System Maintenance Notice

Please note that maintenance work is scheduled between 4 AM and 5 AM - CET. During this time, you may experience reduced performance. Thanks for your patience.

Publications

Journal Article Epublish

PubMed: 42079986 DOI: 10.3389/fnhum.2026.1708832

Impaired event-related theta spectral coherence in emotional facial expression processing in neurodegenerative disorders.

Front Hum Neurosci 20:1708832

Authors: Hakan Uzunlar, Rümeysa Duygun, İlayda Kıyı-Atilla, Tuba Aktürk, Ebru Yıldırım, Nesrin Helvacı Yılmaz, Lütfü Hanoğlu, Henrique Sequeira, David Papo, Massimiliano Zanin, Claudio Babiloni, Görsev Yener, Bahar Güntekin

Affiliations

  • Department of Neuroscience, Graduate School of Health Sciences, Istanbul Medipol University, Istanbul, Türkiye.
  • Research Institute for Health Sciences and Technologies (SABITA), Neuroscience Research Center, Istanbul Medipol University, Istanbul, Türkiye.
  • School of Psychology, University of Sussex, Brighton, United Kingdom.
  • Department of Neurosciences, Institute of Health Sciences, Dokuz Eylül University, Izmir, Türkiye.
  • Section Brain Stimulation and Cognition, Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, Maastricht, Netherlands.
  • Neuroscience and Neurotechnology Center of Excellence (NÖROM), Gazi University, Ankara, Türkiye.
  • Faculty of Medicine, Department of Neurology, Istanbul Medipol University, Istanbul, Türkiye.
  • University of Lille, CNRS, UMR 9193 - SCALab - Sciences Cognitives et Sciences Affectives, Lille, France.
  • Department of Neuroscience and Rehabilitation, Section of Physiology, University of Ferrara, Ferrara, Italy.
  • Center for Translational Neurophysiology, Fondazione Istituto Italiano di Tecnologia, Ferrara, Italy.
  • Instituto de Física Interdisciplinar y Sistemas Complejos IFISC (CSIC-UIB), Parc Bit, Palma de Mallorca, Spain.
  • Department of Physiology and Pharmacology "V. Erspamer", Sapienza University of Rome, Rome, Italy.
  • IRCCS San Raffaele Roma - Cassino, Cassino Site, Cassino, Italy.
  • Department of Neurology, Medical School, Dokuz Eylul University, Izmir, Türkiye.
  • IBG: International Biomedicine and Genome Center, Izmir, Türkiye.
  • Department of Biophysics, School of Medicine, Istanbul Medipol University, Istanbul, Türkiye.

Abstract

INTRODUCTION

The ability to recognize emotional facial expressions relies on brain functional networks, particularly in the right hemisphere, and is impaired in neurodegenerative conditions such as Alzheimer's disease and Parkinson's disease. Given that this ability involves brain networks operating within hundreds of milliseconds, we tested the hypothesis of abnormalities in event-related spectral electroencephalographic coherence, with a focus on the right versus left hemispheres in these patients.

METHODS

Event-related theta (4-7 Hz) magnitude-squared coherence was calculated for both intra-hemispheric (frontal-temporal, frontal-parietal, central-temporal, and related pairs) and inter-hemispheric homologous electrode pairs (F3-F4, C3-C4, T7-T8, TP7-TP8, P3-P4, O1-O2). We enrolled 25 patients with amnestic mild cognitive impairment, 15 Parkinson's disease patients with mild cognitive impairment, 25 Alzheimer's disease patients with dementia, and 16 Parkinson's disease patients with dementia, along with 25 healthy elderly as controls. Participants were presented with three different facial expressions (angry, happy, and neutral) 60 times each in a pseudo-random order.

RESULTS

Theta (4-7 Hz) spectral coherence was higher in the right than the left hemisphere across all groups, with Parkinson's disease patients exhibiting the lowest values. Moreover, interhemispheric theta coherence was lower in Parkinson's disease patients with mild cognitive impairment and dementia compared to the amnestic mild cognitive impairment and healthy elderly groups.

DISCUSSION

These findings indicate that cortical functional connectivity related to emotional facial expression processing is more disrupted in Parkinson's disease than in Alzheimer's disease, at both mild cognitive impairment and dementia stages. This disruption affects not only the right hemisphere but also interhemispheric connectivity. Finally, it would occur at theta frequencies.

MeSH

Dementia, Brain, Cognitive Dysfunction, Aged, Cognition Disorders, Facial Expression, Neurodegenerative Diseases