electrophysiology

Question 1

EEG

Answer 1

measures electrical activity from the scalp

pick up electrical impulse from heart rate
needs to be subtracted using recording of heart rate

Question 2

how does an EEG work?

Answer 2

electrodes far from electrical signal

fire in all directions but only detect those projecting in direction of electrode

multiple layers of skin, bone and tissue before detection

so only detect a tiny fraction of actual brain activity

subtract all noise from environment

Question 3

frequency bands

Answer 3

higher in frequency when more active

gamma - concentration
beta - busy
alpha - restful
theta - drowsy
delta - asleep

Question 4

what is sensory-motor rhythm?

Answer 4

between alpha and beta waves
different for everyone

one frequency band exclusively used by sensory and primary motor cortex

allows clear communication without interference from rest of brain

Question 5

electromyography (EMG)

Answer 5

measures muscle response

senses muscular activity where no movement is produced

reveals nerve or muscle dysfunction
issues with nerve-to-muscle signal transmission

Question 6

how does an EMG work?

Answer 6

detects invisible neuromuscular activity

can be used to detect emotions in experiments
even when face not moving, smiling and growing muscles still receive impulses when emotions experienced

Question 7

electrodermal activity

Answer 7

variation of the electrical conductance of the skin
in response to sweat secretion

essentially detects stress levels by sweating
- stress, arousal, emotion, cognitive load

Question 8

event related potentials (ERP)

Answer 8

event = stimulus

stimulus onset = event to which we relate the electric potentials that we are measuring

look at waveforms, maps and specific sources of impulses

Question 9

how are ERPs categorised?

Answer 9

polarity (positive or negative)

latency (how long after onset)

amplitude (in microvolts)

topographic distribution (maps)

Question 10

descriptive labelling of ERPs

Answer 10

labelled with a P or an N
positive or negative

number is the latency
(how long after onset)

eg N400
negative and 400 milliseconds after hearing meaningful word/stimulus

Question 11

mismatch negativity

Answer 11

negative potential produced when experience something brain doesn’t expect

Question 12

error related negativity

Answer 12

when mistake made

Question 13

bereitschaftspotential

Answer 13

muscle activity when no muscle movement

Question 14

N400

Answer 14

wave pattern happens every time word with meaning heard

Question 15

N400 effect

Answer 15

changes in amplitude of wave
depends on how well word fits with context

Question 16

ERP effect

Answer 16

a modulation of a particular ERP component

or just the difference between 2 conditions in ERP waveform

Question 17

multidimensional nature of the signal

Answer 17

we can measure electrical signals from the scale while people engage with stimuli over time
and look at behaviour

Question 18

continuous nature of signal

Answer 18

task does not need interruptions that interfere with natural behaviour

brain activity can be measured while people lives everyday life

Question 19

strengths of ERPs

Answer 19

high temporal resolution

direct measure of neural activity

Question 20

weaknesses of ERPs

Answer 20

measure only a part of the neural activity

poor spatial resolution

Question 21

open brain EEG (ECoG)

Answer 21

recording EEG signals directly from the surgically exposed cerebral cortex
often used simultaneously with cognitive testing

measure which areas of the brain can be removed or cut into to preserve function

implants can be left in and used wirelessly
firing patterns used to do actions eg type in those who can’t

Question 22

magneto-encephalography (MEG)

Answer 22

function neuroimaging technique for mapping brain activity
by recording magnetic fields

doesn’t record waves but magnetic fields
still only picks up open fields

better source localisation than EEG and fMRI