Consciousness

• seCtIon tWo: tHe BRAIn
  senses in sensory substitution (Chapter 8)? On the ‘moder-
  ate sensory pluralism’ account (Fulkerson, 2014), individ-
  ual senses and the multimodal interactions between them
  have to be differently categorised depending on the con-
  text, so puzzling over the integration of discrete modalities
  may be creating a problem where there isn’t one.
  Some combination of sensory distinctness and multisensory
  integration makes possible a world in which objects can be
  recognised as whole, and as being touched, seen, tasted,
  smelled, or heard, and as being the same thing however we
  perceive them. Many brain areas are known to be involved,
  including primary sensory cortices, frontal lobe, the supe-
  rior colliculus in the midbrain, and many subcortical areas,
  but just how this kind of integration gives rise to the sub-
  jective sense of being one self in a unified world remains to
  be seen.

INTEGRATED INFORMATION

THEORY

The unity of consciousness is the starting point for the inte-

grated information theory (IIT) of consciousness (Tononi,

2004, 2007, 2008, 2015), discussed briefly in Chapter  5. This

developed out of Edelman and Tononi’s (2000a, 2000b)

dynamic core hypothesis, in which re-entrant thalamocortical

loops produce high levels of dynamic complexity that create

consciousness. According to IIT, consciousness corresponds

to the capacity of a system to integrate information. Infor-

mation is integrated if it cannot be localised in any individual

part of the system, or is ‘generated by causal interactions in

the whole, over and above the information generated by the

parts’ (Tononi, 2008, p. 221).

IIT sets out to explain five key features of consciousness.

1 Intrinsic existence. My conscious experience exists here and now, from my

intrinsic perspective.

2 Composition. Consciousness is structured: it is composed of multiple phe-

nomenal distinctions at different levels of generality, like a red colour, a traffic

light, the left side, a red traffic light on the left, etc.

3 Information. Every conscious experience is specific and differentiated from

other possible experiences; its distinctions specify spatial locations, as well

as positive concepts  – like road as opposed to no road, red as opposed to

amber or green, etc. – and negative concepts – no red, no country lane, no

beach, etc.

4 Exclusion. Each experience is definite in both content and spatio-temporal

‘grain’, making some phenomenal distinctions  – driving along a road and

coming to a red light – and not others, and flowing at one speed not another.

5 Integration. Seeing the red traffic light cannot be reduced to seeing the

colour red plus a traffic light.

PRoFILe 6.1

Giulio Tononi

Giulio Tononi is a neuroscientist

and psychiatrist based at the

University of Wisconsin, where

he holds chairs in sleep medi-

cine as well as in consciousness

science. After studying medicine

at the University of Pisa in Italy,

he specialised in psychiatry and

served as a medical officer in

the army before doing a doctorate in neuroscience. Long

fascinated by sleep and the reasons we need so much of

it, he has worked on human, mouse, and fruit-fly models;

explored genetics, proteins, and computer analysis; and,

with Chiara Cirelli, developed the ‘synaptic homeostasis’

hypothesis that sleep serves to regulate the excessive

synaptic activation of wakefulness. Together with Gerald

Edelman, he developed the dynamic core hypothesis, a

model of consciousness which he expanded into integrat-

ed information theory and has continued to update. In

IIT, a system’s consciousness is determined by its caus-

al properties and corresponds to a system’s capacity to

integrate information, an idea which is supported by

the breakdown of information integration in slow-wave

sleep, general anaesthesia, and vegetative states.