Self And The Phenomenon Of Life: A Biologist Examines Life From Molecules To Humanity

Self and Conscious Experience 169

“9x6” b2726 Self and the Phenomenon of Life: A Biologist Examines Life from Molecules to Humanity

also called “rapid-eye-movement” sleep or REM sleep, as it is accom-
panied by rapid oscillation of the eyeballs. REM sleep and dreaming go
hand in hand. Although it can be considered a state of consciousness,
the content of a dream is unrelated to the immediate surroundings, and
it usually cannot be recalled unless the person is awakened at the time
of REM sleep. The physiologic significance of REM sleep is not clear.
We know it is essential to life, since experimental animals subjected to
prolonged deprivation of REM sleep do not survive. There is evidence
that REM sleep enhances memory and learning.^14
Prior to the advent of EEG, electrical activities were detected
only in isolated nerves. EEG provides a direct correlation of conscious-
ness and physical activities inside a living brain. Since then, electrical
circuitry has become the most accepted marker of consciousness. The
main shortcoming of classical EEG is that the signals are weak because
of the intervening skull. Nevertheless, the rhythm and variation in ampli-
tude of the waves are very useful, as they reflect the functions of the

Fig. 8.2. Electro-encephalogram (EEG) of an adult human brain using electrodes
placed at the back of the head. (A) Awake and relaxed (eyes closed), showing alpha
rhythm. (B) Awake and alert (eyes open), showing desynchronized waves. (C to E)
Stages of sleep with increasing depth. (F) Rapid-eye-movement (REM) stage of sleep,
corresponding to a state of dream. [Courtesy Dr. Malcolm Yeh.]