Creierul uman de-a lungul aniilor - imbatranirea Flashcards
what is white matter
structures that hold the grey matter
white matter - axons
-myelinated axons that told to different parts of the brain
not all axons are myelinated- the ones that need to be efficient are. If you lose myelination that becomes a problem to coordinate your body
it’s more active in some parts than others
what is blood flow
brain is bathed in blood
thats where it gets energy from
3 major arteries coming into the brain - anterior, middle posterior cerebral artery
as you go deeper into the brain, arteries become finer
damage seen in ageing is to do with those fine blood vessels no longer functioning well and sending signals
blood carries oxygen to parts of the area that are more active
What are the 3 arteries that provide blood to the brain?
Anterior Cerebral Artery
Middle Cerebral Artery
Posterior Cerebral Artery
Where does brain take oxygen and glucose from?
From the blood stream.
What are the changes in brain with age?
White matter volume decreases
swollen ventricles
more folds
lesions in the brain
what is atrophy
enlarging of ventricles and sulci is related to reduction in brain tissue both in grey and white matter
What is white matter hyper-intensities
white matter lesions
amount of areas that have lesions increase
start as early as in your 60s and go up until old age
white matter across lifespan
increase from 20s and 30s
steady across 40s and 50s
50 and 70 you have beginning of decline
sharp decline from 70 onwards
period of time in which white matter is increasing
grey matter across the lifespan
stays steady throughout life
does not decrease in volume greatly
cognitive changes in ages
working memory
LTM
STM
see a steady decline from 20 onwards
verbal knowledge
stays steady and increases somewhere - you keep adding into your vocabulary
What are the two theories of cognitive ageing?
- Common cause hypothesis
- Specific gain/loss hypothesis
What is the common cause hypothesis?
Deficits in a single ability can explain almost all age-related cognitive decline.
-magic key that explains all deficits
- the cascade effect
-ones this goes down, it affects everything else
So if you are bad in one ability it is said that that can impact all your other abilities.
What is the specific gain/loss hypothesis?
Age-related cognitive decline is best explained by changes in neuroanatomical so structure or function.
-changes to actual physiology of the brain
So this theory says that decline in cognitive ability is due to physical changes in the brain
example of common cause hypothesis
information processing speed
example of specific gain loss
frontal-executive hypothesis
disconnection hypothesis
- what is frontal executive hypothesis
frontal lobes
executive function
personality
higher cognition
Grey matter in frontal lobes is negatively impacted by ageing
So complex processes are going to be impacted
Executive tasks worsen with age - you see decline in grey matter in frontal lobes
- What happens to the executive function as a result of age-related damage to frontal lobes?
Executive function is a primary cognitive deficit in ageing.
So frontal lobes are affected and that in turns affects EF because that’s where it is located in the brain.
This is the frontal executive hypothesis.
What is the role of white matter?
White matter is connecting areas of brain matter across the brain.
- What is the disconnection hypothesis in ageing?
Age-related white matter damage disrupts communication between brain regions.
-ability of brain to talk to different parts is going to be affected
That means complex cognitive abilities that rely on integration of information between brain regions will be affected.
EF relies on communication to and from frontal lobes.
Therefore EF is affected.
What do both frontal executive and disconnection hypothesis suggest?
That executive function is the primary deficit in ageing.
what is support for frontal executive hypothesis
grey matter decline in ageing
cross-sectional MRI study
decline per decade in terms of grey matter
prefrontal cortex has highest decline that any part of the brain - 4.9%
in hippocampus there is a decline but only 2% - hippocampus only areas that has neurogenesis
superior parietal cortex - 4.3% decline
what is support for disconnection hypothesis
white matter volume decreases
and white matter goes through damage as WMH increases
Cross sectional: Diffusion tensor imaging shows sharp decline in white matter integrity with age
Longitudinal: white matter also sensitive to change in 2 years
What happens to executive function with age?
It declines with age.
EF declines can have a knock off effect on LTM. - but not the other way around. EF was the primary deficit in one study
what is the problem with research on executive function
mixed results
not clear whether EF decline is greater than other cognitive types of decline
What is the relationship between grey matter and executive function? in support of frontal executive hypothesis
Frontal grey matter volume is associated with EF in ageing
In older subjects, individuals with lower frontal grey matter, lower scores in EF tasks.
Association does not mean cause
what is the evidence for frontal changes in ageing
young adults used lateralised parts of the brain
as you get older, you start recruiting other parts of the brain
you can adapt to make changes to cope
what is support for disconnection hypothesis
Working memory declined significantly over 2 years
White matter integrity correlated with EF, working memory and information processing speed
What are white matter hyperintensities?
Brain white matter lesions. Larger WMH have been associated with Alzheimer’s disease and cognitive decline.
What happens to WMH with age?
It increases with age. So that suggests that there is damage to white matter with age.
what are problems with executive function hypothesis
evidence for non-frontal grey matter decline - superior parietal loss
EF is not only concentrated in frontal love, its distributed in the brian
What are problems with disconnection hypothesis
Not only EF associated with white matter decline
EF also affected by processing speed and episodic memory
what is the competing hypothesis
they dont have to be mutually exclusive
frontal lobes are connected to the rest of the brain by white matter
if you have effects in white matter, you have effects in frontal lobes
white matter damage occurs across the whole brain and within the frontal lobes
grey matter and white matter are connected and influence each other
What happens as a result of changes in the cardiovascular system?
Changes impact blood supply to the brain.
Interruption to blood supply is associated with WHM and risk of stroke.
What is hypertension?
High blood pressure
What’s the relationship between hypertension and WMH?
Hypertension increase risk of developing WMH.
Hypertension is also related to cognitive difficulties.
