Consciousness

Chapter

Fifteen

Dreaming and beyond

Sleep in other species also seems likely to be very different from adult human sleep
(Empson, 2001). Reptiles do not have REM sleep, but many birds and mammals do.
Bottlenose dolphins, although extremely intelligent, do not seem to, and only one
half of their brain sleeps at a time, in two-hour cycles, so they can keep watch for
predators and know when to rise to the surface for air. REM-like sleep (with rapid eye
movements, changes in body colouration, and arm-twitching) has been observed
in cuttlefish though not octopuses (Frank et al., 2012). Mice and rats, dogs and cats,
monkeys and apes all have REM sleep, and when we see their eyelids flickering or
their whiskers twitching we can easily imagine that they are dreaming. But are we
right to do so? We can guess, based on what we know of their cognitive abilities,
that some of them might be enjoying complex visual and auditory images, perhaps
even with narrative structure, but they cannot describe their dreams in words. So
we cannot ask them and we cannot simply assume that REM equals dreaming.

Where can we go from here?

One possibility is that the physiology and the phenomenology can never be
reduced to, or equated with, each other; that the fathomless abyss can never be
crossed. Another possibility is that with further research, and better understand-
ing of brain states and neurochemistry, we will learn exactly how brain states
relate to the experience of dreaming.

There are already some hints in this direction. Dream contents have long been
known to relate to eye movements, for example when someone reports having
dreamt of watching a tennis match and distinct left–right eye movements are
seen on the EEG recording. The same cortical areas appear to be involved in
rapid eye movements as are involved in waking eye movements, and fMRI scans
suggest that ‘REMs are visually-guided saccades that reflexively explore dream
imagery’ (Hong et al., 2009).

‘Our conscious

awareness during

waking is an obvious

adaptive advantage,

but our conscious

awareness during sleep

may not be’

(Hobson, in Metzinger, 2009,

p. 153)

Waking

High NA

and

serotonin

High ACh

M

External

I

Internal

Low A High

M

I

A

REM

NREM

Lucid

dreaming

State of

diminished

consciousness

(a) (b)

FIGURE 15.3 • AIM model of brain-mind state control. (a) The three dimensional AIM state-space model showing normal
transitions within the AIM state space from waking to nonrapid eye movement (NREM) and then to rapid eye
movement (REM) sleep. The x-axis represents A (for activation), the y-axis represents M (for modulation), and
the z-axis represents I (for input-output gating). (b) Diseases, such as those that produce coma and minimally
conscious states, occupy the left-hand segment of the space, owing to their low activation values. Lucid dreaming,
which is a hybrid state with features of both waking and dreaming, is situated in the middle of the extreme right
hand side of the AIM state space between waking and REM, towards either of which lucid dreamers are drawn
(after Hobson, 2009, p. 808).