Ivan Pavlov - physiology of the mind in conditioning experiments
John B. Watson - focused exclusively on behavior
Contemporary Thinking about Mind and Consciousness
Today, mind and consciousness are defined in physiological, evolutionary, and behavioral terms.
Alertness varies over a 24-hour period, from a complete lack of alertness (during sleep) to a peak during the late afternoon and early evening hours. In the two complete cycles (48 hours), body temperature drops precipitously during sleep, then rises and remains steady throughout most of the day.
Cells that function as timekeepers, cycling on a solar, lunar, or seasonal basis.
Location of Biological Clock
In humans, neurons in the hypothalamus--specifically, in the suprachiasmatic nucleus, or SCN--function as the main biological clock. The SCN is located near the parts of the hypothalamus that monitor body temperature and control eating and drinking.
A stimulus, usually daylight, that entrains a biological clock to the Earth's rotation, preventing an animal's activity level from free-running.
An electroencephalogram is a visual recording of voltage changes in the brain.
Record of a Good Night's Sleep
During an average night's sleep, a typical person cycles through stages 1 through 4 and back several times. Each sleep stage is defined by unique brain wave patterns. This record shows four complete REM episodes and a fifth that was interrupted when the sleeper awoke.
REM sleep is also known as paradoxical sleep, because this sleep stage resembles that of a person who is wide awake--showing beta activity.
In actuality, the sleeper is in a deep sleep.
Sleep Patterns over a Lifetime
Over a lifetime, the cycle of waking states to non-REM and REM sleep varies, exhibiting different patterns at different ages. This shows sleep patterns from birth through old age.
As the dose of a depressant increases, consciousness changes from a normal waking state to mellow relaxation, sedation, and then sleep. Overdoses of many drugs--not just depressants--can lead to coma and death.