Introduction: Visual hallucinations are one of the common non-motor
symptoms of Parkinson’s disease. Although various theories have been
proposed, the pathological mechanism is not fully understood. This
study aimed to investigate spontaneous brain activity in hallucinated
and non-hallucinated patients with Parkinson’s disease (PD) by using EEG
and also its relevance to the behavioral and neuropsychological status
of patients.
Methods: A total of 30 people were included in the study: 10 hallucinated
PD patients, 10 non-hallucinated PD patients, and 10 healthy controls.
Spontaneous EEG data were recorded in eyes-open and eyes-closed
conditions. A neuropsychological battery was used to evaluate visual
and verbal memory, visuo-spatial abilities, executive functions, and
behavioral/emotional status of participants.
Results: The hallucinated group did not show an increase in alpha
power activity in response to eye closure, although healthy controls
showed a significant increase in alpha power in eyes closed condition.
Parkinson’s disease patients with hallucinations showed significantly
higher intra-hemispheric beta and gamma coherence and the nonhallucinated
group demonstrated significantly lower inter-hemispheric
alpha coherence. Additionally, Hallucinated PD patients showed higher
NPI (Neuropsychiatric Inventory) scores and RBD-SQ (REM Behavior
Disorder Screening Questionnaire) scores, lower motor scores (Unified
Parkinson’s Disease Rating Scale – UPDRS), and a higher number of
Stroop Test errors compared to non-hallucinated PD patients.
Conclusion: Increased abnormal resting-state EEG activity and a
tendency towards greater impairment of executive functions were
seen in hallucinated PD patients. These results can be interpreted as an
abnormal resting activity in cortical networks that may underlie their
visual hallucinations symptoms.
Keywords: Coherence analysis, EEG, neuropsychological assessment,
Parkinson’s disease, visual hallucination