H4 The imaged brain Flashcards
structural imaging
measures of the spatial configuration of different types of tissue in the brain (CT & MRI)
CT scan
computerized tomography scan → constructed according to amount of X-ray absorption in different types of tissue
MRI
magnetic resonance imaging → creates images of soft tissue by applying an alternating magnetic field and a brief radio frequency pulse
functional imaging
measures temporary changes in brain physiology associated with cognitive processing (most common= fMRI based on hemodynamic measure)
PET scan
positron emission tomography → measures the changes in blood flow to a region directly
hemodynamic methods
-PET→ measures changes in blood flow
-fMRI & fNIRS → sensitive to concentration of oxygen in the blood
voxel-based morphometry (VBM)
technique for segregating and measuring differences in white and gray matter concentration using MRI
voxel
volume-based unit: in imaging research the brain is divided into many thousands of these
diffusion tensor imaging (DTI)
uses MRI to measure white matter connectivity between brain regions
fractional anisotrophy (FA)
measure of the extent to which diffusion takes place in som directions more than others
BOLD
blood oxygen-level-dependent contrast: the signal measured in fMRI that relates to the concentration of deoxyhemoglobin in the blood
hemodynamic response function (HRF)
changes in the BOLD signal over time
3 phases: - initial dip
- overcompensation
- undershoot
fNIRS
functional near infrared spectroscopy → measures BOLD signal by sending near infrared light instead of magnetic fields BUT can only image shallow neural activity close to scalp
cognitive substraction
type of experimental design in functional imaging in which activity in a control task is compared with activity in an experimental task
assumption of pure insertion
=pure deletion → assumption that adding a different component to a task doesn’t change the operation of other components
cognitive conjuction
method that looks for regions of activation that are shared across several different substractions instead of just 1
efference copy
a motor signal used to predict sensory consequences of an action
functional integration
the way in which different regions communicate with each other
resting state paradigms
technique for measuring functional connectivity in which correlations between several regions/networks are assessed while the participant is not performing any tasks
default mode network
set of brain regions that is more hemodynamically active during rest than during tasks
stereotactic normalization
the mapping of individual differences in brain anatomy onto a standard template
smoothing
redistributing brain activity from neighboring voxels to enhance the signal-to-noice ratio
Talairach coordinates
locations in the brain defined relative to the atlas of Talairach and Tournoux
inhibition
reduction/suppression of the activity of a brain region, triggered by activity in another region
→presynaptic neurons active; postsynaptic switched OFF
excitation
increase of activity of a brain region triggered by activity in another region
→ presynaptic active; postsynaptic switched ON
activation
↑ in physiological processing in 1 condition relative to some other condition(s)
deactivation
↓ in physiological processing in 1 condition relative to some other condition(s)
semantic dementia
progressive loss of information from semantic memory
semantic memory
conceptually based knowledge about the world, including people, places, meaning of objects & words
