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530: Data Acquisition > Chapter 12 p. 1 (EEG) > Flashcards

Chapter 12 p. 1 (EEG) Flashcards

1
Q

EEG is an __ monitoring method for recording the __ of the brain using electrodes placed __, although __ electrodes are occasionally used

A

electrophysiological ; electrical activity; along the scalp; invasive

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2
Q

__ EEG is the most typical

A

non-invasive

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3
Q

2 types of invasive EEG

A

electrocorticography (ECoG), and stereotactic EEG (sEEG)

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4
Q

ECoG is used for __

A

invasive localization of seizures prior to surgery

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5
Q

sEEG is used for __

A

deep brain stimulation (DBS)

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6
Q

EEG measures __ resulting from __ within neurons

A

voltages; ionic currents

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7
Q

EEG can be used to measure __ brain waves (e.g. __(3)) or __ brain waves (__)

A

endogenous; sleep, coma, epilepsy; exogenous; evoked potentials (EPs)

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8
Q

a common class of EPs consists of __ which are averaged EEG response that are __

A

event-related potentials (ERPs); time-locked to complex processing stimuli

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9
Q

ERP research is very common in __ (3)

A

cognitive science, cognitive psychology, and psychophysiological research

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10
Q

because electric potentials are difference in __, each EEG signal is the difference between __

A

voltage between two sites; two voltage waveforms

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11
Q

an EEG montage represents __

A

how the signal is obtained

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12
Q

3 types of EEG montages

A

monopolar, bipolar, Laplacian

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13
Q

monopolar montage: the waveform is the difference between __ and __

A

the signal at the scalp; the signal at a skin location far away (e.g. arm, leg)

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14
Q

bipolar montage: the waveform is the difference between __

A

2 scalp electrode signals

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15
Q

Laplacian montage: the signal is __ minus __

A

the voltage at some point on the scalp; a weighted average of the surrounding electrodes

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16
Q

one version of a monopolar montage

A

the 10-20 montage

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17
Q

it’s named the 10-20 montage because __

A

the angle between electrodes is ~10 degrees

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18
Q

the 10-20 montage uses __ to direct the placement of electrodes

A

the natural landmarks of the head

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19
Q

10-20 montage electrodes are typically named based on __

A

the brain lobe over which they are located

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20
Q

EEG sources are primarily due to __ along the __

A

currents; apical dendrites of pyramidal neurons (PY)

21
Q

pyramidal neurons: somas are in __ and apical dendrites project to __

A

layer V; layers I and II

22
Q

types of neurons other than PYs do not typically generate a strong EEG signal because of __ (e.g. in the case of __)

A

signal cancellation; stellate neurons

23
Q

within white matter fibers, the net electrical currents __ because action potentials travel __ and thus the scalp signal due to these is __

A

cancel out; both ways along the fiber; very weak

24
Q

__ of ions along the dendrite of PY create a __ across the membrane, and the simultaneous activation of PY populations results in a __ which extends to the scalp

A

influx or efflux; net potential difference; measurable electric field

25
Q

PY cell populations within a spatial neighborhood on the cortex can __ and their electric signal can be represented using the __

A

activate simultaneously; current dipole model of EEG

26
Q

in the current dipole model of EEG, electric currents are approximated by vectors which are __ and whose direction is __

A

perpendicular to the surface of the cortex; determined by the direction of the electric currents along the apical dendrites of the PY cells

27
Q

current dipole model of EEG: note that the recorded signal is more __ when a bipolar montage is used, compared to the monopolar montage

A

focal

28
Q

active EEG sources produce distinct patterns at the scalp depending on __, as well as on the __

A

the location where they are generated; orientation of these generators

29
Q

because the orientation of the generators is predicated upon the __ of the cortex at locations which are __, the __ of the brain determines scalp potential patterns

A

gyrification; electrically active; anatomic configuration

30
Q

__ cells generate currents which propagate to the scalp

A

electrically active PY

31
Q

the extent to which currents can travel across tissues which are __ is determined by the __ of these tissues, which is a measure of the physical ability of a material to __

A

interposed between the cortex and the scalp; electrical conductivity; conduct an electric current

32
Q

there are many layers between the brain and the scalp, and each of these __ (e.g. __)

A

has a different conductivity (e.g. that of CSF is very high because it contains Na and Cl ions in water, whereas that of bone is very low)

33
Q

because of the different conductivities of the layers between brain and scalp, the EEG signal is both __ and __, so that scalp potentials provide a measure of __

A

attenuated; spatially smeared; only the strongest cortical currents

34
Q

EEG signals may change __ and/or __ in response to __

A

amplitude; frequency; ERPs

35
Q

5 canonical frequency bands (in order from lowest to highest Hz/frequency)

A

delta, theta, alpha, beta, gamma

36
Q

delta

A

slow-wave sleep, subcortical lesions

37
Q

theta

A

higher in children, drowsiness in adults, encephalopathies

38
Q

alpha

A

eye closing, relaxation, inhibition control, coma

39
Q

beta

A

attention, alertness, anxiety, decreased by GABA agonists (benzos)

40
Q

gamma

A

sensory integration, decreases with cognitive decline

41
Q

the task of localizing EEG currents based on scalp EEG potential recordings is known as

A

the inverse problem of EEG

42
Q

the task of calculating the scalp EEG potential due to a known distribution of electric currents is know as

A

the forward problem of EEG

43
Q

solving the forward problem involves computing the __, which specifies the __

A

lead field of each EEG electrode; areas of cortex from which the electrode can record

44
Q

__ is the most important step required before solving the __, and the accuracy of __ depends on the accuracy of __

A

finding the lead fields of EEG; inverse problem; inverse localization; lead field calculation

45
Q

lead fields are computed based on __

A

appropriate formulations of Maxwell’s Equations

46
Q

the second step to inverse localization involves __. two examples?

A

the creation of realistic models of the head; boundary element models (BEMs), and finite element models (FEMs)

47
Q

BEMs are models which specify the __, and the conductivity within each shell is __ (not particularly accurate due to __)

A

boundaries between tissues; assumed to be constant; conductivity inhomogeneities

48
Q

FEMs are models which discretize/divide the head into __, and each of these has its own __ (much more __ than BEM if the __ is high)

A

small tetrahedra; conductivity; accurate; spatial resolution

49
Q

once the inverse model has been generated, scalp potentials can be __ and the __ can be determined (ex: __)

A

localized to the cortical surface; locations of EEG generators; post-traumatic epileptic spiking

530: Data Acquisition (13 decks)

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