I finally see what you see: Parkinson's disease visual hallucinations captured with functional neuroimaging

Background: Functional neuroimaging studies have described alterations in neural activation in PD patients with chronic hallucinations. These studies have not, however, captured neural activation patterns during an actual hallucinatory event. The objective of this work was to investigate neuroanatomical substrates active during visual hallucinations in a patient with Parkinson's disease (PD). Methods: We conducted an event-related functional magnetic resonance imaging (fMRI) case-study examination of a 66-year-old male PD patient with stereotypic, chronic, and frequent visual hallucinations. Results: The patient reported 16 hallucinations during the fMRI scan. Increased activation during hallucinations was found in the cingulate, insula, frontal lobe, thalamus, and brain stem. Decreased activation was found in the lingual and fusiform gyri, inferior occipital gyrus, and middle frontal and superior temporal lobes. Conclusions: To our knowledge, this report is the first published case documenting the cortical activation patterns using fMRI techniques in a PD patient during active hallucinations. Our results suggest that during a visual hallucination, a marked desynchronization occurs between posterior and anterior cortical areas involved in visual processing.