Class 35: Variations in Consciousness I

Nov. 17, 2025

PSY 101 Class 35: Variations in Consciousness I

Consciousness and Sleep

Have you ever been "unconscious" because of an accident or anesthesia? What happened? What was it like?

A. Consciousness = awareness of internal & external stimuli

Awareness of external events now

Awareness of internal sensations now

Awareness of self as an individual having these experiences

Awareness of having thoughts about these experiences

Other terms:

(the) Unconscious (noun; psychoanalytic term of Freud) = Not accessible to consciousness (e.g.,"The unconscious contains my forgotten wishes")

Unconscious (adjective) = in a coma, e.g. due to a head injury (e.g., "He was in a car accident and is unconscious in the intensive care unit") or the result of anesthesia in a hospital

(the) Subconscious (noun) = not currently part of consciousness (e.g., "I wasn't aware of the smell of the chocolate, but my subconscious probably was and prompted me to buy a bag of M&Ms")

B. Brain Activity & Consciousness

Arises from a distributed network of neural pathways (though damage to the brain stem will impair consciousness)

Measurement of brain activity by electroencephalograph (EEG)

C.The Role of Circadian Rhythms

= Daily cycle of biological changes in humans and other animals (circa diem in Latin means "about a day")

Alertness (Adolescents = tends to be after 10 am!)

Body Temperature (low at night; high in afternoon)

Growth Hormone secretions (during sleep)

Day-Night Cycle: Light sent from the retina of the eye to the Suprachiasmatic nucleus (SCN) which connects through the hypothalamus (located right above the pituitary gland) to signal the => Pineal Gland (pineal = "like a pine cone") which normally secretes => Melatonin into the blood stream

Light has the effect of resetting the day-night cycle

Ambient (surrounding) temperature also tends to be important in promoting sleep. If the ambient temperature is high, it is more difficult for an individual to fall asleep.

Jet Lag & body's biological clock: East to West (easier); West to East (harder)

Melatonin

Inhibited by light; promoted by darkness

Highest level during the night

Promotes drowsiness

Can help individuals who experience jet lag by resetting their biological clocks.

D. Sleep-Wake Cycle

Measurement by electromyograph (EMG; muscles); electrooculograph (EOG; eye movements); electrocardiograph (EKG; heart)

Stages W (Wakefulness), N1, N2, N3 & REM ("Rapid Eye Movement") (Silber et al, 2007)

Stage W: Wakefulness/awake

Stage N1: Theta waves = light sleep

Non-REM Sleep

Stage N2: Sleep spindles & mixed EEG activity

Stages N3 Delta (slow) waves => deep sleep

Associated with dreaming that is vague and sometimes verbal (rather than visual), e.g., thinking of facts.

REM ("Rapid Eye Movement") Sleep

High frequency waves; discovered in 1950s

Associated with dreaming, particularly vivid dreaming

Hard to awaken

Relaxed muscles (almost paralyzed; no movement of arms and legs)

The sleep cycle at different ages

People go through the sleep cycle four to six times a night

Note that N3 (slow-wave or deep sleep) predominates early in sleep and REM sleep later.

Infants: much sleep more more & high amounts of REM sleep (50%->30% over first year)

Adults: REM steady at ca. 20% & less deep sleep needed in old age

Doing without Sleep: The Effects of Deprivation

Complete sleep deprivation: while not terribly harmful in the short term (people don't die of lack of sleep in general), going completely without sleep does increase motor and safety problems and interferes with memory.

There is some evidence that chronic complete sleep deprivation may shorten human life.

Partial sleep deprivation:

Contemporary Americans tend to be chronically deprived of sleep

Adolescents should get about 9 hours of sleep, but few do.

Adolescents in the United States actually get 7.2 hours (African American), 7.6 hours (Hispanic), 7.7 hours (White, non-Hispanic) and 6.9 hours (12th graders; 2006 National Sleep Foundation Study)

28% fall asleep in school; 22% fall asleep doing homework; 51% have driven while drowsy in last year (15% drive drowsy once a week).

Negative effects include motor & safety problems (accidents in cars and the workplace), metabolic and endocrine problems (e.g., weight gain)

Selective (REM is needed!): When deprived of REM selectively at night, individuals will quickly move into REM either in naps or nightly sleep.

Why sleep? Why REM? [Note we will look more deeply at why we need sleep in the next class]

Both REM and slow-wave sleep appear to be directly related to memory and learning, particularly memory consolidation (= stabilize or solidify memories from the day)

Sleep is a time when the brain gets rid of toxic waste that may have built up during the day.

REM may be associated with creativity and insight into problems and problem solving

Students who sleep fewer hours tend to have lower grades on quizzes and tests.

Sleep Loss and Health

Does the lack of adequate sleep on a regular basis have an impact upon our physical health? The data suggest that the answer is "yes".

Lack of sleep tends to trigger hormonal changes leading to increased caloric intake and, possibly, toward obesity

Lack of sleep lowers the responsiveness of the immune system and increases inflammatory processes.

Indeed, research has found a relationship between how many hours we sleep and increased risk of dying (heightened mortality). The figure on the right summarizes heightened risk of dying for both adults without and with Type 2 diabetes in a study of 273,029 US adults (248,817 without diabetes and 24,212 with Type 2 diabetes; Wang et al. 2020).

As an earlier meta-analysis of research on amount of sleep and risk of dying summarizes, "“Our ﬁndings indicate that both short sleepers and long sleepers are at increased risk of all-cause mortality; this is consistent with results from studies examining sleep duration and the development of health conditions as well as the limited evidence pertaining to the physiological eﬀects of sleep at various durations.” (Gallicchio & Kalesan, 2009, p. 156, boldface and italics added)

Insomnia = chronic problems in getting adequate sleep that result in daytime fatigue and impaired functioning

Three forms: getting to sleep, staying asleep, waking up too early
10% of adults = severe; 20-30% = mild or intermittent
Problems: reduced productivity at work, elevated risk of accidents, depression, anxiety, & serious health problems

The line chart to the left illustrates the differences in the incidence of physical medical conditions between patients with or without chronic insomnia in a community-based population sample of 772 men and women (age: 20-98 years; Taylor et al., 2007).

Causes: stress, tension, some health problems, use of stimulants (caffeine and others)
Treatment: Use of sedatives (short term); change the underlying causes (long term)

Notes on Sleeping & Dreaming continued in next class

References

Gallicchio, L., & Kalesan, B. (2009). Sleep duration and mortality: a systematic review and meta-analysis. Journal of Sleep Research, 18, 148-158. https://doi.org/10.1111/j.1365-2869.2008.00732.x

National Sleep Foundation (2006). 2006 Sleep in America poll. Washington, DC: WBA Market Research.

Silber, M. H., Ancoli-Israel, S., Bonnet, M. H. et al. (2007). The visual scoring of sleep in adults. Journal of Clinical Sleep Medicine, 3(2), 121-131.

Taylor, D. J., Mallory, L. J., Lichstein, K. L., Durrence, H. H., Riedel, B. W., & Bush, A. J. (2003). Comorbidity of chronic insomnia with medical problems. Sleep, 30(2), 213-218

Wang, X., Huang, W., O’Neil, A., Lan, Y., Aune, D., Wang, W., Yu, C., & Chen, X. (2020) Association between sleep duration and mortality risk among adults with type 2 diabetes: a prospective cohort study. Diabetologia, 63, 2292-2304. https://doi.org/10.1007/s00125-020-05214-4

Resources

National Sleep Foundation

Dr. Eric Chudler's What Is Sleep? webpage

This page was originally posted on 11/12/03