SLEEP. -in 1953, first demonstration that brain was active during sleep. 4. Stages 3& 4: Delta Waves, large slow waves; deep sleep

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Scot Mark Stephens
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1 SLEEP DEF: altered state, between waking and unconsciousness, defined by specific patterns of brain 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 Vinci 2. Edison 3. Lab assessments 2. Minimum amount of regular sleep - about 4 hrs/night 3. Microsleeps: brief episodes of sleep brain activity that intrude upon waking state as a result of deprivation II. What are the different stages of Sleep? -in 1953, first demonstration that brain was active during sleep 1. Drowsy: alpha waves 2. Stage 1: Light sleep; theta waves; sensation of falling or limbs jerking; geometric shapes, colors 3. Stage 2: sleep spindles; K-complexes( triggered by loud noise, shows brain has to work to keep you asleep) 4. Stages 3& 4: Delta Waves, large slow waves; deep sleep 5. REM: beta waves; short, frequent, desynchronized brain waves, muscle paralysis; PGO waves III. What are the consequences of sleep deprivation? 1. REM Deprivation -irritation, increased aggression, hunger 2. Total Sleep Deprivation: animal & human studies -little effect of short deprivation: decreased performance on boring tasks -eventual death, failure of immune system

2 IV. Function of Sleep A). Stages 3 & 4: 1. Repair Theory: release of growth hormones; immune function is enhanced 2. Brain Temperature Regulation 3. 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 during previous waking activity -indicates that representation of waking experience is instantiated in neuronal pathways during sleep B). 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 drawing 2. Brain Development: promotes neuronal connections, seen in fetuses and newborns at increased rates 3. Erasing unnecessary memories: Crick and Mitchelson -Evidence: familiar environments correlated with frequency of theta waves that facilitate LTD V. Why do we dream? -Occur during both REM and NREM sleep 1. Freud: Royal Road to Unconscious -dreams contain hidden content that represents unconscious conflicts -manifest vs. latent content -wish fulfillment 2. 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: On

3 3. Evolved Threat: dreams simulate threatening events to allow rehearsal of coping strategies VI. Other Issues A). Dreams & creativity -may promote creativity by promoting new, unusual associations B). Pattern and Mental State: Normal Subjects: those with unpleasant day tend to have negative dreams at the beginning of the night, and pleasant at the end Depressed: 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 either wake during nightmare or alter content while asleep.

4 ARTICLE: Aserinsky & Kleitman: first demonstration of REM sleep correlates -Methods: electrodes attached to upper and lower inferior orbital ridges; inrernal & external canthi -Results: mean duration of sleep was 7hrs first appearance of REM 1.40hrs-4.50hours after going to bed range of first REM episode 6-53 min subsequent, lengthier REM episodes occurred REM amplitude was uv, 1 sec EEG was low amplitude( 5-30 uv), irregular, short frequency REM correlated with increased HR, resp 20/27 reported dreams when awakened from REM; other 7 feeling of having dreamed or no recall 19/23 report dreams in NREM Conclusions: changes in EEG, ocular motility, autonomic NS are related and are manifestations of dreams Implications: Technique to study dreams -can be done in animals -can be done without waking subjects ARTICLE: M.A. Wilson & B.L. McNaughton, Reactivation of Hippocampal Ensemble Memories During Sleep, Science 265, p676 (1994) Theories of memory encoding posit that representations of memory are coded by changes in functional interaction between neurons in the hippocampus Hebb: cells that fire together, wire together Previous studies show that hippocampal cells active during waking are reactivated during sleep. Methods: -rats implanted with microdrive arrays -trained in spatial tasks -activity of CA1 cells monitored simultaneously during sleep periods before and after behavior

5 -cell pairs co-active during RUN were examined Post Sleep and compared with cells not coactive during behavior Results: cells coactive during behavior showed increase in correlation during sleep compared to non coactive cells Conclusion: Ensembles of neurons active during waking activity show reinstatement of patterns of activity during sleep -may provide mechanism for memory consolidation: neuronal states encoded during waking in hippocampus are played back and consolidated during SWS

Sleep stages. Awake Stage 1 Stage 2 Stage 3 Stage 4 Rapid eye movement sleep (REM) Slow wave sleep (NREM)

Sleep stages. Awake Stage 1 Stage 2 Stage 3 Stage 4 Rapid eye movement sleep (REM) Slow wave sleep (NREM) Sleep stages Awake Stage 1 Stage 2 Stage 3 Stage 4 Rapid eye movement sleep (REM) Slow wave sleep (NREM) EEG waves EEG Electrode Placement Classifying EEG brain waves Frequency: the number of oscillations/waves