EEG Flashcards
Who came up with EEG
Hans Berger conducted a series of experiments where he found you could measure the electrical activity under scalp
who discovered first EEG component
Grey Walter and colleagues
- contingent negative variation (CNV)
preparatory signal in task when you hear warning signal and have to wait for a specific stimulus to react to (in waiting time, the CNV arises)
P300
Sutton et al.
positive going wave elicited by unpredictable stimulus
- was smaller when stimulus was more expectable
basics of electricity
name what’s behind these physics letters:
I, V, R, Z, Ohms law
I is Current, measured in Amperes
V is Voltage measured in Volts
R is Resistance in Ohms
Z is Impedance
Ohms law: E=I*R
Measurement tools EEG
active electrodes
- number can vary 10/20 international system
ground electrode
reference electrode (i.e. on mastoid bone)
signal amplified (by i.e. 20000)
signal filtered
signal digitized
triggers when events happen so easier to identify on EEG WAVES
how can you average the signal of an EEG
in event windows to specify what you look at
- pre stimulus 200 ms and post up to 1500 ms
average per
- condition
- subject
- grand average
- average noise out
why do neurons need to be similarly oriented ?
postsynaptic potential creates a dipole in neuron
- signal of thousands of these fan be picked up
- only if oriented same way because otherwise different dipoles cancel each other out
- that’s why pyramidal cells are ideal (cortex)
temporal spatial resolution
temporal amazing: ms dimension
spatial: kinda bad because of inverse problem
MEG
picks up on magnetic fields of dipoles
- higher spatial res. because signal for magnetic field not impaired by skull
link novelty attention
is reflexive so exists even in absence of attention
but enhanced through it
actually others say exact opposite
neural oscillations and what they stand for
alpha 8-12 Hz
- wakeful relaxation with closed eyes
beta 12-30 Hz
- normal waking consciousness
gamma 38-100
- working memory, attention and perception
delta 0.1-3
- deep sleep
theta 4-7
- memory formation and navigation
epileptiform EEG terminology
pre-ictal: before seizure
ictal: during
postictal: after seizure
interictal: between seizures
when to use ERPs
to determine what process is affected
for identifying multiple neurocognitive processes
covert monitoring of processing
when not to use ERPs
- if you need exact spatial resolution
- if you’re investigating slow process
- can’t collect large number of trials
- participants can’t keep head still during experiment
- need to investigate speech (tongue strong dipole)
typical waveform
P1 initial sensory response
N1 higher perceptual processes
P2 task dependent organization
N2 response selection
P3 working memory encoding
down curve is post response evaluation (nowadays more detailed investigation of also that which happens beyond 400ms)
