Mismatch negativity (MMN)—a neural marker of prediction-error signaling—has been linked to psychosis across disorders and is reduced in schizophrenia. Its visual form (vMMN) may be especially relevant to Parkinson’s disease psychosis (PDP), where hallucinations are predominantly visual. In a case–control EEG study, patients with Parkinson’s and visual hallucinations (PD-VH) showed diminished vMMN at parieto-occipital and frontal electrodes compared with patients with Parkinson’s without hallucinations. Correlations indicated that greater hallucination severity tracked smaller mismatch responses, aligning with neuroimaging evidence of ventral visual pathway dysfunction and altered attentional networks in PD-VH.
Building on serotonergic mechanisms implicated in visual hallucinations—particularly cortical 5-HT2A signaling—the authors tested whether inhibiting SRC-kinase (a node in Gi/o-biased 5-HT2A pathways) could modulate perception and vMMN. The results nominate vMMN as a sensitive biomarker for PDP and support SRC-kinase/5-HT2A modulation as a mechanistically grounded therapeutic avenue.
Reference: Vignando M, Ffytche D, Mazibuko N, et al. Visual mismatch negativity in Parkinson’s psychosis and potential for testing treatment mechanisms. Brain Commun. 2024;6(5):fcae291. doi: 10.1093/braincomms/fcae291.
Link: https://academic.oup.com/braincomms/article/6/5/fcae291/7748375
