cognitive neuroscience of ageing Flashcards
at what age is the brain fully developed
early 20s
at what age is volume loss seen in brain
from young adulthood
main parts of nerve cell
dendrite
axon
soma
process of action potential in a nerve cell
inside of cell at rest is neg, if stimulus is good strength it alters balance of ions reaching threshold so action potential travels to pre synaptic terminal
what does action potential cause
release of neurotransmitters to synaptic cleft
exitatory or inhibitory (increase or supress)
how is the brain divided
according to structural similarity of neighbouring cells called brodmann’s area
what does it mean by saying brodmann’s area was given functional relevance
instead of BA4, primary motor cortex is said instead
what is the gyri and sulci
gyri = peak
sulci = trough
what are the tissue types in brain
white matter = connections
grey matter = destinations/activity
CSF (cerebral spinal fluid)
what is the cerebellum
not a lobe
-movement and balance
function of:
frontal lobe
temporal lobe
parietal lobe
occipital lobe
frontal = executive hub, decisions
temporal = memory
parietal = attention
occipital = vision
what does cortical and subcortical mean in the brain
cortical = superficial
subcortical = deep
anatomical terms:
anterior
posterior
superior
inferior
dorsal
ventral
rostral
caudal
anterior = front
posterior = behind
superior = above
inferior = below
dorsal = above, anterior posterior axis
ventral = below, anterior posterior axis
rostral = to front, frontal cortex
caudal = to back, occipital cortex or brain stem
what are the methodologies looking at the neuroscience of ageing
PET = positron emission tomography
MRI = magnetic resonance imaging
FMRI = functional magnetic resonance imaging
DWI = diffusion weighted imaging
how do PET, MRI, FMRI and DWI work
PET = shows area of high glucose activity in diff regions
MRI = mm precision and detail
FMRI = shows active regions in specific tasks by looking at metabolic demands (areas with most O2)
DWI = white matter tracks by observing H+ molecules, shows where things happen not when
brain shrinkage and ventricular expansion in older adults
-brain shrinkage and ventricular expansion seen and replaced by CSF
-approx 3% expansion per year in older adults
grey matter and white matter decline research
sullivan et al 2004
-grey matter decline is fairly linear until age 70/80 yrs
-white matter declines after about 45yrs
what does it mean if white and grey matter decline
white matter decline: decline in myelin sheath, slower processing so higher RT
grey matter decline: loss of vol and scope for activation, less available resources to perform cog functions e.g difficulty processing high cog loads and more demand on WM
what is dopamine
a neuromodulator that regulates neurochemicals like GABA
provides evidence for chemical change in older adults
what are the key regions associated with dopamine
striatum (connections with limbic system and frontal regions explaining links with abnormal emotional disorders)
dopamine in older age
reduced binding due to less dopamine from age 50
decreased dopamine research
seeman 1987
- 2-3% decline per decade after age 20
what issues does having less dopamine cause
-problems with brain network dynamics and failure to activate task specific regions and deactivate irrelevant ones
what is an issue and solution for FMRIs
- looks at haemodynamics and cant do this so well with thickened blood vessels that are seen in older adults
e.g tsvetanov 2015: thought they had detected change in brain activity but it was actually change in blood properties
solution: study neurons directly NOT properties of blood by using EEG, MEG etc
what does GABA stand for
what does GABA show
GABA and old age
GABA = gamma aminobutyric acid (primary inhibitory neurotransmitter)
-shows neurochemical changes that take place
-Gao et al 2013: 5% decline per decade of life
-inability to filter out irrelevant items: larger N100 for irrelevant stimuli meaning less able to filter out distractors
-inability to select correct response: RT time delay, increase by 1.5ms per year
-deficits in multisensory integration (Freiherr et al 2013) = not able to distinguish between diff sources e.g crossing busy road
visual perception in older adults
-amount of light entering retina of 60yr old is 1/3 the amount of a 20yr old
-means slower search rates through visual displays
what are the 3 pathways for visual info
dorsal stream = where something is (occipital – parietal – frontal lobe)
ventral stream = what object is (occipital – temporal – frontal)
age and activity in visual regions and why increase in visual regions
decline in activation of visual cortical regions although increase in prefrontal activation
perhaps increase in prefrontal regions as decline in visual processing means frontal cortex must work harder
memory processes research in older adults
Morcom et al 2003
-pp: 21-68 yrs
-FMRI to look at brain activation in line with word judgement task
-recognition memory tested after 10 or 30 min delay
-in older adults we see more bilateral frontal activity
working memory and older adults
what occurs during encoding and retrieval
-task complexity produces greater age differences
-vulnerability of memory due to loss of distractor inhibition
-encoding: irrelevant material enters WM decreasing space for relevant material
-retrieval: finding correct response is harder, many competing possibilities
-WM uses greater bilateral prefrontal activation
-overlap of activation in verbal and spatial areas in older people, these should be encoded separately in young adults
examples of hemispheric specialisation in healthy younger adults
verbal - L
spatial - R
encoding - L
retrieval - R
recall - L
recognition - R
hemispheric specialisation in older adults
less of this, more bilateral activation
what causes reduction in specialisation with age
driven by decline in function
-activity in one hemisphere limits harmful inter hemispheric influence
-age related decline in hemispheric inhibition = failure to inhibit opposite hemisphere/irrelevant input, decline in normal competition between hemispheres
-integrity of corpus callosum decreases with age
how does reducing specialisation with age protect function
-cooperation between regions = compensation
-better to work tog when demand is high and resources low
-to counteract decline older adults use both hemispheres rather than dominant one
-if this was the case we would expect to see increased performance as all resources are being pulled together
research for bilateral activation in older adults
cabeza et al 2002: older adults that perform well have bilateral activation
what are the 4 major models of brain ageing
PASA
HAROLD
CRUNCH
STAC
what is PASA
posterior anterior shift in ageing (grady et al 1994)
-brain reduces activity in posterior regions and shifts dominance to anterior regions
what is HAROLD
hemispheric asymmetry reduction in OLD age (cabeza 2002)
-aims to counteract decline rather than being caused by it (compensation)
what is CRUNCH
compensation related utilisation of neural circuits hypothesis
-reuter lorenz and cappell 2008: pre frontal over activation represents narrowing of focus to support most specific process
what is STAC
scaffolding theory of ageing and cognition
-Park and reuter lorenz 2009: age related reorganisation indicates formation of alternate goal oriented neural circuits to compensate grey matter volume loss
what can be done to mediate neg impact
colcombe and kramer 2003
-aerobic exercise supports executive function in ages 55-79
-normal patterns of decline can be altered in accordance with fitness levels
resnick et al 2001/2003
-grey matter loss mediated in healthy indivs
-declines in white matter decrease in the super healthy
