Memory in older adults Flashcards
1
Q
Effect of ageing on the hippocampus
A
- Loss of ability to rapidly encode and successfully retrieve specific details. Over-reliance on gist and familiarity
- Structure: Integrity of white matter pathway between the entorhinal cortex and hippocampus is affected in ageing
- Function: Lower activity in dentate gyrus is indicative of poor memory performance (Small et al., 2004)
- Underactive dentate gyrus/Overactive CA3 = failure to encode (create unique representations)
2
Q
What is the entorhinal cortex?
A
- Giving memories context: Heavily implicated in formation and consolidation
- Regarded as the hub between sub-cortical (hippocampus) and cortical (PFC) structures
- Deals with autobiographical memories and feelings of familiarity
- Also encodes general information on direction and movement
3
Q
How does ageing affect the entorhinal cortex?
A
- Structure: Atrophy rates of 0.3-2.4% (far more varied than hippocampus: 0.8-2%)
- Accelerated structural decline in those 50+, not linear like other regions of MTL
- Function: EC thickness mediates functional connectivity between hippocampus and DMN
- Memory processes that engage frontal regions during retrieval are related to EC structure
4
Q
How does ageing affect the prefrontal cortex?
A
- Age related deficits in mPFC structure and function underlie issues with working memory performance, based on distractibility
- Lower dlPFC GABA is predictive of greater working memory performance degradation at higher loads
- Poor medial frontal inhibition (linked to GABA levels) leads to poor MoCA performance
- Anodal tDCS to left dlPFC helps reconsolidate episodic memories
5
Q
Episodic memory: Structural change
A
- Highly susceptible to the effects of ageing –> not always aware of (lack of) ability/(in)accuracy of memory
- Reliance on perirhinal cortex rather than hippocampus –> familiarity exhibited rather than explicit knowledge
- Fornix integrity is related to memory impairment (recall and recognition) across the lifespan
- Association between EC volume and scores on the MoCa
- Robust brain-cognition change for episodic memory decline and atrophy in the hippocampus, in those over 65 years of age
- Tracking structural change over 4 years and episodic memory change over 15 years
- Fronto-striatal connections decline: implications for the role of the basal ganglia (&dopamine) as integral for learning and consolidation
- A role for dlPFC has been confirmed with rTMS –> disrupted encoding and retrieval, particularly with regard to novel stimuli
6
Q
Episodic memory: Functional change
A
- Influences memory for associations (complex, resource intensive) more so than memory for items
- Fits with what we know of grey/white matter integrity
- Due to changes in both encoding and retrieval
- Age-related memory decline is evident in reduced activity during encoding in dlPFC but an increase in activity in hippocampus
- In context dependent memory retrieval, there are increases in PFC and hippocampal activity
7
Q
Working memory: Structural decline
A
- Working memory performance suffers in old age, particularly under high loads
- Studies have shown that even simple tasks may involve bilateral frontal activity
- Performance is related to PFC volume/thickness - bigger is better, particularly in lateral/medial regions
8
Q
Working memory: Functional decline
A
- Widespread activation is seen in PFC with ageing: non-specialised regions, within and between hemispheres
- Overactive at low-loads, underactive at high loads
- Less distinctive neural PFC representations in ageing, particularly at high loads
- Not seen in young adults –> they show greater distinctions at high loads, which is adaptive for them
- Older adults don’t have the resources for this, which produces an encoding detriment
- Vulnerability of memory trace due to loss of distractor inhibition
- During encoding, irrelevant material enters working memory and reduces space for important material
- In retrieval, finding the correct response is harder with multiple competing possibilities
