ERP's

Question 1

event related potentials (ERP)

Answer 1

EEG data recorded locked to a specific event

• measures how the brain is responding to a certain stimulus within the time domain

Question 2

how are they measured?

Answer 2

in terms of amplitude, representing the magnitude of peaks and troughs in the waveform

amplitude is measured in terms of microvolts (uV)

Question 3

why are stimuli presented 100’s of times?

Answer 3

because the amplitude of interest (e.g. N170) is typically smaller than the amplitude of ongoing neural activity and artefacts (e.g. eye movement and electrical line noise) measured at the scalp

Question 4

what are epochs?

Answer 4

after presenting the stimulus many times, the continuouse data is segmented into epochs, the epochs typically contain a pre-stimulus baseline period and a few hundred milliseconds after the event of interest.

• response to the time locked stimuli then becomes clearer as artefacts and background noise become zero
• they provide an idea of when processes occur in the brain after experiencing an event

Question 5

what are components?

Answer 5

these responses to time locked stimuli can be separated into components, representing physiological processes

• components are named with 2 parts: a letter and a number. the letter corresponds to the positivity of deflection, whilst the number corresponds to the time after stimulus onset that a response is found (latency)