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.
Transl Psychiatry
December 13, 2023
Marco Onofrj, Mirella Russo, Stefano Delli Pizzi et al.
42 citations
Psychosis in Parkinson's disease and Dementia with Lewy Bodies shares underlying mechanisms with altered states of consciousness seen in REM sleep, psychiatric disorders, and psychedelic drug use. Dysregulated activity in high-order thalamic nuclei, driven by ThalamoCortical Dysrhythmia (TCD), is proposed as a crucial trigger. TCD disrupts finely tuned cortico-cortical modulations normally supported by the thalamus, leading to aberrant Default Mode Network (DMN) activity. This process alters thalamic filtering of internal and external information, causing cortical input overload and DMN decoupling from task-positive networks. These changes destabilize brain metastability, producing dreamlike, dissociative, or altered states. Psychedelic drugs similarly modulate thalamic-cortical pathways. Understanding this pathophysiology bridges neurology and psychiatry, offering promising avenues for investigation and therapy.
NeuroImage
December 1, 2023
Stefano Delli Pizzi, Piero Chiacchiaretta, Carlo Sestieri et al.
27 citations
LSD selectively alters the functional connectivity between specific thalamic nuclei and sensory and associative cortical areas. Using structural and resting-state functional MRI in healthy volunteers under acute LSD administration, researchers found increased coupling of the ventral complex, pulvinar, and non-specific thalamic nuclei with somatosensory and auditory cortices, as well as with associative cortex regions rich in serotonin 2A receptors. At subcortical levels, LSD increased connectivity among these thalamic nuclei but decreased striatal-thalamic connectivity. These nucleus-specific changes help explain LSD's modulation of subcortical-cortical circuits and associated behavioral effects.
Biological psychiatry. Cognitive neuroscience and neuroimaging
July 1, 2023
Stefano Delli Pizzi, Piero Chiacchiaretta, Carlo Sestieri et al.
18 citations
LSD alters brain functional connectivity and local signal amplitude in opposite directions depending on the type of serotonin receptor involved. In healthy volunteers, LSD increased activity and connectivity in cortical regions of the default mode and attention networks, which have high densities of 5-HT2A receptors; these changes correlated with visual hallucinations. Conversely, LSD decreased activity and connectivity in limbic areas rich in 5-HT1A receptors. The spatial patterns of these functional changes overlapped with the distribution of the two serotonin receptor subtypes, suggesting distinct receptor-mediated mechanisms underlie LSD's reorganization of brain networks.