Neural substrates in Parkinson’s Disease psychosis: A systematic review

Neural underpinnings of Parkinson’s Disease psychosis (PDP) remain unclear to this day with relatively few studies and reviews available. Using a systematic review approach, here we aimed to qualitatively synthesize evidence from studies investigating PD psychosis-specific alterations in brain structure, function or chemistry using different neuroimaging modalities. PubMed, Web of Science and Embase databases were searched for fMRI, rsfMRI, DTI, PET, and SPECT studies comparing PDP patients with PD patients without psychosis (PDnP). We report findings from 18 studies (291 PDP patients, mean age ± SD = 68.65 ± 3.76 years; 48.5% males; 433 PDnP patients, mean age ± SD = 66.97 ± 3.80 years; 52% males). Qualitative synthesis revealed widespread patterns of altered brain function across task-based and resting-state fMRI studies in PDP compared to PDnP patients. Similarly, white matter abnormalities were reported in parietal, temporal, and occipital regions. Hypometabolism and reduced dopamine transporter binding were also reported whole brain and in subcortical areas. This suggests extensive alterations affecting regions involved in high order visual processing and attentional networks.