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Sleep and Memory: Overview. Rachel Miriani Neural Systems Nov 29, 2004. Introduction to Memory. Memory. “The mental faculty of retaining and recalling past experiences; the ability to remember.” 1. Introduction to Memory. Memory. Declarative. Non-Declarative.
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Sleep and Memory: Overview Rachel Miriani Neural Systems Nov 29, 2004
Introduction to Memory Memory “The mental faculty of retaining and recalling past experiences; the ability to remember.”1
Introduction to Memory Memory Declarative Non-Declarative “Consciously accessible memories of fact-based information”- The What. Non-conscious
Introduction to Memory Memory Declarative Non-Declarative What. Non-conscious Semantic Episodic Not event specific general knowledge Experiences and events from ones past.
Introduction to Memory Memory Declarative Non-Declarative What. Non-conscious Episodic Semantic Procedural Skills Conditioning Non-associative Priming
Introduction to Memory Memory Declarative Non-Declarative What. Non-conscious Episodic Semantic Procedural Skills Conditioning Non-associative Priming
Introduction to Sleep: REM Sleep REM NREM • REM: Rapid Eye Movement • Muscle tone decreases. • EEG oscillations are desynchronized • Gamma waves appear- 30-80Hz synchronous activity is similar to being awake. • Periodic bursts of rapid eye movement. • PGO waves appear- Phasic endogenous waveforms expressed in the pons (P), lateral geniculate nuclei of the thalamus (G), and the occipital cortex (O). Stages 1 2 3 4
Introduction to Sleep Sleep REM NREM Stage 2 characteristically has phasic electrical events: *K Complexes- Large electrically sharp EEG waves *Sleep Spindles- Short 7-14 Hz synchronized oscillations in the EEG Stages 1 2 3 4 *Increasing depth of sleep *EEG frequency slows down
Introduction to Sleep Sleep REM NREM Stages 1 2 3 4 Stages 3 and 4 are typically grouped together and dubbed Slow Wave Sleep (SWS) due to the low frequency waves (0.5-4 Hz and <1Hz) caused by cortical synchrony Increasing depth of sleep EEG frequency slows down
1 Cycle of REM and NREM takes ~90mins • Ratio of REM to NREM changes with each cycle
Sleep Cycles • One cycle of NREM and REM sleep takes ~90 mins • Ratio of NREM/REM per cycle changes during the night • Initially Stages 3 and 4 of NREM sleep dominate • Near the end of the night REM and stage 2 sleep dominate the cycles
Sleep Stages • Beta waves:+14Hz • Symmetrical distribution and most apparent in the frontal lobe. • Rapid, irregular, and low voltage • Alpha waves: 7.5-13Hz • Best seen on the posterior sides the head but stronger on the dominant side. • Stops when eyes open or alerting by any mechanism (thinking) • Theta waves: 3.5-7.5Hz • Sleep Spindles: 7-14 Hz • Short bursts of high frequency activity • Assumed to be responsible for keeping the individual asleep • K-complexes: • short burst of high amplitude activity • Probably the precursors to delta activity • Delta waves: <4Hz • Highest amplitude, slowest waves • PGO waves: • Associated with increased visual system excitability but arise spontaneously • Influenced by auditory and somatosensory stimuli • Generated in the pontine brain stem
Neurochemistry • Neurochemistry changes with sleep stages • NREM • Significant drop in activity of subcortical cholinergic systems • Reduction in firing rate of aminergic populations • REM • Significant increase in activity of subcortical cholinergic systems • Significant inhibition of aminergic populations • REM sleep is dominated by acetylcholine and essentially absent of aminergic modulation
Developing a Memory • Integration: associating new info with past experiences and knowledge • Translocation: anatomical reorganization • Memory consolidation (MC): memory becomes more stable • Stabilization • Enhancement • Erasure: active removal of memory representations
Subtleties of task alter results post training REM sleep. Sleep and Declarative MC • Old supportive De Koninck: foreign language learning; % increase in REM Sleep ~ degree of successful learning • Old contradictory Meienberg: unrelated word pairs; No evidence of altered post training sleep architecture • New supportive Born: Related word pairs; Improvement in association test and increase in SWS and alterations in sleep characterization
Sleep and Declarative MC • Subtleties of task alter results for post training REM sleep. • Old supportive De Koninck: foreign language learning; % increase in REM Sleep ~ degree of successful learning • Old contradictory Meienberg: unrelated word pairs; No evidence of altered post training sleep architecture • New supportive Born: Related word pairs; Improvement in association test and increase in SWS and alterations in sleep characterization
Differences in studies • Level of difficulty • Emotional saliency • Index of learning • Episodic learning • Semantic learning • Consideration of effects from lack of sleep
Associative memories • Are altered in a state dependent manner • REM- Selective facilitation of accessing weak associations • Enhancement of flexible creative processing of acquired information • Sleep can trigger insight to a problem and thus improve performance strategy
Take Home Message • SWS and REM sleep contribute to the consolidation of complex, emotionally salient declarative memories embedded in networks of previously existing associative memories
Procedural Memories: Motor Tasks • Retention impaired with loss of Stage 2 NREM sleep • Full night of sleep significantly increases the speed and accuracy • Sleep on first night of training critical for delayed performance improvements
Procedural Memories: Visual Task • Performance benefits are completely dependent on the first night of sleep after the training period
Procedural Memories: Auditory • Regardless of morning or evening training improvements only occurred across a full night of sleep • Sleep deprivation inhibited the normal changes in brain evoked response potentials • Subsequent nights of sleep can restore performance to post training levels
E-Physiology • Sleep spindles (Stage 2 NREM) • Phasic REM and PGO waves • Increase amplitude • Phase locked with theta waves • Induced stimulation at the troughs of theta waves yields to LTD
Objections and Contradictions • Importance of considering differences in study protocol • Brief memory test • Affects of Drugs
Untouched areas • Stabilization • Association • Translocation • Reconsolidation
Bibliography • The American Heritage Illustrated Encyclopedic Dictionary; Houghton Mifflin Company, Boston, 1982.