Psyc 220 (Chapter 9)
Variations of consciousness
(awareness of your internal and external surroundings) Coma--low, steady brain activity Vegetative state--alternation between sleep and moderate arousal. Some may have cognitive activity Minimally conscious--slightly more brain activity than vegetative state Brain death--no brain activity
Mechanisms of the Biological Clock
*Suprachiasmatic Nucleus (SCN)--Located just above the optic chiasm. Provides the main control of the circadian rhythms for sleep and body temperature. Damage to the SCN results in erratic bodily rhythms. Generates circadian rhythms in a genetically controlled, unlearned manner. Individual neurons can maintain the rhythms by itself but multiple together sharped the accuracy. If you isolate SCN neurons they action potential in a very regular pattern. Hamsters with a normal clock had neurons from 20-Hour SCN hamsters transferred into them started to show a 20 hour clock too. Light resets the SCN not only from rods and cones but also from the retinohypothalamic path that has its own retinal ganglion cells with their own photopigment called melanopsin. They can respond directly to light even if they don't receive input from rods and cones. Located mainly near the nose and respond to the overall average amount of light not to instantaneous changes.
Sleep Spindle
12 to 14 Hz brain waves in bursts that last at least half a second result from oscillating interaction between cells in the thalamus and the cortex
In terms of sleep, what happens through a night?
4-5 cycles a might that each last 90 minutes more SWS early during the night, and more REM later during the night
Brain areas involved in SWS
Basal Forebrain Preoptic Area Adenosine GABA Prostaglandins (produced when you are feeling pain and/or are sleepy)
What are they different stages of sleep? How do the stages differ from one another (including EEG patterns)
Beta waves are representative of alert wakefulness, and alpha waves for relaxed, right before sleep. o Stage 1 & sometimes Stage 2 • "haven't been asleep" - can't remember you've fallen asleep • Stage 1: theta waves • Stage 2: theta waves, sleep spindles, K-complexes o Stages 3 & 4 (aka SWS) • eyes: up & down • difficult to awaken; groggery • deep form of sleep • Stage 3: delta waves (< 50%) (not shown) • Stage 4: delta waves (> 50%) o REM • rapid eye movement • difficult to awaken; alert when woken up • EEG like Stage 1 sleep/awake • muscle atonia • associated with vivid, narrative dreams • penile erection & ↑ vaginal secretions
Examples of common endogenous circadian rhythms
Blood pressure--blood pressure is highest in the early morning Sleepiness--tend to be sleepiest towards midnight to 2:00am and become less sleepy after that. Only to become more sleepy again around 1:00-3:00pm. But, how much thinking you do increasing your sleepiness due to increased brain metabolic activity Body Temperature--we regulate temperature really tightly in our body but it is lowest during the night
Periodic Limb Movement Disorder (nocturnal myoclonus)
Characterized by repeated involuntary movement of the legs and sometimes arms (every 20-30 seconds) Occurs during NREM sleep because you don't have muscle movement during REM sleep. Associated with restless leg syndrome (restless leg syndrome is an issue when awake as well as when asleep. Periodic limb disorder occurs only during sleep) tranquilizers can help suppress the movements in some cases.
How researchers determined the sleep-wake biological clock in humans
Constant bright light makes the cycle run a little faster Constant darkness makes the cycle run a little slower this suggests that there is an internal clock that runs--regardless of the condition--around an approximate 24 hour cycle
Stage 1 Sleep
EEG is dominated by irregular, jagged, low-voltage waves. Overall brain activity is less than in relaxed wakefulness but higher than in other stages of sleep. presence of theta waves--higher in amplitude and lower in frequency
Acetylcholine
Excitatory. But is good for REM sleep due to cortical desynchrony. released during wakefulness and REM sleep. Is not released during slow wave sleep. Increases cortical desynchrony. When your brain is so active it produces a lot of different brain waves. Some of the many brain waves cancels each other out. SWS is cortical synchrony. During wakefulness, its release sharpens attention--thereby increasing accurate, reliable direction of sensory stimuli.
Sleep and Inhibition of Brain Activity
GABA inhibits synaptic activity This makes sure than stimulation doesn't spreak so that you don't become conscious of whatever stimulation does occur.
Stage 2 Sleep
Has Sleep Spindles, which consist of 12 to 14 Hz waves during a burst that lasts at least half a second. They result from oscillating interactions between cells in the thalamus and cortex. Certain density of sleep spindles per night is correlated with IQ and helps keep you deeply asleep. Sleep spindles decrease with age which might be why it is harder for older people to stay asleep. Also has K-complexes, which is a sleep wave associated with temporary inhibition of neuronal firing. Helps keep you asleep.
Brain areas involved in REM
Increased pons and limbic system. Increased parietal and temporal cortex decreased primary visual cortex, motor cortex, and dorsolateral prefronta cortex
Delta Waves
Large amplitude and low frequency less than 50% of wave form in stage 3 sleep but more than 50% of this wave form in stage 4
Melanopsin-containing ganglion cells via the retinohypothalamic path
Not involved in trying to understand what you are seeing Instead it is involved in determining how much light is in the environment Ambient light is then noted and that information is set to the retinohypothalamic path located near your nose and is sensitive to average amount of light If protein production is inhibited due to light in environment, pineal gland will not release much melatonin so you won't be as sleepy If protein production is high due to not much light in the environment, pineal gland will release a lot of melatonin and you wont be sleepy.
What do researchers know about dreams?
Not much is definitively known about sleep, specifically regarding the exact function of sleep but there are two theories that have attempted to explain the possible function of sleep § Activation-synthesis hypothesis: according to this a dream represents the brain's effort to make sense of sparse and distorted information. The dreams begin with PGO waves in the pons and activate some parts of the cortex but not others § The clinico-anatomical hypothesis: this theory states dreams begin with arousing stimuli that are generated within the brain combined with recent memories and any information the brain is receiving fro the senses. Unlike the activation synthesis theory this theory puts less emphasis on the pons, PGO waves, or REM sleep · Dreams are thinking that occurs under unusual conditions and it is similar to mind-wandering during everyday life
What brain areas and chemicals are involved with REM?
PONS
Genes responsible for circadian rhythm
Period (per) and Timeless (tim) produce proteins called PER and TIM. Together they promote sleep and inactivity. there is also clock and overtime. The concentration of these two proteins oscillates over a day based on a feedback interaction among several sets of neurons. Takes a certain amount of time to create a protein. So when it gets to a certain amount, it triggers another protein to start to synthesize. The amount of protein present helps the neuron keep time.
Brain Areas
Pons - Reticular formation (acetylcholine, glutamate) - Locus Coeruleus (norepinephrine) - Raphe nucleus (Serotonin) Hypothalamus - tuberomammillary nucleus (histamine) - excitatory effects - Lateral and posteriur hypothalamic nuclei (hypocretin/orexin) - good for staying awake for 12 hours Basal Forebrain - acetylcholine - increase arounsal
REM Sleep neurotransmitters
REM sleep depends on a relationship between the neurotransmitters serotonin and acetylcholine. Acetylcholine is important for both REM sleep and wakefulness serotonin and norepiniphren interrupt REM sleep.
Raphe Nucleus
Serotonin. Increases arousal and interpheres with REM projects onto the thalamus, hypothalamus, basal ganglia, hippocampus, and neocortex
What types of sleep disorders exist?
Sleep walking, like night terrors, occurs primarily in children. Sleep walking is occurs most often during stages 3 and 4 of sleep and is not accompanied by dreams. § Sleepwalking has been shown to run in families but the causes for it are not very clear. It has been shown, however, that sleep deprivation and stress can certainly be triggers for sleep walking.
Characteristics of the stages of sleep
Stage 1 and sometimes 2--cannot tell they have been asleep when woken up from this stage Stages 3 and 4 (SWS)--eyes roll up and down slowly and they are difficult to awaken. When they are woken up they are groggy since they have been in a deep form of sleep. REM--rapid eye movement, difficult to awaken, alert when woken up. EEG is like stage 1 sleep/awake. Muscle atonia, vivid dreams, penile erection and vaginal secretions.
How is REM affected when people take Prozac, Paxil, or other SSRIs
These types of medications increase levels of serotonin (agonists) If you take these drugs you have less REM sleep. We dont know what the implications are for this. But there is a relationship between sleep and depression. There is a decrease in depression correlated with treatments that reduce REM sleep.
Why did researchers believe we had an internal clock
When people were exposed to bright or dim light they still experienced a 24 hour cycle w/o any cues
Polysomnograph
a combination of EEG and eye-movement records
Narcolepsy
a condition characterized by frequent period of sleepiness during the day, strikes about 1 person in 1,000 gradual or sudden attacks of sleepiness during the day occasional cataplexy - attack of muscle weakness while awake sleep paralysis - inability to move while falling asleep or waking up hypnagogic hallucinations - dreamlike experiences that person has trouble distinguishing from reality, often occurring at the onset of sleep Condition characterized by frequent periods of sleepiness during the day. Have irresistible attacks of refreshing sleep that occur daily over at least 3 months. Symptoms: gradual or sudden attacks of sleepiness during the day. Wake up feeling refreshed but it doesn't last for long. Occasional cataplexy (an attack of muscle weakness while the person remains awake. Is triggered by strong emotions/stress). Sleep paralysis (an inability to move while falling asleep or waking up). Hypnogogic Hallucinations (dreamlike experiences that the person has trouble distinguishing from reality, often occurring at the onset of sleep but technically occurs while you are awake). Total sleep time is normal and the sleep quality is normal. Cause: related to the neurotransmitter orexin. People with narcolepsy lack the hypothalmic cells that produce and release orexin. (orexin is important for maintaining wakefulness during the day). Seems to be a genetic influence involved or due to an autoimmune disorder as narcolepsy onsets at a teenager age. Treatment: stimulants to work against sleep attacks. Antidepressants used to regulate serotonin (serotonin abolished REM)
Brain Death
a condition with no sign of brain activity and no response to any stimulus pronounced by physicians usually after 24 hours of no brain activity
Jet Lag
a disruption of circadian rhythms due to crossing time zones Flying west and "phase-delay" is easier on your body because it is easier to stay up when you are tired. Flying east and "phase-advancing" is more stressful on your body because it is harder to go to sleepy when you are not tired.
PGO Waves
a distinctive pattern of high-amplitude electrical potentials that occur first in the pons, then in the lateral geniculate, and then in the occipital cortex
Histamine
a neurotransmitter that produces excitatory effects throughout the brain. Helps keep arousal A pathway from the hypothalmus
K-complex
a sharp wave associated with temporary inhibition of neuronal firing
Locus Coeruleus
a small structure in the pons, is usually inactive, especially during sleep, but it emits bursts of impulses in response to meaningful events, especially those that produce emotional arousal
Alpha Waves
a steady series of brain waves at a frequency of 8 to 12 per second that are characteristic of relaxation lower frequency but greater amplitude compared to beta waves
Reticular Formation
a structure that extends from the medulla into the forebrain have axons extending to the brain and spinal cord controls motor areas of the spinal cord and selectively increases arousal and attention in various forebrain areas
damage to pons
acting out dreams
Beta Waves
alert wakefulness quickest waveforms
Pineal Gland
an endocrine gland located just posterior to the thalamus that releases the hormone melatonin Endocrine gland that is controlled by the SNC in order to regulate waking and sleeping. Releases the hormone melatonin that influences both circadian and circannual rhythms. Melatonin is secreted mostly at night, which makes us sleepy at that time.
Coma
an extended period of unconsciousness caused by head trauma, stroke, or disease people experience low level of brain activity, no response to stimuli, movements are purposeless
Basal Forebrain
area anterior and dorsal to the hypothalamus; includes cell clusters that promote wakefulness and sleep
How do you measure sleep?
by polysomnograph (EEG, EOG - eye movements, EMG - skeletal muscles)
What is the purpose of REM?
dreams
Night Terrors
experiences of intense anxiety from which a person awakens screaming in terror more severe than a nightmare occur during NREM sleep and are more common in children dream content, if any, is usually simple, such as a single image
Melatonin
hormone that influences both circadian and circannual rhythms released by the pineal gland, mostly at night makes us sleepy Increases sleepiness exogenous evening dose will have no effect because there are already natural levels of melatonin Exogenous single morning dose will have no effect because it cannot overcome the strong zeitgeber of light Exogenous repeated morning doses and afternoon dose are effective You also produce more melatonin naturally if you wear glasses that filter out blue light waves
Activation-Synthesis Hypothesis
idea that a dream represents the brain's effort to make sense of sparse and distorted information
Clinico-anatomical hypothesis
idea that considers dreams as a type of thinking that occurs under unusual conditions
Sleep Apnea
impaired ability to breather while sleeping people have breathless periods of a minute or so from which they awaken gasping for breath causes sleepiness during the day, impaired attention, depression, and sometimes heart problems people show deficiencies of learning, reasoning, attention, and impulse control Impaired ability to breathe while sleeping that leads to excessive sleepiness or insomnia. Causes: genetics, hormones, old-age deteroation of the brain mechanisms that regulate breathig. Obesity Obstructive: snoring is a sign: enlarged tonsils, deviated septum. Central Nervous System: Don't have automatic control over breathing during sleep. Treatments: people are advised to lose weight and avoid alcohol and tranquilizers. Medical options include surgery to remove tissue that obstructs the trachea or a mask that covers the nose and delivers air under enough pressure to keep the passages open (CPAP).
Insomnia
inadequate sleep caused by noise, uncomfortable temperatures, stress, pain, diet, and medications can also be result of epilepsy, Parkinson's disease, brain tumors, depression, anxiety, or other neurological or psychiatric conditions Difficultly initiating or maintaining sleep, or experiencing non-restorative sleep for at least a month. Inadequate sleep. Usually a symptom of other issues (disease, worries, circadian rhythm issues, periodic limb movmement disorder, sleep apnea, use of sleep medication...) The best gauge of this disorder is how someone feels the following day. If you feel tired, you're not getting enough sleep. Different from a "short-sleeper" who doesn't sleep very long but feels restored. Causes: noise, uncomfortable temperatures, stress, pain, diet, medications...can also be the result of epilepsy, Parkinson's disease, brain tumors, depression, anxiety...ect. First try to identify the reasons for your sleep problems before you try to solve them. treatment--teaching good sleep hygiene, benzodiazepines (decreases CNS arousal but is better for acute use rather than longterm use because dependency is an issue and can lead to medullary system problems), melatonin. phase-delayed--has a hard time falling asleep at the usual time because the hypothalamus doesn't think its late enough yet. phase-advanced--will fall asleep easily but awaken early.
Zeitgebers can affect protein synthesis
light-->SCN--> decreases Tim & Per--> decreases sleepiness Your body is trying to match your endogenous sleep/wake cycle with the environment Bright light during early evening leads to phase-delay of the rhythm because it inhibits some protein production and causes you to be a little more alert and slows down your cycle. Bright light during later part of the night leads to phase-advance of the rhythm by making your cycle faster and waking you up again because protein production has been inhibited.
What is the purpose of sleep (SWS)
memory processing - specifically declarative
Minimally Conscious State
occasional, brief periods of purposeful actions and a limited amount of speech comprehension can last for months or years
Suprachiasmatic nucleus (SCN)
part of the hypothalamus; provides the main control of the circadian rhythms for sleep and body temperature
Pontomesencephalon
part of the reticular formation that contributes to cortical arousal maintains arousal during wakefulness and increases it in response to new or challenging tasks
Orexin or Hypocretin
pathway of the hypothalamus that extends to the basal forebrain and stimulates neurons responsible for wakefulness. Necessary for staying awake (not for waking up) Levels of orexin rise throughout the day and drop off once you go to sleep. Seems to be missing in people that have narcolepsy
REM Behavior Disorder
people move around vigorously during their REM periods, apparently acting out their dreams frequently dream about defending themselves against attack, and may punch, kick, and leap about occur mostly in older people, especially older men with brain diseases (parkinson's)
Orexin (hypocretin)
peptide neurotransmitter that increases wakefulness and arousal
Vegetative State
person alternates between periods of sleep and moderate arousal, although even during the more aroused state, the person shows no awareness of surroundings can last for months or years
Endogenous Circadian Rhythm
self-generated rhythm that lasts about a day Affect waking and sleeping, eating, drinking, urination, secretion of hormones, sensitivity to drugs, body temperature, and other variables. Also have circadian rhythms in mood. Circadian rhythms persist without light, but light is critical for resetting them. Other zeitgebers that help reset them are exercise, tides, arousal of any kind, meals, the temperature of the environment. Social stimuli are weak zeitgbers unless they induce exercise or other vigorous activity. Light is the strongest zeitgeber.
Endogenous Circanual Rhythm
self-generated rhythm that lasts about a year
Paradoxical Sleep (REM)
sleep that is deep in some way and light in others sleep stage with rapid eye movements, high brain activity, and relaxation of the large muscles Sleep that is deep in some ways and light in others. synonymous with Rapid Eye Movement Sleep. During this form of sleep, the EEG shows irregular, low-voltage fast waves that indicate increased neuronal activity. In this regard, sleep is light. The postural muscles of the body, including those that support the head, are more relaxed during REM sleep than in others stages. In this regard, sleep is deep. All stages other than REM sleep are called non-REM sleep. REM and dreams sometimes overlap but are not the same thing. Occurs in higher percentage toward the end of sleep with stages 3 and 4 being most active in early hours of sleep.
Slow-Wave Sleep (SWS)
stages 3 and 4 of sleep, which are occupied by slow, large-amplitude brain waves By these stages, heart rate, breathing rate, and brain activity decrease, while slow, large-amplitude waves become more common. By stage 4, more than half the record includes large waves of at least half-second duration. Slow waves indicate that neuronal activity is highly synchronized which is possible because sensory input to the cerebral cortex is greatly reduced, allowing for the few remaining sources of input to synchronize the many cells.
Non-REM (NREM) Sleep
stages of sleep other than REM
Zeitgeber
stimulus that resets the circadian rhythm
cataplexy
sudden attacks of weakness
Patterns of sleep stages
~5 cycles of per night while each cycle is about 90 minutes long. Less SWS as you get towards morning and more SWS at the beginning of sleep. More REM sleep as you get towards morning.
What brain areas or chemicals are involved with sleep (SWS)?
• adenosine (makes you more sleepy, caffeine blocks these receptors) • prostaglandins (related to pain, sleeping more when sick/sore) • GABA (inhibits CNS function) • brain areas - basal forebrain, preoptic area
Where is this clock? What is involved with this clock to work? Dees anything influence the clock? How does it affect sleep? What happens if you damage the clock? Is this the only clock in our body?
• suprachiasmatic nucleus: o if damaged total sleep time isn't affected but the sleep cycles will be erratic o Zeitgebers influence this clock - bright light during early evening leads to phase-delay; bright light during later part of night leads to phase-advance. Melanopsin-containing ganglion cells via the retinohypothalamic path are sensitive to average amount of light, which provides information about the time of day to SCN? o Zeitgebers can affect protein synthesis - light → SCN → decrease TIM and PER → decrease sleepiness. o Melatonin - pineal gland produces this to increase sleepiness. An evening dose will not do much b/c secreted during this time anyways. repeated morning dose will result in increased sleepiness b/c bypass effects of light. afternoon dose will increase sleepiness (phase-advance?)
What brain areas and chemicals are involved with wakefulness?
•orexin/hypocretin(people with narcolepsy have a lack of this; maintains wakefulness) • pons o reticular formation - acetylcholine, glutamate; maintains arousal but also increases arousal in response to new task. o locus coeruleus - norepinephrine; interferes with REM; responds to meaningful events (emotional) o raphe nucleus - serotonin; increase arousal; interferes with REM • Hypothalamus o tuberomammillary nucleus - histamine; esp. to novel stimuli o lateral hypothalamic nuclei - hypocretin/orexin; maintains arousal. • Basal forebrain o acetylcholine; increases cortical desynchrony
