Disrupted visual-to-semantic dynamics promote visual hallucinations in Parkinson's disease

Area of Science:

• Neuroscience
• Cognitive Science
• Neurology

Background:

• Minor hallucinations are common in Parkinson's disease (PD), often signaling cognitive decline.
• Visual hallucinations in PD may arise from impaired sensory processing and cognitive dysregulation.

Purpose of the Study:

• To investigate the neural mechanisms of visual hallucination vulnerability in non-demented Parkinson's disease patients.
• To examine how visual categorization is affected by hallucinations and cognitive status in PD.

Main Methods:

• Ninety-three non-demented PD patients underwent 19-channel electroencephalography (EEG) during a visual categorization task.
• Patients were grouped by hallucination status and cognitive status (normal or mild cognitive impairment - MCI).
• EEG event-related potentials (ERPs) and source estimation were analyzed.

Main Results:

• Hallucinating PD patients exhibited reduced accuracy in categorizing faces and objects.
• EEG data showed altered N170, N300, and P600 amplitudes in hallucinating patients, especially those with MCI.
• Source analysis indicated disrupted occipito-temporal activation, premature default mode network engagement, and impaired top-down control.

Conclusions:

• Parkinson's disease hallucinations are associated with progressive disruption of visual-semantic integration.
• Findings suggest a convergence of impaired sensory encoding, overactive semantic processing, and weakened cognitive control.
• These neural alterations represent a mechanistic signature of hallucination vulnerability in PD.