U. Bellugi et al. (1999) - Duke-UNC Brain Imaging and Analysis Center

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P ERSPECTIVES ON DISEASEU. Bellugi et al. – Linking cognition and the brainAFreedrawingof a houseBBlockdesigntaskCLocal–globaltaskExampleModelYYYY YYYYYYY YY Y YModellivingroomWilliams syndrome(poor on global organization)roofdoorwindowsdoorswimming poolsidewalktwo-storeyhousewindowsmodifications in volume. Affectivity in lexical devicesis noted in the frequency of exclamatory phrases andother audience engagement devices (for example,‘Suddenly splash! The water came up’; ‘Lo and behold’or ‘Gadzooks! Guess what happened next!’). This patternof increased linguistic affectivity is strikingly differentfrom subjects with DNS, as well as from normalindividuals at any age or other contrast groups (forexample, individuals with early focal brain lesions) 31–33 .Thus, in adolescents and adultswith WMS, expressive language istypically a great strength and isused effectively (and sometimeseffusively) in social situations. Thisis exemplified by the WMS teenagegirl who said, ‘Everyone in the worldis my friend’. Individuals withWMS, therefore, exhibit a strikingcontrast to the social and languageprofiles of individuals with otherdisorders such as autism 31 .Strengths and deficits in visually basedcognition in WMSIn studies that examine spatialcognition, as opposed to language,subjects with WMS are significantlymore impaired than subjectswith DNS across all age rangesexamined 3,34,35 . Indeed, individualswith WMS performed more poorlyin our studies than children withearly right-hemisphere lesions 36 .Difficulties with spatial cognitionin WMS seem to be especially acutewith respect to the global, ratherthan the local, level of spatial organizationacross tasks. Lack of cohesionor global organization is typicalin drawings by subjects withWMS, while subjects with DNStend to show a different effect 37,38 .For example, a subject with WMS might draw a housewith windows and a door as separate entities from thehouse itself, thus lacking global organization (Fig. 2A).By contrast, a typical drawing by a subject with DNSmight be simplified yet exhibit proper gestalt relationshipsamong elements. On block-design tasks, bothWMS and DNS subjects perform poorly, but in differentways, with WMS subjects typically unable to organizethe blocks into a global pattern, and DNS subjectsinstead making errors of internaldetail (Fig. 2B). Difficulties withintegration of simple shapes havealso been shown on tasks thatrequire subjects to copy a drawingof geometric forms from a model 2,3 .When asked to reproduce a largefigure made up of smaller figures(for example, a large ‘D’ made ofsmall ‘Y’s), subjects with WMStend to produce primarily the localconstituent forms sprinkled acrossthe page and fail to reproduce theglobal form, whereas subjects withDNS tend to show the oppositeDown syndrome(poor on internal detail)Fig. 2. Different spatial deficits in Williams syndrome (WMS) and Down syndrome (DNS). (A) The drawings byadolescents and adults with WMS contain many parts of houses but they are not organized coherently. In contrast, thedrawings of age-matched and Full Scale IQ-matched DNS adults are simplified but have the correct overall gestalt. (B)In the block-design task both subjects with WMS and subjects with DNS fail (scaled scores more than 2 SD belownormal), but they fail in very different ways: adolescents and adults with WMS show disjointed and fragmented designs,while age-matched and Full Scale IQ-matched DNS subjects make errors in internal details while maintaining the overallconfiguration. (C) In the Delis hierarchical processing task, subjects are asked to copy a large global figure made ofsmaller local forms (a ‘D’ made out of ‘Y’s). Again, both groups fail but in significantly different ways: subjects withWMS tend to produce the local elements sprinkled across the page, whereas age-matched and Full Scale IQ-matchedsubjects with DNS tend to produce only the global forms.APercent correct10080604020064 53789Model2110118 10 12 12 12 14 14 14 15 15 16 16 17 18 20 22Age (years)BPercent correct100Model8060402008 10 12 12 12 14 14 14 15 15 16 16 17 18 20 22Age (years)Fig. 3. Spatial cognition (impaired) and face processing (relatively spared) in Williams syndrome (WMS). Thestrengths and weaknesses in visuo–spatial processing in WMS show an unusual profile. The results from two tasks thatare both visuo–perceptual tasks, sensitive to right-hemisphere damage, where the correct answer requires only pointingare shown. The results for the same subjects are shown for each task. Note that the same subjects with WMS performvery differently on the two tasks. (A) Subjects with WMS perform very poorly on judging the orientation of lines (Bentonjudgement of line orientation), in keeping with their spatial deficit. Several subjects cannot even pass the warm-up items.(B) In great contrast with this, exactly the same subjects with WMS perform remarkably well on a very difficult face discriminationtask (Benton face recognition), which involves recognizing the same individual under different conditions oflighting, shadow and orientation. In both parts, the performance of normal subjects is indicated by the broken line.pattern 2,37 (Fig. 2C).Face processing is a remarkablestrength in individuals with WMS,in great contrast to their othervisual–spatial cognitive deficits 2,39 .This contrast is highlighted whencomparing two tasks, each ofwhich requires only pointing tothe correct answers: one involvesjudging the orientation of lines (aspatial task) and the other involves200 TINS Vol. 22, No. 5, 1999
discrimination of unfamiliar facesin different conditions of lightingand orientation (a face-processingtask). Individuals with WMS showextreme difficulty with the spatialtask and obtain scores in the rangeconsidered to be severely deficient;sometimes they are not even ableto do the simplest items. In contrast,the same WMS individualsshow a remarkable strength in theability to recognize faces 40,41 (Fig. 3).Across different face-processingtasks (recognition, classification,memory), individuals with WMSshow strong performance 41 .Different trajectories in cognitivedomainsWhat is interesting about individualswith WMS is that there areareas of serious deficits (generalintelligence, visuo–spatial abilities)but also areas of relative strengths(face processing, expressive language).Questions about the relationshipsbetween the deficits andstrengths emerge from the researchfindings on WMS: do the differentcognitive abilities depend on oneanother or can they be dissociatedfrom one another? Do they changethroughout development? What arethe underlying brain systems forthese strengths and deficits in abilitiesin cognitive domains? The associationsbetween and within differenttypes of abilities have beenexamined through correlationalstudies. In WMS, correlations between measures of faceprocessing are strong, but measures of different aspectsof language functioning and visuo–spatial abilities arenot correlated with face-processing abilities 34,41,42 .Across three cognitive domains, distinct trajectories ofdevelopment are found in studies involving individualswith WMS between the ages of 5 and 29 (n 71). InWMS, there are clearly different trajectories across thethree domains reported (lexical knowledge, spatial cognitionand face processing) (Fig. 4A). In contrast, individualswith DNS show essentially uniformly depresseddevelopment (Fig. 4B). In a lexical knowledge task, childrenwith WMS begin with very low scores, but show asharp increase with age (unlike DNS children). On astandard drawing task, individuals with WMS scoreconsistently lower than individuals with DNS at all agelevels and reach a plateau early in development. On aface-processing task, individuals with WMS tend to performvery well, even at a relatively early age, and continueto do well throughout development 35 . Overall,subjects with WMS perform significantly better duringdevelopment than DNS subjects on face-processing andlanguage tasks, but significantly less well than DNSsubjects on visual–spatial tasks 35 (see Fig. 4C).The neurophysiological profile of WMSThe neurobiological profile of individuals with WMSis being revealed through studies of brain function[event-related potentials (ERPs)], brain structure 3DAMental age (years)14106Faces (Benton)Age at test (years)CU. Bellugi et al. – Linking cognition and the brain P ERSPECTIVES ON DISEASEVocabulary(PPVT-R)Spatial(VMI)223 7 11 15 19 23 3 7 11 15 19 23Mental age equivalent10Faces (Benton)8 Vocabulary(PPVT-R)6Spatial(VMI)4WMSBMental age (years)DNSAge at test (years)computer-graphic analyses of MRI) and brain cytoarchitectonicsin autopsy brains. Initial proposalsabout how the cognitive and brain profiles might belinked are presented in this article.Studies using ERP techniques are useful in assessingthe timing and organization of the neural systems thatare active during sensory, cognitive and linguistic processingin subjects with WMS (Refs 43–48). Eventrelatedpotentials provide information about the timingand temporal sequence of neural events and, tosome extent, the location of neural activity. Electrodesare placed on the scalp over specific brain areas whilesubjects are processing information, which, thus,allows the monitoring of the time course of neuralactivation on a millisecond to millisecond basis. Therecorded activity occurs before subjects make an overtresponse. Studies of brain-wave activity during languageand face-processing paradigms in individualswith WMS and normal individuals are reported in thisarticle.A neurophysiological marker for auditory language processingThe morphology of ERP components to auditorywords was dramatically different in individuals withWMS from normal controls. Event-related potentialswere recorded as subjects listened to sentences that werepresented one word at a time. The final word in eachsentence either provided good closure or was semanticallyanomalous (for example, ‘I have five fingers on mymoon’). The results revealed that the morphology of14106Faces (Benton)Spatial (VMI)Vocabulary (PPVT-R)Fig. 4. Three domains of cognition in Williams syndrome (WMS) but not in Down syndrome (DNS). (A) Developmentaltrajectories of contrasts between language, face and space processing in WMS are shown. Subjects of all ageswith WMS show distinctly different trajectories in three cognitive domains: lexical knowledge, spatial cognition and faceprocessing. On a standardized test of vocabulary [the Peabody picture vocabulary test-revised (PPVT-R)], subjects withWMS start with low scores and then show a sharp increase in score with age. On a probe of spatial cognition thatinvolves copying geometric shapes [the developmental test of visual moror integration (VMI)], the performances of subjectswith WMS are consistently below those of subjects with DNS, and plateau at an early age. On a task of face processing(the Benton test of facial recognition), subjects with WMS perform extremely well even at very young ages. (B)Subjects with DNS show essentially the same developmental trajectory across the three domains. In contrast, subjectswith WMS show three distinctly different trajectories. (C) Planned contrasts show that performance on the three testsdiffers significantly within the WMS group, even when controlled for age. No between-test differences are found in theDNS group. A 2 3 (WMS, DNS Benton, VMI, PPVT-R) analysis of covariance with chronological age entered as thecovariate revealed a significant group–test interaction (P 0.0001).TINS Vol. 22, No. 5, 1999 201
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U. Bellugi et al. (1999) - Duke-UNC Brain Imaging and Analysis Center

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