> We obviously cannot (yet) explain consciousness so it is possible that it is impossible to create consciousness with compound parts, we just don't know.

Giulio Tononi's Integrated Information Theory of Consciousness addresses this very notion, and it seems to fit neuroscientific observations quite well.

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Consciousness as Integrated Information: a Provisional Manifesto [1] --Giulio Tononi

Abstract: The integrated information theory (IIT) starts
from phenomenology and makes use of thought experiments to claim that consciousness is integrated information.
Speciﬁcally: (i) the quantity of consciousness corresponds
to the amount of integrated information generated by a
complex of elements; (ii) the quality of experience is speciﬁed by the set of informational relationships generated
within that complex. Integrated information (phi ) is deﬁned
as the amount of information generated by a complex of
elements, above and beyond the information generated by
its parts. Qualia space (Q) is a space where each axis
represents a possible state of the complex, each point is a
probability distribution of its states, and arrows between
points represent the informational relationships among its
elements generated by causal mechanisms (connections).
Together, the set of informational relationships within a
complex constitute a shape in Q that completely and univocally speciﬁes a particular experience. Several observations
concerning the neural substrate of consciousness fall naturally into place within the IIT framework. 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 distinct role of different cortical architectures
in affecting the quality of experience. Equating consciousness with integrated information carries several implications
for our view of nature.

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Theoretical approaches to the diagnosis of altered
states of consciousness [2] --Melanie Boly, Marcello Massimini
and Giulio Tononi

Fig. 1. legend: Information and integration are fundamental properties of conscious experience.

(A) Information: the photodiode thought
experiment. IITC states that consciousness is highly informative, because each conscious experience is implicitly discriminated by
ruling out an inﬁnite number of other available alternatives. According to the theory, the more alternatives you can rule out, the
more informative is your conscious experience, and the higher your level of consciousness. This concept is illustrated when
comparing a photodiode, simple light-sensitive device to anyone of us (here Galileo Galilei, for the sake of the example), facing a
blank screen. According to the theory, the key difference between us and the photodiode relies in the fact that when specifying
‘‘dark,’’ the photodiode discriminates between only two alternatives, while we discriminate it from a large repertoire of other
available percepts. This difference affects the meaning of the discrimination performed, and the amount of information generated.

(B) Integration: the camera thought experiment. By multiplying the number of photodiodes, like in the case of a camera, one can
considerably increase the amount of information generated. The difference between us and the camera is that the information
generated by each photodiode is not communicated to the whole system, that is, the information the systems generates is not
integrated. This is reﬂected by the fact that if one would separate the camera in two parts with an inﬁnitely thin line, this would not
impair its function, nor diminish the amount of information generated. If the same procedure is applied to the brain, this will result in
a split in two independent consciousnesses, similarly to what is observed in split-brain patients. Integration of information allows to
perform a single discrimination at the scale of the whole system, in order to generate a uniﬁed perception.

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A perturbational approach for evaluating the brain’s
capacity for consciousness [3] --Marcello Massimini,
, Melanie Boly
, Adenauer Casali
, Mario Rosanova
and
Giulio Tononi

Abstract: How do we evaluate a brain’s capacity to sustain conscious experience if the subject does not
manifest purposeful behaviour and does not respond to questions and commands? What should we
measure in this case? An emerging idea in theoretical neuroscience is that what really matters for
consciousness in the brain is not activity levels, access to sensory inputs or neural synchronization per se,
but rather the ability of different areas of the thalamocortical system to interact causally with each other
to form an integrated whole. In particular, the information integration theory of consciousness (IITC)
argues that consciousness is integrated information and that the brain should be able to generate
consciousness to the extent that it has a large repertoire of available states (information), yet it cannot be
decomposed into a collection of causally independent subsystems (integration). To evaluate the ability to
integrate information among distributed cortical regions, it may not be sufﬁcient to observe the brain in
action. Instead, it is useful to employ a perturbational approach and examine to what extent different
regions of the thalamocortical system can interact causally (integration) and produce speciﬁc responses
(information). Thanks to a recently developed technique, transcranial magnetic stimulation and highdensity electroencephalography (TMS/hd-EEG), one can record the immediate reaction of the entire
thalamocortical system to controlled perturbations of different cortical areas. In this chapter, using sleep
as a model of unconsciousness, we show that TMS/hd-EEG can detect clear-cut changes in the ability of
the thalamocortical system to integrate information when the level of consciousness ﬂuctuates across the
sleep–wake cycle. Based on these results, we discuss the potential applications of this novel technique to
evaluate objectively the brain’s capacity for consciousness at the bedside of brain-injured patients.

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[1] http://clm.utexas.edu/~compjc/papers/Tononi2008a.pdf Very theoretical/mathematical

[2] http://www.coma.ulg.ac.be/papers/vs/boly_PBR_coma_science_20... A more gentle introduction

[3] http://www.coma.ulg.ac.be/papers/vs/massimini_PBR_coma_scien...