What is a longitudinal study?
- Recruit representative sample + test repeatedly over time
- Cohort studies
- Investigate number of variables
What are the advantages of a longitudinal study?
- Effect of age can be determined on individual bases
- Useful in pinpointing disease precursors
What are the disadvantages of longitudinal studies?
- Expensive
- Time consuming
- High drop out
- Practice effects (get better at same test)
What is a cross-sectional study?
- Recruit diff. groups of people
- Sample across age range, with each being tested once
What are the advantages of cross-sectional studies?
- No re-testing
- Quicker
- Less expensive
- Low drop out rates
What are the disadvantages of cross-sectional studies?
- Performance not related to earlier/future performance
- Cohort effects (born at different times so changes in diet, education, social factors)
Which type of study underestimates age-related changes?
Longitudinal
Practice effects
Which type of study overestimates age-related changes?
Cross-sectional
Cohort effects
What type of memory expands with age?
Semantic memory - vocab + historical facts
Also retain ability to learn + retain new skills
What are the effects of ageing on cognition?
- General mental slowing hypothesis = decreased processing speed due to ageing NS
- Common cause hypothesis = brain deteriorating with other bodily systems
- Inhibition deficit hypothesis = reduced capacity to inhibit irrelevant stimuli > linked with central executive reduced stroop test
What happens to different parts of the brain as it ages?
Overall - Shrinks Ventricles - Expands Frontal lobes - Shrinks most rapidly Temporal lobes - Shrinks slowly Hippocampus - Shrinks slowly then accumulates Occipital lobes - Shrinks slowly
What area of the brain is most vulnerable to ageing?
Frontal white matter
What are the theories of neurocognitive ageing?
- Impaired function of prefrontal cortex - normal ageing
- Disruption of medial temporal lobe memory system (inc. hippocampus) - may be pathological ageing, leads to episodic LTM impairment
Define Dementia
Progressive deterioration of previously acquires intellectual abilities that interferes with social/occupation functioning
What is the diagnostic criteria for Alzheimers?
- Cognitive deficits in memory, lang, action control, judgement, perception, executive function
- Preserved awareness of environment
- Impaired social function
- Continued cognitive decline
What pathological changes are seen in Alzheimers?
- Build up of B amyloid peptide > deposited as neurofibrillary tangles (NFT)
- Accompanied by neuronal loss
- Pathological diagnosis rests on amyloid plaques + NFT’s
Which memory is impaired most in Alzheimers?
- Episodic and also semantic but less and at later stage
- Explicit worse than implicit (which can actually improve)
Anterograde amnesia = cognitive hallmark of AD
What is the best predictor of explicit memory impairment in AD?
Hippocampal atrophy
What is the best predictor of semantic memory impairment in AD?
Distributed neocortical atrophy
What causes vascular dementia?
Lack of O2 to areas of brain = neuronal death
