rome, Italy.
Daniele BirreciDepartment of Human Neurosciences, Sapienza University of Rome, Rome, Italy.
Davide CostaDepartment of Human Neurosciences, Sapienza University of Rome, Rome, Italy.
Luca MarsiliJames J. and Joan A. Gardner Center for Parkinson's disease and Movement disorders, Department of Neurology, University of Cincinnati, Cincinnati, OH, USA.
Matteo BolognaDepartment of Human Neurosciences, Sapienza University of Rome, Rome, Italy. matteo.bologna@uniroma1.it.

Funding

No grant is acknowledged in the PubMed record.

6 · The paper itself

Abstract

backgroundHypomimia is a hallmark of Parkinson's disease (PD), but whether emotional expressions show lateralized abnormalities remains unclear. While asymmetry has been described for posed smiles, no study has examined true spontaneous smile asymmetry in PD. The whistle-smile reflex (WSR), an involuntary smile elicited after voluntary whistling, offers an opportunity to investigate a form of smiling that closely resembles typical spontaneous expressions of joy. In the present study, we aimed to assess the frequency, intensity, and asymmetry of smiling elicited by the WSR in PD compared with healthy controls (HCs) and to explore links between facial and motor asymmetry. Fifty PD patients and 22 age-matched HCs underwent standardized video recording of the WSR. Only participants judged as smiling by ≥ 3/4 raters were included in the chimeric-face analysis. Left-left (LL) and right-right (RR) chimeric images were generated, and seven blinded raters evaluated smile presence and hemiface expressivity. Facial Laterality Index (FLI) and Body Laterality Index (BLI) quantified asymmetries. WSR was less frequent in PD than HCs (video: 44% vs. 72%; mouth-only chimeras: 50% vs. 81%, p < 0.01). PD smiles were more often symmetrical (59% vs. 25%, p = 0.03), with no consistent left-right dominance. Facial and motor asymmetry were unrelated (p > 0.05). Symmetric smilers had higher UPDRS-III scores (p = 0.04). In PD, WSR is reduced and bilaterally flattened, with no lateralized asymmetry, possibly reflecting limbic-subcortical dysfunction. Smile symmetry increases with motor severity, supporting its potential as a simple marker of hypomimia. The WSR and chimeric-smile analysis provide practical tools to assess emotional expressivity in PD.

Indexed as

Emotional expressivityHypomimiaParkinson’s diseaseSpontaneous smilingWhistle–smile reflex

Identifiers

PMID42393353

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Read under generation 80e0d062 · epoch 390. Bibliography from PubMed, PubMed Central and OpenAlex; grants from NIH RePORTER; trial links from ClinicalTrials.gov; estimates, votes and beliefs from the OpenQuestion graph.