Abstract
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 Phi value of a complex of elements.
Phi 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 Phi>0 that is not part of a subset of
higher Phi. 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.
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