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- Created by: 10dhall
- Created on: 19-05-19 22:37
Kanais - meta - key reading
aspects of cognitive function can be predicted from fmri. participant differences can be used to link behaviour to anatomy.
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What are grey, white and csf made up of
grey- neutron bodies, white= nerve fibres, csf= liquid, irrelevant info
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what can mri find?
Brain damage/ anatomy defficiencies- compare brain anatomy between groups
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What is VBM? Voxel Based Morphometry
from MRI= analyse ind anatomical structures e.g. white/ grey to provide function+detect atrophy -
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What is a problem with group anatomical scans?
everyone has a slightly different brain shape- to map areas of similar activities the brain images need to be identical, need to map all image onto standard template using math algorithms to scale
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What template is commonly used?
MNI- montreal neurological institute- formed an anatomy of the brain using 152 adults.
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What are the steps to voxel based morphometry MRI?
fit voxel-by-voxel.Segregation of grey/white/csf using voxel intensity- W lighter than G lighters than C. Use percentage probability of fitting the tissue. smooth over the GM image
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what types of design are effective with VBM?
Longitudinal- track brain over time - change/development. cross sectional - compare 2 different scans or pp.
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Negs of VBM
Multiple comparison problem - analyse over 1 million voxels - prob of going into group - some will be significant by type 2 error- must control for false positives
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Yasuda- 2010 - epilepsy + VBM
MRI grey matter- less grey matter in epileptic patient, suggests neutron cell death - supports epilepsy - shows atrophy
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Giorgio - 2010 - MRI and age
found reduction of grey and white matter as age increased - suggests deterioration of brain tissue as grow older
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Sampaio-Baptista - 2014 - MRI and juggling learning
found former grey matter volume correlated with later learning - learnt better. FURTHER, grey matter increases were correlational to improvements in learning.
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Maguire 2006 - taxi -
before sat-nav taxi drivers used memory - MRI scans and years of driving experience- found correlation between years of driving experience and volume of hippocampus
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Schwarzkopf - perception tasks
ponzo and ebbingaus illusions - MRI and falling for illusion - pp with smaller M1 showed increased likeliness to fall for illusion = decreased perception - has become structural basis for perception
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What is cortical thickness?
the thickness of white, grey and CSF. e.g. the size of matters
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How do we do this?
Gather anatomical map. extract outline of grey matter to rid CSF. inflate brain to rid folds. now the estimation is much easier over a small surfce1
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Zielinski - 2014 - cortical thickness and autism
Found, using VBM 3 abnormal cortical developments in autism compared to control. 1) accelerated expansion(early childhood), 2) accelerated thinning(adolescence), 3) Decelerated thinning (adulthood) - shows how cortical thickness can be found usingmri
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Hutton - 2009 - age
Cortical thickness also decreases with age - some areas(motor cortex) thin faster than others - further MRI thickness - suggests reflectseffectivenes of mri+ decline in cognition to raging
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Caveats to VBM?
very sens to subjects head shape-Use MNI and algorithm to implement to MNI - false positives - millions of voxels so chance of type 1 error
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what is the role of MRS(spectrography)?
distinguishes different NT and chemicals in the brain and measures amount
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extra info?
measures metabolites. dopa/sero occur in too small amounts, measurements taken at rest, non-invasive
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how does it work?
FMRI scan is used, however at a lower pulse as NT levels are low so higher voxel area 3-5mm - usually single voxel scans which takes 10-15 mins
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what is the difficulty with orienting voxel
we want a scan of GM however we don't want fatty edges and skull - so localisation has to be precise using previous scans or studies
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What is the output from an MRS
graph - on its x axis, chemical composition. y axis= number/amount. each peak represents a different chemical - some chemicals have 2 peaks if they are complex
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mutably types
NAA, Creatine, choline, lipids etc
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what do GABA and glutamate look like on graph>
Very small peaks compared to other chemicals- show that scarcer NT will be harder to measure
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What do low levels of NT suggest?
Lower synapse levels/ connectivity levels. GABA in intracortical networks and can affect tasks
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Putts 2011 - tactile stimulation
pp with lower levels of GABA in sensiromotor cortex were less likely to be able to differentiate between levels os electric shock.
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Maltezos - ADHD MRS
decrease in metabolites and NT in certain parts of the brain
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Suggest some healthy chemical levels... (further)
NAA/Cr = 2 . Cho/Cr = 1.2
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Other cards in this set
Card 2
Front
What are grey, white and csf made up of
Back
grey- neutron bodies, white= nerve fibres, csf= liquid, irrelevant info
Card 3
Front
what can mri find?
Back
Card 4
Front
What is VBM? Voxel Based Morphometry
Back
Card 5
Front
What is a problem with group anatomical scans?
Back
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