methods Flashcards
clinical populations
researchers may examine whether degree of brain activation or deactivation shows a significant relationship with a particular characteristic of a clinically relevant group of people
neurologically intact
serve as critical reference population in lesion studies.
how are things working normally? - need to have smt to compare it to
allow researchers to determine the degree to which the performance of individuals with brain damage is compromised
lesion group and neurologically intact control group must be match as thoroughly as possible on demographic characteristics
not always ethical
everyone is difference, what is significant vs. what is natural
MRI
machines create a constant magnetic field
perturbations in this field are induced
the response of the atoms in the brain is used to derive maps of the brain structure and functions
provides info about the size and shape of different brain structures
for cortical structures, research are often examine volume, determining if it differs between groups
for subcortical structures, researchers examine volume and variations in shape
DTI diffusion tensor imaging
provides info about anatomical connectivity between different brain regions, whit matter integrity
use to find if connections between are damaged used a lot in concussions
detects the main axis along which water diffuses in nerve fibers and this indicates themain directional orientations of white-matter tracts
the degree of diffusion provides info on the structural integrity of those tracts
what can DTI be used to do
identity effect of demyelinating disorders
detect areas with partial or complete disconnection between brain regions
examine changes in diffusion during different life stages (ie water leaking out because of damage)
diffusion tractography
uses such diffusion tensor info to build an image of probable white matter tracts
positron emission tomography (PET)
works by introducing radioactive atoms into the blood supply to be carried to the brain (overtaken by MRI)
provides info about: neurotransmitter function, levels of brain metabolism - seeing where blood is going
advantages and disadvantages of PET
pros:
allows researchers to examine how the brain uses specific molecules (ie/ neurotransmitters)
provides info on absolute levels of brain metabolism
disadvantages
involves radiation, can only do 2-5 times per year safely, limited
poor temporal resolution, takes time to circulate from the area of injection
need to continually create radioactive isotope with expensive cyclotron
fMRI
BOLD (blood oxygen level dependent signal)
based on how oxygenated and deoxygenated blood have different magnetic properties
increase in oxygen rich blood in areas where the brain is active
deoxygenated blood hinders ability to get a signal, increase proportion of oxygenated to deoxygenated blood results in increase signal from that region
advantages of fMRI
machines widely available
non-invasive
multiple scans possible
safe for children and women of reproductive agen
measure brain activity over seconds
resting state approaches
examines patterns of activity while the brain is at rest
researchers found independent networks (regions that co activate during specific tasks)
advantages of resting state approaches
does not require specific cognitive ability or engagement from participant
relatively short neuroimaging session (10-15 mins)
functional connectivity
when significant relationships are observed
electromagnetic recording methods ERM
provide the best temporal resolution of brain activity
activity can be measure on a ms to ms basis
do not provide a good measure of where in the brain activity is happening
EEG electroencephalography
measures electrical activity in the brain using electrodes
specifically of cortical neurons near the electrodes on the scalp
can see different levels of activation
continuous measure of brain activity
