Neuroscience and Biobehavioral Reviews
July 1, 2026
Karl Kristjan Kaup, Javier Hidalgo Jiménez, Jaan Aru
Classical serotonergic psychedelics primarily exert their profound effects through agonism at the serotonin 2A (5-HT2A) receptor, which is abundantly expressed in many cortical regions, particularly in layer V pyramidal neurons of associative and visual areas. At the cellular level, these receptors are predominantly localized postsynaptically on the soma and apical dendrites. This review...
Neuroscience and Biobehavioral Reviews
June 1, 2026
Javier Hidalgo Jiménez, Karl Kristjan Kaup, Jaan Aru
1 citation
Serotonergic psychedelics are known for their profound effects on consciousness and are gaining renewed interest as potential psychiatric treatments. These advances underscore the need to clarify the mechanisms of action of these compounds. This systematic review compiles and critically evaluates 23 in vitro and 26 in vivo electrophysiological studies on psychedelic compounds, with an emphasis...
PsyArXiv
May 29, 2026
Zefan Zheng, Robert Chis-Ciure, Peter Thestrup Waade et al.
1 citation
preprint
Consciousness science is fragmented, and empirical investigations are confined within each theory of consciousness’ (TOC) framework. Proliferating ToCs accumulate anomalies without progress, operating orthogonally. The principle of recurrency – functional and architectural – offers a unifying, mechanistic scaffold for consciousness to arise. We show that all theories tacitly invoke feedback...
Journal of Psychopharmacology
February 16, 2026
Marten Kase, Karl Kristjan Kaup, Jaan Aru
1 citation
We carried out a systematic review of modern-era (1990-2025) placebo-controlled studies assessing the acute and post-acute effects of lysergic acid diethylamide, dimethyltryptamine and psilocybin on cognitive and psychological functions. From February 28 to March 19, 2025, PubMed and APA PsychINFO were systematically searched for placebo-controlled studies examining the influence of...
Neuroscience and Biobehavioral Reviews
February 1, 2026
Borjan Milinkovic, Jaan Aru
7 citations
The rapid advances in the capabilities of Large Language Models (LLMs) have galvanised public and scientific debates over whether artificial systems might one day be conscious. Prevailing optimism is often grounded in computational functionalism: the assumption that consciousness is determined solely by the right pattern of information processing, independent of the physical substrate. Opposing...
Philosophical Psychology
2026
Juensung J. Kim, Kadi Tulver, Jaan Aru et al.
1 citation
We argue that the powerful transformative effects of mystical-type experiences can be understood using the same machinery that underlies insight problem solving, and that both mystical experiences and insight are species of a genus of “realization experiences”: experiences wherein some phenomenon or piece of information becomes suddenly experienced as real or true. Specifically, we argue that...
arXiv (Cornell University)
November 20, 2025
Andres Campero, Derek Shiller, Jaan Aru et al.
We develop a taxonomical framework for classifying challenges to the possibility of consciousness in digital artificial intelligence systems. This framework allows us to identify the level of granularity at which a given challenge is intended (the levels we propose correspond to Marr's levels) and to disambiguate its degree of force: is it a challenge to computational functionalism that leaves...
arXiv Preprint Archive
June 26, 2025
Jaan Aru
The science of consciousness has been successful over the last decades. Yet, it seems that some of the key questions remain unanswered. Perhaps, as a science of consciousness, we cannot move forward using the same theoretical commitments that brought us here. It might be necessary to revise some assumptions we have made along the way. In this piece, I offer no answers, but I will question some...
Frontiers in Neuroscience
2025
Albert Gidon, Jaan Aru, Matthew E Larkum
1 citation
Artificial neural networks are becoming more advanced and human-like in detail and behavior. The notion that machines mimicking human brain computations might be conscious has recently caused growing unease. Here, we explored a common computational functionalist view, which holds that consciousness emerges when the right computations occur-whether in a machine or a biological brain. To test...
Neuron
May 15, 2024
Johan F. Storm, P Christiaan Klink, Jaan Aru et al.
108 citations
How is conscious experience related to material brain processes? A variety of theories aiming to answer this age-old question have emerged from the recent surge in consciousness research, and some are now hotly debated. Although most researchers have so far focused on the development and validation of their preferred theory in relative isolation, this article, written by a group of scientists...
February 12, 2024
Kadi Tulver, Kristjan Kaup, Jaan Aru
preprint
We present a novel framework for understanding the diverse spectrum of mental breakthrough events, ranging from problem-solving insights to profound personal transformations. We propose that these events, while varied in expression and impact, share common underlying mechanisms of representational change. We also hypothesise that the differences in phenomenological intensity can be...
Trends in Neurosciences
December 1, 2023
Jaan Aru, Matthew E Larkum, James M Shine
Interactions with large language models (LLMs) have led to the suggestion that these models may soon be conscious. From the perspective of neuroscience, this position is difficult to defend. For one, the inputs to LLMs lack the embodied, embedded information content characteristic of our sensory contact with the world around us. Secondly, the architectures of present-day artificial intelligence...
Proceedings of the National Academy of Sciences of the United States of America
November 14, 2023
Brandon R Munn, Eli J Müller, Jaan Aru et al.
Understanding the neurobiological mechanisms underlying consciousness remains a significant challenge. Recent evidence suggests that the coupling between distal-apical and basal-somatic dendrites in thick-tufted layer 5 pyramidal neurons (L5PN), regulated by the nonspecific-projecting thalamus, is crucial for consciousness. Yet, it is uncertain whether this thalamocortical mechanism can support...
May 28, 2023
Timo Siimon, Kadi Tulver, Kristjan Kaup et al.
2 citations
preprint
The goal of the present work was to study the potential of facilitating creative insight in a real-life setting. To that end, participants were recruited who were struggling with a creative problem and had reached an impasse. Based on previous research, we hypothesized that solutions might be facilitated through virtual reality that replicates visual content experienced under the influence of...
Front Psychiatry
March 1, 2023
Karl Kristjan Kaup, Madis Vasser, Kadi Tulver et al.
22 citations
Psychedelic replications in virtual reality and their potential as a therapeutic instrument: an open-label feasibility study.
Consciousness and Cognition
February 1, 2023
Talis Bachmann, Jaan Aru
Progress in the science of consciousness depends on the experimental paradigms and varieties of contrastive analysis available to researchers. Here we highlight paradigms where the object is represented in consciousness as a set of its features but the interpretation of this set alternates in consciousness. We group experimental paradigms with this property under the label "conscious...
Frontiers in Psychiatry
2023
Karl Kristjan Kaup, Madis Vasser, Kadi Tulver et al.
3 citations
correction
Karl Kristjan Kaup1*, Madis Vasser1, Kadi Tulver1, Mari Munk2, Juhan Pikamäe1,3, Jaan Aru1*correcting author names or adding authors. Insert the correct version of the author list)1 Institute of Computer Science, University of Tartu, Estonia2 Psychiatry Clinic of North Estonia Medical Centre3 Institute of Molecular and Cell Biology, University of Tartu, Estonia* Correspondence:...
Brain : a journal of neurology
September 14, 2022
James M Shine, Claire O'Callaghan, Ishan C Walpola et al.
63 citations
The neuromodulatory arousal system imbues the nervous system with the flexibility and robustness required to facilitate adaptive behaviour. While there are well understood mechanisms linking dopamine, noradrenaline and acetylcholine to distinct behavioural states, similar conclusions have not been as readily available for serotonin. Fascinatingly, despite clear links between serotonergic...
November 26, 2021
Kadi Tulver, Karl Kristjan Kaup, Ruben Laukkonen et al.
16 citations
preprint
Occasionally, a solution or idea arrives as a sudden understanding - an insight. Insight has been considered an “extra” ingredient of creative thinking and problem-solving. Here we propose that insight is central in seemingly distinct areas of research. Drawing on literature from a variety of fields, we show that besides being commonly studied in problem-solving literature, insight is also a...
Frontiers in Systems Neuroscience
August 30, 2019
Jaan Aru, Mototaka Suzuki, Renate Rutiku et al.
One fundamental feature of consciousness is that the contents of consciousness depend on the state of consciousness. Here, we propose an answer to why this is so: both the state and the contents of consciousness depend on the activity of cortical layer 5 pyramidal (L5p) neurons. These neurons affect both cortical and thalamic processing, hence coupling the cortico-cortical and thalamo-cortical...
Consciousness and Cognition
August 1, 2017
Jaan Aru, Talis Bachmann
42 citations
Conscious experience is modulated by attention and expectation, yet is believed to be independent of attention. The experiments on iconic memory (IM) are usually taken as support for this claim. However, a recent experiment demonstrated that when attention is diverted away from the IM letter display subjects fail to see the absence of IM letters. Here we contribute to the ongoing debate by...
Neuroscience of Consciousness
2016
Jaan Aru, Renate Rutiku, Michael Wibral et al.
Constructive theories of brain function such as predictive coding posit that prior knowledge affects our experience of the world quickly and directly. However, it is yet unknown how swiftly prior knowledge impacts the neural processes giving rise to conscious experience. Here we used an experimental paradigm where prior knowledge augmented perception and measured the timing of this effect with...
Advances in Consciousness Research
June 17, 2015
Jaan Aru, Talis Bachmann, Wolf Singer et al.
It has been proposed that one key step for solving the mystery of consciousness is to locate the neural correlates of consciousness (NCC). The experimental paradigms for revealing the NCC have commonly applied the contrast between conditions with and without conscious perception. However, such contrast does not exclusively reveal the neural processes directly related to conscious experience of...
Neuroscience & Biobehavioral Reviews
December 17, 2011
Jaan Aru, Talis Bachmann, Wolf Singer et al.
612 citations
Solving the problem of consciousness remains one of the biggest challenges in modern science. One key step towards understanding consciousness is to empirically narrow down neural processes associated with the subjective experience of a particular content. To unravel these neural correlates of consciousness (NCC) a common scientific strategy is to compare perceptual conditions in which...