Neuron
May 15, 2024
Johan F Storm, P Christiaan Klink, Jaan Aru et al.
108 citations
Consciousness may be explained by multiple, partly compatible theories rather than a single winner. A group of scientists representing different theories argue that various accounts often address different aspects or mechanistic levels of conscious experience, so they do not necessarily contradict each other. Instead, several theories may converge on fundamental neuronal mechanisms and be complementary, allowing multiple perspectives to simultaneously advance understanding. The authors advocate for unifying, integration-oriented approaches that combine valuable elements from diverse theories, an approach that has so far been largely neglected.
Brain : a journal of neurology
September 14, 2022
James M Shine, Claire O'Callaghan, Ishan C Walpola et al.
63 citations
Serotonin in the brain can be understood as an extension of the gut's serotonergic system, which controls digestion. Central serotonin activity mimics a digestion/satiety circuit, where low serotonergic tone facilitates cognitive automaticity and higher tone helps identify flexible solutions when initial responses fail. This perspective explains serotonin's roles in reward processing, exploration, and psychedelic experiences, and clarifies links between serotonergic dysfunction and psychiatric symptoms.
Consciousness and cognition
August 1, 2017
Jaan Aru, Talis Bachmann
42 citations
Conscious experience depends on attention and expectation, but some argue it can occur without attention. Experiments on iconic memory (IM) are often cited as evidence for attention-independent consciousness. A prior study found that when attention is diverted from an IM letter display, people fail to notice missing letters. This work replicates and extends that finding by measuring subjective visibility and testing post-cue effects. Results show that participants who do not realize letters are absent perceive illusory letters, indicating phenomenal consciousness persists even without attention. Expectation generates illusory content that overwrites valid IM content, suggesting this experimental paradigm cannot reliably assess iconic memory content.
November 26, 2021
Kadi Tulver, Karl Kristjan Kaup, Ruben Laukkonen et al.
16 citations
preprint
Insight, the sudden understanding of a solution or idea, is not only central to creative problem-solving but also plays a key role in psychotherapy, meditation, the emergence of delusions in schizophrenia, and the therapeutic effects of psychedelics. This integrative review draws on literature from multiple fields to examine the event of insight, its prerequisites, and its consequences. It highlights commonalities and differences across these domains, aiming to bridge gaps between disparate research traditions and inspire interdisciplinary efforts to understand this core cognitive process.
Neuroscience and biobehavioral reviews
February 1, 2026
Borjan Milinkovic, Jaan Aru
7 citations
Consciousness in biological systems arises from two fundamental computational features absent in current artificial intelligence: scale-inseparable, substrate-dependent multiscale processing as a metabolic optimization strategy, and continuous-valued computations performed by the fluidic substrate alongside discrete operations. These features are essential to the brain's mode of computation. The absence of consciousness in artificial systems reflects a deeper divide between digital and biological computation, not merely missing functional organization. The authors outline foundational principles of a biological theory of computation and explain why current AI systems are unlikely to replicate conscious processing as it arises in biology.
July 5, 2022
Kristjan Kaup, Madis Vasser, Kadi Tulver et al.
7 citations
preprint
A 2-day virtual reality intervention called Psyrreal, designed to mimic the phenomenological components of psychedelic experiences, combined with psychological support, led to significant decreases in depressive symptoms at a 2-week follow-up in ten participants with mild-to-moderate depression. The intervention also appeared to promote insight and alterations in the sense of self in some people, based on thematic analysis of semi-structured interviews. These preliminary results suggest potential for VR experiences in treating depressive symptoms and warrant further research.
Frontiers in psychiatry
January 1, 2023
Karl Kristjan Kaup, Madis Vasser, Kadi Tulver et al.
3 citations
correction
No Summary
May 28, 2023
Timo Siimon, Kadi Tulver, Kristjan Kaup et al.
2 citations
preprint
A psychedelic virtual reality environment, which replicates visual content experienced under the influence of psychedelics, helped people stuck on a real-life creative problem reach new insights more effectively than a control VR environment. The thematic analysis indicated that the psychedelic VR supported several aspects of creative insight, likely by relaxing the person's fixed assumptions about their problem. The results are encouraging but need to be tested in larger studies.
Neuroscience and biobehavioral reviews
June 1, 2026
Javier Hidalgo Jiménez, Karl Kristjan Kaup, Jaan Aru
1 citation
Psychedelics such as LSD and NBOH produce complex, heterogeneous effects on brain cells, challenging the idea that they simply increase cortical excitability. A systematic review of 23 in vitro and 26 in vivo electrophysiological studies found that these compounds modulate both excitatory and inhibitory processes in a cell-type- and compartment-specific manner, with biphasic, dose-dependent, and context-sensitive responses. Activation of 5-HT2A receptors triggers intricate calcium signaling, downregulating excitatory currents and firing rates in many neurons while enhancing glutamate release and activating a subset of projection fibers. Modulation of presynaptic and extrasynaptic GluN2B-containing NMDA receptors appears central to these effects.
Journal of Psychopharmacology
February 16, 2026
Marten Kase, Karl Kristjan Kaup, Jaan Aru
1 citation
A systematic review of 32 placebo-controlled studies from 1990 to 2025 examined the acute and post-acute effects of LSD, DMT, and psilocybin on cognitive and psychological functions. Psychedelics tended to enhance emotional empathy but had no effect on cognitive empathy. Effects on memory varied by task and timing, with some impairments, enhancements, or no change. Dose-dependent impairments occurred in reaction time, attention, and inhibition tasks, though some studies found no effects. Recognition of negative stimuli was impaired under acute effects. Findings on cognitive flexibility were mixed. Many studies had small samples, and finding a reliable placebo is challenging due to psychedelics' unique subjective effects.
Frontiers in neuroscience
January 1, 2025
Albert Gidon, Jaan Aru, Matthew E. Larkum
1 citation
Simulating a simple computation in an artificial neural network, researchers recorded neuron activity during visual stimulation and replayed those signals back into the same neurons. This replay degraded the computation by erasing counterfactual activity patterns—alternative neural states that could have occurred—while leaving ongoing brain activity unchanged. This outcome reveals a disconnect between neural activity and computational structure, challenging the computational functionalist view that consciousness emerges from the right computations, whether in machines or biological brains.
February 12, 2024
Kadi Tulver, Kristjan Kaup, Jaan Aru
preprint
A new framework proposes that diverse mental breakthroughs—from everyday problem-solving insights to profound personal transformations—share common mechanisms of representational change. The model identifies three core components—tension, altered salience, and enhanced flexibility—as prerequisites for cognitive restructuring, interacting in an iterative cycle that influences insight emergence. The intensity and impact of an 'aha-moment' depend on how central the conflict is within one's conceptual landscape and the degree to which existing mental models are challenged. Drawing on psychotherapy, contemplative science, and psychedelic research, this theoretical account aims to unify explanations of insight phenomena across disciplines.
arXiv Preprint Archive
June 26, 2025
Jaan Aru
The science of consciousness has made progress, but key questions remain unanswered. Moving forward may require revising fundamental assumptions rather than relying on the same theoretical commitments. A key assumption is that neural correlates of consciousness are found at the level of spiking responses, but this should not be taken for granted. Another assumption is that the computations underlying consciousness are close to being understood, yet they may be far more complex than current theories envision, and there is little reason to think consciousness is an abstract computation. Consciousness research could benefit from investigating internal changes like aha-moments. The piece questions what theories the science of consciousness truly needs.