Cerebral Cortex
April 24, 2012
Renaud Jardri, Pierre Thomas, Christine Delmaire et al.
180 citations
Hallucinations in psychosis may arise when the brain's default-mode network (DMN) disengages abnormally, similar to its response to real external stimuli. In 20 drug-free adolescents with brief psychotic disorder, multimodal MRI showed that during auditory, visual, and multisensory hallucinations, cortical thickness was reduced and blood oxygen level-dependent signal increased in modality-dependent association sensory cortices, while primary sensory cortex recruitment was not systematic and linked to greater vividness. DMN disengagement coincided with hallucinations, and spatial and temporal instabilities of the DMN correlated with hallucination severity and persisted even without symptoms. This suggests hallucinations emerge from spontaneous DMN withdrawal, offering a model beyond the auditory modality.
BioMed Research International
January 1, 2014
Benjamin Rolland, Renaud Jardri, Ali Amad et al.
96 citations
Hallucinations arise from at least three distinct pharmacological pathways: activation of dopamine D2 receptors by psychostimulants, activation of serotonin 5HT2A receptors by psychedelics, and blockage of glutamate NMDA receptors by dissociative anesthetics. In schizophrenia, the relative roles of NMDA and dopamine receptors remain debated, and slight clinical differences appear depending on the cause. This narrative review synthesizes how leading researchers have approached whether the concept of hallucination is clinically and neurobiologically homogeneous. Some favor a single mechanism, while others propose integrated theories based on pharmacological psychosis models. The authors suggest that although common neurobiological pathways may exist, each system likely has unique properties that explain observed clinical differences.
Schizophrenia Bulletin
August 5, 2020
Pantelis Leptourgos, Martin Fortier-Davy, Robin Carhart‐Harris et al.
88 citations
A multidisciplinary working group reviewed evidence on the similarities and differences between hallucinations induced by psychedelics and those occurring in schizophrenia-spectrum disorders, examining data from pharmacology, brain imaging, phenomenology, and anthropology. The authors highlight both shared features and distinct characteristics across these scales, and attempt to integrate findings using computational approaches. They conclude with recommendations for future research, emphasizing the need for further study to clarify the relationship between these types of hallucinations.
Neuroscience and biobehavioral reviews
July 1, 2023
Daniel Collerton, James Barnes, Nico J Diederich et al.
80 citations
Eight distinct models of complex visual hallucinations have been proposed since 2000, each based on different views of brain organization. Researchers from each model group have now agreed on an integrated Visual Hallucination Framework that aligns with current theories of both real and hallucinatory vision. The Framework identifies cognitive systems involved in hallucinations and enables systematic investigation of how hallucination experiences relate to changes in underlying cognitive structures. The episodic nature of hallucinations points to separate factors for their onset, persistence, and end, suggesting a complex relationship between temporary states and long-term traits of hallucination risk. The Framework also suggests new research directions and potential treatments for distressing hallucinations.
Schizophrenia bulletin
October 6, 2025
Charles Fernyhough, Janna De Boer, Paige E Davis et al.
3 citations
Hallucinations, which occur in many psychiatric disorders, may be better understood through the lens of developmental psychology. Their clinical significance depends on when they appear in a person's life. Key cognitive-developmental processes—such as engaging with imaginary entities, adverse events, executive functioning, social cognition, and language development—shape how hallucinations arise across different sensory modalities. Atypical developmental trajectories, as seen in certain conditions, also influence hallucination prevalence and phenomenology. Integrating developmental and psychiatric perspectives could yield mutual benefits for future research.
Schizophrenia Bulletin
April 17, 2025
Nathan H. Heller, Frederick S. Barrett, Tobias Buchborn et al.
3 citations
Visual hallucinations in Lewy body diseases (Parkinson's disease and dementia with Lewy bodies) and those induced by serotonergic psychedelics (psilocybin, mescaline) share overlapping phenomenology and neural mechanisms, despite different underlying causes. Both conditions produce visual aberrations from minor distortions to complex hallucinations, including illusory motion and entity encounters. Neuroimaging shows a common pattern of overactive associative cortex and underactive sensory cortex. Serotonin 2A receptor modulation is involved in both: psychedelics act through 5-HT2A and 5-HT1A receptors, while in Lewy body diseases, 5-HT2A receptor upregulation correlates with increased hallucinations, and blocking it with pimavanserin reduces them. Shared cortical signatures include reduced visual evoked responses and shifts toward visual excitation.