Neurochemistry of Consciousness. Neurotransmitters in Mind

359 Pages·2002·3.434 MB·English

by  E.K. Perry, Heather Ashton, Allan Young

NeurochemistryofConsciousness
Advances in Consciousness Research
Advances in Consciousness Research provides a forum for scholars from
differentscientificdisciplinesandfieldsofknowledgewhostudyconsciousness
initsmultifacetedaspects.ThustheSerieswillinclude(butnotbelimitedto)
thevariousareasofcognitivescience,includingcognitivepsychology,linguis-
tics, brain science and philosophy. The orientation of the Series is toward
developingnewinterdisciplinaryandintegrativeapproachesfortheinvestiga-
tion, description and theory of consciousness, as well as the practical conse-
quencesofthisresearchfortheindividualandsociety.
SeriesA:TheoryandMethod.Contributionstothedevelopmentoftheoryand
methodinthestudyofconsciousness.
Editor
MaximI.Stamenov
BulgarianAcademyofSciences
EditorialBoard
DavidChalmers,UniversityofArizona
GordonG.Globus,UniversityofCaliforniaatIrvine
RayJackendoff,BrandeisUniversity
ChristofKoch,CaliforniaInstituteofTechnology
StephenKosslyn,HarvardUniversity
EarlMacCormac,DukeUniversity
GeorgeMandler,UniversityofCaliforniaatSanDiego
JohnR.Searle,UniversityofCaliforniaatBerkeley
PetraStoerig,UniversitätDüsseldorf
FranciscoVarela,C.R.E.A.,EcolePolytechnique,Paris
Volume36
NeurochemistryofConsciousness:Neurotransmittersinmind
EditedbyElainePerry,HeatherAshtonandAllanYoung
Neurochemistry of
Consciousness
Neurotransmitters in mind
WithaForewordbySusanGreenfield
Edited by
Elaine Perry
Heather Ashton
Allan Young
UniversityofNewcastle
Newcastle-upon-Tyne
JohnBenjaminsPublishingCompany
Amsterdam(cid:1)/(cid:1)Philadelphia
TM ThepaperusedinthispublicationmeetstheminimumrequirementsofAmerican
8
NationalStandardforInformationSciences–PermanenceofPaperforPrinted
LibraryMaterials,ansiz39.48-1984.
LibraryofCongressCataloging-in-PublicationData
Neurochemistryofconsciousness.Neurotransmittersinmind.WithaforewordbySusan
Greenfield/editedbyElainePerry,HeatherAshton,andAllanYoung.
p. cm.(AdvancesinConsciousnessResearch,issn1381–589X;v.36)
Includesbibliographicalreferencesandindex.
1. Consciousness. 2. Neurotransmitters. 3. Neurochemistry. 4. Neurobehavioral
disorders.I.Perry,E.K.(ElaineK.)II.Ashton,Heather.III.Young,Allan,1983-IV.Series.
QP411.N485 2002
153--dc21 2001052834
isbn902725156(cid:2)8(Eur.)/158811124(cid:2)5(US)(pbk.)
©2002–JohnBenjaminsB.V.
Nopartofthisbookmaybereproducedinanyform,byprint,photoprint,microfilm,orany
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JohnBenjaminsNorthAmerica·P.O.Box27519·Philadelphiapa19118-0519·usa
Table of contents
Foreword 
SusanGreenfield
Preface 
I. NeurotransmitterSystems
. Neurotransmitternetworks 
ElainePerryandAllanYoung
. Cholinergictransmission:Novelsignaltransduction 
NancyJ.Woolf
II. NaturalAlterationsofConsciousness
. Attention 
AndrewScholey
. Memory 
CarolineStewart
. Motivation:Rewardandpunishmentsystems 
HeatherAshton
. Sleep:Slowwaveandnon-REMstages 
AnnL.Sharpley
. Dreaming:Cholinergicanddopaminergichypotheses 
MarkSolms
. Dreaming:Monoaminergicdisinhibitionhypothesis 
ClaudeGottesmann
 Tableofcontents
III. Drug-InducedAlterationsinConsciousness
. Generalanesthetics 
PamelaFlood
. Effectsofdrugsonsleep 
HeatherAshton
. Neuroleptics 
CliveBallardandMargaretPiggott
. Deliriumandhallucinations 
HeatherAshton
. Plantsofthegods:Ethnicroutestoalteredconsciousness 
ElaineK.Perry
IV. BrainPathologyandConsciousness
. Alzheimer’sdisease:Focusonthecholinergicsystem 
DanielI.Kaufer
. Parkinson’sdisease 
DagAarslandandRandiStarrfelt
. DementiawithLewybodies:Adisorderofconsciousness? 
MatthewWalkerandElainePerry
. Schizophrenia 
GavinP.Reynolds
. Mooddisorders 
R.HamishMcAllister-Williams
. Mentalretardationandautism 
GregoryO’BrienandLouiseBarnard
Envoi 
Index 
Foreword
SusanGreenfield
The biggestquestion,arguably,thatanyscientistor indeedhuman beingcan
ask, is how the mass of tissue in the brain can generate the inner experi-
ence that we call consciousness: the state that no one else can access. How-
ever articulate, poetic, musical or close to someone you may be, that elusive
subjectivity,—the directfirst-hand‘feel’of the sunon yourface,orthe grass
between bare toes,—is quintessentially personal, utterly subjective. This si-
multaneouslyelusive,yetintimatephenomenonhas,ofcourse,keptdrovesof
philosophers occupied throughout the ages. But it is only in the last ten or
twentyyears,thatsciencehasactuallymovedin.
Sincescientistsaretrainedtobeutterlyobjective,—wedon’tevenusethe
activevoice,butpreferthefarmoreclumsy,passive;‘asolutionwasmadeup’
for example—it is small wonder that it goes against the grain now to bring
the machineryofscientificmethodtobearagainstsuch anintractabletarget.
Hencemanyscientists,includingandparticularlybrainscientists,tendtodis-
tancethemselvesfromthisareaofstudy,onthegroundsthatitisimpossible,
given current technologies and state of knowledge, to make any progress. As
oneparticularcolleagueofmine,anexpertonAlzheimer’sDisease,remarked,
“Ijusttakeconsciousnessforgranted”.Ontheotherhand,ifwearetoworkon
thebrain,thensurelysuchanapproachisindefensible:asthephilosopherJohn
Searle remarked, for brain scientists to ignore consciousness is like someone
workingonthestomachtosaytheyarenotinterestedindigestion.
Other scientists, nonetheless,fascinated by consciousness, simply cannot
raise the funds for empirical investigation. Given the mystic-like image the
word still conjures up to the mind-set of grant review panels, approaches
have been sardonically dubbed ‘a career limiting move’. But despite this
hostile culture there is, to their credit, a third, growing band of scientists
who, nonetheless,are squaring up to the problem.Curiously, however,brain
scientists have been conspicuously absent, in the early days, from this group
ofpioneers.Forexamplethemathematician,RogerPenrose,andthephysicist,
 SusanGreenfield
Brian Josephson,havemade importantcontributionstothe field.Evenwhen
bio-medicalscientistsdotakethecentre-stage,asinthecaseofFrancisCrick,
or Gerry Edelman, an immunologist, they are not necessarily known from
their grounding in the basic brain sciences. An interesting feature, however,
oftheindividualsmentioned,isthatthereisahighproportionofNobelPrize
Winners!
Untilnow,itseems,onlythosewhoalreadyhaveastrongscientificreputa-
tionand,perhaps,thetimetoreflectontheseissuesawayfromthehurly-burly
of peer-review papers and grant writing are able to contemplate this biggest,
and most exciting question.However,the landscape is rapidly changing, and
nowanincreasingnumberofneuroscientistsareexploringwhatcontributions
theycanactuallymake.
We are now looking beyond the stumbling block of causality: the water
of neuronalsignalling, translatedinto the wine of subjective experience.The
philosopherDavidChalmershasreferredtothisimpasseasthe‘HardProblem’.
Where neurosciencenow might make a contribution,albeit a lessglamorous
one than coming up with a simple rubric for the conversion, is in showing
increasingly sensitive and precise correlations of consciousness, i.e. matching
uphowpeoplefeelwithwhatisoccurringinthebrain.
Giventhismorerealisticgoal,itissurprisinghowthefieldhaspreviously
been dominated by mathematical models of networks of neurons. We know
that such neuronal networks are quasi-permanent, slow to form, and highly
localwithinthebrain.Althoughtheymaybeabasisforlearningandmemory,
weknowthatyoucanbeconsciouswithoutlearningorrememberinganything
and,similarly,thatcomputerprocessescanoccurthatwillmodifyresponsesto
subsequentstimulus,butatthesametimedonotentailaconsciousexperience.
Ifwearetolookforacorrelationofconsciousness,thendrugsofferaperfect
RosettaStone,—afterall,bymanipulatingthechemicalsinourbrainwithcer-
taindrugs,wecan,ontheonehand,reportchangesinhowwefeelbut,atthe
sametime,matchthisupwiththechemistryofthebrain.Moreover,giventhat
psychoactivedrugsmodifyouremotions,anddosobymodifyingchemicalsin
thebrain,itfollowsthatemotionshaveachemicalbasis.Nowweconsiderthat
although learningandmemory can be dissociated fromconsciousness,emo-
tions cannot (we are always feeling something, howeverlow level). It follows
that clearly chemicals, forming the basis as they do of brain function, must
alsoformthebuildingblocksofconsciousness.
Howstrangethen,thatupuntilnow,thesilentsectorofthebrainresearch
communityhasbeentheneurochemistsandtheneuropharmacologists.
Foreword 
Thisbook isnowsettobuckthe trend.Starting with ageneralintroduc-
tion to brain chemistry, the reader can take a journey through normal brain
processes,intotheworldofdrug-inducedchangesinconsciousness,andfinally
intothe chilling worldofdysfunctionsin consciousness.Subjects coveredare
trulycomprehensiveandofsuchanastonishingrange,thateventhededicated
brain specialist will be able to learn something, as well as the non-specialist,
andgainawonderfuloverviewofhowconsciousnessmighttakeplacewithin
the brain. The Hard Problem, of course, remains unsolved. But it is only by
a trulyscientific approach, such as found in these pages, that by building on
whatweknow,wewillbeabletomakeanyprogressatall.