#19:Sleep and Dreams Nov 23, 2004 Lecture 19 - Sleep and Dreams The Abstract: You spend about one third of your life asleep or, at least, you were built todo so. Why? And what happens if you abuse the system? This lecture will focus on fourquestions: 1) What does sleep behavior look like? How is it structured? 2) Why do we sleep? And what happens if we don't? 3) Why do we dream? 4) Can we extract any meaning from our dreams? The answers, in a nutshell, are: We were designed by nature to sleep in a consolidatedperiod of about 8 hours during the night. Within that 24 hour structure is another structurethat sends us into dreaming sleep every 90 minutes or so. We dream as a by product of thebiology. Freud didn't know the biology and had an elaborate theory of the role of dreams asa safe venting of repressed wishes. It is possible to reconcile Freud's core ideas withmodern sleep research and we will try to do that by the end. Lecture Notes Why do you spend about 1/3 of your life in an altered state of consciousness? PART ONE: What does the behavior look like? The drive to sleep in driven by two (main) forces Force #1: Circadian rhythms Approx 24 hrs How do we measure this? This picture shows running wheel activity in a mouse.Each line is a day (plotted twice). Black = activity. The horizontal arrow shows the day onwhich the light was turned on continuously. page 1 of 5 Graph removed for copyright reasons.#19:Sleep and Dreams Nov 23, 2004 Circadian rhythms can beEntrained (to what?) or Free running (This mouse free runs with a cycle of about 23.5 hrs) How do we measure this in humans? Core body temp in humans Circulating hormones (e.g. melatonin) Force #2: Homeostatic sleep pressure = time awake (more or less) Bring these two together and you have a mechanism for producing 8 hrs sleep. The behavior changes with age: The national debt (sleep debt, that is) Many bad things are associated with sleepiness There is structure within sleep, too AWAKE DEEP SLEEP "REM" EEG ElectroEncepholoGraphy EOG ElectroOculoGraphy EMG ElectroMyoGraphy (myo = muscle And….More structure: The interaction of circadian and 90 minute cycles page 2 of 5#19:Sleep and Dreams Nov 23, 2004 A larger scale structure to a night of sleepmore Slow wave early and more REM late. It matters when you sleep, not just how much PART TWO: Why do we sleep? Some theories 1) 2) 3) …more The role of sleep in learning perceptual learning studies What is the texture learning task? Karni, A., & Sagi, D. (1993). The time course of learning a visual skill. Nature, 365(16Sept), 250-252. Stickgold, R., James, L., & Hobson, J. A. (2000). Visual discrimination learning requiressleep after training. Nature Neuroscience, 3(12), 1237-1238. page 3 of 5#19:Sleep and Dreams Nov 23, 2004 The power of napping! Mednick S, Nakayama K, Stickgold R. 2003. Sleep-dependent learning: a nap is as good asa night. Nat Neurosci 6: 697-8 Can you do your problem set in your sleep?" Wagner U, Gais S, Haider H, Verleger R, Born J. 2004. Sleep inspires insight. Nature 427: 352-5 Sleep deprivation makes you… Slow (what is the evidence) Careless Not to mention stupid and sleepy Will sleep deprivation kill you?�What about REM deprivation?�PART THREE: Why do we dream? (well, we have sort of talked about this by now, so… PART FOUR: Can we extract any meaning from our dreams? differences from waking consciousness. Dreams seem to cry out for interpretation In about 1900, Freud published "The Interpretation of Dreams" A quick version of Freud's theory�Purpose: Part 1- to release unconscious steam�What is Wish fulfillment�What kind of wishes? What is the Day residue page 4 of 5#19:Sleep and Dreams Nov 23, 2004 Is there any evidence that you dream about the prior day? Stickgold R, Malia A, Maguire D, Roddenberry D, O'Connor M. 2000. Replaying thegame: hypnagogic images in normals and amnesics. Science 290: 350-3 Purpose: Part 2 - protect the sleeper�From what?�another Freudian defense mechanism What is the latent content of the dream? What is the manifest content? A standard complaint about the idea of disguise. Cautions and comments about Freudian dream interpretaiton Problems with Freudian theory�Problems from within psych.�The BIG problem of REM and the structure of sleep Who has REM? What is REM sleep for? (recap) Can we reconcile Freud with the biology of dreams? A hypothesis fromThe New Psychology of Dreaming. by Richard M Jones. Pelican 1978 page 5 of