Invariant aging hypothesis
Which cognition improves w/ age? (reasoning, spatial visualization, memory, speed, vocabulary knowledge)
- When do they peak + when do they decline significantly
- Which has largest decline
Aging is an inevitable biological reality
Vocab knowledge
- Peak at 20, decline at 60
- Speed (reaction time)
Younger vs older adults reaction time and accuracy
Low education vs high education in cognitive decline
Rxn time decreases but accuracy doesnt
Educated people show less cognitive decline
Brain regions most vulnerable to cortical thinning (4)
Accelerated thinning in temporal cortex associated with w/?
Brain reserve theory
- Superior, middle, inferior frontal gyri
- Superior, middle temporal gyri
- Precuneus, inferior, superior parietal cortices
- Temporo-parietal junction
—
Future cognitive impairment + higher risk of disease
—
We have more cells than we need; Wr receive impairment when reserve of cells go under required to function normally
Meditators show less age-related atrophy in which areas (5)
Study shows brain of long term meditators was how many years younger
In controls but not meditators, aging is associated w/? (3)
- Hippocampus/Amygdala
- Posterior cingulate
- Orbital gyrus
- Anterior cingulate gyrus
- Mid cingulate gyrus
—
7.5 years
— - Reduced GM
- Impaired attention
- Increased RT
Raven’s progressive matrices
- Typically used in what assessments
- Performance in controls vs meditators and yogi
Nonverbal test of fluid intelligence (reasoning of abstract concepts)
- Used in IQ assessments
- Performance declines w/ age, but less in meditators and yogi
What tracts (white matter) maintain integrity w/ age
Glucose metabolism (effects strongest where? 3)
Regions associated with meditation (insula, hippocampus, amygdala, ACC)
—
Declines w/ age but less significant in meditators
- vmPFC, pCC, insula
Mechanisms of meditation on aging/cortical thinning (4)
- Reduced anxiety and depression, improves stress regulation (less cortisol, less hippocampal atrophy)
- Improved sleep amount and quality
- Cardiovascular effects (blood pressure, heart rate variability)
- Neuroplasticity (Lower cortical atrophy, increased thickness)
PTSD highest cortical thinning where?
Depression causes more cortical thinning where?
- Frontal cortex, temporal lobe
- Hippocampus
Controversies w/ meditation and brain changes:
- Gray matter
- Mechanism for cortex changes unclear
- Functional effects of cortex changes
- Study design
- Sample size
- Bias
Age-well randomized clinical trial (RCT)
- Not all studies show increased gray matter volumes w/ meditation, some go down
- Reduced gray matter changes may reflect a number of changes in brain other than neuronal loss
- Often untested; usually measure either brain changes or cortical changes, not both
- Usually cross-sectional and observational, no causal relationship
- Small sample size
- Usually high risk of bias
— - Large sample, controlled, experimental, low attrition
- Shows no fx on brain structure/perfusion, but higher global composite score (reflects multiple abilities)
Hayflick limit
- Telomeres
- Telomerase
- Effect of meditation, effect greatest in who
Cells can only divide a finite number of tines
- Imperfect copy/mitosis process bcuz entire DNA strand can’t be copied every time
Telomeres usually cut instead of DNA but shorten w/ cell division
- Telomerase maintains telomere length and prevents shortening, but activity reduced by chronic stress
- Activity enhanced by meditation (ppl w/ personality traits high in neuroticism and low agreeableness)
Caveats of telomere studies:
- Effects measured where
- Mechanism
- Length
- Sample size
- White blood cells (leukocytes) but not neurons
- No known mechanism by which telomeres may affect neuronal function
- Some studies report increased length (controversial)
- Sample size small
More DNA methylation = ___ gene expression
- As we age, there is increases/decreased methylation in DNA sequence
- Epigenetic clock
Meditators vs controls in methylation (30-60 years old)
Older meditators (>52 years), relationship between epigenetic clock and meditation practice (years)
Problems w/ studies (4)
- Less
- Increased
- Methylation can be used to predict age; More methylation = faster aging
— - No evidence of slowed aging w/ meditation
- Meditators show downward trajectory (lower methylation patterns) w/ age
— - Epigenetic effects rarely examined
- Implications of Epigenetic modifications unclear (specific patterns of gene methylation and protein expression)
- Might not be feasible to investigate (requires older participants, observed over years)
- Aging-related changes may be distinct from short-term changes
Alzheimer’s disease
- Features (4)
- Risk factors + modulated by what
- What’s most sensitive to meditation in elderly ppl + major difficulties sensitive to meditation in AD
- Problems w/ studies (5)
- Neuronal loss
- Neurofibrillary tangles
- Amyloid plaques
- Reduced acetylcholine transmission
— - Hypertension, blood perfusion, stress
- Meditation may slow progression + rescue lost cognitive function
— - Attention
- Disrupted mood + sleep
— - Few studies
- Designs lack control groups
- Biomarkers related to AD not reported
- Hyperfixation in cognition in AD
- Narrow examination; only focuses on AD patients
