kellogg02.qxdd 7/11/02d 10:27d AMd Paged 25
CHAP TE R 2
COGNITIVE NEUROSCIENC d
E
T
hedfielddofdcognitivedneurosciencedaddressesdhowdmentaldfunctionsdar
edsupporteddbydthedbrain.dThisdclosedrelativedofdcognitivedpsychologydisdexp
lodingdwithdnewdfindingsdasdadresultdofdtheddiscoverydofdmethodsdfordimagi
ngd thed workingsd ofd thed livingd brain.d Neuroimagingd technologiesd havedrev
olutionizeddthedstudydofdthedbrain,dbutdasdwilldbedseendindthisdchapter,dtheirde
ffectived used requiresd thed behaviorald measures,d researchd strategies,d andd
theoriesdofdcognitivedpsychology.dItdisdalsodimportantdtodunderstanddthatdth
edcoredquestionsdofdcognitivedpsychologydcannotdbedanswereddjustdbydviewi
ngdthedbraindindaction.dOnedmustdfirstdknowdwhichdcognitivedfunctions,dsuch
dasdshort-
termdmemory,dtodlookdfordindadhighlydcomplexdorgan.dIndotherdwords,dcogni
tived psychologyd providesd thed theoriesd thatd guided thed searchd intod the
structuresdanddactivitiesdofdthedbrain.
Thedchapterdbeginsdwithdandintroductiondtodthedproblemdofdhowdthedmin
ddanddbraindaredrelateddtodeachdother.dNext,dadbriefdtourdofdfunctionaldneu-
droanatomydisdprovided,dfolloweddbydaddiscussiondofdthedmethodsduseddindc
ognitivedneuroscience.dLastly,dthedfundamentaldpropertiesdofdconnectionistd
modelsd ared presented.d Asd notedd ind Chapterd 1,d thesed ared highlyd simplifie
d
25
,kellogg02.qxdd 7/11/02d 10:27d AMd Paged 26
26d ●d SCOPEdANDdMETHODS
modelsdofdthedbraindusingdartificialdneuronsdthatdmimicdsomedofdthedbasicdp
ropertiesdofdrealdneurons.dConnectionistdmodelsdarednowdadcentraldtooldindc
ognitivedneurosciencedanddthedbroaderdfielddofdcognitivedpsychology.
● MINDd ANDd BRAIN
Cognitivedneurosciencedconfrontsdusdwithdonedofdthedmostdchallenging,difdn
otdthedmostdchallenging,dphilosophicaldanddscientificdquestions.dWhatdexactl
ydisdthedrelationdbetweendthedminddanddthedbody?dPutddifferently,dhowdisdco
n-
dsciousnessdproduceddby dthedbrain?dIsdadmentaldstatedreducibledtodadphysica
ldstatedofdthedbrain,dordaredtheydseparatedphenomena?
Onedviewdofdthedrelationdbetweendthedbraindanddthedminddisdthatdtheyda
redonedanddthedsame.dMaterialismdregardsdthedminddasdthedproductdofdthedb
raindandditsdphysiologicaldprocesses.dThedmindddoesdnotdexistdindependentl
ydofdthednervousdsystem,daccordingdtodmaterialism.dOnedversiondofdmaterial
ismdcontendsdthatditdisdpossibledindtheorydtodreducedalldcognitivedprocessesd
toddescriptionsdofdneuraldeventsd(Crick,d1994).dThedreductionisticdpointdofdv
iewdwasdwell-expresseddbydDennettd(1991)dindthesedwords:
Thedprevailingdwisdom,dvariouslydexpresseddanddargueddfor,disdmaterial
-dism:dtheredisdonlydonedsortdofdstuff,dnamelydmatter—
thedphysicaldstuffdofdphysics,dchemistry,danddphysiology—
anddthedminddisdsomehowdnothingdbutdadphysicaldphenomenon.dIndsho
rt,dthedminddisdthedbrain.dAccordingdtodthedmaterialists,dwedcand(indprin
ciple!)daccountdfordeverydmentaldphenomenondusingdthedsamedphysicald
principles,dlaws,danddrawdmaterialsdthatdsufficedtodexplaindradioactivity,
dcontinentalddrift,dphotosynthesis,dreproduction,dnutrition,danddgrowth
.d(p.d33)
Notdalldversionsdofdmaterialismdcontenddthatdthedminddcandbedreduceddt
odaddescriptiondofdbraindstates.dAndalternativedversiondregardsdmentaldstate
sdasdemergentdpropertiesdofdneuraldfunctioningd(Scott,d1995).dAndemergentd
propertydimpliesd thatd thed wholed isd greaterd thand thed sumd ofd itsd parts.d Itd i
sdnotdpossibledtodpredictdthedbehaviordofdthedwholedjustdfromdknowingdthed
behaviordofdthedparts.dIndaddition,ditdisdnecessarydtodunderstanddhowdalldofdt
hedpartsdinteractdwithdonedanotherdtodproducedthedwhole.dAdmentaldstatedca
ndbedviewed,dthen,dasdadwholedthatdisdmoredthandthedsumdofdthedindividualdn
euronsdfiring.dRegardingdthedminddasdandemergentdpropertydisdmentalisticdb
utdstaysdwithindthedconfinesdofdmaterialism.dMentaldexperienceddependsdon,
danddisdadfunctionaldpropertydof,dandactivedlivingdbrain.dSperryd(1980)dexpla
ineddthedmentalisticdapproachdtodmaterialismdindthedfollowingdpassage:
,kellogg02.qxdd 7/11/02d 10:27d AMd Paged 27
Cognitived Neuroscienced ●d 27
Oncedgenerateddfromdneuraldevents,dthedhigherdorderdmentaldpatternsd
anddprogramsdhavedtheirdowndsubjectivedqualitiesdanddprogress,doperat
e,danddinteractdbydtheirdowndcausaldlawsdanddprinciplesdwhichdareddiffer
entdfromdanddcannotdbedreduceddtodthosedofdneurophysiology.d(p.d201)
Andalternativedtodmaterialismdcontendsdthatdattemptsdtodconnectdment
Fordmaterialists,dmental
aldstatesdwithdbraindstatesdaredmistaken.dDualismdholdsdthatdthedminddisdand
dexperiencesdcandbedre
immaterialdentitydthatdexistsdindependentlydofdthedbraindanddotherdbodilydo duceddtodstatesdofdthedb
rgans.dThisdideadcandbedtraceddatdleastdasdfardbackdasdthedFrenchdphilosophe rain,dordtheydmaydbeda
rdRenédDescartes.dFordaddualist,dthedattemptdtodreducedmentaldstatesdtodbrai ndemergentdproperty,d
ndstatesdisdmistakendbecauseditdmisinterpretsdcorrelationdasdcausation.dTheddua meaningdthatdthedmind
disddifferentdfromdtheds
listdaccountdrecognizesdthatdadsubjectivedexperiencedisdcorrelateddwithdactiviti
umdofdthedactivitydofdn
esdindthedbrain.dButdasdalldstudentsdofdpsychologydaredaware,dcorrelationddo eurons.dForddualists,d
esdnotdprovedcausation.dPerhapsdminddanddbraindaredcorrelateddanddhavedn mentaldstatesdaredcorr
odinflu- elateddwithdbraindstat
dencedondeachdother,dordperhapsdthedminddactuallydcausesdbraindactivitydrath esdanddmaydevendinter
erdthandvicedversa.dDescartesdassumed,dasddodcontemporaryddualists,dthatdt actdwithdneuraldproces
ses,dbutdthedminddisdnot
hedimmaterialdminddinteractsdwithdthedbraindthroughdadflowdofdinformation
dseendasdrooted
dindwaysdnotdyetdunderstoodd(Eccles,d1966,d1994;dPopperd&dEccles,d1977).
indmatter.
Clearly,dtheseddeepdfundamentaldquestionsdwilldnotdsoondbedresolved.dBu
tdprogressdindcognitivedpsychologydanddcognitivedneuroscienceddoesdnotdde
penddondresolvingdthem,danddmeasurementsdatddifferentdlevelsdofdanalysisda
redappropriatedanddnecessary.dMeasurementsdofdbraindactivitydcandbeduseful,
dbutdtheydarednotdsufficientdbydthemselves.dBehavioraldmeasurementsdsuchd
asdverballydreportingdadmemory,ddescribingdthoughtsdleadingdtodthedsolution
dofdadproblem,danddmakingdaddecisiondanddrapidlydpressingdadbuttondreveald
thedminddindadwaydthatdbraindactivitydcannot.dCognitivedpsychologists,dthen,d
oftendadoptddualismdasdadmethodologicaldapproachdtodresearch,dasdHilgardd
(1980)dobserved:
Mydreactiondisdthatdpsychologistsdanddphysiologistsdhavedtodbedmodest Thedcognitivedsciencesd
todaydrecognizedthatdb
dindthedfacedofdthisdproblemd(consciousness)dthatdhasdbaffleddthedbestdp
ehavioraldtechniquesda
hilosophicaldmindsdfordcenturies.dIddodnotdseedthatdourdmethodsdgived redneededdtodmeasured
usdanydadvantagedatdthedultimatedleveldofdmetaphysicaldanalysis.dAdheuri mentaldstatesdatdtheds
s- amedtimedasdneuraldte
dticdsolutiondseemsdtodmedtodbedquitedappropriate.d d Thatdis,dtheredare
chniquesdaredneededdt
odmeasuredbraindstates.d
consciousdfactsdanddeventsdthatdcandbedshareddthroughdcommunication
Neitherdreplacesdthedo
dwithdothersdlikedourselves,danddtheredaredphysicaldeventsdthatdcandbed
ther.
observeddordrecordeddondinstruments,danddthedrecordsdthendobservedd
anddreflecteddupon.dNeitherdofdthesedsetsdofdfactsdproducesdinfallibledd
ata.d d d Itd isd thed taskd ofd thed scientistd tod used thed mostd availabled tech
-
niquesdfordverificationdofdtheddatabasedanddfordvalidationdofdthedinfer-
dencesdfromdtheseddata.d(p.d15)
, kellogg02.qxdd 7/11/02d 10:27d AMd Paged 28
28d ●d SCOPEdANDdMETHODS
2.1.
d d d d d d
● FUNCTIONALdNEUROANATOMY
Thedhumandbraindmaydwelldbedthedmostdcomplexdstructuredindthedknowndu
niverse.dConsiderdjustdadfewdofdthedbrain’sdpropertiesdtodunderstanddthisdpoint
d(Sejnowskid&dChurchland,d1989).dAdneurondis d1dofdaboutd200ddifferentdtypes
dofdcellsdthatdmakedupdthed100dtrilliond(10 ) dcellsdofdthedhumandbody.dAsdsho
14
wndindFigured2.1,dadneurondincludesddendritesdfordreceivingdsignalsdfromdoth
erdneu-
drons,dadcelldbody,danddandaxondfordtransmittingdadsignaldtodotherdneuronsdvi
adadsynapticdconnection.dThisdisdandidealizeddillustrationdofdonedofdseveraldcl
assesdofdneuronsdthatdvarydindthedsize,dshape,dnumber,danddarrangementsdof
dtheirddendritesdanddaxons. dTheddendrites dofdadsingledneurondmaydreceivedasd
manydasd10,000dsynapticdconnectionsdfromdotherdneurons.dThedcentraldnervo
usdsystemdisdcompriseddofd1dtrilliond(1012)dneuronsdofdalldkindsdanddaboutd1
,000dtrilliond(1015)dsynapticdconnectionsdamongdthesedneuronsd(seedFigured
2.1).
Atdadlargerdscale,dthedbraindisdorganizeddintodmajordstructuresdsuchdasd
thed lobesd ofd thed cerebrald cortex.d Shownd ind Figured 2.2d ared thed fourd lob
esdfromdadlateraldviewd(a),dadmedialdviewd(b),daddorsaldviewd(c),danddadventrald
view
(d).dThesedregionsdaredseparateddindpartdbydanatomicaldmarkersdcalleddthed
centraldsulcus,dlateraldfissure,danddlongitudinaldfissure.dThedlobesdofdthedneo
cortexdareddivideddintodadleftdanddrightdhemispheredbydthedlongitudinaldfiss
ure.dLargedfoldsdindthedcortexdidentifydthedboundariesdamongdfourdlobesdof
CHAP TE R 2
COGNITIVE NEUROSCIENC d
E
T
hedfielddofdcognitivedneurosciencedaddressesdhowdmentaldfunctionsdar
edsupporteddbydthedbrain.dThisdclosedrelativedofdcognitivedpsychologydisdexp
lodingdwithdnewdfindingsdasdadresultdofdtheddiscoverydofdmethodsdfordimagi
ngd thed workingsd ofd thed livingd brain.d Neuroimagingd technologiesd havedrev
olutionizeddthedstudydofdthedbrain,dbutdasdwilldbedseendindthisdchapter,dtheirde
ffectived used requiresd thed behaviorald measures,d researchd strategies,d andd
theoriesdofdcognitivedpsychology.dItdisdalsodimportantdtodunderstanddthatdth
edcoredquestionsdofdcognitivedpsychologydcannotdbedanswereddjustdbydviewi
ngdthedbraindindaction.dOnedmustdfirstdknowdwhichdcognitivedfunctions,dsuch
dasdshort-
termdmemory,dtodlookdfordindadhighlydcomplexdorgan.dIndotherdwords,dcogni
tived psychologyd providesd thed theoriesd thatd guided thed searchd intod the
structuresdanddactivitiesdofdthedbrain.
Thedchapterdbeginsdwithdandintroductiondtodthedproblemdofdhowdthedmin
ddanddbraindaredrelateddtodeachdother.dNext,dadbriefdtourdofdfunctionaldneu-
droanatomydisdprovided,dfolloweddbydaddiscussiondofdthedmethodsduseddindc
ognitivedneuroscience.dLastly,dthedfundamentaldpropertiesdofdconnectionistd
modelsd ared presented.d Asd notedd ind Chapterd 1,d thesed ared highlyd simplifie
d
25
,kellogg02.qxdd 7/11/02d 10:27d AMd Paged 26
26d ●d SCOPEdANDdMETHODS
modelsdofdthedbraindusingdartificialdneuronsdthatdmimicdsomedofdthedbasicdp
ropertiesdofdrealdneurons.dConnectionistdmodelsdarednowdadcentraldtooldindc
ognitivedneurosciencedanddthedbroaderdfielddofdcognitivedpsychology.
● MINDd ANDd BRAIN
Cognitivedneurosciencedconfrontsdusdwithdonedofdthedmostdchallenging,difdn
otdthedmostdchallenging,dphilosophicaldanddscientificdquestions.dWhatdexactl
ydisdthedrelationdbetweendthedminddanddthedbody?dPutddifferently,dhowdisdco
n-
dsciousnessdproduceddby dthedbrain?dIsdadmentaldstatedreducibledtodadphysica
ldstatedofdthedbrain,dordaredtheydseparatedphenomena?
Onedviewdofdthedrelationdbetweendthedbraindanddthedminddisdthatdtheyda
redonedanddthedsame.dMaterialismdregardsdthedminddasdthedproductdofdthedb
raindandditsdphysiologicaldprocesses.dThedmindddoesdnotdexistdindependentl
ydofdthednervousdsystem,daccordingdtodmaterialism.dOnedversiondofdmaterial
ismdcontendsdthatditdisdpossibledindtheorydtodreducedalldcognitivedprocessesd
toddescriptionsdofdneuraldeventsd(Crick,d1994).dThedreductionisticdpointdofdv
iewdwasdwell-expresseddbydDennettd(1991)dindthesedwords:
Thedprevailingdwisdom,dvariouslydexpresseddanddargueddfor,disdmaterial
-dism:dtheredisdonlydonedsortdofdstuff,dnamelydmatter—
thedphysicaldstuffdofdphysics,dchemistry,danddphysiology—
anddthedminddisdsomehowdnothingdbutdadphysicaldphenomenon.dIndsho
rt,dthedminddisdthedbrain.dAccordingdtodthedmaterialists,dwedcand(indprin
ciple!)daccountdfordeverydmentaldphenomenondusingdthedsamedphysicald
principles,dlaws,danddrawdmaterialsdthatdsufficedtodexplaindradioactivity,
dcontinentalddrift,dphotosynthesis,dreproduction,dnutrition,danddgrowth
.d(p.d33)
Notdalldversionsdofdmaterialismdcontenddthatdthedminddcandbedreduceddt
odaddescriptiondofdbraindstates.dAndalternativedversiondregardsdmentaldstate
sdasdemergentdpropertiesdofdneuraldfunctioningd(Scott,d1995).dAndemergentd
propertydimpliesd thatd thed wholed isd greaterd thand thed sumd ofd itsd parts.d Itd i
sdnotdpossibledtodpredictdthedbehaviordofdthedwholedjustdfromdknowingdthed
behaviordofdthedparts.dIndaddition,ditdisdnecessarydtodunderstanddhowdalldofdt
hedpartsdinteractdwithdonedanotherdtodproducedthedwhole.dAdmentaldstatedca
ndbedviewed,dthen,dasdadwholedthatdisdmoredthandthedsumdofdthedindividualdn
euronsdfiring.dRegardingdthedminddasdandemergentdpropertydisdmentalisticdb
utdstaysdwithindthedconfinesdofdmaterialism.dMentaldexperienceddependsdon,
danddisdadfunctionaldpropertydof,dandactivedlivingdbrain.dSperryd(1980)dexpla
ineddthedmentalisticdapproachdtodmaterialismdindthedfollowingdpassage:
,kellogg02.qxdd 7/11/02d 10:27d AMd Paged 27
Cognitived Neuroscienced ●d 27
Oncedgenerateddfromdneuraldevents,dthedhigherdorderdmentaldpatternsd
anddprogramsdhavedtheirdowndsubjectivedqualitiesdanddprogress,doperat
e,danddinteractdbydtheirdowndcausaldlawsdanddprinciplesdwhichdareddiffer
entdfromdanddcannotdbedreduceddtodthosedofdneurophysiology.d(p.d201)
Andalternativedtodmaterialismdcontendsdthatdattemptsdtodconnectdment
Fordmaterialists,dmental
aldstatesdwithdbraindstatesdaredmistaken.dDualismdholdsdthatdthedminddisdand
dexperiencesdcandbedre
immaterialdentitydthatdexistsdindependentlydofdthedbraindanddotherdbodilydo duceddtodstatesdofdthedb
rgans.dThisdideadcandbedtraceddatdleastdasdfardbackdasdthedFrenchdphilosophe rain,dordtheydmaydbeda
rdRenédDescartes.dFordaddualist,dthedattemptdtodreducedmentaldstatesdtodbrai ndemergentdproperty,d
ndstatesdisdmistakendbecauseditdmisinterpretsdcorrelationdasdcausation.dTheddua meaningdthatdthedmind
disddifferentdfromdtheds
listdaccountdrecognizesdthatdadsubjectivedexperiencedisdcorrelateddwithdactiviti
umdofdthedactivitydofdn
esdindthedbrain.dButdasdalldstudentsdofdpsychologydaredaware,dcorrelationddo eurons.dForddualists,d
esdnotdprovedcausation.dPerhapsdminddanddbraindaredcorrelateddanddhavedn mentaldstatesdaredcorr
odinflu- elateddwithdbraindstat
dencedondeachdother,dordperhapsdthedminddactuallydcausesdbraindactivitydrath esdanddmaydevendinter
erdthandvicedversa.dDescartesdassumed,dasddodcontemporaryddualists,dthatdt actdwithdneuraldproces
ses,dbutdthedminddisdnot
hedimmaterialdminddinteractsdwithdthedbraindthroughdadflowdofdinformation
dseendasdrooted
dindwaysdnotdyetdunderstoodd(Eccles,d1966,d1994;dPopperd&dEccles,d1977).
indmatter.
Clearly,dtheseddeepdfundamentaldquestionsdwilldnotdsoondbedresolved.dBu
tdprogressdindcognitivedpsychologydanddcognitivedneuroscienceddoesdnotdde
penddondresolvingdthem,danddmeasurementsdatddifferentdlevelsdofdanalysisda
redappropriatedanddnecessary.dMeasurementsdofdbraindactivitydcandbeduseful,
dbutdtheydarednotdsufficientdbydthemselves.dBehavioraldmeasurementsdsuchd
asdverballydreportingdadmemory,ddescribingdthoughtsdleadingdtodthedsolution
dofdadproblem,danddmakingdaddecisiondanddrapidlydpressingdadbuttondreveald
thedminddindadwaydthatdbraindactivitydcannot.dCognitivedpsychologists,dthen,d
oftendadoptddualismdasdadmethodologicaldapproachdtodresearch,dasdHilgardd
(1980)dobserved:
Mydreactiondisdthatdpsychologistsdanddphysiologistsdhavedtodbedmodest Thedcognitivedsciencesd
todaydrecognizedthatdb
dindthedfacedofdthisdproblemd(consciousness)dthatdhasdbaffleddthedbestdp
ehavioraldtechniquesda
hilosophicaldmindsdfordcenturies.dIddodnotdseedthatdourdmethodsdgived redneededdtodmeasured
usdanydadvantagedatdthedultimatedleveldofdmetaphysicaldanalysis.dAdheuri mentaldstatesdatdtheds
s- amedtimedasdneuraldte
dticdsolutiondseemsdtodmedtodbedquitedappropriate.d d Thatdis,dtheredare
chniquesdaredneededdt
odmeasuredbraindstates.d
consciousdfactsdanddeventsdthatdcandbedshareddthroughdcommunication
Neitherdreplacesdthedo
dwithdothersdlikedourselves,danddtheredaredphysicaldeventsdthatdcandbed
ther.
observeddordrecordeddondinstruments,danddthedrecordsdthendobservedd
anddreflecteddupon.dNeitherdofdthesedsetsdofdfactsdproducesdinfallibledd
ata.d d d Itd isd thed taskd ofd thed scientistd tod used thed mostd availabled tech
-
niquesdfordverificationdofdtheddatabasedanddfordvalidationdofdthedinfer-
dencesdfromdtheseddata.d(p.d15)
, kellogg02.qxdd 7/11/02d 10:27d AMd Paged 28
28d ●d SCOPEdANDdMETHODS
2.1.
d d d d d d
● FUNCTIONALdNEUROANATOMY
Thedhumandbraindmaydwelldbedthedmostdcomplexdstructuredindthedknowndu
niverse.dConsiderdjustdadfewdofdthedbrain’sdpropertiesdtodunderstanddthisdpoint
d(Sejnowskid&dChurchland,d1989).dAdneurondis d1dofdaboutd200ddifferentdtypes
dofdcellsdthatdmakedupdthed100dtrilliond(10 ) dcellsdofdthedhumandbody.dAsdsho
14
wndindFigured2.1,dadneurondincludesddendritesdfordreceivingdsignalsdfromdoth
erdneu-
drons,dadcelldbody,danddandaxondfordtransmittingdadsignaldtodotherdneuronsdvi
adadsynapticdconnection.dThisdisdandidealizeddillustrationdofdonedofdseveraldcl
assesdofdneuronsdthatdvarydindthedsize,dshape,dnumber,danddarrangementsdof
dtheirddendritesdanddaxons. dTheddendrites dofdadsingledneurondmaydreceivedasd
manydasd10,000dsynapticdconnectionsdfromdotherdneurons.dThedcentraldnervo
usdsystemdisdcompriseddofd1dtrilliond(1012)dneuronsdofdalldkindsdanddaboutd1
,000dtrilliond(1015)dsynapticdconnectionsdamongdthesedneuronsd(seedFigured
2.1).
Atdadlargerdscale,dthedbraindisdorganizeddintodmajordstructuresdsuchdasd
thed lobesd ofd thed cerebrald cortex.d Shownd ind Figured 2.2d ared thed fourd lob
esdfromdadlateraldviewd(a),dadmedialdviewd(b),daddorsaldviewd(c),danddadventrald
view
(d).dThesedregionsdaredseparateddindpartdbydanatomicaldmarkersdcalleddthed
centraldsulcus,dlateraldfissure,danddlongitudinaldfissure.dThedlobesdofdthedneo
cortexdareddivideddintodadleftdanddrightdhemispheredbydthedlongitudinaldfiss
ure.dLargedfoldsdindthedcortexdidentifydthedboundariesdamongdfourdlobesdof
