Recent years have seen a blossoming of theories about the biological and physical basis of consciousness. Good theories guide empirical research, allowing us to interpret data, develop new experimental techniques and expand our capacity to manipulate the phenomenon of interest. Indeed, it is only when couched in terms of a theory that empirical discoveries can ultimately deliver a satisfying understanding of a phenomenon. However, in the case of consciousness, it is unclear how current theories relate to each other, or whether they can be empirically distinguished. To clarify this complicated landscape, we review four prominent theoretical approaches to consciousness: higher-order theories, global workspace theories, re-entry and predictive processing theories and integrated information theory. We describe the key characteristics of each approach by identifying which aspects of consciousness they propose to explain, what their neurobiological commitments are and what empirical data are adduced in their support. We consider how some prominent empirical debates might distinguish among these theories, and we outline three ways in which theories need to be developed to deliver a mature regimen of theory-testing in the neuroscience of consciousness. There are good reasons to think that the iterative development, testing and comparison of theories of consciousness will lead to a deeper understanding of this most profound of mysteries.
This is a preview of subscription content, access via your institution
Open Access articles citing this article.
Erkenntnis Open Access 14 October 2022
Subscribe to Nature+
Get immediate online access to Nature and 55 other Nature journal
Subscribe to Journal
Get full journal access for 1 year
only $6.58 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Tax calculation will be finalised during checkout.
Get time limited or full article access on ReadCube.
All prices are NET prices.
Crick, F. & Koch, C. Towards a neurobiological theory of consciousness. Semin. Neurosci. 2, 263–275 (1990).
Metzinger, T. (ed.) Neural Correlates of Consciousness: Empirical and Conceptual Questions (MIT Press, 2000).
Koch, C., Massimini, M., Boly, M. & Tononi, G. Neural correlates of consciousness: progress and problems. Nat. Rev. Neurosci. 17, 307–321 (2016).
de Graaf, T. A., Hsieh, P. J. & Sack, A. T. The ‘correlates’ in neural correlates of consciousness. Neurosci. Biobehav. Rev. 36, 191–197 (2012).
Aru, J., Bachmann, T., Singer, W. & Melloni, L. Distilling the neural correlates of consciousness. Neurosci. Biobehav. Rev. 36, 737–746 (2012).
Tsuchiya, N., Wilke, M., Frassle, S. & Lamme, V. A. No-report paradigms: extracting the true neural correlates of consciousness. Trends Cogn. Sci. 19, 757–770 (2015).
Klein, C., Hohwy, J. & Bayne, T. Explanation in the science of consciousness: from the neural correlates of consciousness (NCCs) to the difference-makers of consciousness (DMCs). Philos. Mind Sci. https://doi.org/10.33735/phimisci.2020.II.60 (2020).
Michel, M. et al. Opportunities and challenges for a maturing science of consciousness. Nat. Hum. Behav. 3, 104–107 (2019).
Seth, A. K. Consciousness: the last 50 years (and the next). Brain Neurosci. Adv. 2, 2398212818816019 (2018).
Seth, A. K. Explanatory correlates of consciousness: theoretical and computational challenges. Cogn. Comput. 1, 50–63 (2009).
Searle, J. The Rediscovery of the Mind (MIT Press, 1992).
Varela, F. J. Neurophenomenology: a methodological remedy for the hard problem. J. Conscious. Stud. 3, 330–350 (1996).
Seth, A. K. Being You: A New Science of Consciousness (Faber & Faber, 2021).
Dennett, D. C. Welcome to strong illusionism. J. Conscious. Stud. 26, 48–58 (2019).
Frankish, K. Illusionism as a Theory of Consciousness (Imprint Academic, 2017).
Wiese, W. The science of consciousness does not need another theory, it needs a minimal unifying model. Neurosci. Conscious. 2020, niaa013 (2020).
Melloni, L., Mudrik, L., Pitts, M. & Koch, C. Making the hard problem of consciousness easier. Science 372, 911–912 (2021). This work sets out how an adversarial collaboration is planning to arbitrate between integrated information and global workspace ToCs.
Hameroff, S. & Penrose, R. Consciousness in the universe: a review of the ‘Orch OR’ theory. Phys. Life Rev. 11, 39–78 (2014).
Chalmers, D. J. & McQueen, K. in Quantum Mechanics and Consciousness (ed Gao, S.) (Oxford Univ. Press, 2022).
Nagel, T. What is it like to be a bat? Philos. Rev. 83, 435–450 (1974).
Bayne, T., Hohwy, J. & Owen, A. M. Are there levels of consciousness? Trends Cogn. Sci. 20, 405–413 (2016). This work challenges the common unidimensional notion of ‘level of consciousness’, outlining an alternative, richer, multidimensional account.
Metzinger, T. Being No-One (MIT Press, 2003).
Damasio, A. Self Comes To Mind: Constructing the Conscious Brain (William Heinemann, 2010).
Park, H. D. & Tallon-Baudry, C. The neural subjective frame: from bodily signals to perceptual consciousness. Philos. Trans. R. Soc. Lond. B Biol. Sci. 369, 20130208 (2014).
Bayne, T. The Unity of Consciousness (Oxford Univ. Press, 2010).
Bayne, T. & Chalmers, D. J. in The Unity of Consciousness: Binding, Integration, and Dissociation (ed Cleeremans, A.) 23–58 (Oxford Univ. Press, 2003).
Cummins, R. Functional analysis. J. Philos. 72, 741–765 (1975).
Blake, R., Brascamp, J. & Heeger, D. J. Can binocular rivalry reveal neural correlates of consciousness? Philos. Trans. R. Soc. Lond. B Biol. Sci. 369, 20130211 (2014).
Signorelli, C. M., Szczotka, J. & Prentner, R. Explanatory profiles of models of consciousness — towards a systematic classification. Neurosci. Conscious. 2021, niab021 (2021).
Lau, H. & Rosenthal, D. Empirical support for higher-order theories of conscious awareness. Trends Cogn. Sci. 15, 365–373 (2011). This work presents a summary of empirical evidence favouring higher-order ToCs.
Rosenthal, D. Consciousness and Mind (Clarendon, 2005).
Brown, R. The HOROR theory of phenomenal consciousness. Philos. Stud. 172, 1783–1794 (2015).
Cleeremans, A. Consciousness: the radical plasticity thesis. Prog. Brain Res. 168, 19–33 (2008).
Cleeremans, A. et al. Learning to be conscious. Trends Cogn. Sci. 24, 112–123 (2020).
Fleming, S. M. Awareness as inference in a higher-order state space. Neurosci. Conscious. 2020, niz020 (2020).
Lau, H. Consciousness, metacognition, and perceptual reality monitoring. Preprint at ArXiv https://doi.org/10.31234/osf.io/ckbyf (2020).
Gershman, S. J. The generative adversarial brain. Front. Artif. Intell. https://doi.org/10.3389/frai.2019.00018 (2019).
Cohen, M. A., Dennett, D. C. & Kanwisher, N. What is the bandwidth of perceptual experience? Trends Cogn. Sci. 20, 324–335 (2016).
Haun, A. M., Tononi, G., Koch, C. & Tsuchiya, N. Are we underestimating the richness of visual experiences? Neurosci. Conscious. 3, 1–4 (2017).
Odegaard, B., Chang, M. Y., Lau, H. & Cheung, S. H. Inflation versus filling-in: why we feel we see more than we actually do in peripheral vision. Philos. Trans. R. Soc. Lond. B Biol. Sci. https://doi.org/10.1098/rstb.2017.0345 (2018).
LeDoux, J. E. & Brown, R. A higher-order theory of emotional consciousness. Proc. Natl Acad. Sci. USA 114, E2016–E2025 (2017).
Morrison, J. Perceptual confidence. Anal. Philos. 78, 99–147 (2016).
Peters, M. A. K. Towards characterizing the canonical computations generating phenomenal experience. Preprint at PsyArXiv https://doi.org/10.31234/osf.io/bqfr6 (2021).
Rosenthal, D. Consciousness and its function. Neuropsychologia 46, 829–840 (2008).
Charles, L., Van Opstal, F., Marti, S. & Dehaene, S. Distinct brain mechanisms for conscious versus subliminal error detection. Neuroimage 73, 80–94 (2013).
Brown, R., Lau, H. & LeDoux, J. E. Understanding the higher-order approach to consciousness. Trends Cogn. Sci. 23, 754–768 (2019).
Baars, B. J. A Cognitive Theory of Consciousness (Cambridge Univ. Press, 1988).
Dehaene, S. & Changeux, J. P. Experimental and theoretical approaches to conscious processing. Neuron 70, 200–227 (2011).
Mashour, G. A., Roelfsema, P., Changeux, J. P. & Dehaene, S. Conscious processing and the global neuronal workspace hypothesis. Neuron 105, 776–798 (2020). This work presents a summary of the neuronal GWT and its supporting evidence.
Dehaene, S., Sergent, C. & Changeux, J. P. A neuronal network model linking subjective reports and objective physiological data during conscious perception. Proc. Natl Acad. Sci. USA 100, 8520–8525 (2003).
Naccache, L. Why and how access consciousness can account for phenomenal consciousness. Philos. Trans. R. Soc. Lond. B Biol. Sci. https://doi.org/10.1098/rstb.2017.0357 (2018).
Mashour, G. A. Cognitive unbinding: a neuroscientific paradigm of general anesthesia and related states of unconsciousness. Neurosci. Biobehav. Rev. 37, 2751–2759 (2013).
Demertzi, A. et al. Human consciousness is supported by dynamic complex patterns of brain signal coordination. Sci. Adv. 5, eaat7603 (2019). This large empirical study of functional connectivity patterns across different global states of consciousness focuses on how these patterns relate to underlying structural connectivity.
Barttfeld, P. et al. Signature of consciousness in the dynamics of resting-state brain activity. Proc. Natl Acad. Sci. USA 112, 887–892 (2015).
Uhrig, L. et al. Resting-state dynamics as a cortical signature of anesthesia in monkeys. Anesthesiology 129, 942–958 (2018).
Carruthers, P. Human and Animal Minds: The Consciousness Questions Laid to Rest (Oxford Univ. Press, 2019).
Tononi, G. Consciousness as integrated information: a provisional manifesto. Biol. Bull. 215, 216–242 (2008).
Tononi, G. Integrated information theory of consciousness: an updated account. Arch. Ital. Biol. 150, 293–329 (2012).
Tononi, G., Boly, M., Massimini, M. & Koch, C. Integrated information theory: from consciousness to its physical substrate. Nat. Rev. Neurosci. 17, 450–461 (2016). This work presents an account of the core claims and concepts of the integrated information ToC.
Oizumi, M., Albantakis, L. & Tononi, G. From the phenomenology to the mechanisms of consciousness: integrated information theory 3.0. PLoS Comput. Biol. 10, e1003588 (2014).
Tononi, G. & Koch, C. Consciousness: here, there and everywhere? Philos. Trans. R. Soc. Lond. B Biol. Sci. https://doi.org/10.1098/rstb.2014.0167 (2015).
Haun, A. M. & Tononi, G. Why does space feel the way it does? Towards a principled account of spatial experienc. Entropy 21, 1160 (2019).
Albantakis, L., Hintze, A., Koch, C., Adami, C. & Tononi, G. Evolution of integrated causal structures in animats exposed to environments of increasing complexity. PLoS Comput. Biol. 10, e1003966 (2014).
Marshall, W., Gomez-Ramirez, J. & Tononi, G. Integrated information and state differentiation. Front. Psychol. 7, 926 (2016).
Lamme, V. A. Towards a true neural stance on consciousness. Trends Cogn. Sci. 10, 494–501 (2006).
Lamme, V. A. & Roelfsema, P. R. The distinct modes of vision offered by feedforward and recurrent processing. Trends Neurosci. 23, 571–579 (2000).
Hohwy, J. & Seth, A. K. Predictive processing as a systematic basis for identifying the neural correlates of consciousness. Philos. Mind Sci. 1, 3 (2020).
Lamme, V. A., Super, H., Landman, R., Roelfsema, P. R. & Spekreijse, H. The role of primary visual cortex (V1) in visual awareness. Vis. Res. 40, 1507–1521 (2000).
Pascual-Leone, A. & Walsh, V. Fast backprojections from the motion to the primary visual area necessary for visual awareness. Science 292, 510–512 (2001). This early study uses transcranial magnetic stimulation to reveal a role for re-entrant activity in conscious visual perception in humans.
Boehler, C. N., Schoenfeld, M. A., Heinze, H. J. & Hopf, J. M. Rapid recurrent processing gates awareness in primary visual cortex. Proc. Natl Acad. Sci. USA 105, 8742–8747 (2008).
Lamme, V. A. How neuroscience will change our view on consciousness. Cogn. Neurosci. 1, 204–220 (2010).
von Helmholtz, H. Handbuch der Phsyiologischen Optik [German] (Voss, 1867).
Clark, A. Whatever next? Predictive brains, situated agents, and the future of cognitive science. Behav. Brain Sci. 36, 181–204 (2013). This work presents a classic exposition of predictive processing and its relevance for perception, cognition and action.
Friston, K. J. The free-energy principle: a unified brain theory? Nat. Rev. Neurosci. 11, 127–138 (2010).
Seth, A. K. in Open MIND (eds Windt, J. M. & Metzinger, T.) (MIND Group, 2015).
Friston, K. J. Am I self-conscious? (Or does self-organization entail self-consciousness?). Front. Psychol. 9, 579 (2018).
Seth, A. K. & Tsakiris, M. Being a beast machine: the somatic basis of selfhood. Trends Cogn. Sci. 22, 969–981 (2018).
Bruineberg, J., Dolega, K., Dewhurst, J. & Baltieri, M. The Emperor’s new Markov blankets. Behav. Brain Sci. https://doi.org/10.1017/S0140525X21002351 (2021).
Hohwy, J. The Predictive Mind (Oxford Univ. Press, 2013).
Rao, R. P. & Ballard, D. H. Predictive coding in the visual cortex: a functional interpretation of some extra-classical receptive-field effects. Nat. Neurosci. 2, 79–87 (1999).
Teufel, C. & Fletcher, P. C. Forms of prediction in the nervous system. Nat. Rev. Neurosci. 21, 231–242 (2020).
Friston, K. J., Daunizeau, J., Kilner, J. & Kiebel, S. J. Action and behavior: a free-energy formulation. Biol. Cybern. 102, 227–260 (2010).
Parr, T. & Friston, K. J. Generalised free energy and active inference. Biol. Cybern. 113, 495–513 (2019).
Pennartz, C. M. A. Consciousness, representation, action: the importance of being goal-directed. Trends Cogn. Sci. 22, 137–153 (2018).
Williford, K., Bennequin, D., Friston, K. & Rudrauf, D. The projective consciousness model and phenomenal selfhood. Front. Psychol. 9, 2571 (2018).
Hohwy, J. New directions in predictive processing. Mind Lang. 35, 209–223 (2020).
Seth, A. K. A predictive processing theory of sensorimotor contingencies: explaining the puzzle of perceptual presence and its absence in synesthesia. Cogn. Neurosci. 5, 97–118 (2014).
O’Regan, J. K. & Noë, A. A sensorimotor account of vision and visual consciousness. Behav. Brain Sci. 24, 939–973; discussion 973–1031 (2001). This primary description of the sensorimotor ToC argues that conscious perception is intimately related to action.
Seth, A. K. Interoceptive inference, emotion, and the embodied self. Trends Cogn. Sci. 17, 565–573 (2013). This work presents a theoretical application of predictive processing to interoception and physiological regulation, relating this to experiences of emotion and selfhood.
Barrett, L. F. The theory of constructed emotion: an active inference account of interoception and categorization. Soc. Cogn. Affect. Neurosci. 12, 1833 (2017).
Solms, M. The hard problem of consciousness and the free energy principle. Front. Psychol. 9, 2714 (2018).
Hohwy, J., Roepstorff, A. & Friston, K. Predictive coding explains binocular rivalry: an epistemological review. Cognition 108, 687–701 (2008).
Parr, T., Corcoran, A. W., Friston, K. J. & Hohwy, J. Perceptual awareness and active inference. Neurosci. Conscious. 2019, niz012 (2019).
Friston, K. J., FitzGerald, T., Rigoli, F., Schwartenbeck, P. & Pezzulo, G. Active inference: a process theory. Neural Comput. 29, 1–49 (2017).
Boly, M. et al. Preserved feedforward but impaired top-down processes in the vegetative state. Science 332, 858–862 (2011). This neuroimaging study uses dynamic causal modelling to show that loss of consciousness in the vegetative state is associated with impaired top-down connectivity from frontal to temporal cortices.
Parr, T. & Friston, K. J. Working memory, attention, and salience in active inference. Sci. Rep. 7, 14678 (2017).
Chalmers, A. What is This Thing Called Science? (Queensland Univ. Press, 2013).
Godfrey-Smith, P. G. Theory and Reality: An Introduction to the Philosophy of Science 2nd edn (Univ. Chicago Press, 2021).
Lipton, P. Inference to the Best Explanation (Routledge, 2004).
Lau, H. & Passingham, R. E. Relative blindsight in normal observers and the neural correlate of visual consciousness. Proc. Natl Acad. Sci. USA 103, 18763–18768 (2006). This empirical study compares conscious and unconscious visual perception in humans, controlling for performance, and reveals differences in prefrontal activation.
van Vugt, B. et al. The threshold for conscious report: signal loss and response bias in visual and frontal cortex. Science 360, 537–542 (2018). This empirical study tracks the time course of neural signals in primate frontal cortex, showing that perceived stimuli elicit sustained activity, when compared with non-perceived stimuli.
Gaillard, R. et al. Converging intracranial markers of conscious access. PLoS Biol. 7, e61 (2009).
Panagiotaropoulos, T. I., Deco, G., Kapoor, V. & Logothetis, N. K. Neuronal discharges and gamma oscillations explicitly reflect visual consciousness in the lateral prefrontal cortex. Neuron 74, 924–935 (2012).
Kapoor, V. et al. Decoding internally generated transitions of conscious contents in the prefrontal cortex without subjective reports. Nat. Comm. 13, 1535 (2022).
Bellet, J. et al. Decoding rapidly presented visual stimuli from prefrontal ensembles without report nor post-perceptual processing. Neurosci. Conscious. 2022, niac005 (2022).
Levinson, M., Podvalny, E., Baete, S. H. & He, B. J. Cortical and subcortical signatures of conscious object recognition. Nat. Commun. 12, 2930 (2021).
Boly, M. et al. Are the neural correlates of consciousness in the front or in the back of the cerebral cortex? Clinical and neuroimaging evidence. J. Neurosci. 37, 9603–9613 (2017).
Raccah, O., Block, N. & Fox, K. C. R. Does the prefrontal cortex play an essential role in consciousness? Insights from intracranial electrical stimulation of the human brain. J. Neurosci. 41, 2076–2087 (2021).
Odegaard, B., Knight, R. T. & Lau, H. Should a few null findings falsify prefrontal theories of conscious perception? J. Neurosci. 37, 9593–9602 (2017).
Brascamp, J., Blake, R. & Knapen, T. Negligible fronto-parietal BOLD activity accompanying unreportable switches in bistable perception. Nat. Neurosci. 18, 1672–1678 (2015). This empirical ‘no-report’ study shows that fronto-parietal activity does not track switches in perceptual dominance when subjective reports are not required.
Sergent, C. et al. Bifurcation in brain dynamics reveals a signature of conscious processing independent of report. Nat. Commun. 12, 1149 (2021).
Siclari, F. et al. The neural correlates of dreaming. Nat. Neurosci. 20, 872–878 (2017).
Wong, W. et al. The Dream Catcher experiment: blinded analyses failed to detect markers of dreaming consciousness in EEG spectral power. Neurosci. Conscious. 2020, niaa006 (2020).
Block, N. Consciousness, accessibility, and the mesh between psychology and neuroscience. Behav. Brain Sci. 30, 481–548 (2007). This work argues that research in psychology and neuroscience shows that there is a real and not merely conceptual distinction between phenomenal consciousness (that is, experience) and cognitive access to phenomenal consciousness.
Musgrave, A. in Relativism and Realism in Science (ed Nola, R.) 229–252 (Kluwer, 1988).
Song, C., Haun, A. M. & Tononi, G. Plasticity in the structure of visual space. eNeuro https://doi.org/10.1523/ENEURO.0080-17.2017 (2017).
Marshel, J. H. et al. Cortical layer-specific critical dynamics triggering perception. Science https://doi.org/10.1126/science.aaw5202 (2019).
Dembski, C., Koch, C. & Pitts, M. Perceptual awareness negativity: a physiological correlate of sensory consciousness. Trends Cogn. Sci. 25, 660–670 (2021).
Sanchez, G., Hartmann, T., Fusca, M., Demarchi, G. & Weisz, N. Decoding across sensory modalities reveals common supramodal signatures of conscious perception. Proc. Natl Acad. Sci. USA 117, 7437–7446 (2020).
Sergent, C. The offline stream of conscious representations. Philos. Trans. R. Soc. Lond. B Biol. Sci. https://doi.org/10.1098/rstb.2017.0349 (2018).
Michel, M. & Doerig, A. A new empirical challenge for local theories of consciousness. Mind Lang. https://doi.org/10.1111/mila.12319 (2021).
Sergent, C. et al. Cueing attention after the stimulus is gone can retrospectively trigger conscious perception. Curr. Biol. 23, 150–155 (2013). This empirical study reveals that conscious perception of a stimulus can be influenced by events happening (hundreds of milliseconds) after the stimulus appeared (‘retro-perception’).
Roseboom, W. et al. Activity in perceptual classification networks as a basis for human subjective time perception. Nat. Commun. 10, 267 (2019).
Kent, L. & Wittmann, M. Special Issue: Consciousness science and its theories. Time consciousness: the missing link in theories of consciousness. Neurosci. Conscious. 2021, niab011 (2021).
Husserl, E. Ideas: A General Introduction to Pure Phenomenology (Collier Books, 1963).
Yaron, I., Melloni, L., Pitts, M. & Mudrik, L. The ConTraSt database for analyzing and comparing empirical studies of consciousness theories. Nat. Hum. Behav. https://doi.org/10.1038/s41562-021-01284-5 (2022). This work presents an online resource of empirical studies of consciousness, organized with respect to different ToCs.
Joglekar, M. R., Mejias, J. F., Yang, G. R. & Wang, X. J. Inter-areal balanced amplification enhances signal propagation in a large-scale circuit model of the primate cortex. Neuron 98, 222–234.e8 (2018).
VanRullen, R. & Kanai, R. Deep learning and the global workspace theory. Trends Neurosci. 44, 692–704 (2021).
Shea, N. & Frith, C. D. The global workspace needs metacognition. Trends Cogn. Sci. 23, 560–571 (2019).
Suzuki, K., Roseboom, W., Schwartzman, D. J. & Seth, A. K. A deep-dream virtual reality platform for studying altered perceptual phenomenology. Sci. Rep. 7, 15982 (2017).
Vilas, M. G., Auksztulewicz, R. & Melloni, L. Active inference as a computational framework for consciousness. Rev. Philos. Psychol. https://doi.org/10.1007/s13164-021-00579-w (2021).
Browning, H. & Veit, W. The measurement problem in consciousness. Philos. Top. 48, 85–108 (2020).
Seth, A. K., Dienes, Z., Cleeremans, A., Overgaard, M. & Pessoa, L. Measuring consciousness: relating behavioural and neurophysiological approaches. Trends Cogn. Sci. 12, 314–321 (2008).
Michel, M. Calibration in consciousness science. Erkenntnis https://doi.org/10.1007/s10670-021-00383-z (2021).
Birch, J., Schnell, A. K. & Clayton, N. S. Dimensions of animal consciousness. Trends Cogn. Sci. 24, 789–801 (2020).
Bayne, T., Seth, A. K. & Massimini, M. Are there islands of awareness? Trends Neurosci. 43, 6–16 (2020). This work presents an examination of the possibility of consciousness in isolated neural systems such as brain organoids, disconnected cortical hemispheres and ex cranio brains.
Dehaene, S., Lau, H. & Kouider, S. What is consciousness, and could machines have it? Science 358, 486–492 (2017).
Hu, H., Cusack, R. & Naci, L. Typical and disrupted brain circuitry for conscious awareness in full-term and pre-term infants. (2021).
Owen, A. M. & Coleman, M. R. Detecting awareness in the vegetative state. Ann. N Y Acad. Sci. 9, 130–138 (2008).
Cleeremans, A. The radical plasticity thesis: how the brain learns to be conscious. Front. Psychol. 2, 86 (2011).
Jackendoff, R. Consciousness and the Computational Mind (MIT Press, 1987).
Prinz, J. The Conscious Brain: How Attention Engenders Experience (Oxford Univ. Press, 2012).
Chang, A. Y. C., Biehl, M., Yu, Y. & Kanai, R. Information closure theory of consciousness. Front. Psychol. 11, 1504 (2020).
Tononi, G. & Edelman, G. M. Consciousness and complexity. Science 282, 1846–1851 (1998). This work presents an early proposal of how measures of neural complexity might relate to phenomenological properties of (all) conscious experiences.
Edelman, G. M. Neural Darwinism: The Theory of Neuronal Group Selection (Basic Books 1987).
Edelman, G. M. The Remembered Present (Basic Books, 1989).
Damasio, A. The Feeling of What Happens: Body and Emotion in the Making of Consciousness (Harvest Books, 2000).
Graziano, M. S. A. The attention schema theory: a foundation for engineering artificial consciousness. Front. Robot. AI 4, 60 (2017).
Dennett, D. C. Consciousness Explained (Little, Brown, 1991).
Ginsburg, S. & Jablonka, E. The Evolution of the Sensitive Soul: Learning and the Origins of Consciousness (MIT Press, 2019).
Aru, J., Suzuki, M. & Larkum, M. E. Cellular mechanisms of conscious processing. Trends Cogn. Sci. 24, 814–825 (2020).
McFadden, J. Integrating information in the brain’s EM field: the cemi field theory of consciousness. Neurosci. Conscious. 2020, niaa016 (2020).
Fleming, S. M., Ryu, J., Golfinos, J. G. & Blackmon, K. E. Domain-specific impairment in metacognitive accuracy following anterior prefrontal lesions. Brain 137, 2811–2822 (2014).
Fox, K. C. R. et al. Intrinsic network architecture predicts the effects elicited by intracranial electrical stimulation of the human brain. Nat. Hum. Behav. 4, 1039–1052 (2020).
Dehaene, S. & Naccache, L. Towards a cognitive neuroscience of consciousness: basic evidence and a workspace framework. Cognition 79, 1–37 (2001).
Sergent, C., Baillet, S. & Dehaene, S. Timing of the brain events underlying access to consciousness during the attentional blink. Nat. Neurosci. 8, 1391–1400 (2005).
Mediano, P. A. M., Seth, A. K. & Barrett, A. B. Measuring integrated information: comparison of candidate measures in theory and simulation. Entropy 21, 17 (2019).
Casali, A. G. et al. A theoretically based index of consciousness independent of sensory processing and behavior. Sci. Transl. Med. 5, 198ra105 (2013). This empirical study shows that a measure of the complexity of the cortical response to transcranial magnetic stimulation distinguishes between a range of global conscious states, including disorders of consciousness.
Luppi, A. I. et al. Consciousness-specific dynamic interactions of brain integration and functional diversity. Nat. Commun. 10, 4616 (2019).
Hardstone, R. et al. Long-term priors influence visual perception through recruitment of long-range feedback. Nat. Commun. 12, 6288 (2021).
de Lange, F. P., Heilbron, M. & Kok, P. How do expectations shape perception? Trends Cogn. Sci. 22, 764–779 (2018).
Melloni, L., Schwiedrzik, C. M., Muller, N., Rodriguez, E. & Singer, W. Expectations change the signatures and timing of electrophysiological correlates of perceptual awareness. J. Neurosci. 31, 1386–1396 (2011). This empirical study uses a perceptual hysteresis paradigm to show that expectations enhance and accelerate conscious perception.
Pinto, Y., van Gaal, S., de Lange, F. P., Lamme, V. A. & Seth, A. K. Expectations accelerate entry of visual stimuli into awareness. J. Vis. 15, 13 (2015).
Chalmers, D. J. Facing up to the problem of consciousness. J. Conscious. Stud. 23, 200–219 (1995). This work presents the classic statement of the philosophical distinction between the ‘hard’ and ‘easy’ problems of consciousness.
Levine, J. Materialism and qualia: the explanatory gap. Pac. Philos. Q. 64, 354–361 (1983).
Seth, A. K. The Real Problem (Aeon, 2016).
Balog, K. in The Oxford Handbook of Philosophy of Mind (eds Beckermann, A., McLaughlin, B. P., & Walter S.) 292–312 (Oxford Univ. Press, 2009).
Perry, J. Knowledge, Possibility, and Consciousness (MIT Press, 2001).
Varela, F. J., Thompson, E. & Rosch, E. The Embodied Mind: Cognitive Science and Human Experience (MIT Press, 1993).
Carvalho, G. B. & Damasio, A. Interoception and the origin of feelings: a new synthesis. Bioessays 43, e2000261 (2021).
Solms, M. The Hidden Spring: A Journey to the Source of Consciousness (Profile Books, 2021).
Merker, B. Consciousness without a cerebral cortex: a challenge for neuroscience and medicine. Behav. Brain Sci. 30, 63–81; discussion 81–134 (2007).
Parvizi, J. & Damasio, A. Consciousness and the brainstem. Cognition 79, 135–160 (2001).
Naber, M., Frassle, S. & Einhauser, W. Perceptual rivalry: reflexes reveal the gradual nature of visual awareness. PLoS ONE 6, e20910 (2011).
Casarotto, S. et al. Stratification of unresponsive patients by an independently validated index of brain complexity. Ann. Neurol. 80, 718–729 (2016).
Shea, N. & Bayne, T. The vegetative state and the science of consciousness. Br. J. Philos. Sci. 61, 459–484 (2010).
Birch, J. The search for invertebrate consciousness. Noûs 56, 133–153 (2020).
Phillips, I. The methodological puzzle of phenomenal consciousness. Philos. Trans. R. Soc. Lond. B Biol. Sci. https://doi.org/10.1098/rstb.2017.0347 (2018).
A.K.S. is Co-Director of, and T.B. is a Fellow in, the CIFAR Program on Brain, Mind, and Consciousness. A.K.S. is additionally grateful to the European Research Council (Advanced Investigator Grant 101019254) and the Dr. Mortimer and Theresa Sackler Foundation.
The authors declare no competing interests.
Peer review information
Nature Reviews Neuroscience thanks L. Melloni, C. Sergent and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
- Neural correlates of consciousness
(NCCs). The minimal set of neural events that is jointly sufficient for a conscious state.
- Explanatory gap intuitions
Intuitions that there is no prospect of a fully satisfying explanation of consciousness in physical, mechanistic terms.
- Adversarial collaborations
Research projects in which proponents of different theories together design an experiment to distinguish their preferred theories, and agree in advance about how the outcome will favour one theory over the other(s).
- Global states
Relating to an organism’s overall state of consciousness, usually linked to arousal and behavioural responsiveness, and associated with the ‘level’ of consciousness.
- Local states
Relating to particular conscious mental states, such as a conscious perception, emotion or thought. Local states are also often called conscious contents.
- Binocular rivalry
A phenomenon in which different images are presented to each eye, and conscious perception alternates between the two images.
- Phenomenal character
The experiential nature of a local state, such as the ‘redness’ of an experience of red or the pain of a toothache — sometimes also called qualia.
A mental representation that has as its target another mental representation
- No-report paradigms
Behavioural experiments in which participants do not provide subjective (verbal, behavioural) reports.
The amount of information specified by a system that is irreducible to that specified by its parts. There are many variations of Φ, each calculated differently and making different assumptions.
- Posterior hot zone
A range of brain regions towards the rear of the cortex, including parietal, temporal and occipital areas, as well as regions such as the precuneus.
In integrated information theory (IIT), a subset of a physical system that underpins a maximum of irreducible integrated information.
- Interoceptive predictions
Predictions about the causes of sensory signals originating from within the body (interoception refers to perception of the body ‘from within’).
- Unity of consciousness
The fact that that the experiences that a single agent has at a time seem always to occur as the components of a single complex experience.
- Cognitive access
A functional property whereby a mental state has access to a wide range of cognitive processes, usually including verbal and/or behavioural report.
- Computational (neuro)phenomenology
The use of computational models to account for the phenomenal character of a conscious state in terms of (neural) mechanisms.
- The measurement problem
The problem of identifying whether a particular mental state is conscious, or determining whether an organism or other system is, or has the capacity to be, conscious.
- Cerebral organoids
Laboratory-grown neural structures that self-organize into systems with cellular and network features resembling aspects of the developing human brain.
About this article
Cite this article
Seth, A.K., Bayne, T. Theories of consciousness. Nat Rev Neurosci 23, 439–452 (2022). https://doi.org/10.1038/s41583-022-00587-4
This article is cited by