AN INFORMATION INTEGRATION THEORY OF CONSCIOUSNESS
GIULIO TONONI
Department of Psychiatry, University of Wisconsin,
Madison, USA Email:
Giulio Tononi* - gtononi@wisc.edu
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An Information Integration Theory of Consciousness
Giulio Tononi
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Background
Consciousness poses two main problems. The
first is understanding the conditions that
determine to what extent a system has conscious
experience. For instance, why is our consciousness
generated by certain parts of our brain,
such as the thalamocortical system, and not
by other parts, such as the cerebellum? And
why are we conscious during wakefulness and
much less so during dreamless sleep? The
second problem is understanding the conditions
that determine what kind of consciousness
a system has. For example, why do specific
parts of the brain contribute specific qualities
to our conscious experience, such as vision
and audition?
Presentation of the hypothesis
This paper presents a theory about what consciousness
is and how it can be measured. According
to the theory, consciousness corresponds
to the capacity of a system to integrate
information. This claim is motivated by two
key phenomenological properties of consciousness:
differentiation - the availability of a very
large number of conscious experiences; and
integration - the unity of each such experience.
The theory states that the quantity of consciousness
available to a system can be measured as
the ? value of a complex of elements. ? is
the amount of causally effective information
that can be integrated across the informational
weakest link of a subset of elements. A complex
is a subset of elements with ?0 that is not
part of a subset of higher ?. The theory
also claims that the quality of consciousness
is determined by the informational relationships
among the elements of a complex, which are
specified by the values of effective information
among them. Finally, each particular conscious
experience is specified by the value, at
any given time, of the variables mediating
informational interactions among the elements
of a complex.
Testing the hypothesis
The information integration theory accounts,
in a principled manner, for several neurobiological
observations concerning consciousness. As
shown here, these include 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.
Implications of the hypothesis
The theory entails that consciousness is
a fundamental quantity, that it is graded,
that it is present in infants and animals,
and that it should be possible to build conscious
artifacts.
Background
Consciousness is everything we experience.
Think of it as what abandons us every night
when we fall into dreamless sleep and returns
the next morning when we wake up [1]. Without
consciousness, as far as we are concerned,
there would be neither an external world
nor our own selves: there would be nothing
at all. To understand consciousness, two
main problems need to be addressed. [2,3].
Thefirst problem is to understand the conditions
that determine to what extent a system has
consciousness. For example, why is it that
certain parts of the brain are important
for conscious experience, whereas others,
equally rich in neurons and connections,
are not? And why are we conscious during
wakefulness or dreaming sleep, but much less
so during dreamless sleep, even if the brain
remains highly active? The second problem
is to understand the conditions that determine
what kind of consciousness a system has.
For example, what determines the specific
and seemingly irreducible quality of the
different modalities (e. g. vision, audition,
pain), submodalities (e. g. visual color
and motion), and dimensions (e. g. blue and
red) that characterize our conscious experience?
Why do colors look the way they do, and different
from the way music sounds, or pain feels?
Solving the first problem means that we would
know to what extent a physical system can
generate consciousness - the quantity or
level of consciousness. Solving the second
problem means that we would know what kind
of consciousness it generates - the quality
or content of consciousness.
PRESENTATION
OF THE HYPOTHESIS
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AN INFORMATION INTEGRATION
THEORY OF CONSCIOUSNESS
GIULIO TONONI
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