Question of the Day. Biological Rhythms. Three Minute Review - Motivation. Circadian Rhythms

Transcription

1 Question of the Day Patients with spinal cord damage do not feel as many effects of sympathetic nervous system activation as normal subjects. These patients also report feeling less intense emotions than normal subjects. In fact, the degree of emotional loss is greater the higher up in the spinal cord the damage occurred. Which of the following theories of emotion best explains this result? A. Common Sense theory B. Cannon-Bard theory C. James-Lange theory D. Facial Attribution theory E. Misattribution of Emotions theory Three Minute Review - Motivation MOTIVATION Pleasure centre similar effects in humans & rats rats go to extremes to stimulate pleasure centre dopamine appears to be critical neurotransmitter EMOTION Why do we have emotions? Communication, decision-making, attention & memory, interpersonal relations Two dimensions emotion x arousal Arousal sympathetic vs. parasympathetic nervous system Yerkes-Dodson law subjects perform best at moderate levels of arousal optimal level of arousal depends on difficulty of task Biological Rhythms Circannual rhythms ~1 year e.g., migration, hibernation Infradian rhythms >1 day, < 1 year e.g., menstruation Circadian rhythms ~1 day circ = about + dia = day ( about a day) e.g., sleep, temperature Ultradian rhythms < 1 day e.g., heartbeat, respiration Theories of Emotion 1. Common Sense bear fear heart races 2. James-Lange bear heart races fear facial feedback theory 3. Cannon-Bard bear heart races & fear 4. Schachter s Attribution Theory emotion is a combination of bodily sensations and cognitive appr aisal of situation bear heart races & realize dangerous situation fear misattribution of emotion Circadian Rhythms Brain Areas Involved in Emotion amygdala daylight cues bodily changes: temperature and sleep 1

2 Other Sleep Disruptions Video (Brain, Disk 1, #13, Sleep & Circadian Rhythms, start at 2:20, ends at 6:03, 3:43 total) How did Michel Siffre study the circadian rhythm for 7 months in 1972? What cues to time were available to him? How did his body know what time it was? How long is the natural circadian rhythm for the majority of adults? Desynchronized Cycles Switch to daylight savings time lose an hour of sleep in April à 7% more traffic accidents Blue mondays Shift work more accidents happen after employees have undergone shift changes accidents due to human error are most likely to happen in the middle of the night (Three Mile Island, 1979; Chernobyl, 1986; Exxon Valdez, 1989) or with sleepdeprived employees or decision makers (Space Shuttle Challenger, 1986). How does the body know what time it is? aside from the primary visual pathway (retina à thalamus à occipital lobe), other pathways from the retina go to other areas suprachiasmatic nucleus (SCN) in the hypothalamus SCN ð pineal gland Jet Lag flying westbound time is earlier there so you have to stay up later leave London Ontario 9:00 p.m. (2:00 a.m. in the UK) arrive London UK 8:00 a.m. (3:00 a.m. in Ontario) Do you nap right away (then your schedule is way off) or stay up all day till it s local bedtime? arrive London Ontario 2:00 p.m. (7:00 p.m. in the UK) Just try to stay up a few extra hours and you ll be fine leave London UK 1:00 p.m. (8:00 a.m. in Ontario) flying eastbound time is later there so you have to go to bed earlier most people find this much harder baseball teams that fly east win fewer games than those that fly west (37% vs. 44%) Pineal Gland Rene Descartes thought it was the seat of the soul Really, it s just an endocrine (hormone) gland secretes melatonin at night (with little secreted during the day) melatonin taken 1-2 hours before bed may help induce sleep some people use it to treat jet lag 2

3 Do you really need sleep? Peter Tripp, 1959 Radio DJ who participated in a Wake -a-thon sleep deprived for 200 hours (8 days) took a lot of amphetamines to keep awake hallucinations, paranoia, psychosis; friends said he was never quite the same afterward was it the speed or the sleep deprivation? What do the waves mean? specific wave forms are reliably associated with specific states each electrode sums the output of many, many neurons Analogy: like holding a microphone over a football stadium and trying to figure out what the group sounds are telling you Randy Gardner, 1963 science fair project broke record for continuous wakefulness: 264 hours (11 days) used no drugs, not even caffeine supervised by William Dement, sleep researcher managed remarkably well some hallucinations, irritability, slurred speech, confusion, paranoia slept 15 hours after waking marathon ended Sleep Deprivation What do the waves mean? become really tired, esp. 2:00-6:00 a.m. can cause lapses in attention and memory microsleeps fall asleep for a few seconds or a minute eyelids droop and you become less responsive to stimuli people are often unaware that they blanked out can be fatal when driving driving tired can be worse than driving drunk after being awake 18 hours, your performance is comparable to a blood alcohol level of 0.05% (~ 3 drinks in one hour for a 150 lb male) How can we measure sleep? Electroencephalogram (EEG) measures voltage difference between any two points on the scalp (usually with many pairs of electrodes compared) different states à different waveforms When each neuron is doing its own thing, the pattern looks like irregular high frequency noise When the neurons are doing things in synchrony, the pattern looks like regular low frequency noise Sleep Waves different waves characterize different stages awake, REM sleep irregular high frequency waves indicate unsynchronized activity middle stages weird blips like spindles and K-complexes deep sleep low frequency waves (e.g., delta waves in Stage 4) indicate synchronized activity 3

4 Rapid Eye Movement (REM) Sleep eyes move rapidly under closed eyelids when awoken from REM sleep, subjects are most likely to report that they were dreaming (though in non-rem sleep, subjects may report sleep thoughts (Ever had a Tetris dream?) lose muscle tone paralyzed (but can move during non-rem sleep, tossing and turning) Animals that graze and browse sleep only 2 or 3 hours every 24 hrs. The rest of the time they are eating and keeping an eye out for predators Predators, like the lion, spend more than 60% of their life asleep. The do not have to spend so much time eating as grazing animals -- and they also do not have to worry about predators. Progression through the stages Things to note: progress from Stage 1 to 4 then back up and into REM first REM period after ~90 minutes (if not sleep-deprived) and ~every 90 minutes thereafter spend more time in deep stages in early evening, more time in light stages towards morning REM periods typically get longer as evening progresses Early humans probably slept at night because their hunting and gathering skills were dependent on using vision -- a sense that works best in daylight hours. The rest of the time they were better off sleeping in a protected shelter hidden away from predators. Why do we sleep? Isn t sleep just a waste of time? Why bother? No one knows for sure, but there are some interesting ideas floating around 1. Restoration Theory Your body needs to rest and recover runners sleep more after a marathon regular exercise can help sleep 2. Preservation Theory why risk being killed if you can only get food in the day? Is there a blood chemical that accumulates while we re awake? Eng and Chang Bunker Some Siamese twins who share a common blood supply show independent sleep cycles. Fully Awake Right Hem Asleep Left Hem Asleep Dolphins show independent sleep/wake cycles in the two hemispheres 4

5 Brain Structures Involved in Sleep Infants dream a lot! Reticular Activating System (RAS) stimulation awakelike EEG waves damage coma, sleeplike EEG waves Pons ( bridge ) damage to pons can reduce or abolish REM sleep has connections to other brain areas to activate cortex, start eye movements and block movements during REM perhaps this indicates that dreaming is crucial for developing brain pathways? What do dreams mean?: Two Theories Dreaming May Help You Remember Sigmund Freud 1) The Interpretation of Dreams (1900) dreams are a meaningful output of the subconscious mind manifest content: the dream as the dreamer remembers it latent content: what the dream symbolizes that is disguised to protect the dreamer REM sleep may help you consolidate memories (i.e., encode them from short term to long term memory) Sleep helps you learn (Karni et al., 1994) trained subjects on a hard visual task subjects with normal night s sleep performed well the next day subjects who had been awoken during non-rem periods performed well the next day subjects who had been awoken during REM sleep performed poorly the next day Even naps may help (Mednicket al., 2002) trained subjects on a hard visual task for a long time as training wore on, subjects who did not nap got worse subjects who took a nap maintained good performance a 1-hour nap was better than a 30-minute nap What do dreams mean?: Two Theories J. Allan Hobson (contemporary sleep expert) 2) Activation Synthesis Hypothesis neural stimulation from the pons activates other brain areas that are involved in waking consciousness the sleeping mind tries to make sense of random neural firing by weaving a story during REM, frontal lobes are deactivated (dreams lack logical planning and thinking) and limbic system is activated (dreams often have emotional content, esp. negative emotions) dreams are side effects of random neural activity 5