Sleep and memory overview
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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

Sleep and Memory: Overview

Rachel Miriani

Neural Systems

Nov 29, 2004


Introduction to memory

Introduction to Memory

Memory

“The mental faculty of retaining and recalling past experiences; the ability to remember.”1


Sleep and memory overview

Introduction to Memory

Memory

Declarative

Non-Declarative

“Consciously accessible memories of fact-based information”- The What.

Non-conscious


Sleep and memory overview

Introduction to Memory

Memory

Declarative

Non-Declarative

What.

Non-conscious

Semantic

Episodic

Not event specific general knowledge

Experiences and events from ones past.


Sleep and memory overview

Introduction to Memory

Memory

Declarative

Non-Declarative

What.

Non-conscious

Episodic

Semantic

Procedural Skills

Conditioning

Non-associative

Priming


Sleep and memory overview

Introduction to Memory

Memory

Declarative

Non-Declarative

What.

Non-conscious

Episodic

Semantic

Procedural Skills

Conditioning

Non-associative

Priming


Sleep and memory overview

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

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


Sleep and memory overview

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


Sleep and memory overview

  • 1 Cycle of REM and NREM takes ~90mins

  • Ratio of REM to NREM changes with each cycle


Sleep and memory overview

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 and memory overview

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

  • 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

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


Sleep and declarative mc

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 memory overview

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

Differences in studies

  • Level of difficulty

  • Emotional saliency

  • Index of learning

  • Episodic learning

  • Semantic learning

  • Consideration of effects from lack of sleep


Associative memories

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

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

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

Procedural Memories: Visual Task

  • Performance benefits are completely dependent on the first night of sleep after the training period


Procedural memories auditory

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


Neuroimaging not so instant replay

Neuroimaging: Not so Instant Replay


E physiology

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


Gene expression

Gene Expression


Objections and contradictions

Objections and Contradictions

  • Importance of considering differences in study protocol

    • Brief memory test

  • Affects of Drugs


Sleep and memory overview

  • Untouched areas

    • Stabilization

    • Association

    • Translocation

    • Reconsolidation


Bibliography

Bibliography

  • The American Heritage Illustrated Encyclopedic Dictionary; Houghton Mifflin Company, Boston, 1982.


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