Ageing 9: Neurological Flashcards
(24 cards)
How do grey and white matter, ventricular volume, and cortical thickness of the brain change with age?
- Grey and white matter decrease (grey faster than white; grey = old, so grey is lost)
- Cortical thickness decreases slowly after childhood
- Ventricular volume increases in response to decrease of other substances in the cranium
Brain volume decreases _% per decade after age 40, and decreases more steeply after age __.
- 5% per year after 40
-Decreases more steeply after 70
Describe the gradient of loss of brain matter with age, including the two most affected lobes (in order). Is any region unaffected?
- Brain is lost from anterior to posterior
- Most affected is frontal, then temporal (incl. hippocampus)
- Posterior regions (e.g. occipital) no real change
True or false: there’s a direct correlation between volume of white matter and axonal function
- False
- Quality of white matter is also important
Patterns of brain loss in women vs men w/ age
- Men lose frontotemporally (makes sense_
- Women lose hippocampal (memory) and parietal (touch); can’t remember or feel touch ???
Brain volume decreases with age, but neuronal loss is modest. What might be causing this instead?
- Decreased synaptic density
- Loss of myelin in some areas (not all)
- Microglial inflammation
- Cerebral microvascular disease
Changes to Acetylcholine system with age
- Reduced cholinergic neurons
- Some nicotinic receptors are reduced/eliminated (quitting smoking in old age)
Changes to Dopamine with age
- Decrease in dopamine synthesis, binding affinity, and receptor number
- Dopamine levels decrease by ~10% each decade after age 40 (double that of brain mass decrease)
(This is the most marked reduction of all neurotransmitters; this is why old people are sad)
Changes to Serotonin with age
- Receptor number decreases
- Serotonin transporter binding capacity decreases
How does synaptic/neuroplasticity change with age?
- Thought to be reduced with age
- New research suggests that it may simply be dysregulated
Which brain functions decline most/least with age
- Most durable: reading, vocab, long-term memory (Munger)
- Least: Visuo-spatial, motor speed, processing speed (athlete)
Changes to absolute/relative intelligence over lifespan
- Relative intelligence remains stable
- Absolute intelligence climbs until around 35-40, then declines into older age
Where are the three places our brain can store stimuli as data?
- Sensory memory (as sensations are experienced)
- Working memory (being actively processes)
- Long term memory (encoded for later retrieval)
Changes in long-term vs working memory with age (+ assoc brain areas)
- Working memory declines with age (prefrontal cortex)
- Long-term memory also declines, particularly episodic memory (medial temporal lobe; hippocampus/parahippocampal cortex)
What is the upper limit of long-term memory? What bottlenecks retention?
- Long term memory is theoretically infinite
- Practically, however, it relies on retention of information to keep retention going
Hippocampal atrophy may be the earliest marker of cognitive decline and disease like AD. Why does this matter?
- Fewer cells, same number of memories
- More “overlap” of memories, and lower resolution
Age-related cognitive decline vs dementia trajectory
Age related cognitive decline is less severe; does not cross MCI and dementia thresholds
How does aging affect balance?
- Aging assoc with decline in balance
- Unclear whether this is overactive compensation for ↓ postural stability
How does aging affect gait? How does this explain why old people get tired faster when walking?
- Older adults walk more proximal to distal in terms of leg muscles, causing ↑ reliance on hips
- They also have greater double support time (WIT?), shorter strides, and reduced range of motion in jonts (esp ankle)
- ↑ Reliance on hip explains higher metabolic cost
Why, at a granular level, do older people move slower than young people at the muscular level?
- Reduced number of alpha motor neurons
- Remaining neurons sprout new axons to occupy vacated muscle fibres (↑ innervation ratio; WIT?)
- Result is larger, slower motor units -> slower movement
How, mechanistically, can aging affect muscle coordination?
- Increased/inappropriate activity of antagonist muscle
- Less granular control of movement; worse coordination
The only early life prevention for dementia is…
Dementia
True or false: dementia occurs as a result of many overlapping failures of redundancies, resulting in risk factors accumulating right before disease onset
- False
- In fact, many risk factors present in mid life, ~20 years before the disease itself begins
Non-childhood preventitive measures for dementia
- Restoring sensory acuity (exposure to truth)
- Reducing TBI (think: hyperphosphorylated tau in CTE)
- Reduce obesity, hypertension, and diabetes (exercise)
