Sleep-dependent Learning in Aging

Study Overview
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Brief Summary
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The specific objective of this proposed research is to understand whether deficits in sleep-dependent memory changes reflect age-related changes in sleep, memory, or both. The central hypothesis is that changes in both memory and sleep contribute to age-related changes in sleep-dependent memory processing. To this end, the investigators will investigate changes in learning following intervals of sleep (overnight and nap) and wake in young and older adults.

Detailed Description
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Exp 1: Using neuroimaging, the investigators will consider whether differences in brain areas engaged during memory encoding contribute to age-related changes in sleep-dependent memory consolidation for a word-pair learning task. Exp 2: The investigators will examine the rate of memory decay between encoding and sleep using two probes of declarative memory (word-pair learning and visuo-spatial learning). Exp 3: The investigators will provide additional opportunity for encoding of the word-pair and visuo-spatial learning tasks. Exp 4: Using neuroimaging, the investigators will examine neural engagement during encoding and performance following intervals of sleep and wake. Exp 5: The investigators will examine the rate of decay of motor sequence learning. Exp 6: The investigators will examine whether enhanced training ('overtraining') improves sleep-dependent memory consolidation for older adults.

Official Title
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What is Sleep's Role in Alzheimer's Disease? Insight From Healthy Aging

Conditions
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Sleep

Intervention / Treatment
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* Behavioral: Sleep


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Age 18-75 yrs Healthy sleeper No diagnosed sleep or neurodegenerative disorder Exclusion Criteria: Past diagnosis of any sleep disorder or evidence of a sleep disorder as assessed by self-reported sleep quality assessments, a standardized diagnostic interview, and an acclimation night of polysomnography. Using acclimation-night polysomnography, participants will be excluded with an Apnea-Hypopnea Index >15; a Period-Limb Movement in Sleep index of >15/hr; sleep-onset latency > 45 min (indicative of insomnia); or sleep efficiency < 80% (see Edinger et al., Sleep, 2004). In cases in which questions arise regarding a participants' inclusion or sleep records, a practicing neurologist board-certified in sleep medicine will review the documentation. Past diagnosis neurological illness or head injury Reported average sleep per night < 5 or > 9 hrs Current employment involving shift work or an inability to keep a regular sleep schedule during the week prior to testing Current use of psychotropic, recreational drugs, or sleep-altering medications (sleep medications, cold medicines within the past week, clonidine, sympathomimetic stimulants) Daily caffeine intake of > 4 cups (coffee, tea, colas) Weekly alcohol intake of > 10 cups Pregnancy or < 12 months post-partum History of bipolar disorder, mania, or current evidence of depression as measured by Beck Depression Inventory score > 25 Abnormal sleep (e.g., shift work, travel across >2 time zones within the past 3 months). Diagnosis of any Axis I disorder, neurological illness or head injury (according to Demographic and Health History form); Score indicative of cognitive dysfunction (subtest scores < 40) Beck Depression Scale score indicative of depression (> 19). Additionally, individuals will be excluded from magnetic resonance imaging studies (Exps 1, 4) for: Left handed or ambidextrous Claustrophobia Presence of metal (thoroughly screened via questionnaire and metal detector) Pregnancy

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 75 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Basic Science
Allocation: Non-Randomized
Intervention Model: Parallel Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Sleep<br>Individuals will either nap (Exps 1, 4) or have overnight sleep (Exps 2, 3, 5, 6) | Behavioral: Sleep<br>* Participants will sleep (either a mid-day nap or normal overnight sleep)<br>|
| No Intervention: Wake<br>Individuals will stay awake for the same amount of time as they slept in the sleep condition | |

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change in memory accuracy for intervention compared to control | We will measure memory accuracy before the sleep/wake interval and subtract this from memory accuracy after the sleep wake interval. If sleep benefits memory then this value will be greater in the sleep condition compared to the wake condition. | 2 hours (Experiments 1,4) or 12 hours (Experiments 2,3,5,6) |