Electroencephalography (EEG) &
Evoked Potentials Exam Questions and
Answers
1. iiEEG iidefined
a. iiThe iiEEG iiis iia iimeasurement iiof ii?. iiThese iivoltage iifluctuations iiare iicalled?
b. iiEEG iirecording:
i. iiIn iihumans, iithe iielectrodes iiare iismall iimetal iidisks iipasted iito iithe iisurface iiof iithe
iiscalp iiby iian iielectricity iiconducting iigel.
ii. iiThere iiare iitwo iielectrodes iiplugged iiinto iieach iiamplifier iion iithe iiEEG iimachine. iiThe
iiEEG iirecorder iidetects iithe iivoltage iidifferences iibetween iithe iirecording iiand iireference
iielectrode iifor iieach iichannel iiof iidetection. iiThe iiamplifier iicompares iithe iitwo iielectrode
iisignals iicoming iiinto iiit iiand iicancels iiout iisignals iithat iiare iithe iisame. iiTherefore iithe
iiEEG iisignal iiis iithe iidifference iiin ii?
iii. iiOne iielectrode iipair iiis iireferred iito iias iia ii?. iiModern iiEEG iirecordings iihave iifrom ii?
iichannels iito iiproduce iia iimultichannel iirecording iias iishown iihere.
iv. iiThe iiplacement iiof iithe iielectrodes iiis iiimportant iibecause iithe iicloser iithe iielectrodes
iiare iito iieach iiother iithe ii?. iiIf iithe iielectrodes iiare iitoo iiclose, iithe iiEEG iichannel iiwill
iidisplay iia iistraight iiline. iiTherefore, iiwhen iir ii- iiAnswers ii--voltage iifluctuations iiat iithe
iisurface iiof iithe iiscalp iigenerated iiby iithe iielectrical iiactivity iiof iithe iibrain
- iibrain iiwaves iiand iiare iirecordings iiof iivoltage iidifference iiversus iitime.
-electrical iiactivity iidetected iiby iitwo iielectrodes.
-channel
-8 iito ii40
-less iidifferences iiin iitheir iibrain iiwaves
Figure ii3: iiStandard iiplacement iiof iielectrodes iion iia iisubject iifor iimultichannel iiEEG
iirecording. iiAbbreviations: iiA, iiauricle; iiC, iicentral; iiCz, iivertex; iiF, iifrontal; iiFP iifrontal
iipole; iiO, iioccipital; iiP, iiparietal; iiT, iitemporal.
i. iiThe iivoltage iiemitted iifrom iithe iiscalp iiis iion iithe iiorder iiof iimicrovolts ii(10-6 iivolts).
iiThe iiEEG iiamplifiers iiincrease iithis iisignal iiby iia iifactor iiof iiseveral iihundred iithousand
ii(105) iifor iidetection iiand iirecording.
ii. iiDetected iisignals iiare iieither iitraced iion iistrip iichart iipaper iior, iimore iilikely
iinowadays, iiare iipassed iithrough iian iianalog-to-digital iiprocessor iiand iistored iiin iidigital
iiformat.
iii. iiThe iidigitized iidata iican iithen iibe iianalyzed iiby iiFourier iitransforms ii(FT) iiand
iifiltering. iiFT iiis iia iimathematical iiway iito ii?
, Figure ii4: iiFourier iitransform iiof iiraw iiEEG iidata. iiLeft, ii5 iidifferent iiraw iiEEG iichannels
iiof iivoltage iivs iitime iitaken iifrom ii5 iidifferent iielectrodes. iiRight, iiFourier iitransform iiof
iichannel ii2 iiconverts iiaxes iito iiintensity ii(Y iiaxis) iivs iifrequency ii(X iiaxis). iiYou iican iis ii-
iiAnswers ii--convert iithe iiwave iidata iifrom iibeing iia iifunction iiwhere iivoltage iivaries iiwith
iitime iito iia iidescription iiof iihow iimuch iiof iithe iiEEG iisignal ii(called iipower) iion iiany iigiven
iichannel iioccurs iiat iia iigiven iifrequency.
2. iiReading iiEEGs ii- iiEEGs iihave iithree iiaspects: ii?
a. iiArtifacts: iiArtifacts iiare?, iiusually iitransitory, iiand iiinclude: iielectrode iimovement, iiwith
iiloss iiof iicontact; iimuscle iiactivity iiobscuring iithe iiEEG, iimovements iiof iithe iihead,
iiscratching iithe iiscalp; iiand iisweating. iiFigure ii2 iiillustrates iieye iimovement iiartifacts iiin
iithe iimultichannel iiEEG iirecording.
b. iiBrain iiwaves: iiThese iiare iilisted iifrom iihighest iito iilowest iifrequency iiin iithe iitable
iibelow. iiThe iivarious iibrain iiwaves iiare iiassociated iiwith iiglobal iiaspects iiof iiawareness
iiand iisubjectivity iias iilisted iibelow iiin iiTable ii1. ii
Note: ii1 iiHz iiis iione iicycle/second.
Figure ii5: iiillustration iiof iithe ii4 iimain iiclasses iiof iibrain iiwaves
(gamma iiare iidetected iiby ii? iiand iinot iivisible iiin iithe iiraw ii?). ii- iiAnswers ii--(1) iiartifacts,
ii(2) iibrain iiwaves iioccurring iiat iidifferent iifrequencies, ii(3) iia iinumber iiof iispecific iitypes
iiof iiwave iipatterns.
- iidisturbances iicaused iiby iitechnical iidefects
-Fourier iianalysis, iiEEG iitracing
Name
Give: ii-Frequency
ii-Description
gamma?
Beta?
alpha?
Theta?
delta? ii- iiAnswers ii-> ii40 iiHz
a. iiWidely iispread iiout iibrain iiareas iithat iiare iiactive iiat iithe iisame iitime iidisplay iigamma
iioscillations.
b. iiGamma iifrequencies iiare iithought iito iireflect iiwhat iiis iicalled iibinding. iiThis iiis iithe
iiproperty iiof iithe iibrain iithat iiunifies iiour iiawareness iiinto iia iisingle iigestalt.
Evoked Potentials Exam Questions and
Answers
1. iiEEG iidefined
a. iiThe iiEEG iiis iia iimeasurement iiof ii?. iiThese iivoltage iifluctuations iiare iicalled?
b. iiEEG iirecording:
i. iiIn iihumans, iithe iielectrodes iiare iismall iimetal iidisks iipasted iito iithe iisurface iiof iithe
iiscalp iiby iian iielectricity iiconducting iigel.
ii. iiThere iiare iitwo iielectrodes iiplugged iiinto iieach iiamplifier iion iithe iiEEG iimachine. iiThe
iiEEG iirecorder iidetects iithe iivoltage iidifferences iibetween iithe iirecording iiand iireference
iielectrode iifor iieach iichannel iiof iidetection. iiThe iiamplifier iicompares iithe iitwo iielectrode
iisignals iicoming iiinto iiit iiand iicancels iiout iisignals iithat iiare iithe iisame. iiTherefore iithe
iiEEG iisignal iiis iithe iidifference iiin ii?
iii. iiOne iielectrode iipair iiis iireferred iito iias iia ii?. iiModern iiEEG iirecordings iihave iifrom ii?
iichannels iito iiproduce iia iimultichannel iirecording iias iishown iihere.
iv. iiThe iiplacement iiof iithe iielectrodes iiis iiimportant iibecause iithe iicloser iithe iielectrodes
iiare iito iieach iiother iithe ii?. iiIf iithe iielectrodes iiare iitoo iiclose, iithe iiEEG iichannel iiwill
iidisplay iia iistraight iiline. iiTherefore, iiwhen iir ii- iiAnswers ii--voltage iifluctuations iiat iithe
iisurface iiof iithe iiscalp iigenerated iiby iithe iielectrical iiactivity iiof iithe iibrain
- iibrain iiwaves iiand iiare iirecordings iiof iivoltage iidifference iiversus iitime.
-electrical iiactivity iidetected iiby iitwo iielectrodes.
-channel
-8 iito ii40
-less iidifferences iiin iitheir iibrain iiwaves
Figure ii3: iiStandard iiplacement iiof iielectrodes iion iia iisubject iifor iimultichannel iiEEG
iirecording. iiAbbreviations: iiA, iiauricle; iiC, iicentral; iiCz, iivertex; iiF, iifrontal; iiFP iifrontal
iipole; iiO, iioccipital; iiP, iiparietal; iiT, iitemporal.
i. iiThe iivoltage iiemitted iifrom iithe iiscalp iiis iion iithe iiorder iiof iimicrovolts ii(10-6 iivolts).
iiThe iiEEG iiamplifiers iiincrease iithis iisignal iiby iia iifactor iiof iiseveral iihundred iithousand
ii(105) iifor iidetection iiand iirecording.
ii. iiDetected iisignals iiare iieither iitraced iion iistrip iichart iipaper iior, iimore iilikely
iinowadays, iiare iipassed iithrough iian iianalog-to-digital iiprocessor iiand iistored iiin iidigital
iiformat.
iii. iiThe iidigitized iidata iican iithen iibe iianalyzed iiby iiFourier iitransforms ii(FT) iiand
iifiltering. iiFT iiis iia iimathematical iiway iito ii?
, Figure ii4: iiFourier iitransform iiof iiraw iiEEG iidata. iiLeft, ii5 iidifferent iiraw iiEEG iichannels
iiof iivoltage iivs iitime iitaken iifrom ii5 iidifferent iielectrodes. iiRight, iiFourier iitransform iiof
iichannel ii2 iiconverts iiaxes iito iiintensity ii(Y iiaxis) iivs iifrequency ii(X iiaxis). iiYou iican iis ii-
iiAnswers ii--convert iithe iiwave iidata iifrom iibeing iia iifunction iiwhere iivoltage iivaries iiwith
iitime iito iia iidescription iiof iihow iimuch iiof iithe iiEEG iisignal ii(called iipower) iion iiany iigiven
iichannel iioccurs iiat iia iigiven iifrequency.
2. iiReading iiEEGs ii- iiEEGs iihave iithree iiaspects: ii?
a. iiArtifacts: iiArtifacts iiare?, iiusually iitransitory, iiand iiinclude: iielectrode iimovement, iiwith
iiloss iiof iicontact; iimuscle iiactivity iiobscuring iithe iiEEG, iimovements iiof iithe iihead,
iiscratching iithe iiscalp; iiand iisweating. iiFigure ii2 iiillustrates iieye iimovement iiartifacts iiin
iithe iimultichannel iiEEG iirecording.
b. iiBrain iiwaves: iiThese iiare iilisted iifrom iihighest iito iilowest iifrequency iiin iithe iitable
iibelow. iiThe iivarious iibrain iiwaves iiare iiassociated iiwith iiglobal iiaspects iiof iiawareness
iiand iisubjectivity iias iilisted iibelow iiin iiTable ii1. ii
Note: ii1 iiHz iiis iione iicycle/second.
Figure ii5: iiillustration iiof iithe ii4 iimain iiclasses iiof iibrain iiwaves
(gamma iiare iidetected iiby ii? iiand iinot iivisible iiin iithe iiraw ii?). ii- iiAnswers ii--(1) iiartifacts,
ii(2) iibrain iiwaves iioccurring iiat iidifferent iifrequencies, ii(3) iia iinumber iiof iispecific iitypes
iiof iiwave iipatterns.
- iidisturbances iicaused iiby iitechnical iidefects
-Fourier iianalysis, iiEEG iitracing
Name
Give: ii-Frequency
ii-Description
gamma?
Beta?
alpha?
Theta?
delta? ii- iiAnswers ii-> ii40 iiHz
a. iiWidely iispread iiout iibrain iiareas iithat iiare iiactive iiat iithe iisame iitime iidisplay iigamma
iioscillations.
b. iiGamma iifrequencies iiare iithought iito iireflect iiwhat iiis iicalled iibinding. iiThis iiis iithe
iiproperty iiof iithe iibrain iithat iiunifies iiour iiawareness iiinto iia iisingle iigestalt.
