Consciousness

• seCtIon FIVe: BoRDeRLAnDs
  two dimensions: irrationality and ability to hal-
  lucinate. By plotting a person’s position in this
  space, he imagined just three major clusters
  corresponding to the states of dreaming, lucid
  dreaming (Chapter  15), and ordinary conscious-
  ness. All other positions in the space cannot be
  occupied, or are unstable. So you may briefly
  hover between waking and dreaming, but this
  state is unstable and rapidly gives way to one
  of the others. For this reason, Tart refers to the
  occupied areas as ‘discrete states of conscious-
  ness’. To move out of such a region, you have
  to cross a ‘forbidden zone’ where you cannot
  stably function or have experiences, until you
  reach a discretely different experiential space. In
  other words, you can be here or there, but not in
  between. Just how many states are discrete like
  this we do not know: Tart’s scheme was only a
  limited and quite informal way of starting to map
  states into a space.
  A second and more systematic two-dimensional space is described by Steven
  Laureys (2005). His dimensions are completely different: level of arousal and
  awareness of environment and self. Arousal refers to physiological wakefulness
  or the ‘level’ of consciousness and is dependent on the brainstem arousal sys-
  tem. Awareness of environment and self refers to the ‘content’ of consciousness
  and requires a functionally integrated cortex with its subcortical loops. A simple
  diagram shows that for most states level and content are positively correlated.
  As Laureys puts it, ‘You need to be awake in order to be aware (REM sleep being
  a notable exception)’ (2009, p. 58). Other exceptions discussed by Laureys are the
  vegetative state, sleepwalking, and some kinds of seizure, all of which involve
  some wakefulness with no apparent awareness.
  The AIM model is a three-dimensional map developed by American psychiatrist
  and sleep researcher Allan Hobson (1999), and named after its dimensions. Acti-
  vation energy is similar to arousal and can be measured, for example, using EEG.
  Input source can vary between entirely ‘external’ or entirely ‘internal’ sources of
  information. Mode is the ratio of amines to cholines. During waking, the amine
  neurotransmitters and neuromodulators, including noradrenaline and serotonin,
  predominate and are essential for rational thought, volition, and directing atten-
  tion. During REM sleep acetylcholine takes over and thinking becomes delusional,
  irrational, and unreflective. The ratio of these two is Hobson’s mode.
  States can now be positioned in what Hobson calls ‘brain–mind space’ by measuring
  them along these three dimensions. He stresses that it is an entirely artificial model,
  yet is based on specific data and recognises the continuously changing nature of
  brain–mind states. Unlike in Tart’s early model, any state of the brain–mind can be
  positioned within it, and any area in the space can in theory be occupied.
  Other dimensional models derive from studies of specific corners of the vast
  consciousness state–space. A  survey of ‘meditation depth’ amongst 300 yoga,
  Buddhist, and TM meditators resulted in another three dimensions: mystical

HIGH

LOW HIGH

LOW

(STAGE1–STATREMDE2REAMING)

(LUCID DREAMING)STATE3

(ORDINARY CONSCIOUSNESS)STATE1

DIMENSION2(RAT IONALITY)

DIMENSION 1

(ABILITYT

O HALLUCINATE)

FIGURE 13.3 • Tart’s plot of three discrete
altered states in a space with
two dimensions: irrationality and
ability to hallucinate (after Tart,
1975, Fig. 5.1).