Altered dynamic functional connectivity and reduced higher order information interaction in Parkinson's patients with hyposmia.

Hyposmia, a common non-motor symptom in Parkinson's disease (PD) linked to reduced odor sensitivity, is associated with brain structural and functional changes, but dynamic brain activity and altered regional information exchange remain underexplored, limiting insight into underlying brain states. We selected 15 PD patients with severe hyposmia (PD-SH), 15 PD patients with normal cognition (PD-CN), and 15 healthy controls (HC). Using functional MRI, we assessed the brain's spatiotemporal connectivity (brain-state) alterations, and the brain's capacity for higher-order information exchange (synergy and redundancy). A dynamic brain state with complex-long-range connections was significantly reduced in PD-SH and PD-CN, compared to HC. Brain-states consisting of modular-clusters in sensorimotor and frontal areas occurred more frequently in PD-SH than in PD-CN and HC. Higher-order information flow was reduced in PD patients, with PD-SH showing a greater reduction in synergetic information flow in frontal, insula, and left sensory-motor. These findings suggest potential discriminative biomarkers for PD-SH.