Cognition and neuroscience Flashcards
What does it mean for an older person to show bilateral frontal activations during a memory task?
Aktivering av båda sidor av frontalloben.
Ett sätt för äldre personer att kompensera för loss of normal cognition.
HAROLD
What is the disconnection hypothesis of brain aging?
cognitive deficits associated with aging links to disconnection in white matter tracts.
At the structural level, what happens to the hippocampus and frontal cortex when a person ages?
PASA and parahippcampus activation
In episodic memory, why does an older individual morle likely activate parahippocampal than hippocampal regions?
to compensate. More is not always better
Why is it interesting to study deactivations in brain aging?
How can brain structure influence brain activity?
gray matter tract - reduced cognitive resources
white matter tract - slower speed and connectivity
tre metoder för att relatera brain med cognition
styrkor och svagheter
- Neuropsychological apporach - not used anymore. Studied healthy versus pathological populations to study similarities and dissimilarities. What is due to pathology and what is normal aging?
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Correlations between brain measures and cognitive performance
e. g. MRI: Brain Volume - cognitive task
Fractional anisotrophy DTI: White matter tracts - perceptual speed
- Activation task with fMRI
Strength and weaknesses: In the first two you don’t have a direct relationship, just separate measures that you connect. In fMRI activation tasks you will get a direct brain connection relationship but the question is if the brain region is useful…
What happens generally with normal aging at a structural level?
Frontal lobe hypothesis
First - in- last -out hypothesis
Atrophy - loss of gray matter (neuron bodies), reduced cortical thickness, enlarged lateral ventricles
Atrophy starts at 60 (cross-sectional study, 6 year follow up, measured hippocampus) and then there is an acceleration except for the last follow up (84-90) probably the healthiest came back or not much tissue left to loose at this age
Frontal lobe hypothesis states that atophy is not uniform across the brain but the frontal cortex deteriorate first (executive functions, inhibition, working memoty, episodic memory, attention)
First - in- last -out hypothesis (phylogenetic and ontogenetic axis): Frontal cortex will deteriorate first since is was last in, develops until early 20s. Hippocampus and amygdala will deteriorate last (without pathology)
Are bigger brain volume correlated with better performance?
Van Petten meta analysis 2004: 39 studier, 107 long-term memory tasks in relation to hippocampal volume.
Inconsistent results. Not so sure but inconsistency may be due to:
- Age of sample (negative volume performance associations for children and positive in older persons)
- Differences in tasks (maybe some tasks was not related to hippocampus)
- Methodological differences in volume measurement.
Conclusion: In general, in older persons, bigger is better.
In another study, an association between volume of lateral frontal cortex and executive functioning in people older than 40 y/o was found.
Why?
Notion of compensation and
Notion of threshold - how much atrophy to be able to do something
Association white matter integrity and cognition in aging
Disconnection hypothesis - cognitive deficits associated with aging links to disconnection in white matter tracts.
Mean diffusivity increases with age due to death of neurons and loss of myelin. The water can move more freely.
Fractional anisotrophy - diminishes with age. less coherence in the white matter tracts because of age deterioration - leads to interruption of communication among brain networks.
Decline of white matter tracts impact cognition (perceptual speed, working memory, executive functioning, memory). Mostly speed.
Over and underactivation of brain regions in young and old persons
fMRI task related
we will see an underactivation for older persons in comparison to young and overactivation in old compared the young in tasks.
Why underactivation?
- loss neural resources
- inefficient use of neural resources
In a study made by Logan et al 2002. Unga och gamla skulle memorera ord med egna strategier. Man såg mindre aktivering av frontalloben hos de äldre som är förknippad med framgångsrik inkodning.
När de bad försökspersonerna att inkoda djupt och ytligt såg man samma aktivering hos både unga och äldre - underrecruitment can be reversed with supportive task conditions.
Conclusion: Frontal resouces are available to healthy older adults but are not spontanously used.
The aging the brain undergoes structural changes, such as grey matter atrophy and loss of white matter integrity. First, please describe a detailed description of these age related gray-matter and white-matter changes. Second, based on examples, explain how these structural changes may impact brain activity and cognition.
When studying neural correlates of various cognitive processes with functional fMRI both activation and deactivation patterns can be revealed.
Which neural network is typically deactivated when performing a cognitively demanding task, and why is it deactivated?
Discuss the impact of aging on this network’s deactivation, and discuss how this age effect on this network contribute to cognitive aging.
The default mode network is typically deactivated when performing a cognitvely demanding task. DMN is activated during relaxation, when the person doesn’t engage in anything particular.
It is deactivated to provide the resources needed for a demanding task. This can be seen in young adults when the person starts engaging in a task.
Similar patterns of brain activity can be seen in older adults in DMN state but the DMN does not deactivate to the same extent as in younger people. This results in less neural resources being available for the task. It is thus a diminished flexibility to go from relaxtion to activation.
The diminished ability of the aging brain to recruit all resources to a cognitively demanding task obviously contribuets to cognitive aging. Since less resources are available compared to younger individuals, it can have an impact on many cognitive processes. This is especially true for mor demanding tasks. It has been shown that when the task is not so difficult, the patterns of deactivation differs less between young and old adults.
Healthy younger and older adults were scanned with fMRI during an episodic retrieval memory task.
Older perticipants separated in two groups: those who performed as well as the younger adults and those who performed worse compared to the younger group.
Based on models of neurocognitive aging and theories that you will describe, please state your expectations in terms of frontal activation when comparing each older group to the younger group.
older audlts that performed as well as younger adults might have an youth like pattern in the frontal area - the pattern og HERA (encoding left, retrieval right (like this task)) Maybe those individual’s brains is better preserved and maintained.
Older adults that performed worse than younger adults might follow the HAROLD pattern of brain activity (hemispheric assymetry reduction in older adults). They overrecruit and compensate for the cognitive decline and need to activate both areas to perform. Might be due to the lesser specialization older adults have in their brain - the dedifferentiation. Age and task complexity determines the correlation of pattern shown.
A study also showed when older adults under recruit from the frontal areas. Not given strategies vs given strategies. Evidence fot the theory of underrecruitment - the older adults can do it but does not do it spontanously and therefore underrecruit. Might be due to neural decline but also that they might not use their neural resouces efficently.
Did the older adults that performed as good as the younger use encoding strategies?
Why bihemispheric recruitment in older adults? (HAROLD)
Compensation
- if compensation it has to be useful = enhanced cognitive performance
- left activation during episodic retrieval also seen in young adults when the task is difficult, maybe the same for older adults?
Dedifferentiation
- with age the neural networks loose their specificity. Upp och nedvänd u kurva. Ospecifierad i tidig ålder, blir bättre uppemot 9 års ålder, når sin peak och sedan gradvis försämring. (functional differentiation reversed with age). Different functions begin to rely on similar executive functions. correlations between cognitive measures tend to increase with age.
In a study they measured episodic retrieval in younger and older adults and devided the older group in two. Those who performed well and those who performed worse. Results: Right activation in younger adults, overactivation in right frontal cortex for the low performing older adults and bilateral rectruitment in high performing older adults. Conclusion: support for compensation. It helps cognitive performance.
