Mental imagery

195 Pages·2013·18.16 MB·English

MENTAL IMAGERY
Topic Editors
Joel Pearson and Stephen M. Kosslyn
PSYCHOLOGY HUMAN NEUROSCIENCE
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July 2013 | Mental Imagery | 1
MENTAL IMAGERY
Topic Editors:
Joel Pearson, The University of New South Wales, Australia
Stephen M. Kosslyn, Stanford University, USA
Our ability to be conscious of the world
around us is often discussed as one of the most
amazing yet enigmatic processes under scientific
investigation today. However, our ability to
imagine the world around us in the absence of
stimulation from that world is perhaps even
more amazing. This capacity to experience
objects or scenarios through imagination, that
do not necessarily exist in the world, is perhaps
one of the fundamental abilities that allows us
successfully to think about, plan, run a dress rehearsal of future events, re-analyze past
events and even simulate or fantasize abstract events that may never happen.
Empirical research into mental imagery has seen a recent surge, due partly to the
development of new neuroscientifc methods and their clever application, but also due
to the increasing discovery and application of more objective methods to investigate this
inherently internal and private process.
As this topic is being cross-hosted in both Frontiers in Human Neuroscience and Frontiers
in Perception Science, we invite researchers from different fields to submit opinionated but
balanced reviews, new empirical, theoretical, philosophical or technical papers covering any
aspect of mental imagery. In particular, we encourage submissions focusing on different
sensory modalities, such as olfaction, audition somatosensory etc. Similarly, we support
submissions focusing on the relationship between mental imagery and other neural and
cognitive functions or disorders such as visual working memory, visual search or disorders
of anxiety.
Together, we hope that collecting a group of papers on this research topic will help to unify
theory while providing an overview of the state of the field, where it is heading, and how
mental imagery relates to other cognitive and sensory functions.
July 2013 | Mental Imagery | 2
Table of Contents
05 Mental Imagery
Joel Pearson and Stephen M. Kosslyn
06 Hemispheric Differences with in the Fronto-Parietal Network Dynamics
Underlying Spatial Imagery
Alexander T. Sack and Teresa Schuhmann
16 Unmasking the Perky Effect: Spatial Extent of Image Interference on Visual
Acuity
Adam Reeves and Catherine Craver-Lemley
23 Training Visual Imagery: Improvements of Metacognition, But not Imagery
Strength
Rosanne L. Rademaker and Joel Pearson
34 New Percepts via Mental Imagery?
Fred W. Mast, Elisa M. Tartaglia and Michael H. Herzog
39 An Emerging Paradigm: A Strength-Based Approach to Exploring Mental
Imagery
Tadhg E. MacIntyre, Aidan P. Moran, Christian Collet and Aymeric Guillot
51 Vividness of Visual Imagery and Incidental Recall of Verbal Cues, When
Phenomenological Availability Reflects Long-Term Memory Accessibility
Amedeo D’Angiulli, Matthew Runge, Andrew Faulkner, Jila Zakizadeh, Aldrich Chan
and Selvana Morcos
69 The Effects of Visual Imagery on Face Identification: An Erp Study
Jianhui Wu, Hongxia Duan, Xing Tian, Peipei Wang and Kan Zhang
77 Electrophysiological Potentials Reveal Cortical Mechanisms for Mental Imagery,
Mental Simulation, and Grounded (Embodied) Cognition
Haline E. Schendan and Giorgio Ganis
99 A Cross-Modal Perspective on the Relationships Between Imagery and Working
Memory
Lora T. Likova
113 Verbal to Visual Code Switching Improves Working Memory in Older Adults: An
fMRI Study
Mariko Osaka, Yuki Otsuka and Naoyuki Osaka
121 Mental Imagery for Musical Changes in Loudness
Freya Bailes, Laura Bishop, Catherine J. Stevens and Roger T. Dean
130 Imagining is Not Doing but Involves Specific Motor Commands: A Review of
Experimental Data Related to Motor Inhibition
Aymeric Guillot, Franck Di Rienzo, Tadhg MacIntyre, Aidan Moran and
Christian Collet
July 2013 | Mental Imagery | 3
152 Mental Imagery of Speech: Linking Motor and Perceptual Systems Through
Internal Simulation and Estimation
Xing Tian and David Poeppel
163 Effect of Biomechanical Constraints in the Hand Laterality Judgment Task:
Where Does It Come from?
Gilles Vannuscorps, Agnesa Pillon and Michael Andres
172 Understanding Immersivity: Image Generation and Transformation Processes in
3D Immersive Environments
Maria Kozhevnikov and Rupali P. Dhond
182 Abacus in the Brain: A Longitudinal Functional MRI Study of a Skilled Abacus
User with a Right Hemispheric Lesion
Satoshi Tanaka, Keiko Seki, Takashi Hanakawa, Madoka Harada, Sho K. Sugawara,
Norihiro Sadato, Katsumi Watanabe and Manabu Honda
July 2013 | Mental Imagery | 4
EDITORIAL
published:23April2013
doi:10.3389/fpsyg.2013.00198
Mental imagery
JoelPearson1*andStephenM.Kosslyn2
1SchoolofPsychology,TheUniversityofNewSouthWales,Sydney,NSW,Australia
2MinervaUniversity,SanFrancisco,CA,USA
*Correspondence:[email protected]
Editedby:
PhilippeG.Schyns,UniversityofGlasgow,UK
Reviewedby:
PhilippeG.Schyns,UniversityofGlasgow,UK
Ourabilityto beconsciousoftheworldaroundusisoften dis- it could be argued that this ability is one of the main factors
cussedasoneofthemostamazingyetenigmaticprocessesunder that have allowed us as a species to dominate our planet so
scientificinvestigationtoday.However,ourabilitytoimaginethe profoundly.
worldaroundusintheabsenceofstimulationfromthatworldis Empirical research into mental imagery has seen a recent
perhapsevenmoreamazing. surge, which is partly a result of new neuroscientific methods
Ourcapacityto re-experience objects orscenariosthat we’ve andtheircleverapplication—butisalsoduetothediscoveryand
encountered before,andtonoticenewthingsaboutthoseexpe- applicationofadditionalsortsofobjectivemethodstoinvestigate
riences, is itself remarkable. But perhaps more remarkable still thisinherentlyinternalandprivateprocess.
is our ability to experience objects or events that do not exist Here we introduce an inspiringly broad range of work that
in the world, through our imagination. This is perhaps one of focuses onmental imagery. This ebook contains the work from
the fundamental abilities that allow us successfully to plan, run a broad range of researchers in different fields, both empirical
dress rehearsals of future events, re-analyze the past—and even work and reviews. Chapters range from the role of imagery in
simulate or fantasize events that may never happen. In short, music, biomechanics, and mathematics to the functions of the
cerebralhemispheresinimageryandimagery’seffectsonsensory
perception.
This collection provides a cohesive and broad-spectrum
additiontotherapidlygrowingfieldofmentalimagery.Thisset
of articles provides theoretical insights and an overview of the
state of empirical understanding, where it is heading, and how
mentalimageryrelatestoothercognitiveandsensoryfunctions.
Received:24March2013;accepted:02April2013;publishedonline:23April2013.
Citation:PearsonJandKosslynSM(2013)Mentalimagery.Front.Psychol.4:198.doi:
10.3389/fpsyg.2013.00198
ThisarticlewassubmittedtoFrontiersinPerceptionScience,aspecialtyofFrontiers
inPsychology.
Copyright © 2013 PearsonandKosslyn.Thisisanopen-accessarticledistributed
underthetermsoftheCreativeCommonsAttributionLicense,whichpermitsuse,
distributionandreproduction in otherforums, provided theoriginalauthors and
sourcearecreditedandsubjecttoanycopyrightnoticesconcerninganythird-party
graphicsetc.
www.frontiersin.org April2013|Volume4|Article198|5
REVIEWARTICLE
published:28June2012
doi:10.3389/fpsyg.2012.00214
Hemispheric differences within the fronto-parietal network
dynamics underlying spatial imagery
AlexanderT.Sack*andTeresaSchuhmann
FacultyofPsychologyandNeuroscience,MaastrichtUniversity,Maastricht,Netherlands
Editedby: Spatial imagery refers to the inspection and evaluation of spatial features (e.g., distance,
JoelPearson,TheUniversityofNew relativeposition,configuration)and/orthespatialmanipulation(e.g.,rotation,shifting,reori-
SouthWales,Australia
enting)ofmentallygeneratedvisualimages.Inthepastfewdecades,psychophysicalas
Reviewedby:
well as functional brain imaging studies have indicated that any such processing of spa-
RaymondVanEe,UniversityUtrecht,
Netherlands tiallycodedinformationand/ormanipulationbasedonmentalimages(i)issubjecttosimilar
AngelikaLingnau,Universityof behavioraldemandsandlimitationsasinthecaseofspatialprocessingbasedonrealvisual
Trento,Italy images,and(ii)consistentlyactivatesseveralnodesofwidelydistributedcorticalnetworks
*Correspondence: inthebrain.Thesenodesincludeareaswithinboth,thedorsalfronto-parietalaswellasven-
AlexanderT.Sack,Facultyof
traloccipito-temporalvisualprocessingpathway,representingthe“what”versus“where”
PsychologyandNeuroscience,
MaastrichtUniversity, aspectsofspatialimagery.Weheredescribeevidencefromfunctionalbrainimagingand
Universiteitssingel40,6200MD braininterferencestudiesindicatingsystematichemisphericdifferenceswithinthedorsal
Maastricht,Netherlands. fronto-parietal networks during the execution of spatial imagery. Importantly, such hemi-
e-mail:[email protected]
spheric differences and functional lateralization principles are also found in the effective
brainnetworkconnectivitywithinandacrossthesenetworks,withadirectionofinforma-
tionflowfromanteriorfrontal/premotorregionstoposteriorparietalcortices.Inanattempt
tointegratethesefindingsofhemisphericlateralizationandfronto-to-parietalinteractions,
we argue that spatial imagery constitutes a multifaceted cognitive construct that can be
segregatedinseveraldistinctmentalsubprocesses,eachassociatedwithactivitywithin
specificlateralizedfronto-parietal(sub)networks,formingthebasisofthehereproposed
dynamicnetworkmodelofspatialimagery.
Keywords:spatialimagery,objectimagery,brainimaging,imageryandparietalcortex,imageryandpremotor
cortex,imageryandfrontalcortex,spatialattention,spatialworkingmemory
SPATIALIMAGERY–AMULTIFACETED Objects in visual imagery can be manipulated much like actual
COGNITIVE-PSYCHOLOGICALCONSTRUCT objects.Hence,amentallygeneratedinnerimagecaneasilyalsobe
Humansarecapableofperformingavarietyofhigherordercog- mentallytransformed,distorted,orrotatedinourmind.Thiscan
nitiveabilitiessuchasproblemsolving,reasoning,contemplating, helptoreasonabouttheconsequencesofapotentialcorrespond-
butalsolanguagecomprehension,objectrecognition,spatialori- ing physical manipulation (Kosslyn et al., 1998). (Visuo)Spatial
entation, or the vivid re-experience of previously perceived or imageryparticularlyreferstotheinspectionandevaluationofspa-
processed information stored in memory. All of these cognitive tialfeatures(e.g.,distance,relativeposition,configuration)and/or
functionsrequire,andaretoalargeextentbasedon,ourability the spatial manipulation (e.g.,rotation,shifting,reorienting) of
togenerate,inspect,andmanipulateinnermentalrepresentations mentally generated visual images. When we speak about spatial
ofobjects,events,andscenesthatarenotphysicallypresent.This imageryintheremainderofthisarticle,wethusrefertothemental
ability of mental imagery thus describes a multi-facetted set of representationofvisualobjects,events,orsceneswhichareeither
cognitiveprocessesthatareattheheartofmostformsofabstract mainlydefinedbyspatialcharacteristics(e.g.,thevisualimagina-
reasoning or contemplating (Kosslyn et al., 1995; Cohen et al., tionofaspatialconfiguration)and/orwhichrequireinadditionto
1997; Kanwisher and Wojciulik, 2000; Riesenhuber and Poggio, themeregenerationofthementalrepresentation,aspatialanaly-
2000). sisormanipulationtobementallyperformeduponthismental
While mental imagery by itself is a multifaceted psychologi- visualimage.
calconstructthatshowsconceptualandneurobiologicaloverlap Spatialimagery,justlikeallformsofimagery,isbydefinition
with related cognitive processes such as attention and memory, asubjective,privateexperiencethatcannotbemeasureddirectly,
it is useful to also subdivide mental imagery according to the buthastobeempiricallyinferredbyindirectmeasures.Thesemea-
sensory modality based on which the mental representation is suresvaryfromsubjectiveselfreportsonthevividnessorsizeof
generated.Inthissense,theprocessesthatareinvolvedingenerat- thementalimage,tomoreobjectivetaskssuchasmentallyrotat-
ing,inspecting,andmanipulatingvisualimagesintheabsenceof ingavisuallypresentedobjecttoassesswhetheritmatches,oris
visualinputarereferredtoasvisualmentalimagery(Finke,1989). mirroredto,asecondvisualobject(ShepardandMetzler,1971).
www.frontiersin.org June2012|Volume3|Article214|6
SackandSchuhmann Networkmodelofspatialimagery
Itisbelievedthatthecompletionofsuchmentalrotationsrely,at and in some tasks early visual cortex (EVC; Stokes et al., 2011)
leastpartly,onspatialmentalimagery.Inlinewiththisrational, and/orevenprimaryvisualcortex(Kosslynetal.,1999;Slotnick
somestudieshaveshownthatmentalrotationtasksareindeedper- etal.,2005;deBorstetal.,2012).Likewise,brainregionswithin
formedbymentallyrotatinganobjectasifitweremovingthrough thedorsalvisualprocessingpathwayarerecruitedduringthespa-
the intermediate positions along a trajectory, as would occur if tial processing or manipulation of these mental representations
the object was physically rotated (Kosslyn et al., 1998; Carpen- (Kawashima et al., 1995;Mellet et al., 1995, 1996; Cohen et al.,
teretal.,1999;Richteretal.,2000).Sinceaccuracyandresponse 1996;Tagarisetal.,1997;Kosslynetal.,1998;Sacketal.,2002,2005,
latencyof thesementalspatialrotationscanbeobjectivelymea- 2008).Thesecorticalregionswithinthedorsalpathwaythatinthis
suredandcomparedwithotherexperimentalconditionsof,e.g., sensearemaybemorestrictlyrelatedtothespatialaspectofspa-
realmanualrotation(Sacketal.,2007),suchpsychophysicalexper- tialimageryarethebilateralinferiorandsuperiorparietallobule
imentsofferameansforassessingspatialimageryperformancein (SPL;Richteretal.,1997;Knauffetal.,2000;Trojanoetal.,2000,
abehaviorallymorecontrolledmanner. 2002;Sack et al., 2002, 2005, 2008), bilateral intraparietal sulcus
Although it appeared that the question of which exact brain (IPS);precuneus;(Melletetal.,1996;Trojanoetal.,2000;Sacketal.,
areasareactivatedduringspatialimagerylargelydependsonthe 2002, 2005, 2008), middle forntal gyrus (MFG), supplementary
specificfeaturesoftheimagerytaskbeinginvestigated,e.g.,which motorarea(SMA),frontaleyefields(FEF),andpremotorcortex
spatial operation has to be performed based on which mental (PMC; Kawashima et al., 1995;Mellet et al., 1995, 1996; Cohen
object,theemergingpictureof brainimagingstudiesisthatour etal.,1996;Tagarisetal.,1997;Kosslynetal.,1998;Richteretal.,
capability to mentally visualize,inspect,and manipulate objects 2000;Trojanoetal.,2000;Lammetal.,2001;Sacketal.,2002,2005,
issubservedbydistributedcorticalnetworksthatincluderegions 2008;Sack,2009;deBorstetal.,2012).Regardingthisspatialaspect
thataresimilarlyactivatedwhenperformingcomparablepercep- ofspatialimagery,Thompsonetal.(2009)suggesteddifferentiat-
tual operations (Thompson et al., 2009; Cichy et al., 2011; but ing between visualizing spatial locations versus mentally trans-
see also Lee et al., 2011, nicely showing that although imagery forming locations,both relying on distinct neural sub networks
and perception have similar neural substrates,they may involve within the dorsal pathway. Concretely,whereas the visualization
differentnetworkdynamics;Seurincketal.,2011).Anotherimpor- ofspatiallocationsrecruitedmainlyareaswithinoccipito-parietal
tantandconvergingfindingof thesepreviousimagingstudiesis sulcus,medialposteriorcingulate,andprecuneus,mentalspatial
thatbothconceptuallyandintermsofunderlyingneuralmecha- transformations were correlated more with activation in supe-
nismsitseemsimportanttodistinguishcorticalregionsandneural rior portions of the parietal lobe and in the postcentral gyrus.
mechanismsinvolvedintasksthatrequireparticipantstomentally Still,sinceanyspatialinspectionormanipulationduringspatial
representspecificobjectcategories(Ishaietal.,2000)orspecific imageryrequiressomesortofmental(object)representationupon
features of objects (e.g., color, size, shape), from those cortical whichthespatialoperationcanbebasedandperformedon,the
regions and neural mechanisms involved in tasks that explic- core neural network of spatial imagery typically includes brain
itly require processing of spatially coded information or spatial areasofboththedorsalfronto-parietalaswellasventraloccipito-
manipulation(Trojanoetal.,2000).Thisdistinctionofobjectver- temporal visual processing pathway. Figure 1 depicts this core
susspatialimagerycanberegardedasanalogstothedichotomy network of spatial imagery in the brain, segregated and color-
between ventral (what) versus dorsal (where) information pro- codedinordertodistinguishthespatialdorsal(red-colored)from
cessingduringvisualperception(MishkinandUngerleider,1982; thecontentventral(rose-colored)networkinthebrainactivated
Mishkinetal.,1983;Haxbyetal.,1991,1994). duringspatialimagery.
THENEUROBIOLOGICALSEGREGATIONOFWHAT AND HEMISPHERICLATERALIZATIONDURINGSPATIALIMAGERY
WHERE DURINGSPATIALIMAGERY AscanbeseeninFigure1,mostfunctionalimagingstudiesshow
Theneurobiologicalmechanismsunderlyingspatialimageryare bilateralfronto-parietalnetworkstobeactivatedduringtheexecu-
characterizedbywidelydistributedcorticalnetworkswithamul- tionofspatialimagery.Thefactthatboth,leftandrightposterior
titudeofnodesandinteraction-patternsinthebrain.Numerous parietal cortex (PPC; mostly SPL and IPS) is recruited during
neuropsychological (Levine et al., 1985; Farah et al., 1988) and spatialimagery,is,atfirstglance,incontrasttomostneuropsycho-
neuroimagingstudies(Cohenetal.,1996;Melletetal.,1996,1998; logicalstudiesonpatientswithfocalbrainlesionswhichgenerally
D’Esposito et al., 1997; Richter et al., 1997; Knauff et al., 2000; proposeadominantroleofthelefthemisphereinvisualimagery
Trojano et al.,2000) have aimed at unraveling the neural foun- (Farah et al.,1985; D’Esposito et al.,1997). In a critical clinical
dationsof mentalimageryusingawidevarietyof imagerytasks reviewonvisualmentalimagery,TrojanoandGrossi(1994)pre-
(forareviewseeKosslynetal.,2001).Theseimagingstudieshave sented a number of single cases as well as group studies which
consistentlyrevealedthatthepureimaginationandmentalrep- demonstrate a dominant role of left posterior parietal areas for
resentation of a specific mental object results in neural activity mentalimagery.Nonetheless,theauthorsalsoreportedevidence
withincategory-specificoccipital-temporalregionsoftheventral of the role of the right hemisphere in visuospatial imagery as
visualprocessingpathway(Ishaietal.,2000,2002;O’Cravenand well as in perceptual visuospatial processing. Right brain dam-
Kanwisher,2000),includingsuperioroccipitalareas(Melletetal., agedpatientswithneglectalsoshowneglectsymptomsinimagery
1995,1996;D’Espositoetal.,1997;deBorstetal.,2011),inferior tasks,andnon-neglectrighthemispherepatientsshowvisuospatial
temporalregions(Carpenteretal.,1999;Mechellietal.,2004;de deficitsinperceptualvisuospatialprocessingandduringimagery
Borstetal.,2012),parahippocampalcortex(deBorstetal.,2012), tasks.Whilethelefthemisphereseemstohaveaspecificrolefor
FrontiersinPsychology|PerceptionScience June2012|Volume3|Article214|7
SackandSchuhmann Networkmodelofspatialimagery
FIGURE1|Thecoreneuralnetworkofspatialimagery.Thisfigure lobe;IPS,Intraparietalsulcus;MFG,middleforntalgyrus;DLPFC,
depictstheneuralnetworkofspatialimageryincludingbrainareasofboth dorsolateralprefrontalcortex;FEF,frontaleyefields;PMC,premotor
thedorsalfronto-parietal(red-colored)aswellasventraloccipito-temporal cortex;Precuneus;andSMA,supplementarymotorarea.Mostprominent
(rose-colored)visualprocessingpathway.Itsummarizesinonefigurethe regionswithintheventraloccipito-temporalnetworkincludebilateralEVC,
differentregionsidentifiedinvariousimagerystudiesasdescribedinthe earlyvisualcortex;IT,inferiortemporalcortex;IO,inferioroccipitalcortex;
Section“Theneurobiologicalsegregationofwhatandwhereduring PHG,parahippocampalgyrus.Themesialsuperiorfrontalgyrus(mSFG)
spatialimagery”ofthecurrentmanuscript.Mostprominentregionswithin playsaspecialintegrativeroleinthecontextofspatialimageryandis
thedorsalfronto-parietalnetworkincludebilateralSPL,superiorparietal thereforecolor-codedseparately.
mentalimagery,therighthemisphereseemstobeofamoregeneral correlatewithreactiontimeduringspatialimageryperformance.
relevanceforvisuospatialfunctions(TrojanoandGrossi,1994). These results support the involvement of both parietal lobes in
Our group has contributed to the question of hemispheric mentalimagery,butsuggestthateachparietallobemighthavea
lateralization within bilateral parietal cortex (PC) during spa- distinctfunctionalroleatdifferentmomentsintime.Thesequen-
tial imagery by using conventional functional magnetic reso- tialactivationfromlefttorightsuggeststhattheearlyleftandlate
nanceimaging(Trojanoetal.,2000),fMRImentalchronometry rightparietalactivationduringspatialimagerysupportdifferent
(Formisanoetal.,2002),repetitive(Sacketal.,2002),andtime- componentsofthecognitiveprocess,forexamplethegeneration
resolved (Sack et al., 2005) transcranial magnetic stimulation and subsequent analysis of the visual image. We therefore con-
(TMS)experiments.Byusingaspatialimagerytaskthatinvolves cludedthatwithinthebilateralPPCactivityduringspatialimagery,
thegenerationaswellasspatialcomparisonofmentalimages,we theleftPPCunderliesthegenerationofmentalimages,whilethe
demonstrated,usingevent-relatedfMRI,thatthebilateralparietal rightPPCsubservesthespatialprocessingupontheseimages.
activity associated with this task includes a temporal activation Suchmodularmodelsofspatialimagerythatproposeadivision
sequencefromlefttorightPC.Whenrelatingandmodelingdif- of labor between hemispheres in which the generation of men-
ferentfeaturesofthefMRIresponsestothebehavioralmeasures, tal representation from memory rely primarily on structures in
we found that the duration of activation of the early left pari- theposteriorlefthemisphere,whilespatialoperationsuponthese
etalactivationandtheonset ofthe(late)rightparietalactivation mentalrepresentationrelyprimarilyonstructuresintheposterior
www.frontiersin.org June2012|Volume3|Article214|8
SackandSchuhmann Networkmodelofspatialimagery
righthemisphere,alsoprovideasolutiontotheaforementioned Carpenter et al., 1999; Knauff et al., 2000;Trojano et al., 2000,
apparent discrepancy between lesion and imaging studies with 2002; Lamm et al., 2001;Sack et al., 2002, 2005, 2008; de Borst
regardtothehemisphericlateralizationofvisualimagery,andare etal.,2012).Withregardtothespatialprocessingcomponentof
inthissenseinagreementwithbothneuropsychologicallesionas spatialimagery,astrongfocushasbeenputonthebilateralPPC
wellasbrainimagingfindingsof spatialimagery(forreviewsee activation due to the prominent role of PPC within the dorsal
Sack,2009).However,fromfMRImeasurementsaloneonecannot spatial processing stream. Carpenter et al. (1999) correlated the
assesstheexactfunctionalnecessityorbehavioralcontributionof incrementofreactiontimeduringmentalrotationofcubeswith
agivenbrainareaforaspecificmentalsubprocess,suchasmental changesinregionalcerebralactivation.Withhigherangulardis-
imagegenerationversusspatialanalysis.Wethereforeusednon- parity, activation increased in the parietal lobes bilaterally, but
invasive functional brain stimulation to focally and transiently notinthetemporallobe.ThisdiscrepancyindicatesthatthePC
disrupt neural processing in either left or right PC during spa- playsacentralroleinthevisuospatialtransformationsofmental
tialimagery,andassessedtherespectivebehavioraleffectof this rotation (Goebel et al.,1998;Formisano et al.,2002;Sack et al.,
unilateralfunctionallesionwithinPPConspatialimageryperfor- 2002)whereastheventral(temporal)pathway,whichisessential
mance(Sacketal.,2002).Thisbraininterferencestudyrevealed for identifying a figure, does not specifically support this oper-
ahemisphere-specificeffectofparietalstimulationwithonlythe ation. This againseems to strengthenand justifythe prominent
rightparietaldisruptionleadingtospatialimageryimpairments. roleofPPCinspatialimageryresearch.However,importantly,this
These results contribute new constraints to the modular model studyalsorevealedthattheactivityinthemotorareasofthefrontal
of bilateral activation in spatial imagery and are at first glance lobewassignificantlyhigherduringthementalrotationparadigm
notinaccordancewiththeaforementionedhemisphericlateral- ascomparedtoamotorcontrolcondition,suggestingthat“theso-
izationanddivisionoflaborbetweenhemispheresduringspatial calledmotorareasarenotsimplyinvolvedinmotorplanningand
imagery. Indeed, if left PPC underlies the generation of men- execution”(Carpenteretal.,1999),butplayacrucialroleinthe
tal representations and right PPC reflects the spatial operations computationof imaginedmotionof objectsaswell.Inasimilar
uponthesementalrepresentations,asuppressionofeitherofthese vein,Richteretal.(2000)usedfMRItoinvestigatetheparticipa-
brain regions should result in impaired spatial imagery perfor- tionof theneocorticalmotorareasintheShepardandMetzler’s
mance.Fortunately,basedonacombinedfMRIandtranscranial (1971)mentalrotationtask.Sevenregionsofinterest(ROIs)were
magnetic stimulation study (Sack et al., 2002), we were able to analyzedseparately:LeftandrightSPL,SMA,andleftandright
furtherfractionatespecializedprocessingcomponentsintheright premotorareas.Theresultsshowedthattheobservedactivation
PPCandrevealedtheexistenceofhighlydynamiccompensatory inpremotorareaswaslikelyrelatedtotheveryexecutionof the
mechanismsbetweentheleftandrighthemisphereduringtheexe- mentalrotationtask(Richteretal.,2000).
cutionofspatialimagery(Sacketal.,2005).Thisstudysuggested Thesestudiesthusindicatethepotentialfunctionalcontribu-
thatalthoughtheleftPPCispredominantlyspecializedinmen- tionofprefrontalandpremotorbrainareasduringspatialimagery.
talimagegenerationandtherightPPCinspatialcomparisonsof The question remained, however, whether these prefrontal and
imaginedcontent,therighthemisphereisalsoabletoimmediately premotoractivitiesduringmentalrotationtasksaremorerelated
compensatefor(virtual)lesionsofthelefthemispherebytaking to the potential involvement of visual working memory rather
overitsspecificfunction,butnotviceversa.Hence,incaseofleft thanbeingcriticalneuralstructuresforthevisualimageryprocess
parietal functional lesion, the right PC will now subserve both perse. Orinotherwords,whatwouldhappentothehereiden-
functions, mental image generation, and spatial analysis of the tified premotor and prefrontal activations in case of pure visual
mentalimage.Discrepanciesacrossstudiesconcerningthehemi- imagery,i.e.,when generating mental representations of objects
sphericlateralizationduringmentalimagerylikelyarisebecause that have never been perceived before? In such cases,the gener-
differentaspectsof imageryarecarriedoutbydifferentpartsof ation of visual images does not result from the reactivation of
abi-hemisphericneuralnetwork.Thefactthatanisolateddeficit previouslystoredmemoriesbutdoesresultfromanonlinecon-
oftheabilitytogenerateinnervisualimagesfollowingunilateral structionofimagesbasedontheprocessingof,e.g.,verbalinstruc-
lesionisclinicallyhardlyreportedcouldalsobeexplainedonthe tions and their encoding in a visual format. Mellet et al. (1996,
basisofthecompensatoryprocessesrevealedinourstudy(Sack, 1998, 2000) used PET to monitor regional cerebral blood flow
2009,2010).Interestingly,suchhemisphericasymmetriesbetween variationswhileparticipantswereconstructingmentalimagesof
leftandrightPPCapplytoboth,thedirectfunctionalrelevance objectsmadeofthree-dimensionalcubeassembliesfromacousti-
(onlyrightparietaldisruptionleadstobehavioralimpairments) callypresentedinstructions.Comparedtoacontrolcondition,the
aswellasabilityofinter-hemisphericcompensation(rightPCcan mentalconstructiontaskspecificallyactivatedabilateraloccipito-
compensateforleftPC,butnotniceversa). parietal-frontalnetwork,includingthesuperioroccipitalcortex,
theinferiorPC,andagainalsothePMC.Thesestudiesthussug-
DYNAMICANTERIOR-TO-POSTERIORBRAINNETWORK gest that in addition to the well-established functional role of
CONNECTIVITYDURINGSPATIALIMAGERY posterior parietal cortices during spatial imagery, also the pre-
Theexecutionof variousspatialimageryparadigmsconsistently frontalandpremotoractivationsrevealedduringimagerytaskare
activates core areas of the dorsal fronto-parietal visual path- of direct functional relevance for the imagery performance and
way, including bilateral parietal, prefrontal, and premotor areas likely also sub serve specific cognitive sub functions within the
(Kawashima et al., 1995;Mellet et al., 1995, 1996; Cohen et al., multifacetedcognitive-psychologicalconstructofimagery.How-
1996;Richteretal.,1997;Tagarisetal.,1997;Kosslynetal.,1998; ever, as described above, while some of the previous functional
FrontiersinPsychology|PerceptionScience June2012|Volume3|Article214|9