LECTURE 11 Flashcards
Consciousness
our subjective awareness of ourselves and our environment
Dualism
the idea that the mind, a nonmaterial entity, is separate from (although connected to) the physical body. In contrast to the dualists, psychologists believe that consciousness (and thus the mind) exists in the brain, not separate from it. In fact, psychologists believe that consciousness is the result of the activity of the many neural connections in the brain, and that we experience different states of consciousness depending on what our brain is currently doing
Unconscious
behavior caused by forces outside our awareness
The experience of consciousness
Our experience of consciousness is functional because we use it to guide and control our behavior, and to think logically about problems. Consciousness allows us
to plan activities and to monitor our progress toward the goals we set for ourselves.
And consciousness is fundamental to our sense of morality—we believe that we have the free will to perform moral actions while avoiding immoral behaviors. But in some cases consciousness may become aversive, for instance when we become aware that we are not living up to our own goals or expectations, or when we believe that other people perceive us negatively. In these cases we may engage in behaviors that help us escape from consciousness, for example through the use of alcohol or other psychoactive drugs.
Because the brain varies in its current level and type of activity, consciousness is transitory. If we drink too much coffee or beer, the caffeine or alcohol influences the activity in our brain, and our consciousness may change. When we are anesthetized before an operation or experience a concussion after a knock on the head, we may lose consciousness entirely as a result of changes in brain activity. We also lose consciousness when we sleep, and it is with this altered state of consciousness that we
begin our chapter.
biological rhythms
The lives of all organisms, including humans, are influenced by regularly occurring cycles of behaviors. One important biological rhythm is the annual cycle that guides the migration of birds and the hibernation of bears. Women also experience a 28-day cycle that guides their fertility and menstruation.
circadian rhythm
guides the daily waking and sleeping cycle in many animals.
seasonal affective disorder (SAD)
We are more likely to experience depression during the dark winter months than during the lighter summer months. Exposure to bright lights can help reduce this depression.
Many biological rhythms are coordinated by changes in the level and duration of ambient light, for instance, as winter turns into summer and as night turns into day. In some animals, such as birds, the pineal gland in the brain is directly sensitive to light and its activation influences behavior, such as mating and annual migrations. Light also has a profound effect on humans.
Sleep is also influenced by ambient light
The ganglion cells in the retina send signals to a brain
area above the thalamus called the suprachiasmatic nucleus, which is the body’s primary circadian “pacemaker.” The suprachiasmatic nucleus analyzes the strength and duration of the light stimulus and sends signals to the pineal gland when the ambient light level is low or its duration is short. In response, the pineal gland secretes melatonin, a powerful hormone that facilitates the onset of sleep.
suprachiasmatic nucleus
a brain area above the thalamus the ganglion cells in the retina send signals to
Sleep stages are of two major types
Rapid eye movement (REM) sleep is a sleep stage characterized by the presence of quick
fast eye movements and dreaming. REM sleep accounts for about 25% of our total sleep time. During
REM sleep, our awareness of external events is dramatically reduced, and consciousness is dominated
primarily by internally generated images and a lack of overt thinking. During this sleep stage our muscles shut down, and this is probably a good thing as it protects us from hurting ourselves or trying to act out the scenes that are playing in our dreams.
The second major sleep type, non-rapid eye movement (non-REM) sleep is a deep sleep, characterized by very slow brain waves, that is further subdivided into three stages: N1, N2, and N3. Each of the sleep stages has its own distinct pattern of brain activity. During a typical night, our sleep cycles move between REM and non-REM sleep, with each cycle repeating at about 90-minute intervals. The deeper non-REM sleep stages usually occur earlier in the night.
N1
When we are awake, our brain activity is characterized by the presence of very fast beta waves. When we first begin to fall asleep, the waves get longer (alpha waves), and as we move into stage N1 sleep, which is characterized by the experience of drowsiness, the brain begins to produce
even slower theta waves. During stage N1 sleep, some muscle tone is lost, as well as most awareness of the environment. Some people may experience sudden jerks or twitches and even vivid hallucinations during this initial stage of sleep. Normally, if we are allowed to keep sleeping, we will move from stage N1 to stage N2 sleep.
N2
During stage N2, muscular activity is further decreased and conscious awareness of the environment is lost. This stage typically represents about half of the total sleep time in normal adults. Stage N2 sleep is characterized by theta waves interspersed with bursts of rapid brain activity
known as sleep spindles.
N3
A period of deep sleep, characterized by an increased
proportion of very slow delta waves. This is the stage in which most sleep abnormalities, such as sleepwalking, sleep-talking, nightmares, and bed-wetting occur. Some skeletal muscle tone remains, making it possible for affected individuals to rise from their beds and engage in sometimes very complex behaviors, but consciousness is distant. Even in the deepest sleep, however, we are still
aware of the external world. If smoke enters the room or if we hear the cry of a baby we are likely to react, even though we are sound asleep. These occurrences again demonstrate the extent to which we process information outside consciousness.
REM
After falling initially into a very deep sleep, the brain begins to become more active again, and wenormally move into the first period of REM sleep about 90 minutes after falling asleep. REM sleep is accompanied by an increase in heart rate, facial twitches, and the repeated rapid eye movements that give this stage its name. People who are awakened during REM sleep almost always report that they were dreaming, while those awakened in other stages of sleep report dreams much less often. REM sleep is also emotional sleep. Activity in the limbic system, including the amygdala, is increased during REM sleep, and the genitals become aroused, even if the content of the dreams we are having is not sexual. A typical 25-year-old man may have an erection nearly half of the night, and the common
“morning erection” is left over from the last REM period before waking. Normally we will go through several cycles of REM and non-REM sleep each night (Figure 5.5 “EEG
Recordings of Brain Patterns During Sleep”). The length of the REM portion of the cycle tends to increase through the night, from about 5 to 10 minutes early in the night to 15 to 20 minutes shortly before awakening in the morning. Dreams also tend to become more elaborate and vivid as the night goes on. Eventually, as the sleep cycle finishes, the brain resumes its faster alpha and beta waves and we
awake, normally refreshed.
Insomnia
persistent difficulty falling or staying asleep. Most cases of
insomnia are temporary, lasting from a few days to several weeks, but in some cases insomnia can last for years. Insomnia can result from physical disorders such as pain due to injury or illness, or from psychological problems such as stress, financial worries, or relationship difficulties. Changes in sleep patterns, such as jet lag, changes in work shift, or even the movement to or from daylight savings time can produce insomnia. Sometimes the sleep that the insomniac does get is disturbed and non-restorative, and the lack of quality sleep produces impairment of functioning during the day. Ironically, the problem may be compounded by people’s anxiety over insomnia itself: Their fear of being unable to sleep may
wind up keeping them awake. Some people may also develop a conditioned anxiety to the bedroom or the bed.
