Ch1 - Intro to fMRI

Question 1

fMRI

Answer 1

(functional magnetic resonance imaging)
neuroimaging technique using MRI to investigate functions over time
- functional connectivity, individual differences in personality, genetic differences, neurological & psychiatric disorders

Question 2

static magnetic field

Answer 2

magnetic field at center of MRI scanner (in tesla(T))
- ranges from 1.5T - 7T+

Question 3

pulse frequence

Answer 3

series of changing magnetic field gradients & electromagnetic pulses that allow to create images sensitive to particular physical properties
- e.g. the frequency of hydrogen to image structures in humans

Question 4

structural neuroimaging

Answer 4

class of research techniques that create image of the brains physical structure
- e.g. location and distribution of tissue types

Question 5

functional neuroimaging

Answer 5

class of research techniques that create images of functional properties
- aspects of cognition, functions of distributed networks

Question 6

PET

Answer 6

(positron emission tomography)

functional neuroimaging technique that creates images based on movement of injected radioactive tracer
- pro: metabolic rates (e.g. neurotransmitters)
- con: invasiveness, slow speed of image acquisition, radioactive isotopes

Question 7

EEG

Answer 7

(electroencephalography)

measurement of electrical properties of the brain
- rapid changes: allows to detect timing of brain processes

Question 8

MEG

Answer 8

(magnetoencephalography)

noninvasive measure of small changes in magnetic fields caused by electical activity of neurons
- potentially high spatial and temporal resolution

Question 9

TMS

Answer 9

(transcranial magnetic stimulation)

technique to temporarily stimulate brain regions to disrupt function
electromagnetic coil placed close to scalp, passing current generates magnetic field and produces localized electrical currents

Question 10

Contrast

Answer 10

1) intensity difference between quantities measured by imaging system
2) physical quantity being measured (e.g. T1 contrast)
3) statistical comparison of activation evoked by 2 (or more) experimental conditions in order to get hypothesis

Question 11

contrast-to-noise ration

Answer 11

(CNR)

magnitude of intensity differences between different quantities divided by variability in measurement
- contrast expressed in relation to background variations

Question 12

functional contrast

Answer 12

type of contrast that provides information about a physiological correlate of brain function
- e.g. changes in blood oxygenation
- PET studies: based on emitted radioactive decay particles

Question 13

spatial resolution

Answer 13

ability to distinguish changes in image across spatial locations

Question 14

pixel

Answer 14

smallest element that can be resolved in 2D space

Question 15

voxel

Answer 15

basic sampling unit of MRI
3D volume element
- in humans: 1mm (MRI) & 3mm (fMRI)

Question 16

sampling rate

Answer 16

frequency in time with which a measurement is made
- rate of acquiring images

Question 17

temporal resolution

Answer 17

ability to distinguish changes in signal across time
- in fMRI: 1 brain volume/1-2 sec

Question 18

functional resolution

Answer 18

ability to map measured physiological variation to underlying mental processes or behaviors

Question 19

oscillating magnetic field

Answer 19

magnetic field whose intensity changes periodically over time
- in MRI: radiofrequency fields = frequency range of radio waves (MHz)

Question 20

magnetic resonance

Answer 20

absorption of energy from magnetic field that oscillates at a particular frequency
- frequency of oscillating field matched to spin frequency of atomic nuclei

Question 21

resonant frequency

Answer 21

frequency of oscillation that provides the maximum energy transfer to system

Question 22

transmitter coil

Answer 22

electromagnetic coil that generates oscillating magnetic field at resonant frequency of the atomica nuclei within sample

Question 23

detector coil

Answer 23

electromagnetic coil that measures energy emitted back to the environment after initial absoption by sample

Question 24

nuclear induction

Answer 24

magnetic resonance effect (s. magnetic resonance)
but termed by other guy named Bloch

Question 25

nuclear magnetic resonance

Answer 25

(NMR)

measurable changes in magnetic properties of atomic nuclei induced by application of oscillating magnetic field at resonant frequency of the nuclei

Question 26

spatial gradiants

Answer 26

magnetic field whose strength varies systematically over space

Question 27

EPI

Answer 27

(echo-planar imaging)
technique that allows collection of an entire 2D image by changing spatial gradients rapidly following a single excitation pulse from transmitter coil

Question 28

ionizing radiation

Answer 28

electromagnetic radiation with sufficient energy to break chemical bonds
- negative health connotations
- does NOT occur during MRI

Question 29

BOLD contrast

Answer 29

(Blood-oxygenation-level-dependent contrast)
difference in signal on T2-weighted images as a function of the amount of deoxygenated hemoglobin
- metabolic correlate of neuronal activity (indirect measure)