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Krasnow Institute > Monday Seminars > Abstracts
An information integration theory of consciousness Giulio Tononi Department of Psychiatry, University of Wisconsin, Madison Neuroscience tells us that our conscious experience depends on certain parts of the brain and not others. For example, neurons in corticothalamic circuits are essential for conscious experience, whereas cerebellar neurons, despite their huge numbers, are not. Neuroscience also tells us that consciousness depends on the way our brain is functioning. For example, consciousness wanes during slow wave sleep and generalized seizures, despite levels of neural activity that are comparable to wakefulness. To understand why this is so, empirical observations on the neural correlates of consciousness must be related to a principled notion of subjective experience. Taking its start from phenomenology and making a critical use of thought experiments, the information integration theory claims that a physical system has subjective experience to the extent that it is capable of integrating information. This notion is made precise by providing a mathematical definition of information integration, or Φ, which is the value of effective information for the minimum information bipartition of a complex of elements. The theory then proceeds to show that, if subjective experience corresponds to a system’s capacity to integrate information, several observations concerning the neural substrate of consciousness fall naturally into place. Among them are the association of consciousness with certain neural systems rather than with others; the fact that neural processes underlying consciousness can influence or be influenced by neural processes that remain unconscious; the reduction of consciousness during dreamless sleep and generalized seizures; and the time requirements on neural interactions that support consciousness. The information integration theory is unique among neurobiological approaches in that it addresses the hard problem of consciousness head-on, it accounts for disparate neurobiological facts in terms of a single fundamental quantity, and it predicts the possibility of experience in non-neural systems.
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