SLEEPDEF: altered state, between waking and unconsciousness, defined by specific patterns ofbrain activity.I. How much sleep do I need?1. Long vs. Short Sleepers-across developmental stages-individual variations-Assessing claims that some people sleep as little as one hour per night:1. Da Vinci2. Edison3. Lab assessments2. Minimum amount of regular sleep- about 4 hrs/night3. Microsleeps: brief episodes of sleep brain activity that intrude upon waking state as aresult of deprivationII. What are the different stages of Sleep?-in 1953, first demonstration that brain was active during sleep1. Drowsy: alpha waves2. Stage 1: Light sleep; theta waves; sensation of falling or limbs jerking; geometric shapes,colors3. Stage 2: sleep spindles; K-complexes( triggered by loud noise, shows brain has to workto keep you asleep)4. Stages 3& 4: Delta Waves, large slow waves; deep sleep5. REM: beta waves; short, frequent, desynchronized brain waves, muscle paralysis; PGOwavesIII. What are the consequences of sleep deprivation?1. REM Deprivation-irritation, increased aggression, hunger2. Total Sleep Deprivation: animal & human studies-little effect of short deprivation: decreased performance on boring tasks-eventual death, failure of immune systemIV. Function of SleepA). Stages 3 & 4:1. Repair Theory: release of growth hormones; immune function is enhanced2. Brain Temperature Regulation3. Memory Consolidation:- consolidation of new declarative or explicit memory-Evidence: McNaughton study of hippocampal place cells-replay during sleep of neuronal firing patterns recorded in rat hippocampus duringprevious waking activity-indicates that representation of waking experience is instantiated in neuronal pathwaysduring sleepB). REM:1. Facilitates Procedural or emotional memory processing-forms new associative links between memory traces already stored in the cortex-Stickgold Study: off-line processing-Evidence: REM deprivation decreases performance on mirror drawing2. Brain Development: promotes neuronal connections, seen in fetuses and newborns atincreased rates3. Erasing unnecessary memories: Crick and Mitchelson-Evidence: familiar environments correlated with frequency of theta waves that facilitateLTDV. Why do we dream?-Occur during both REM and NREM sleep1. Freud: Royal Road to Unconscious-dreams contain hidden content that represents unconscious conflicts-manifest vs. latent content-wish fulfillment2. Hobson & McCarley: Activation-Synthesis-based on results from brain activity patterns during sleep-Dreams are a narrative structure we impose on random firing of neurons-neocortex creates meaning , just as it does in real life. But, DorsolateralPFC, rational center,is off-PONS: LC, Raphe off : ACH ON-Dorsolateral PFC: deactivated-Amygdala, Visual association areas Primary is off), sensory cortex: ON-Vestibular system: On3. Evolved Threat: dreams simulate threatening events to allow rehearsal of copingstrategiesVI. Other IssuesA). Dreams & creativity-may promote creativity by promoting new, unusual associationsB). Pattern and Mental State:Normal Subjects: those with unpleasant day tend to have negative dreams at the beginningof the night, and pleasant at the endDepressed: dreams bland at beginning , negative at end-but if pattern reverses, predicts recovery from depression.C). Guided Visualization: patients taught to visualize neutral task during day, then eitherwake during nightmare or alter content while asleep.ARTICLE: Aserinsky & Kleitman: first demonstration of REM sleep correlates-Methods: electrodes attached to upper and lower inferior orbital ridges; inrernal & externalcanthi-Results:mean duration of sleep was 7hrsfirst appearance of REM 1.40hrs-4.50hours after going to bedrange of first REM episode 6-53 minsubsequent, lengthier REM episodes occurredREM amplitude was 300-400 uV, 1 secEEG was low amplitude( 5-30 uV), irregular , short frequencyREM correlated with increased HR, resp20/27 reported dreams when awakened from REM; other 7 “feeling of havingdreamed” or no recall19/23 report dreams in NREMConclusions: changes in EEG, ocular motility, autonomic NS are related and aremanifestations of dreamsImplications: Technique to study dreams-can be done in animals-can be done without waking subjectsARTICLE: M.A. Wilson & B.L. McNaughton, Reactivation of Hippocampal EnsembleMemories During Sleep, Science 265, p676 (1994)Theories of memory encoding posit that representations of memory are coded by changesin functional interaction between neurons in the hippocampusHebb: cells that fire together, wire togetherPrevious studies show that hippocampal cells active during waking are reactivated duringsleep.Methods:-rats implanted with microdrive arrays-trained in spatial tasks-activity of 50-100 CA1 cells monitored simultaneously during sleep periods before andafter behavior-cell pairs co-active during RUN were examined Post Sleep and compared with cells notcoactive during behaviorResults: cells coactive during behavior showed increase in correlation during sleepcompared to non coactive cellsConclusion:Ensembles of neurons active during waking activity show reinstatement of patterns ofactivity during sleep-may provide mechanism for memory consolidation: neuronal states encoded during wakingin hippocampus are played back and consolidated during