Cognitive and visual processing performance in Parkinson's disease patients with vs without visual hallucinations: A...

Area of Science:

• Neuroscience
• Cognitive Science
• Clinical Psychology

Background:

• Parkinson's Disease Psychosis (PDP) is associated with cognitive and visual impairments.
• Visual hallucinations (VHs) are a common symptom in PDP, but the specific visuo-cognitive profile linked to VH vulnerability is unclear.
• Existing research is limited by small sample sizes and restricted test selections.

Purpose of the Study:

• To conduct the first meta-analysis quantifying visuo-cognitive impairments in PDP patients with and without VHs (PDVH vs. PDnoVH).
• To assess a broad spectrum of cognitive and visual function tests.
• To account for potential confounding factors like medication, illness duration, and general cognitive ability.

Main Methods:

• Systematic search of four databases (PubMed, PsychINFO, Scopus, WebOfScience) up to February 2020.
• Extraction of means and standard deviations for visual and cognitive tasks.
• Calculation of standardized mean differences (SMDs) and Hedges' g effect sizes, synthesized using random-effects meta-analyses with robust-variance-estimation.

Main Results:

• Included 99 studies with 2508 PDVH patients and 5318 PDnoVH patients.
• PDVH patients demonstrated significantly worse performance than PDnoVH patients across all cognitive and visual processing measures.
• The most substantial differences were observed in executive functions, attention, episodic memory, and visual processing.

Conclusions:

• Current models of PDVH should integrate a wider array of cognitive and processing domains.
• Further research is needed to establish the temporal relationship between cognitive/visual deficits and VHs.
• Early identification of at-risk individuals could potentially mitigate later outcomes, such as dementia progression.