NEUROLOGICAL PROGRESS Large-Scale Neurocognitive Networks and Distributed Processing for Attention, Language,and Memory M-Marsel Mesulam,MD tion and ment are subserved by inter high-eve com ing aard sim ultiple po e to this del co mplexb ed at than sp cal sit ioa.coatetand The relationship be een brain structure and complex play a de det .Mos ber of weak traints o that the system n rela oduct of the rapid computai ons required orentdlactivig enab Pprocessadditionlcog There ed at the ch,Pitts,a networks iences now allow ontain an int atnoedea processing,McCle an mediate al netw hecshnotoanlocdne etworks. rom Bullard and De ries,Divis ot Neu te p esmrDcnd m Copyright1990 by the American Neurological Association 597
difficul howe is of comple cognitvedomains.g st ap the on,an will be used as a paradigm [1]. guage,memory,and frontal lobe function. Network for the Distribution relevant of thex Fig 1.A large-scale for adaptive be ior.Profound Patients with this syndrome do no MPC r primary sensory m e he ftward negle after right thalamic pulvinar nucleus)are connected to at least eft her Neglect ed into perceptual that di Th ued large-scale ork that c ontains three co the ,f ch providing environment.Thc osterior sentation of the extrape fo head,dm componcntofneglectbchag There is am d he ng value to dinate The of the negle th all three c A ortan projections acti of the re neglectwecorticallcs ns tha the activation bias (or level of Lesions in any of th 1)the teral t or to the inrerco cortex the natter）cai I result ir these th ingulate gyt are linked to each other by synaptic The add ized and inrerc (the superior esions inany one of several different sites 598 Annals of Neurology Vol 28 No 5 November 1990
of the damage urns{asinpri )bu is e ation and eye posi p of PG neglec a5 15a sions includes a c ected hem pace [14 of huma ubjects to prismat hat similar distinctions can [101.Shifts of neuro gical obse with eye pos ion or stimulus locarion.Cor keys have elucida of the ifts h t o in a way tha tra able the covert movement of ntion that area PG re sextensively pre s [5)have dem ation icnswihpostetiorpaietallesiog casca they cannot disengage the focus of proximal (upstream)sc inform attention for con sive shift provide to (and eventually to arise thr ough is impo PG m un d s the as.Accordi PG in the form of a co thus in oor sensory nation (3)en Such a distr ibute (an hiness of se L nantic imnar t of certain stimuli aded)infor ation in pq spatial coordinates on corresponding groups of PG ome of the ne PG increase firing able information has also been gathered on ce is made beh but not hen th ent h ng di consequ behav t objecs or to thei of the ote atedwithsimilar activity. hat normal the PG plexand tsk-reaed rather mal's ability determin the rela e Dosition of ex or co 21 des and may also infue the sho ic visa nation abou movements since damage to one d ye po n [10].An individual PG neuron olishes the 1261 The supor coliculus may be its retinotonic feld de on eye position,and a mportantfor fovearing the gen eral area of iner f that regio Nerolopical prosrress:Mesulam:Neurocognitive Networks 599
The and the 0 subserve orientation to "fa egio es substa ntial neural input from the sam ct to the erior parietal co 2 eg27 lhcontrasttoprimi motor cortex where Furthermore,the ntermediate (oculo motor)laver o rep body d on the PPin reas ap behavioral poir t of view,a s ory represc tation a exp arms crossed.reaction time nd ing ha dating per er sho compo ofuniareral ect are ing used (13.Thes examples my show that explo not absolute are organize accordin absence of one ent but the rela ng on the ather sire of the lesion three nponents in Figure ording to these obs the Fean PG have are for pe eural cor me the tar ofehacan grasp, ts are probab atten tasks nd subiective ar tional lande hiecFEF ng are olan the sraegy for navigating them.The sum of percet t of this rk.Lesio ot the syndro eafcontralarernal tional)quality of the Is im with m hat thi arg cale network posit emi vanon during state dd of F51 could ibution of visua ing of the ape It is re Areas such as the FEF and PG that he FEF ut the behavi hav nshrough or synchro ponent [18 bet sens and moto omy mat resp ectively by PGand FEP. 1 e gyrus but also mo th tion and p te [11.Complex p nodal prefrontal nd the TE-TH region [18.32.37 or fe pair o schema [301 whi rex is likely to additional cortical connect member of the pair.Th and the FE ann need not be identical and can vary 600 Annals of Neurology Vol 28 No 5 November 1990
terconnected noda areas which are in turo other. is man 13]info chronize all d pro ride ne there is vity en one thalami y nucleus and 8 from all cortical comp ts of a ral ne 5 a for the a al network .O0 ical exp the mo d in The c diag Fiz 2.(A)A ger sho viding the 足d 2T distribuion of spa XA dBY.(B do no for ae tha r may thus FEF t (34). fearure of networks is the absence of o-one espondence TH:Lp:INE in Fisure3A Let be oralphacocrespondo PG= area PG.an ces in the relariv of an individual cor in the FEF but to a ction or by h ng s igu exter k PG that include e medial pulving tha Th not the FEF)recei om the lateroposterior thala on,an VA-VL)that is ot. rwoses.Thergliagto0p0eg al plane ure 2A show yadic hub-and-spoke etwork formed around wo in cognitive planes is depi Neurological Progress:Mesulam:Neurocognitive Networks 601
psnglephiotoaemisioncon tex and ive defici a de ngoa distribu ted and interactive but als omp vior.This comput the netwo 3.(A)T between behavior and site. asic patients during the 19th 42431.Thc handers.The relatively the gre eat of righ ger here provides one ible anatomical co 4.The Wernicke's area in froncl operculum [421.The n an Broca's ar in the for sustaining the ba- cts of purposeful ang tial (holistic)nor modular (insul the brain.The o nodal regions and ma that pro cortex be synrax,and The mapp Ge.Posteriorparietallesion to yield multiple of the rocessing in addition to nd he will focus on spol esions (or elec. 602 Annals of Neurology Vol 28 No 5 November 1990
or es area o regions both degenerate and coarse erior temporal gyrus a mor oup encoding in a wa s been to accep the audicory that may ion in socAp)as the n area PG ing c ar attentional pe odal 37,39P,and )(PG)withir without stric Patients e's aphasia produce Auent aphas area (ie.the region associa d with Broce 47.12.and 6.Of these areas. oor(motor assoc eplaced by ineff circum neo of the iation comn hat no nd and with Bro is another central fea nt (phras ngth s aphas A that ithy ane sense ome is lesion in nded rds,mos of which are appro ubects who are and on sions of artices,pr and ning to wore whe ectric tion in at the f47 s01 with the anatomica ent's reference for arsimony,othe e's are the hav mul .Patients with Broca's aphas have ab The clinical tha repe spe ars to provide an ent vian areas,sti ca's arc ses th point for the chunking of audiory se nto ne 48,5 then trigge that in the sphere,shows me activation in ing and volve specc that Broca's area lies at e:th ollection of spe ord co the s cke is thu a n word vity that contains infor abou sound- ke's area bu other parts of th At the ou h e of Br hunking of th oughts words that an comme ing phonemes,morphem into entences in a wa that infuences syntax curs oueh simultaneous parallel appr mea ng.If Werni esachieved wih how to order and utter them in the most meaning omeaning [51].Whe Wernicke's tro to think of Wernicke's inrended thouht is diminishe area as a receptive(or sensory)region and Broca's area ading Progress:Mesulam:Neurxcognitive Networks 603
ons and no aph tha dinate praxis,writing. ing statements the mea The oach to the neurology of end by prepositions and wor anguage recogn the importance of everal addi elicis fBroc'sarea ad electrical stimu nage to th supplem entar motor area moda the r conne ctions vith Broca" pnas s have but with prese ved repetition [61).This this area5] not sia.The suppl mentar n th Wernicke's area and planning of s and the a maio They also Some nts motor apha som structu where ds from A thin a cor ctly tion in Wernicke'sa comp (or to its ctions with t ca's are aph ith which isdef ernicke's rea are als have a tran epetiti dich for adeguat int pt the ative expected with a show seve def ompre Th that Broca's not consecutively 60]. as mani sted by 5P s simult righ ulation. The and gr dcieu5Povid no hi the words ic d paral tic pro rd c ust as choi n.In the en during silen an ed to the articu dary product n the dditive nd t (i.e..pure but a dis in concert. oca's a a or to its the abno ch arti of the lan esions wil nixed deficits in s in the attentional nerwork the comprehension but with different combinations 604 Annals of Neurology Vol 28 No 5 November 1990
and emp There is no good animal model for language.Som A aphical consideratio region of the rhe key bratn responding and(and 6v),the :B ,and area PRCO Fig icke'sr rapart of areas PE (P)n PGPG) superior tempor MI MC cortex :0A ons that cor ond to broca's area and Wernicke rea inthe monk brain may each be =h :the supplem ntary motor cor the cinguare gyrus, art of area he an erior supe or temporal sulcu the nd t are two ents are p I by proj Br lear if ther is hndthhniciclesforh sites ndid in lan uage functi [48 usly (and itera )cons de many per aph ia when dar ctly but also through the mediation o very exte Neurological Progress:Mesulam:Neurocognitive Networks 605
[70].These obse nave led to the postul 5B multiple ro For ple,a phon B,wherea anticall 6-E the that have g 1 .Th ative in the normal brain. The dis the const view seems to imply, on the pri an ture of ca's an Wernicke's ar or the man Fig 6.(A) syndrom Pacients with thi show a global deficit in new learning. /R tha ,125 f at- Amnestic states can be cau irome bas been epor thalamu PE PE or posterior cerebral arte diencephal 1(as1 of the tempora obe A bord!a ty:TP= ws tha the olve on network(Fig 6A)The memory and learning can he dissoci several behavioral components such as iaredinty 73 retrie al bu not nec ly in homolo s are ust scanreutinagiobdlar,e nd m call can be declarative memories),procedural (the learning ski) 606 Annals of Neurology Vol 28 No 5 November 1990