what do we want from an idea technique
-taps in mental processes (the role that structure etc plays in behavior)
-informs us about the brain
-high spatial resolution
-large spatial coverage
-produces measureable variability
-healthy human population
-non invasive
Angelo Mosso
-first brain imaging technique
-Picked up on subtle changes in the weight of the brain
--If more blood is flowing into the brain, the brain will get heavier. Would do something such as playing a loud sound to get the brain engaged and see if there were an
types of naturally occurring brain damage
strokes
tumors, degenerative and infectious disorders
traumatic head injuries
lesions
studies of people with brain damage...
often have poor spatial resolution and temporal resolution s
stroke
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tumor
displace or destroy healthy cells
traumatic brain injury
-when an external force physically injures the brain
- classified based on severity, mechanism, or location
problems with interpreting studies of naturally occurring lesions
-low samples
-damage is often widespread
-damage not confined to particular region
-damage correlated with other clinical health issues
-difficult to make causal interpretations
structural imaging
enables viewing the anatomy of the brain (parts of it, the tissue)
spatial resolution
ability to tell precisely WHERE in the brain activity is occurring
temporal resolution
ability to tell precisely WHEN activity in the brain is occurring
angiograms
- x-ray based
-allows you to view the arteries of the brain
-inject contrast agen into blood vessels so you can view them
-shows you structure. not much about behavior
-can locate vascular damage
computerized axial tomograph (CAT
- a measure of x-ray absorption at several positions around the head, maps tissue density
-take a bunch of 2d images around the head and then put them together to make a 3d image
where a tumor is, how big it is, where damage occured
-relatively good spati
MRI (magnetic resonance imaging)
-structural
-strong magnets cause proteins in brain tissue to line up in parallel --> a pulse of radio waves knocks protons over and causes them to reconfigure themselves, emitting radio waves that differ by tissue density
-large confined and loud machine
DTI (diffusion tensor imaging)
-structural imaging technique
-also an MR based technique
-means of studying tracts connecting brain areas (shows connections in the brain) (axon bundles)
-measures diffusion of water molecules in the axons --> water molecules contained within axons are c
PET (positron emission tomography)
-functional activity
-inject radioactive tracers that is taken up by energy consuming cells and accumulates in active neurons
-radiation detectors detect where the concentration of blood is
-decent spatial resolution and low temporal resolution (meaning i
fMRI
-detects small changes in brain metabolism (oxygen use) in active brain areas
-possible because of two attributes: active areas of the brain take up oxygenated blood and more of it than less active areas; oxygenated blood has magnetic properties that infl
BOLD signal
-in the fMRI
-the amount of oxygen available is measured indirectly on the basis of blood flow or the state of hemoglobin in blood
-stands for blood oxygen level dependent
advantage of fMRI over PET
-nothing has to be injected
-provides both structural and functional info
-better spatial resolution