Theta oscillations and minor hallucinations in Parkinson's disease reveal decrease in frontal lobe functions and later cognitive decline

Abstract

Cognitive decline and hallucinations are common and debilitating non-motor symptoms, occurring during later phases of Parkinsons disease (PD). Minor hallucinations (MH), appear at early phases and have been suggested to predict cognitive impairment in PD, however, this has not been well-established by clinical research. Here, we investigated whether non-demented PD patients with MH show altered brain oscillations and whether such MH-related electrophysiological changes are associated with cognitive impairments that increase over time. Combining model-driven EEG analysis with neuropsychiatric and neuropsychological examinations in 75 PD patients, we reveal enhanced frontal theta oscillations in PD patients suffering from MH and link these oscillatory changes with lower cognitive frontal-subcortical functions. Neuropsychological follow-up examinations five years later confirmed MH-specific theta oscillations and revealed a stronger decline in frontal-subcortical functions in MH-patients with stronger frontal theta alterations, defining an MH and theta oscillation-based early marker of a cognitive decline in PD.