Sleep-dependent Learning in Aging

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

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.

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.

Inclusion Criteria:

• Age 18-80 yrs
• Healthy sleeper
• No diagnosed sleep or neurodegenerative disorder

Exclusion Criteria:

1. 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.
2. Past diagnosis neurological illness or head injury
3. Reported average sleep per night < 5 or > 9 hrs
4. Current employment involving shift work or an inability to keep a regular sleep schedule during the week prior to testing
5. Current use of psychotropic, recreational drugs, or sleep-altering medications (sleep medications, cold medicines within the past week, clonidine, sympathomimetic stimulants)
6. Daily caffeine intake of > 4 cups (coffee, tea, colas)
7. Weekly alcohol intake of > 10 cups
8. Pregnancy or < 12 months post-partum
9. History of bipolar disorder, mania, or current evidence of depression as measured by Beck Depression Inventory score > 25
10. Abnormal sleep (e.g., shift work, travel across >2 time zones within the past 3 months).
11. Diagnosis of any Axis I disorder, neurological illness or head injury (according to Demographic and Health History form);
12. Score indicative of cognitive dysfunction (subtest scores < 40)
13. Beck Depression Scale score indicative of depression (> 19).

Additionally, individuals will be excluded from magnetic resonance imaging studies (Exps 1, 4) for:

1. Left handed or ambidextrous
2. Claustrophobia
3. Presence of metal (thoroughly screened via questionnaire and metal detector)
4. Pregnancy