brain imaging techniques

Question 1

what does EEG stand for?

Answer 1

electroencephalogram

Question 2

what does an EEG do?

Answer 2

records electrical activity on the surface of the scalp through electrodes

Question 3

what does the 10-20 system refer to?

Answer 3

the universal system for placing electrodes on the scalp in eeg

Question 4

what is the EEG recording?

Answer 4

the difference in potential between different electrodes

Question 5

what are oscillations?

Answer 5

postsynaptic potentials - they change in frequency and amplitude (waves)

Question 6

what does hertz mean?

Answer 6

cycles per second

Question 7

what is monopolar montage?

Answer 7

potential difference between a referent site and all other brain sites

Question 8

what is REM sleep?

Answer 8

• rapid eye movement
• most accociated with dreaming
• oscillations look very similar to those when the body is awake
• the source of information is internal

Question 9

what is paradoxical sleep?

Answer 9

the brain appears to be awake from the EEG but the musculater is flacid and unresponsive.

Question 10

what does ERP stand for?

Answer 10

event related potentials

Question 11

what are erps?

Answer 11

averages EEG recordings that measure brain responses to repeated presentations of a stimulus

Question 12

what is good about ERPs?

Answer 12

they cancel out any noise from an EEG

- responses to discrete stimuli can only be seen by averaging

Question 13

what is mismatch negativity? (MMN)

Answer 13

indicates that the person has detected a stimulus that deviates from the preceding stimuli.
the more complex the stimulus, the later the MMN.

Question 14

this only appears if the stimulus is task relevant and the individual is attending to the stimulus

Answer 14

N2

Question 15

what does the P3 reflect?

Answer 15

the conscious resolution of the task eg detecting the target.

• the top of the wave - highest point
• can be used to measure the depth of processing as larger p3s indicate deeply processed words.

Question 16

what does Computerised Tomography (CT) do?

Answer 16

uses x rays to measure tissue density

Question 17

what is tomography

Answer 17

taking multiple pictures

Question 18

what is the main issue with xray?

Answer 18

its a 2D image

- does not provide adequate info about the brain

Question 19

how is a CT scan conducted?

Answer 19

1. xray source is moved in steps in an arc around the head
2. at each point, detectors measure the amount of xray radiation passing through - the value is proportional to the density of the tissue
3. a computer deconstructs the results into an anatomical map of the brain

Question 20

what downside is there to CT?

Answer 20

its a medium resolution image

- difficult to distinguish brain structures.

Question 21

what is Magnetic Resonance Imaging? (MRI)

Answer 21

uses magnetic energy to generate images and provide information about tissue composition

Question 22

how are MRIs conducted?

Answer 22

1. patients head is placed in the center of a v powerful circular magnet. electrical fields in the brain line up parallel
2. removing the magnetic field makes the atoms go back to where they were before - RELAXATION
3. each atom has a different rate of relaxation meaning that you can distinguish which types of atoms are which depending on the rate of relaxation
4. this info is computerized into a sectional map of the brain.

Question 23

what is important about the relaxation rate of hydrogen?

Answer 23

different brain areas contain different levels of hydrogen.

MRI therefore lets us see the differenet brain structures

Question 24

what positives are there to tomography?

Answer 24

• 3D info at different levels

- provides more info on the extent of brain lesions and brain structure in mental illness

Question 25

what is interesting about the ventricles in schizophrenic brains?

Answer 25

they are larger.

Question 26

what is Positron Emission Tomography? (PET)

Answer 26

requires the injection of a radioactive substance | measures brain metabolism

Question 27

what substances are injected during PET scans?

Answer 27

glucose - direct measure | water - measures blood flow

Question 28

limitations of PET?

Answer 28

- invasive - constrained as can only be used 2/3 times - expensive

Question 29

explain the process of a PET scan

Answer 29

1. when a positron is emittedm it travels a certain distance. when is has expended all of its kinetic energy, it meets with a free electron 2. they mutually annihilate one another and give off 2 gamma ray photons. 3. the gamma rays are detected and information is used to reconstruct an image of the collision sites

Question 30

gamma ray photons are emitted at what angle

Answer 30

180 from one another

Question 31

what is the key point to be made about PET?

Answer 31

they detect the collision between a positron and an electron, NOT the source of the electrical activity.

Question 32

what is useful about the mean difference image from PET scans?

Answer 32

can compare brain activity from contrasting stimulus and create a difference image which reflects the areas of the brain that were the most active during the experiment.

Question 33

what is fMRI measuring?

Answer 33

the change in blood flow. | - difference in oxegenated and deoxygenated blood - changes.

Question 34

what is haemoglobin?

Answer 34

iron and oxygen.

Question 35

what is blood level dependency imaging? (BOLD)

Answer 35

1. blood is brought ot tissue through the artery and contains lots of haemoglobin 2. the arterty breask up into capillaries which allows substance to go from the blood into tissue. oxygen leaves. 3. as oxygen leaves the blood the capillaries become deoxgenated. 4. this then leaves deoxygenated haemoglobin

Question 36

what is the basis of thought for fMRI?

Answer 36

active neurons attract more arterial blood flow and more oxygenated haemoglobin. - areas that are more active will generate more action potentials and therefore more use of the Na/K pump

Question 37

what is the main difference between PET and fMRI?

Answer 37

fMRI can be repeated many times unlike PET

Question 38

what is good about event related fMRI?

Answer 38

responses can be averaged

Question 39

what is good about tomographic fMRI?

Answer 39

can compute different slices of the brain to see activity at different sites done without injection of a radioactive substance.

Question 40

what imaging techniques measure brain structure?

Answer 40

CT and MRI

Question 41

what imaging techniques measure brain metabolism?

Answer 41

PET and fMRI.