We agree that consciousness, as we know it, is inextricably biological - but not every biological detail is essential. Identifying which features are necessary, across scales, is vital for assessing the limits of computationalism. This process will reveal a richer, more biologically informed computationalism - one that future machines could, in principle, instantiate, but only after much deeper...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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, 2023Timo 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...
When do we die and what happens in the brain when we die? The mystery around these questions has engaged mankind for centuries. Despite the challenges to obtain recordings of the dying brain, recent studies have contributed to better understand the processes occurring during the last moments of life. In this review, we summarize the literature on neurophysiological changes around the time of...
Background: Recent research has shown promising results for the therapeutic benefits of psychedelics. One popular view claims that these benefits are mediated by the subjective experiences induced by these substances. Based on this, we designed a virtual reality experience, Psyrreal, that mimics the phenomenological components of psychedelic experiences. Aims: We aimed to investigate the...
This primer aims to provide a concise description of the Dendritic Integration Theory (DIT) of consciousness. We consider the motivation for DIT, the evidence for it, and how it fits with other theories of consciousness.
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...
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:...
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...
Rapid advances in neuroscience have provided remarkable breakthroughs in understanding the brain on many fronts. Although promising, the role of these advancements in solving the problem of consciousness is still unclear. Based on technologies conceivably within the grasp of modern neuroscience, we discuss a thought experiment in which neural activity, in the form of action potentials, is...
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...
Recent breakthroughs in neurobiology indicate that the time is ripe to understand how cellular-level mechanisms are related to conscious experience. Here, we highlight the biophysical properties of pyramidal cells, which allow them to act as gates that control the evolution of global activation patterns. In conscious states, this cellular mechanism enables complex sustained dynamics within the...
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...