Neuroscience and biobehavioral reviews
September 1, 2026
Jeremy I Skipper, Daniel R Lametti, David W Green
Aberrations in inner speech are linked to psychotic symptoms such as thought insertion and auditory verbal hallucinations, which may arise from failures in prediction and source monitoring. Normally, efference copies of speech motor commands suppress auditory responses to self-generated input; if suppression malfunctions, predicted auditory input becomes perceptually salient. Impaired self-monitoring regions (e.g., anterior cingulate cortex) may cause inner speech to be misattributed as external. Neuroimaging meta-analyses of neurotypical participants and psychosis spectrum participants showed increased activity in motor-related regions (e.g., ventral premotor cortices) and decreased grey matter in auditory cortices and ACC. These regions form distinct, inversely coupled audiomotor networks, supporting the proposal that psychotic symptoms derive from hyperactivation in inner speech regions producing insufficiently suppressed efference copy signals.
Neuroscience and biobehavioral reviews
August 1, 2026
Fabrizio Ascone, Diletta Giangiacomo, Viviana Trezza
A review of preclinical studies finds that classic psychedelics affect behavioral domains overlapping with autism spectrum disorder (ASD), including social interaction, communication, repetitive behaviors, anxiety-like traits, and cognitive function. The neurobiological mechanisms involve serotonergic signaling, glutamatergic neurotransmission, neuroinflammatory processes, BDNF/TrkB pathways, and oxytocinergic and dopaminergic modulation. Mechanistic convergence with neurobiological alterations implicated in ASD is identified, but significant gaps constrain interpretation, including a scarcity of studies in established animal models of ASD, reliance on simplified behavioral assays, and uncertainty about how ASD-specific circuit alterations may influence responses to psychedelics.
Neuroscience and biobehavioral reviews
August 1, 2026
Stéphane Mathis, Gwendal Le Masson
Whether consciousness persists after decapitation has been debated for over two centuries, from guillotine-era anecdotes to modern neuroscience. This review synthesizes historical controversies—facial movements in severed heads and early galvanism experiments—with contemporary neurophysiological evidence. The authors trace the evolution of hypotheses from philosophical speculation to EEG-based debates and finally to neuroimaging of the 'wave of death,' an irreversible neuronal depolarization occurring approximately 27 seconds after decapitation. By integrating comparative studies across rats, lambs, and humans, and drawing clinical parallels with brain death and traumatic brain injury, the review highlights neurophysiological mechanisms and ethical implications. It provides a critical perspective on the neural correlates of consciousness and the boundaries between life and death.
Neuroscience and biobehavioral reviews
July 13, 2026
Nelson Cowan, Leonel A Gomez
Scientific theories of human consciousness differ in how much of the brain they require to support conscious experience. Most current theories assume a big-tent, integrated neural substrate that must combine many types of information—sensations, perceptions, thoughts, and emotions. This paper argues that small-tent theories, which propose a more localized neural basis, remain plausible. In a small-tent account, multiple brain processes selectively funnel information into a critical conscious area, but no single input is necessary. The embedded-processes theory exemplifies this, positing that the left and right intraparietal sulcus and their connection form a capacity-limited focus of attention synonymous with consciousness, embedded within a larger field of unconscious memory activation. The paper explores what evidence could determine where on the big-tent to small-tent continuum consciousness falls.
Neuroscience and biobehavioral reviews
May 1, 2026
Esmaeel G Gojani, Houman Farzin, Robert J Sutherland et al.
Alzheimer's disease involves amyloid-β accumulation, tau pathology, synaptic dysfunction, and neuroinflammation, driving progressive memory loss and cognitive decline. Epigenetic dysregulation is increasingly recognized as contributing to these processes by altering gene expression. Serotonergic psychedelics, acting as agonists of the serotonin 2A receptor, promote neuroplasticity and induce sustained transcriptional changes in the brain. Preclinical studies suggest these compounds can modulate epigenetic mechanisms, including histone modifications and DNA methylation. This review proposes that targeted engagement of 5-HT2A receptors may help counteract epigenetic abnormalities that contribute to Alzheimer's disease pathogenesis.
Neuroscience and biobehavioral reviews
January 1, 2026
Charlène Aubinet, Olivia Gosseries, Steve Majerus
Language and consciousness interact in complex ways, with high-level semantic and sentence integration requiring conscious processing, while lower-level phonetic, phonological, and lexico-semantic processes can function without consciousness. Evidence from neuroimaging, cognitive, and neuropsychological studies shows parallel recovery trajectories between aspects of language and states of consciousness, and language processing may influence consciousness content or precede the reemergence of consciousness. Associations between language processing and higher-order conscious thought exist, but observed links may reflect broader integration disruptions rather than language-specific mechanisms. Theoretical implications and methodological challenges, especially regarding causal direction, are discussed.
Neuroscience and biobehavioral reviews
July 1, 2025
Rumi Murayama, Yi Cai, Hiroyuki Nakamura et al.
Loss of myelin sheaths around neuronal axons is increasingly recognized as a key factor in a broad range of psychiatric and neurological disorders, including schizophrenia, major depressive disorder, bipolar disorder, post-traumatic stress disorder, autism spectrum disorder, substance use disorders, Alzheimer's disease, Parkinson's disease, and multiple sclerosis. This review examines core mechanisms driving demyelination, its clinical impact, and emerging therapeutic strategies. Key contributors include genetic predisposition, environmental triggers, immune dysregulation, neuroinflammation, and alterations in the gut-brain axis mediated by the vagus nerve.
Neuroscience and biobehavioral reviews
December 1, 2024
Pedro T Palhares, Madalina I Sas, Óscar F Gonçalves
Music reliably alters mental and physical states, making it a natural tool for studying consciousness. This narrative review assesses how empirical research in music psychology and neuroscience has contributed to understanding non-ordinary states of consciousness, including absorption, mind wandering, and creative thought. The authors argue that music's unique capacity to induce such states offers special insight into consciousness, yet music-related studies remain marginalized in the broader field. They critically evaluate key contributions and identify how music's distinctive aspects can shape future investigations. The review concludes that integrating music into consciousness research is essential and highlights promising interdisciplinary avenues for exploration.
Neuroscience and biobehavioral reviews
June 1, 2024
Robert Chis-Ciure, Lucia Melloni, Georg Northoff
A novel framework called the Measure Centrality Index (MCI) enables systematic comparison of consciousness theories by assessing how important a given empirical measure is for each theory. Applying the MCI to Global Neuronal Workspace Theory, Integrated Information Theory, and Temporospatial Theory of Consciousness shows that direct comparisons are meaningful for measures such as Lempel-Ziv Complexity, Autocorrelation Window, and possibly Mutual Information, but problematic for anatomical and physiological neural correlates of consciousness because these measures carry different weight across theories. The approach addresses isolated theory evolution and confirmatory bias in consciousness science.
Neuroscience and biobehavioral reviews
April 1, 2024
Niklas Reich, Michael Mannino, Steven Kotler
Caffeine, a non-selective adenosine receptor antagonist, may facilitate the flow state—an intrinsically rewarding condition of total task absorption and optimal performance—through several biological mechanisms. These include upregulating dopamine D1/D2 receptor affinity in reward-related brain areas, protecting dopaminergic neurons, increasing norepinephrine release and alertness, heightening parasympathetic high frequency heart rate variability, modifying striatal endocannabinoid-CB1 receptor signaling, and shifting brain network activity toward executive function. The review also discusses caffeine's application for attention deficit hyperactivity disorder and notes caveats, aiming to inspire future studies on caffeine-induced flow.
Neuroscience and biobehavioral reviews
October 1, 2023
Ruben E Laukkonen, Margaret Webb, Carola Salvi et al.
Feelings of insight help people select ideas from the stream of consciousness by capturing attention and generating intuitive confidence, enabling fast action under uncertainty. This 'Eureka heuristic' is explained through active inference: implicit restructuring via Bayesian reduction produces a higher-order prediction error (the content of insight), while dopaminergic precision-weighting of that error accounts for the confidence, pleasure, and attentional capture (the feeling of insight). The account aligns with the phenomenology, accuracy, and neural unfolding of insight, as well as its effects on belief and decision-making. Dangers include the formation and entrenchment of false beliefs and vulnerability of insights under psychoactive substances and misinformation.
Neuroscience and biobehavioral reviews
September 1, 2022
Jeremy I Skipper
Language, especially inner speech, is hypothesized to generate and sustain higher-order self-awareness. A 'HOLISTIC' model proposes a core set of inner speech production regions that initiate the experience of feeling and hearing words, which acquire affective qualities through activation of associated sensory, motor, and emotional representations in a largely unconscious dynamic periphery distributed throughout the brain. Responding to these words sustains network activity involving default mode activation and prefrontal and thalamic/brainstem selection of contextually relevant responses. The model offers a more parsimonious account of the neural correlates of consciousness and has implications for mental health and wellbeing.
Neuroscience and biobehavioral reviews
May 1, 2013
Zoran Vukadinovic, Merrill S Herman, Ivana Rosenzweig
Cannabis use is a strong environmental risk factor for schizophrenia, but the mechanism is unknown. This theoretical paper argues that exogenous cannabinoids may directly affect T-type calcium channels in the thalamus. These channels are critical for amplifying corticothalamic inputs and generating neuronal burst firing, which is important for trans-thalamic cortico-cortical interactions. Interference with burst firing could impair these interactions, leading to a relative disconnection between cortical areas, reduced ability to recognize re-afferent sensory inputs, and psychosis. Δ(9)THC may be more detrimental than cannabidiol because it increases thalamic neuron excitability through its direct effect on T-type calcium channels.
Neuroscience and biobehavioral reviews
July 1, 2008
Věra Bubeníková-valešová, Jiří Horáček, Monika Vrajová et al.
Research using non-competitive NMDA receptor antagonists—phencyclidine, ketamine, and dizocilpine—produces behavioral changes in humans and rats that resemble schizophrenia symptoms. Acute and chronic administration models show phenomenological validity and help test potential antipsychotic drugs. However, schizophrenia's pathophysiology remains unexplained. The neurodevelopmental model suggests that early-life NMDA receptor antagonism increases apoptosis or alters glutamatergic receptor function during central nervous system development, leading to psychosis that often emerges only in adulthood. Chronic antagonist administration triggers adaptation mechanisms that match findings in schizophrenia patients, making this model useful for studying the disease's pathophysiology.
Neuroscience and biobehavioral reviews
January 1, 1998
F Sams-Dodd
Phencyclidine (PCP) can induce a model psychosis in humans that mimics both positive and negative symptoms of schizophrenia. In the social interaction test, PCP causes stereotyped behavior and social isolation in rats, which can be inhibited by antipsychotic drugs. To further evaluate this model's predictive validity, drugs without antipsychotic activity—diazepam (0.02–17.5 µmol/kg), citalopram (0.62–19.8 µmol/kg), methadone (0.36–5.8 µmol/kg), and naloxone (0.34–22.0 µmol/kg)—were tested. None specifically inhibited PCP-induced behaviors, suggesting that only antipsychotic drugs can do so.