Sleep, Learning, and Dreams: Off-Line Memory Reprocessing Stickgold, Hobson, Fosse, Fosse Group #1 D. Doan, B. Gee, E. Lee, J. Tran February 13, 2008

Introduction Association between sleep, learning, and memory Association between sleep, learning, and memory Behavioral studies Behavioral studies Physiology of sleep Physiology of sleep Cognitive processing in REM and NREM Cognitive processing in REM and NREM Dreams and memory Dreams and memory Theories of dreams Theories of dreams

Behavioral Studies of Learning and Memory in Sleep REM sleep plays a role in: REM sleep plays a role in: Learning Learning Procedural memory Procedural memory Emotional memories Emotional memories Modifying neocortical networks Modifying neocortical networks

Behavioral Studies of Learning and Memory in Sleep Animal studies Animal studies Smith (1985) Smith (1985) “REM windows” “REM windows” Occurred after procedural training Occurred after procedural training REM sleep increases REM sleep increases REM deprivation leads to diminished retention REM deprivation leads to diminished retention Deprivation-induced stress Deprivation-induced stress

Behavioral Studies of Learning and Memory in Sleep Human studies Human studies Posttraining REM deprivation impairs procedural learning Posttraining REM deprivation impairs procedural learning Enhanced recall for emotional memories after REM sleep Enhanced recall for emotional memories after REM sleep e.g. major depression and PTSD e.g. major depression and PTSD

Behavioral Studies of Learning and Memory in Sleep Visual texture discrimination task Visual texture discrimination task

Behavioral Studies of Learning and Memory in Sleep Visual texture discrimination task Visual texture discrimination task

Behavioral Studies of Learning and Memory in Sleep REM and Modification of Neocortical Networks REM and Modification of Neocortical Networks Not just procedural learning Not just procedural learning Complex logic games Complex logic games Foreign language acquisition Foreign language acquisition Intensive studying Intensive studying

Sleep Architecture and Physiology Synchronous brain activity Synchronous brain activity SWS sleep SWS sleep Cortical long-term potentiation (LTP) Cortical long-term potentiation (LTP) Sharp wave potentials Sharp wave potentials REM sleep REM sleep Hippocampal LTP Hippocampal LTP Hippocampo-neocortical dialog Hippocampo-neocortical dialog

Sleep Architecture and Physiology Synchronous brain activity cont. Synchronous brain activity cont. Ponto-geniculo-occipital (PGO) waves Ponto-geniculo-occipital (PGO) waves Visual cortex Visual cortex Motor cortex Motor cortex Amygdala Amygdala Hippocampus Hippocampus Transition from NREM to REM Transition from NREM to REM Gamma waves Gamma waves Binding problem Binding problem

Sleep Architecture and Physiology Neuronal Replay Neuronal Replay SWS SWS Neuronal replay occurs after half an hour Neuronal replay occurs after half an hour REM REM Neuronal replay occurs after 24 hours Neuronal replay occurs after 24 hours Implications Implications

Sleep Architecture and Physiology Neuromodulators Neuromodulators Noradrenergic (NE) locus coeruleus Noradrenergic (NE) locus coeruleus Serotonergic (5-HT) dorsal Raphe nucleus Serotonergic (5-HT) dorsal Raphe nucleus Cholinergic (Ach) nuclei of dorsolateral pons Cholinergic (Ach) nuclei of dorsolateral pons

Sleep Architecture and Physiology Regional Brain Activation Regional Brain Activation PET studies PET studies SWS SWS All brain regions less active than waking All brain regions less active than waking REM REM Dorsolateral prefrontal cortex (DLPFC) ↓ Dorsolateral prefrontal cortex (DLPFC) ↓ Anterior cingulate and medial orbitofrontal cortices ↑ Anterior cingulate and medial orbitofrontal cortices ↑ Amygdala ↑ Amygdala ↑

Sleep Architecture and Physiology Plasticity and Learning Plasticity and Learning Pontine reticular formation (PRF) activation and PGO waves Pontine reticular formation (PRF) activation and PGO waves Consolidate learning and form new associations Consolidate learning and form new associations Protein synthesis and phosphokinase A (PKA) Protein synthesis and phosphokinase A (PKA) Hippocampal learning Hippocampal learning

Sleep Architecture and Physiology Plasticity and Learning Plasticity and Learning Visual deprivation cat studies Visual deprivation cat studies

Cognitive Processing in REM and NREM Approaches to studies of dreaming Approaches to studies of dreaming Identifying isomorphisms between Identifying isomorphisms between Neurophysiological features of REM Neurophysiological features of REM Formal properties of REM dreams Formal properties of REM dreams Measuring cognitive processes Measuring cognitive processes

Cognitive Processing in REM and NREM Measuring cognitive processes Measuring cognitive processes Semantic priming favors weaker associations after REM awakenings than after NREM awakenings Semantic priming favors weaker associations after REM awakenings than after NREM awakenings Solving anagrams is similarly enhanced after REM compared with NREM awakenings Solving anagrams is similarly enhanced after REM compared with NREM awakenings

Cognitive Processing in REM and NREM Semantic priming across wake-sleep states Semantic priming across wake-sleep states

Cognitive Processing in REM and NREM REM favors more fluid thinking than NREM REM favors more fluid thinking than NREM

Cognitive Processing in REM and NREM Physiological characteristics of REM Physiological characteristics of REM Shift in neuromodulatory balance Shift in neuromodulatory balance ↓ activity in DLPFC & ↑ activity in anterior cingulate cortex and amygdala ↓ activity in DLPFC & ↑ activity in anterior cingulate cortex and amygdala Decreased outflow of information from hippocampus to neocortex Decreased outflow of information from hippocampus to neocortex

Cognitive Processing in REM and NREM The brain in REM is tuned more for the processing of associative memories than for the simple consolidation of recent memory traces The brain in REM is tuned more for the processing of associative memories than for the simple consolidation of recent memory traces

Dreams and Memory Verbal reports Verbal reports More hallucinations and less directed thinking More hallucinations and less directed thinking Memory sources Memory sources Episodic memory Episodic memory

Dreams and Memory Emotions and dreaming Emotions and dreaming Physiology Physiology Sleep onset dreaming Sleep onset dreaming Video game studies Video game studies

Dream Theories Important Questions Important Questions How dreams are constructed How dreams are constructed What is the purpose of the construction What is the purpose of the construction Non-uniform states Non-uniform states Unique REM physiology Unique REM physiology Weak neo-cortical associations Weak neo-cortical associations

Dream Theories Role of dreaming Role of dreaming Evaluating neocortical association Evaluating neocortical association Strengthening or weakening associations Strengthening or weakening associations

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