The Functional Connectivity of Hallucinations in Psychiatric Disorders and Neurodegenerative Disorders: A Systematic Review
Yifan Ren, Huyen Ngoc Pham, Xiong Xiong, Shun-Chin Jim Wu, Emilio Fernández-Egea, John T. O’Brien, Graham K. Murray, John Suckling
September 16, 2026 preprint DOI: 10.31234/osf.io/dt7gn_v1 (opens in new tab)
Study at a glance
AI-extracted from the abstract| Characteristics | Systematic review |
|---|---|
| Key findings | Across 198 functional connectivity studies, hallucinations consistently involved dysconnectivity among default mode, salience, and central executive networks, sensory systems, and subcortical circuits, with psychiatric hallucinations linked to auditory-language and cortico-striatal patterns and neurodegenerative hallucinations to visual and attentional network dysfunction. The authors argue that functional connectivity is sensitive to hallucinations and supports their transdiagnostic nature, but that the literature does not converge on a unified cognitive or consciousness-based theory. |
Abstract
Background: Hallucinations span psychiatric and neurodegenerative disorders, yet unified neurobiological or consciousness-based explanations remain uncertain. Functional connectivity (FC) provides a network-level view with highly heterogeneous findings.Methods: Following PRISMA, we included studies with FC of hallucinations to ask whether it is sensitive to hallucinations, can distinguish different disorders, and if adopted theories are explanatory.
Results: 198 studies were included, with far fewer studies in neurodegenerative (35) than psychiatric disorders (163). Across conditions, hallucinations consistently involved dysconnectivity among default mode (DMN), salience (SN), central executive (CEN), sensory systems, and subcortical circuits. Shared alterations included disrupted SN modulation of sensory gating, altered DMN-sensory coupling and within DMN coherence, limbic system involvement, and reduced CEN regulation of perceptual networks. Disorder‑specific patterns were evident: psychiatric hallucinations preferentially involved auditory-language networks, cortico‑striatal circuits, and salience hubs, whereas neurodegenerative hallucinations were characterised by visual and attentional network dysfunction, including dorsal and ventral attention systems and visual cortices.Conclusions: FC is sensitive to hallucinations and shows different disorder-linked patterns while revealing shared mechanisms, supporting the transdiagnostic nature of hallucinations at the level of functional brain networks. Despite the involvement of multiple transdiagnostic networks, the current literature does not converge on a unified cognitive or consciousness-based theory of hallucinations, underscoring a critical theoretical gap and the need for integrative models.