Body Rhythms and Mental States

A biological clock in our brains governs:

the waxing and waning of hormone levels

urine volume

blood pressure

the responsiveness of brain cells to stimulation

Circadian Rhythms (3 of 5)

Biological rhythms are typically in tune with:

external time cues, such as changes in clock time, temperature, daylight

Many rhythms continue to occur even in the absence of such cues.

endogenous, generated from within

Circadian fluctuations:

occur about once a day

are governed by a biological clock in the suprachiasmatic nucleus (SCN) of the hypothalamus

Circadian Rhythms (4 of 5)

The SCN regulates and, in turn, is affected by the hormone melatonin.

Melatonin is responsive to changes in light and dark and increases during the dark hours.

secreted by the pineal gland, deep within the brain

induces sleep

helps keep biological clock in phase with light–dark cycle

Circadian Rhythms (5 of 5)

When our normal routine changes, we may experience internal desynchronization.

Example: taking airplane flights across time zones

The usual circadian rhythms are thrown out of phase with one another.

Sleep and wake patterns adjust quickly but temperature and hormone cycles can take days to return to normal.

Jet lag affects energy level, mental skills, motor coordination.

Moods and Long-Term Rhythms (1 of 5)

Some people experience depression every winter in a pattern that has been labeled seasonal affective disorder (SAD).

During the winter months, SAD patients report:

feelings of sadness

lethargy

drowsiness

craving for carbohydrates

Moods and Long-Term Rhythms (2 of 5)

The causes of SAD, which is relatively uncommon, are not yet clear.

SAD is not recognized as an official disorder.

Much of the research to date has been flawed.

Light treatments can be effective in alleviating symptoms.

SAD may occur in people whose circadian rhythms are out of sync.

In essence, they have a chronic form of jet lag.

Moods and Long-Term Rhythms (3 of 5)

Another long-term rhythm is the menstrual cycle, during which various hormones rise and fall.

Well-controlled, double-blind studies have been conducted on premenstrual syndrome.

These studies do not support claims that emotional symptoms are reliably and universally tied to the menstrual cycle.

Moods and Long-Term Rhythms (4 of 5)

How both sexes interpret bodily and emotional changes is affected by:

expectations

learning

Few people of either sex are likely to undergo dramatic monthly mood swings or personality changes because of hormones.

Moods and Long-Term Rhythms (5 of 5) Figure 5.1 Mood Changes in Men and Women

(McFarlane, Martin, & Williams, 1988)

In a study that challenged popular stereotypes about premenstrual syndrome, college women and men recorded their moods daily for 70 days without knowing the purpose of the study. At the end of the study, the women thought their moods had been more negative premenstrually than during the rest of the month (green line), but their daily diaries showed otherwise (blue line). Both sexes experienced only moderate mood changes, and there were no significant differences between women and men at any time of the month (McFarlane, Martin, & Williams, 1988).

The Rhythms of Sleep

LO 5.2.A Describe the four stages of sleep, and explain the primary features of each stage.

LO 5.2.B List the mental consequences of sleeplessness and the mental benefits of a good night’s sleep.

The Realms of Sleep (1 of 6)

During sleep, periods of rapid eye movement (REM) alternate with non-REM (NREM) sleep in approximately a 90-minute rhythm.

The REM periods last from a few minutes to as long as an hour.

They average about 20 minutes in length.

The Realms of Sleep (2 of 6)

Non-REM sleep is divided into stages on the basis of characteristic brain-wave patterns.

Alpha waves gradually slow down, passing through three stages, each deeper than the previous one:

Stage NREM-1

Stage NREM-2

sleep spindles

Stage NREM-3

delta waves

The Realms of Sleep (3 of 6)

During REM sleep, the brain is active, and there are other signs of arousal.

Most of the skeletal muscles are limp.

Vivid dreams are reported most often during REM sleep.

REM and non-REM sleep continue to alternate throughout the night.

The Realms of Sleep (4 of 6) Figure 5.2 Brain-Wave Patterns during Wakefulness and Sleep

Most types of brain waves are present throughout sleep, but different ones predominate at different stages.

The Realms of Sleep (5 of 6) Figure 5.3 A Typical Night’s Sleep for a Young Adult

In this graph, the thin horizontal red bars represent time spent in REM sleep. REM periods tend to lengthen as the night wears on, but Stage 3, which dominates during non-REM sleep early in the night, may disappear as morning approaches.

The Realms of Sleep (6 of 6) Table 5.1 Characteristics of Sleep Stages

REM sleep Active brain but inactive muscles
NREM-1 Period when the sleeper is on the edge of consciousness, in a light sleep
NREM-2 Sleep stage characterized by short bursts of rapid waves
NREM-3 Sleep stage characterized by very slow waves with high peaks
Alpha waves Brain activity during a state of relaxed wakefulness
Sleep spindles Short, high-peaking waves
Delta waves Waves present during deep sleep
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Why We Sleep (1 of 4)

Sleep is necessary for:

bodily restoration

normal mental functioning

Sleep appears to provide a time-out period, so that the body can:

eliminate waste products from muscles

repair cells

conserve or replenish energy stores

strengthen the immune system

recover abilities lost during the day

Why We Sleep (2 of 4)

Many people get less than the optimal amount of sleep, perhaps suffering from:

insomnia

sleep apnea

narcolepsy

REM behavior disorder

The most common reason for daytime sleepiness is probably a simple lack of sleep.

Most adults need more than 6 hours for optimal performance, and many adolescents need 10.

Why We Sleep (3 of 4)

Sleep may contribute to:

the consolidation of memories

subsequent problem solving

These benefits have been associated most closely with slow-wave sleep.

also with REM sleep

The underlying biology appears to involve:

the formation of new synaptic connections

the weakening of connections that are no longer needed

Why We Sleep (4 of 4) Figure 5.4 Sleep and Consolidation in Memory

Exploring the Dream World

LO 5.3.A Discuss explanations for why we dream.

LO 5.3.B Summarize the strengths and weaknesses of each major dream theory.

Explanations of Dreaming (1 of 7)

Freud thought that:

dreams allow us to express forbidden or unrealistic desires

these desires have been forced into the unconscious part of the mind

There is no objective way to verify Freudian interpretations of dreams.

There is no convincing support for most of his claims.

Explanations of Dreaming (2 of 7)

Three modern theories of dreaming emphasize the connections between dreams and waking thoughts:

problem-focused approach

cognitive approach

activation–synthesis theory

Explanations of Dreaming (3 of 7)

The problem-focused approach holds that:

dreams express current concerns

may even help us solve current problems

In this approach, the symbols and metaphors in a dream:

do not disguise its true meaning

they actually convey it

Example of problem focus in dreams: Text-anxiety dreams are common among college students.

Explanations of Dreaming (4 of 7)

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Body Rhythms and Mental States