Lecture 3 & 4: Electroencephalography
(EEG) Exam Questions and Answers
What iiis iiElectroencephalography ii(EEG)? ii- iiAnswers ii-A iimethod iiof iidetecting iineural
iiactivity iiby iiplacing iielectrodes iion iithe iiscalp
How iidoes iiEEG iiwork? ii- iiAnswers ii-Electrodes iipick iiup iismall iifluctuations iiof
iielectrical iisignals, iioriginating iifrom iiactivity iiof ii(mostly iicortical) iineurons
Nature iiof iielectrical iisignals ii- iiAnswers ii-Very iinoisy iiand iimight iinot iilook iilike iimuch
iibut iisystematically iirelated iito iicognitive iiprocesses
How iiis iiEEG iirecorded? ii- iiAnswers ii-Either iiat iithe iiscalp ii(non-invasive) iibut iialso
iipossible iito iirecord
intra-cranial iiEEG iiby iimeasuring iiactivity iidirectly iiat iithe iiexposed iicortex
Logistics iiof iiEEG ii- iiAnswers ii-Cheap iiand ii(relatively) iieasy iito iiconduct
Hans iiBerger ii(1873-1941) ii- iiAnswers ii-Detected iithe iifirst iiEEG iisignal iiin ii1924 iiwith
iielectrodes iiattached iito iithe iiscalp iiof iia iihuman ii(his iiwife) iiand iireported iithe iiresults iiin
ii1929
Why iidid iiBurger iistudy iimedicine? ii- iiAnswers ii-Because iihe iiwas iiconvinced iithat iithere
iiis ii"psychic iienergy", iiwhich iimight iiallow iifor iitelepathy
He iiwanted iito iidiscover iithe iiobjective iiactivity iiin iithe iibrain iiand ii"psychic iiphenomena",
iibut iihe iidid iinot iirealise iithe iibasis iiand iipotential iiof iihis iidiscovery iiat iithe iitime
What iielse iidid iiBurger iidescribe? ii- iiAnswers ii-Alpha iirhythm: iicharacteristic iifrequency
iiof iielectrical iisignal iiwhen iieyes iiclosed
What iiis iithe iicharacteristic iifrequency iiof iialpha iirhythm? ii- iiAnswers ii-8-13 iiHz
How iidid iiBurger iimeasure iielectrical iiactivity? ii- iiAnswers ii-Initially, iihe iiused iitwo
iielectrodes, iione iiattached iito iithe iifront iiof iithe iihead iiand iione iito iithe iirear, iiand
iirecorded iithe iipotential ii(i.e. iivoltage) iidifference iibetween iithem.
Initially, iielectrodes iiwere iisilver iiwires iiplaced iiunder iithe iiscalp
Later, iisliver iifoil iiplaced iion iithe iiscalp
, Advantage iiof iiEEG ii- iiAnswers ii-Great iitemporal iiresolution
Disadvantage iiof iiEEG ii- iiAnswers ii-Poor iispatial iiresolution
In iithe iielectrode iicap, iion iiwhich iiside iiare iiodd iinumbers? ii- iiAnswers ii-Left iiside
In iithe iielectrode iicap, iion iiwhich iiside iiare iieven iinumbers? ii- iiAnswers ii-Right iiside
What iidoes iiEEG iiactivity iireflect? ii- iiAnswers ii-The iiEEG iiactivity iidoes iinot iireflect
iiaction iipotentials iibut iioriginates iimostly iifrom iipost-synaptic iipotentials ii- iivoltages iithat
iiarise iiwhen iineurotransmitters iibind iito iireceptors iion iithe iimembrane iiof iithe iipost-
synaptic iicell ii
This iicauses iiion iichannels iito iiopen iior iiclose, iileading iito iigraded iichanges iiin iithe
iipotential iiacross iithe iimembrane
What iican iithese ii"graded iichanges" iiin iipotential iiacross iithe iimembrane iibe
iiunderstood iias? ii- iiAnswers ii-A iismall ii"dipole": iisignals iifrom iisingle iicells iiare iinot
iistrong iienough iito iibe iirecorded iioutside iiof iithe iihead, iibut iiif iimany iineurons iispatially
iialign, iithen iitheir iisummed iipotentials iiadd iiup iiand iicreate iithe iisignals iiwe iican iirecord
Where iidoes iithis iipooled iiactivity iifrom iigroups iiof iisimilarly iioriented iineurons iicome
iifrom? ii- iiAnswers ii-Mostly iicomes iifrom iilarge iicortical iipyramid iicells
Functional iiunit iiof iisimultaneously iiactivated iineurons iifor iiEEG ii- iiAnswers ii->10,000
iineurons iisimultaneously iiactivated
What iidetermines iithe iisign iiof iithe iirecorded iipotential ii(negative iior iipositive)? ii-
iiAnswers ii-The iiorientation iiof iithe iineurons
What iihappens iiif iineurons iiare iiperpendicular iito iithe iiscalp? ii- iiAnswers ii-NO iiSignal!
When iican iisignals iinot iibe iirecorded? ii- iiAnswers ii-When iithe iiorientation iiof iithe
iineurons iiis iinot iiconducive iito iia iihomogenous iisignal iias iimeasured iiby iithe iiscalp
Limitations iiof iiEEG ii- iiAnswers ii-Biased iito iisignals iigenerated iiin iisuperficial iilayers iiof
cerebral iicortex iion iithe iigyri ii(ridges) iidirectly iibordering iithe iiskull
The iimeninges, iicerebrospinal iifluid ii(CSF) iiand iiskull ii"smear" iithe
EEG iisignal, iimaking iiit iidifficult iito iilocalise iithe iisource
Inverse iiproblem
Signals iiin iithe iisulci iiare ii...? ii- iiAnswers ii-Harder iito iidetect iithan iifrom iigyri, iiand iimay
iiadditionally iibe iimasked iiby iithe iisignals iifrom iithe iigyri
(EEG) Exam Questions and Answers
What iiis iiElectroencephalography ii(EEG)? ii- iiAnswers ii-A iimethod iiof iidetecting iineural
iiactivity iiby iiplacing iielectrodes iion iithe iiscalp
How iidoes iiEEG iiwork? ii- iiAnswers ii-Electrodes iipick iiup iismall iifluctuations iiof
iielectrical iisignals, iioriginating iifrom iiactivity iiof ii(mostly iicortical) iineurons
Nature iiof iielectrical iisignals ii- iiAnswers ii-Very iinoisy iiand iimight iinot iilook iilike iimuch
iibut iisystematically iirelated iito iicognitive iiprocesses
How iiis iiEEG iirecorded? ii- iiAnswers ii-Either iiat iithe iiscalp ii(non-invasive) iibut iialso
iipossible iito iirecord
intra-cranial iiEEG iiby iimeasuring iiactivity iidirectly iiat iithe iiexposed iicortex
Logistics iiof iiEEG ii- iiAnswers ii-Cheap iiand ii(relatively) iieasy iito iiconduct
Hans iiBerger ii(1873-1941) ii- iiAnswers ii-Detected iithe iifirst iiEEG iisignal iiin ii1924 iiwith
iielectrodes iiattached iito iithe iiscalp iiof iia iihuman ii(his iiwife) iiand iireported iithe iiresults iiin
ii1929
Why iidid iiBurger iistudy iimedicine? ii- iiAnswers ii-Because iihe iiwas iiconvinced iithat iithere
iiis ii"psychic iienergy", iiwhich iimight iiallow iifor iitelepathy
He iiwanted iito iidiscover iithe iiobjective iiactivity iiin iithe iibrain iiand ii"psychic iiphenomena",
iibut iihe iidid iinot iirealise iithe iibasis iiand iipotential iiof iihis iidiscovery iiat iithe iitime
What iielse iidid iiBurger iidescribe? ii- iiAnswers ii-Alpha iirhythm: iicharacteristic iifrequency
iiof iielectrical iisignal iiwhen iieyes iiclosed
What iiis iithe iicharacteristic iifrequency iiof iialpha iirhythm? ii- iiAnswers ii-8-13 iiHz
How iidid iiBurger iimeasure iielectrical iiactivity? ii- iiAnswers ii-Initially, iihe iiused iitwo
iielectrodes, iione iiattached iito iithe iifront iiof iithe iihead iiand iione iito iithe iirear, iiand
iirecorded iithe iipotential ii(i.e. iivoltage) iidifference iibetween iithem.
Initially, iielectrodes iiwere iisilver iiwires iiplaced iiunder iithe iiscalp
Later, iisliver iifoil iiplaced iion iithe iiscalp
, Advantage iiof iiEEG ii- iiAnswers ii-Great iitemporal iiresolution
Disadvantage iiof iiEEG ii- iiAnswers ii-Poor iispatial iiresolution
In iithe iielectrode iicap, iion iiwhich iiside iiare iiodd iinumbers? ii- iiAnswers ii-Left iiside
In iithe iielectrode iicap, iion iiwhich iiside iiare iieven iinumbers? ii- iiAnswers ii-Right iiside
What iidoes iiEEG iiactivity iireflect? ii- iiAnswers ii-The iiEEG iiactivity iidoes iinot iireflect
iiaction iipotentials iibut iioriginates iimostly iifrom iipost-synaptic iipotentials ii- iivoltages iithat
iiarise iiwhen iineurotransmitters iibind iito iireceptors iion iithe iimembrane iiof iithe iipost-
synaptic iicell ii
This iicauses iiion iichannels iito iiopen iior iiclose, iileading iito iigraded iichanges iiin iithe
iipotential iiacross iithe iimembrane
What iican iithese ii"graded iichanges" iiin iipotential iiacross iithe iimembrane iibe
iiunderstood iias? ii- iiAnswers ii-A iismall ii"dipole": iisignals iifrom iisingle iicells iiare iinot
iistrong iienough iito iibe iirecorded iioutside iiof iithe iihead, iibut iiif iimany iineurons iispatially
iialign, iithen iitheir iisummed iipotentials iiadd iiup iiand iicreate iithe iisignals iiwe iican iirecord
Where iidoes iithis iipooled iiactivity iifrom iigroups iiof iisimilarly iioriented iineurons iicome
iifrom? ii- iiAnswers ii-Mostly iicomes iifrom iilarge iicortical iipyramid iicells
Functional iiunit iiof iisimultaneously iiactivated iineurons iifor iiEEG ii- iiAnswers ii->10,000
iineurons iisimultaneously iiactivated
What iidetermines iithe iisign iiof iithe iirecorded iipotential ii(negative iior iipositive)? ii-
iiAnswers ii-The iiorientation iiof iithe iineurons
What iihappens iiif iineurons iiare iiperpendicular iito iithe iiscalp? ii- iiAnswers ii-NO iiSignal!
When iican iisignals iinot iibe iirecorded? ii- iiAnswers ii-When iithe iiorientation iiof iithe
iineurons iiis iinot iiconducive iito iia iihomogenous iisignal iias iimeasured iiby iithe iiscalp
Limitations iiof iiEEG ii- iiAnswers ii-Biased iito iisignals iigenerated iiin iisuperficial iilayers iiof
cerebral iicortex iion iithe iigyri ii(ridges) iidirectly iibordering iithe iiskull
The iimeninges, iicerebrospinal iifluid ii(CSF) iiand iiskull ii"smear" iithe
EEG iisignal, iimaking iiit iidifficult iito iilocalise iithe iisource
Inverse iiproblem
Signals iiin iithe iisulci iiare ii...? ii- iiAnswers ii-Harder iito iidetect iithan iifrom iigyri, iiand iimay
iiadditionally iibe iimasked iiby iithe iisignals iifrom iithe iigyri
