Pt 1 - SleepWhat techniques are used to understand brain and muscle activity during sleep?EEG: electroencephalogramEMG: electromyogram, an electrical potential recorded from an electrode placed on or in a muscle (chin)EOG: electro-oculogram, an electrical potential from the eyes, recorded by means of electrodes placed on the skin around them – detects eye movementsWe also measure heart rate, respiration, etc.Know the order in which we move thru the stages of sleep, and generally that brain activity slows and becomes more synchronized (from low-amplitude high-frequency activity to high-amplitude low- frequency) as we get into deep sleep, and how REM sleep is different. Know when we would see alpha activity vs beta activity vs delta activity, and what sleep spindles and k-complexes are associated with.Awake: alpha activity (relaxation), beta activity (arousal)Stage 1: theta activitytransition between wakefulness and sleep, neurons in cortex becoming more synchronizedStage 2: sleep spindle, k complexStage 3: Delta activityStage 4: Delta activitySynchronous activity during the deepest stages of slow-wave sleepDown state: neurons are resting, hyperpolarizedUp state: neurons excited/firing, depolarizedREM: Theta activity, Beta activityCompare and contrast REM sleep and non-REM sleep in terms of functions of each (we spent a bit of time on this), EEG activity, muscle tone, and ability to rouse.SWS (slow-wave): stages 3-4, synchronized EEG activity, hard to rouse (groggy), no dreaming but possible thoughts of emotionsFunctions: function is to rest the brain (not body)REM: Desynchronized EEG activity, rapid eye movements, muscle paralysis, dreaming, easy to rouse (would appear alert)Functions: brain development and learningWhat brain regions are active and inactive during REM sleep (think of this in terms of dreaming)? BTW, can dreams occur in non-REM sleep? What is more common (cognitively) than dreaming in non-REM sleep?REM: low activity in prefrontal cortex (poor organization and lack of logic in dreams), low activity in v1 (no visual input), high activity in visual association cortex (hallucinations/dreams), rapid eye movementsDreams CAN occur in non-REM sleep, but more common in REMWhat is evidence that REM and non-REM sleep might be involved in consolidating different types of memories?REM: facilitates consolidation of implicit (non-declarative) memoryLearn a non-declarative task in morning  nap  tested in eveningNo nap  test performance worse than at end of trainingNo REM nap  test performance about the same as end of trainingREM nap  test performance improved over end of trainingSWS: facilitates consolidation of declarative memoryLearning is even better if “thinking” about that info during SWSLearn list of paired words (declarative) vs. mirror drawing (non)SWS nap improved performance of declarative but not non-declarative taskWhat are symptoms of sleep deprivation?Affects cognitive more than physical abilities – can tolerate a lot – but can also be fatalSymptoms: confusion, weight loss, inability to regulate body temperatureWhat is the role of adenosine in sleep?Glycogen is stored energy for neurons – can be converted to glucose for neurons to useMore brain activity  glycogen level fall (from being used)Decreased glycogen is associated with increased adenosine (breakdown of ATP)Adenosine is inhibitoryAdenosine is sleep promotingIntracerebroventricular infusion  increase sleepAdenosine receptor antagonist (caffeine)  decrease sleepEspecially important for SWSLess adenosine  less time in SWSSlower breakdown of adenosine  more SWSWhat neurotransmitters are “wakefulness promoting”?NT: Acetycholine, Noepinephrine, Serotonin, Histamine, Orexin/HypocretinHigh during wakefulness, low during SWS, low during REM sleep (except Ach)We discussed 3 general factors controlling sleep: homeostatic, allostatic, and circadian. Understand these, and what chemical signals are important for each.Homeostatic: go without sleep, sleep longer to make up your sleep debtAdenosine is importantAllostatic: Ractions to stressful factors in the environment that override homeostatic controlStress hormones very important, as well as neuropeptides involved in hunger and thirstMight stay awake when tired if being threatened, or if really hungry or thirstyCircadian: Restrict sleep to certain portions of the daySuprachiasmic nucleus (SCN) and melatonin from pineal gland very importantUnderstand the sleep-wake flip-flop, and the role of orexin in this system. In what major brain region in the “sleep promoting” region?How does adenosine affect the sleep-wake flip-flop? How do other things like circadian signals and hunger or satiety signals affect it?Sleep-wake flip flop (Saper 2001): this system is good bc flip flop happens quickly, best thing is to be asleep or awake; not somewhere in betweenSleep promoting region: vlPOAOther factors:Bad because it is unstable  but Orexin provides stability to systemExcitatory: circadian signals and hunger signalsInhibitory: satiety signals and adenosineWhat brainstem regions are important in REM sleep, and what do they do?Excitatory projections from pons (REM-ON;1)Activate cholinergic cells in midbrain  directly or indirectly depolarize thalamic neuronsMRF also activates cells for control of eye movementInhibitory reticulospinal neuronsDecrease muscle toneGenerally speaking what is insomnia? What are some causes of insomnia?Insomnia: trouble going to sleep or staying asleepCauses: psychiatric distress (depression), chronic medical disorders, pain, elderly, drug dependency insomnia (caused by side effects of ever-increasing doses of sleeping medications)What is sleep apnea?Cessation of breathing while sleepingDuring an episode, level of CO2 stimulates chemoreceptors which wakes person up gasping for air  O2 returns to normal, cycle repeatsCauses:Airway obstructed during sleep (obesity)Brain mechanisms for breathing cease to function properly (elderly)What is narcolepsy? Understand the various components that can occur along w/ narcolepsy.Narcolepsy: A sleep disorder (genetic and environmentally influenced) characterized by periods of irresistible sleep, attacks of cataplexy, sleep paralysis, and hypnagogic hallucinationsSleep attack: an irresistible urge to sleep during the day, after which the person awakens feeling refreshed (2-5 mins)Happens when boredCataplexy: complete paralysis that occurs during wakingSame mechanism