Attentional processes in Parkinson’s Disease: a meta-analysis

Parkinson's disease (PD) is typically known as a neurodegenerative disorder affecting motor skills and is characterized by the loss of dopamine-producing neurons in the substantia nigra and subsequent accumulation of Lewy bodies in the residual neurons. While motor symptoms are hallmark features of PD, increasing evidence suggests that non-motor symptoms, such as attentional deficits, significantly impact the quality of life. Therefore, the present meta-analysis aims to investigate attentional function in individuals with Parkinson's disease (PD) compared to healthy controls (HC), focusing exclusively on studies using computer-based tasks to ensure accurate and comparable data. The systematic review was conducted according to the PRISMA Statement method and registered in PROSPERO. At the end of the process, 42 studies were included in the meta-analysis. Results consistently showed that PD patients have slower reaction times (RT) and reduced accuracy compared to healthy controls (HC). These deficits were observed across various tasks, including the Flanker Task, Attentional Network Task, and Simple and Choice Reaction Time Tasks. The meta-analysis revealed a large effect size for RT differences and a moderate effect for accuracy. Notably, no significant differences were found between congruent and incongruent stimuli and between ON and OFF medication states, indicating that attentional impairments may not be solely due to dopaminergic therapy. These findings indicate that brain changes in PD likely impair information processing and hinder compensatory mechanisms during attention tasks. Variability across studies may reflect the disease’s heterogeneous effects on neural networks, highlighting the need for sensitive, task-specific tools to assess attentional function.