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Brain and Cognition 44, 166–191 (2000)

doi:10.1006/brcg.2000.1227, available online at http://www.idealibrary.com on

The Role of the Dynamic Body Schema in Praxis: Evidencefrom Primary Progressive Apraxia

Laurel J. Buxbaum,*,† Tania Giovannetti,* and David Libon‡

*Moss Rehabilitation Research Institute, Philadelphia, Pennsylvania;†Temple University Medical Center, Philadelphia, Pennsylvania; and

‡Crozer-Chester Medical Center, Upland, Pennsylvania

Published online August 15, 2000

On an influential model of limb praxis, ideomotor apraxia results from damageto stored gesture representations or disconnection of representations from sensoryinput or motor output (Heilman & Gonzalez Rothi, 1993; Gonzalez Rothi et al.,1991). We report data from a patient with progressive ideomotor limb apraxia whichcannot be readily accommodated by this model. The patient, BG, is profoundlyimpaired in gesturing to command, to sight of object, and to imitation, but gesturesnearly normally with tool in hand and recognizes gestures relatively well. In addi-tion, performance is profoundly impaired on imitation of meaningless gestures andon tasks requiring spatiomotor transformations of body-position information. Weprovide evidence that BG’s apraxia is largely attributable to impairments externalto the stored gesture system in procedures coding the dynamic positions of the bodyparts of self and others; that is, the body schema. We propose a model of a dynamic,interactive praxis system subserved by posterior parietal cortex in which stored rep-resentational elements, when present, provide ‘‘top-down’’ support to spatiomotorprocedures computed on-line. In addition to accounting for BG’s performance, thismodel accommodates a common pattern of ideomotor apraxia more readily thancompeting accounts. 2000 Academic Press

Key Words: body schema; body representation; body-centered coding; praxis;apraxia; ideomotor apraxia; gesture.

Ideomotor apraxia (IM) is a disorder of complex movement characterizedby spatiotemporal errors in tool use, gesture pantomime, and/or gesture imi-tation (Heilman & Gonzalez Rothi, 1993). There are numerous subtypes of

This research is supported by a grant to the first author from the National Institute forNeurological Disorders and Stroke (No. R29-DC03179-01).

Address correspondence and reprint requests to Laurel J. Buxbaum, Moss RehabilitationResearch Institute, 1200 West Tabor Rd., Philadelphia, PA 19141. E-mail: [email protected].

1660278-2626/00 $35.00Copyright 2000 by Academic PressAll rights of reproduction in any form reserved.

BODY SCHEMA AND PRAXIS 167

the disorder. Some IM patients can recognize gestures but not produce themin any context (Piccirilli, D’Alessandro, & Ferroni, 1990; Rapcsak, Ochipa,Anderson, & Poizner, 1995), while others are able to gesture to commandbut not imitate or recognize gesture (Gonzalez Rothi, Ochipa, & Heilman,1991). Some patients show input-modality-specific deficits (e.g., inability topantomime or imitate to visual input). At least one patient has been reportedwith intact gesture recognition in the context of moderately impaired gestureto command and severely impaired imitation (Ochipa, Rothi, & Heilman,1990). The presence of these and other patterns has proven challenging toinvestigators attempting to model the subcomponents of the praxis produc-tion and recognition system(s).

An influential contemporary model of the praxis system accounts for vari-ous patterns of apraxia in terms of two routes to praxis production, recog-nition, and imitation (Gonzalez Rothi, Ochipa, & Heilman, 1991). The modelincludes a lexical route to gesture comprehension and production involv-ing stored gesture representations at two loci (the input and output praxi-cons, respectively). Each praxicon contains stored spatiomotor gesture repre-sentations which provide the ‘‘time-space-form picture of the movement’’(Liepmann & Maas, 1907) and confer a processing advantage for skilledgestures. The two-route model also contains a direct or nonlexical routewhich can be used in gesture imitation. Figure 1 is a simplified schematicof this model.

On this model, different patterns of ideomotor apraxia are viewed as hav-ing parallels in aphasic disorders and are attributed to deficits in stored ges-ture representation, access, or egress. For example, impairments in gesturecomprehension with spared gesture to command is viewed as akin to ‘‘worddeafness’’ in Wernicke’s aphasia: Sensory signals fail to gain access to theinput praxicon. Intact gesture comprehension with impaired gesture produc-tion, like Broca’s aphasia, is proposed to result from impairments in theoutput praxicon. Impairments of gesture imitation in the context of intactgesture comprehension, similar to relatively severe repetition deficits in con-duction aphasia, are posited to result from lesions between the input andoutput praxicons. Reliance on the direct route from vision to action explainsthe performance of IM patients who, akin to transcortical sensory aphasics,are able to imitate (‘‘repeat’’) gestures they cannot comprehend.

Although the two-route model successfully accounts for numerous sub-types of apraxia, it does not appear to explain a common pattern of the disor-der. Many patients with IM as assessed by gesture pantomime, object use,and/or meaningful imitation tasks exhibit relatively greater difficulty in imi-tating meaningless movements (Kimura & Archibald, 1974; De Renzi,Motti, & Nichelli, 1980; Pieczuro & Vignolo, 1967). On the two-route ac-count, this is suggestive of dual lesions to the lexical and direct routes, withthe lesion to the direct route the relatively more severe. In this study, we

168 BUXBAUM, GIOVANNETTI, AND LIBON

FIG. 1. A schematic of the model of the praxis system proposed by Gonzalez Rothi,Ochipa, and Heilman (1991).

explore a more parsimonious possibility: that this pattern reflects damage toa unitary set of procedures or representations common to both lexical anddirect routes.

Consider that both skilled and novel movements are likely to require spa-tial coding of the dynamic locations of body parts relative to one another(what we will term intrinsic spatial coding of body part positions, to be distin-guished from extrinsic egocentric coding of object locations with respectto body parts). Several lines of evidence suggests that such information iscomputed by the brain. Physiologic data indicate that computation of spatialcoordinates for action includes calculation of the positions of the fingers withrespect to one another (e.g., Gallese, Fadiga, Fogazzi, & Rizzolatti, 1996),of the eye with respect to the head, and of the head with respect to the torso(e.g., Snyder, Grieve, Brotchie, & Andersen, 1998). In addition, there is evi-dence that neurons in the superior parietal lobe (area PE in monkeys) inte-grate inputs from primary somatosensory cortex to construct complex repre-sentations of body postures. For instance, coding of a posture in which the


left hand contacts the right shoulder may occur at the level of the singleneuron (Sakata, Takaoka, Kawarasaki, & Shibutani, 1973; see also Gurfin-kel & Levick, 1998). It has been suggested that such coding may be the basisfor a mental model of the body (Bonda, Frey, & Petrides, 1996). Accordingto Jeannerod and colleagues (Jeannerod, Arbib, Rizzolatti, & Sakata, 1995),schemas for coding the positions and movements of body parts relative toone another may form a basic vocabulary from which many skilled move-ments can be constructed.

There is also evidence that the same spatiomotor body representations maybe invoked in production, recognition, and imitation tasks. For example,there are data suggesting that the perception and representation of others’bodies, and of action, is constrained by implicit knowledge of the movementsthe system is able to produce. Parsons (1987, 1994) elegantly demonstratedthat left/right decisions about hands are made by mentally rotating ones’own motor hand image into congruence with the view depicted; responselatencies indicated that the mental rotations took into account the startingposition of subjects’ arms and hands and the mechanical (joint) constraintsof rotation in one or another direction. Subsequent PET studies have indi-cated that such judgments are accompanied by activation in superior parietaland intraparietal cortex (Bonda et al., 1996). Reed and Farah (1995) pre-sented data from whole-body-position judgment tasks similarly consistentwith involvement of a dynamic spatiomotor body representation: Subjects’response latencies to perform same/different judgments about others’ bodypositions was affected by the subjects’ own position during the judgment.That judgment and matching of body-part positions differs qualitatively frommatching of visual stimuli was confirmed by a recent PET study demonstrat-ing that comparison of the positions of hand stimuli, but not abstractbranching shapes, activates regions of premotor and motor cortex (Kosslyn,Digirolamo, Thompson, & Alpert, 1998). Finally, several physiologic studiesindicate the presence of ‘‘mirror’’ neurons in the superior temporal sulcusand frontal lobe which discharge both during monkeys’ active movementsand observation of the same movements by others. Rizzolatti and co-workers(1988) have proposed that such observation/execution mechanisms play arole in comprehension of action. Similarly, Jeannerod has suggested that anobserved action can be understood and imitated whenever it becomes thesource of a representation of the same action within the brain of the observer(Jeannerod, 1999). In sum, then, there is evidence that the representationsand procedures providing for ‘‘intrinsic’’ spatial coding of the dynamic posi-tions of body parts may be used both for planning one’s own actions as wellas in recognizing the actions in others.

In cognitive neuropsychological terms, there is historical precedent forcharacterizing dynamic body-part location coding as one of the functions ofthe so-called ‘‘body schema’’ or ‘‘plastic schema’’ (Head & Holmes, 1911/1912), an ‘‘on-line’’ map of the position of the body parts in space over


time which enables measurement of postural changes and appreciation ofpassive movement. As noted by Mussa Ivaldi, Morasso, and Zaccaria (1988),‘‘the concept of an internal model (of the body) is a way to deal at the sametime with many frames of reference and to emphasize one with respect tothe others during the planning process according to specific task needs; itcan be considered as a revisitation of the old neurological concept of thebody schema’’ (p. 53). It is of note that in discussing the left/right handdiscrimination findings just described, Parsons (1994) suggested, ‘‘Becausethe kinematic configuration of the body that is represented and transformedin mental simulations of action matches the actual current kinematic config-uration of one’s body, the representation underlying performance is likelywhat has been termed ‘body schema’ ’’ (p. 726).

Several investigators have noted that gesture pantomime and imitationmay rely on the body schema or something akin to it (e.g., Heilman, Gonza-lez Rothi, Mack, Feinberg, & Watson, 1986; Kimura, 1977; Russell, 1976).For example, Heilman et al. (1986) reported a patient with superior parietal(area 5) damage whose apraxia they attributed to deficits in a proprioceptivecomparator system which transcodes visual information into somatestheticspatial coordinates. They postulated that the superior parietal lobe is criticalfor transcoding praxicons into a somatesthetic spatial code. Kimura (1977)discussed the dependence of praxis upon internal spatial functions responsi-ble for encoding changes in the position of one body part relative to therest. Generally, however, such intuitions have not been tested with measuresdesigned to assess body schema integrity, nor explicitly incorporated intomodels of the praxis system.1

We present data from a primary progressive apraxic woman which cannotbe accommodated by the two-route model without augmentation. The dataare consistent with a revised model of the praxis system which explicitlyincorporates the role of intrinsic spatial coding of body-part positions in bothlexical and direct gesture processing. In this manuscript, we use the term‘‘body schema’’ as a shorthand for the procedures and representations in-volved in the on-line coding of the position of body parts with respect toone another over time and resulting in an internal dynamic model of thebody; note that this usage appears similar to those intended by other contem-porary investigators mentioned above (Mussa Ivaldi et al., 1988; Parsons,1994). We demonstrate that a revised model of the praxis system explicitly

1 There is some controversy about the degree to which the body schema may be impairedin other parietal syndromes. While there is evidence that the schema for the left hand maybe impaired in personal neglect (Coslett, 1998), it is not as clear whether autotopagnosia(Ogden, 1985) and Gerstmann’s syndrome (Benton & Sivan, 1993) should be considered bodyschema impairments as well. There is evidence suggesting that the impairment in autotopag-nosia is rather in a system of body-specific visual structural descriptions (Sirigu et al., 1991;Buxbaum & Coslett, 1998a; in press).


FIG. 2. A saggital view of a T1-weighted MRI demonstrating prominent atrophy of poste-rior parietal and frontal cortex, with relative preservation of prefrontal and occipital cortex.

incorporating the role of the body schema can accommodate the performanceof a common IM subtype more readily than the original two-route account.

Patient Description

BG was a 67-year-old left-handed woman with a 12th-grade educationwho complained of the slow onset of articulatory speech problems 2 yearsprior to the present investigations. She denied memory or concentration prob-lems, but suspected that her thinking was ‘‘not as sharp’’ as it had beenseveral years previously. She also admitted to becoming confused when at-tempting to navigate in unfamiliar environments.

Repeated neurological evaluations over the course of a 2-year period cor-roborated BG’s subjective impression of ‘‘slowed speech’’ as well as hypo-phonia, but revealed normal limb strength, proprioception, and sensation bi-laterally, intact cranial nerves, and the absence of pathologic reflexes.Diagnoses under consideration included Pick’s Disease, corticobasal degen-eration, and Alzheimer’s Disease. An MRI revealed moderate cortical andcerebellar atrophy (see Fig. 2). A SPECT scan was remarkable for decreasedactivity in the mesial temporal lobes as well as in the superior posteriorparietal lobes, left greater than right.

BG exhibited a WAIS-R IQ of 90 (25th percentile), reflecting probablemild decline from premorbid levels given a NART IQ score of 100.6 (Nel-son & O’Connell, 1978). Language testing revealed dysarthria and articula-


tory deficits affecting repetition and fluency, but no evidence of aphasia. Ascan be seen in Table 1, motor functioning was normal with the left handand just below normal with the right. BG made substitution errors in pointingto named body parts on the left, right, and midline (total 19/35 correct), butperformed relatively accurately in body-part pointing upon imitation (33/35 correct; both errors on the right). There were mild deficits in right–leftdiscrimination. There were also severe deficits on tests of finger gnosis andgraphisthesis (recognition of numbers written on fingertips), bilaterally. Fi-nally, BG performed poorly with arithmetic calculations (12/20 correct onone-step addition, subtraction, multiplication, and division). Thus, she exhib-ited three of four components of Gerstmann’s syndrome (right–left confu-sion, finger agnosia, and acalculia, but not agraphia) as well as evidence ofa more general parietal syndrome. Table 1 provides a summary of the resultsof these and other background tests.

BG’s performance was rapid and accurate bilaterally on tests of reachingto targets in peripheral vision while fixating on the examiner’s face; i.e., shedid not exhibit optic ataxia. She was likewise unimpaired in reaching to theremembered locations of coins that were placed on a large (36″ 3 48″) sheetof paper and then removed. Comparatively severe deficits were evident onclinical tests of limb praxis. When asked to pantomime the use of commonobjects (e.g., hammer, scissors) with either hand, BG frequently performeda small, circular ‘‘rubbing’’ gesture upon her thigh or a tabletop. She ap-peared to improve only slightly with vision of the target objects. Thus,apraxia was by far the most prominent feature of the progressive degenera-tive process, consistent with the syndrome of primary progressive apraxia.

These observations prompted a more thorough investigation of the deficitsunderlying BG’s limb praxis, informed by a working model of the praxissystem. In the first several studies, we provide evidence that BG has severeIM and that her gesture representations are largely intact and accessible. Inthe second set of studies, we demonstrate that BG’s gesture impairment islikely to be attributable to deficits in procedures and representations used tocode the intrinsic positions of the body in space over time.

EXPERIMENTAL STUDIES

Study 1: Gesture Production

Methods. BG was asked to produce common gestures in three conditions. In the Commandcondition, she was asked to produce 18 transitive gestures (e.g., ‘‘show me how to use ahammer’’), imagining that she was holding and using the specified tool. Tools were not insight. In the Use condition, she was permitted to actually hold and use the same set of 18tools. Finally, in the Imitation condition, she viewed a videotaped model performing 10 transi-tive gestures performed without tools and 5 intransitive gestures (e.g., waving, beckoning‘‘come here,’’ signaling ‘‘stop’’) and performed the same gestures; she was permitted to beginwhile watching the model. Gestures in all conditions were performed with both left and righthands; hand was blocked in an ABBA order.


TABLE 1BG’s Performance on Neuropsychological Tests

Neuropsychological test Score Comments

Motor FunctionFinger Tapping 45 L, 20 R T scores: L 5 55, R 5 25a

Grooved Pegboard 105″ L, 139″ R T scores: L 5 35, R 5 30a

Grip Strength 25 L, 24 R T scores: L 5 49, R 5 55a

Sensory FunctionFinger gnosis 50%L, 38%R Bilateral impairmentTactile double simult. stimulation 100%L, 100%R Normal

(hands)Visual double simult. stimulation 28% (all R misses) R extinction

LanguageReal object naming (sight) 21/22 NormalBoston Diag. Aphasia Exam

(BDAE)b

Complex ideational material 9/12 Cntl. M 5 11.2, SD 5 1.0Word reading 9/10 Cntl. M 5 8.0, SD 5 0.2Spell to dictation 12/12 Cntl. M 5 8.4, SD 5 1.4High-probability repetition 1/8 Cntl. M 5 7.9, SD 5 0.4Low-probability repetition 1/8 Cntl. M 5 7.7, SD 5 0.5

Visual/Spatial ProcessingRey–Osterrieth Complex Fig— 25/36 ,10th percentilec

CopyLetter Cancellationd Errors: 3L, 8R Impaired

MemoryNine-Item California Verbal Learn-

ing Teste

Trials 1–5 30/45 Cntl. M 5 37.1, SD 5 4.3Delay free recall 3/9 Cntl. M 5 7.1, SD 5 1.7Delay cued recall 4/9 Cntl. M 5 7.4, SD 5 1.5Recognition discriminability 94% Cntl. M 5 95.5, SD 5 4.8

Rey–Osterrieth Complex Figure— 25/36 ,10th percentilec

Immediate recallRey–Osterrieth Complex Figure— 16.5/36 ,10th percentilec

Delay recall

Executive FunctionAutomized mntl ctrl (count M 5 100% Cntl. M 5 98.7, SD 5 2.3f

backwds., alphabet, months)Nonautom. mntl ctrl (count 3’s, M 5 93% Cntl. M 5 91.1%, SD 5

months backward, rhymes, let- 10.6f

ter imagery)Trail Making Testa—Part A 58″, O errors T Score 5 40Trail Making Test—Part B 148″, O errors T Score 5 35

a Norms from Heaton, Grant, and Matthews (1991).b Goodglass and Kaplan (1983).c Lezak (1995).d Mesulam (1985).e Libon et al. (1996).f Cloud et al. (1994).


TABLE 2BG’s Performance on Tests of Praxis (Percent Correct)

Hand Grasp Traject. Amplit. Timing Total

Tool UseRight 84 89 84 83 86Left 84 95 95 83 90

Gesture to CommandRight 33 61 67 72 57Left 39 72 78 61 63

Gesture ImitationRight 33 53 73 67 57Left 40 60 73 87 65

Each gesture was initially rated for content: substitutions of recognizable gestures (e.g.,‘‘sawing’’ → ‘‘hammering’’) received ‘‘incorrect content’’ scores and were not further coded.Gestures with correct content were scored for the spatial/temporal components grasp, trajec-tory, amplitude, and timing (4 points maximum for each gesture) by two independent codersaccording to detailed criteria (see Appendix 1). Interrater agreement for content was 100%.Mean interrater agreement across all spatial/temporal gesture components was 84% (grasp84%, trajectory 85%, amplitude 87%, timing 80%). Scores for which there was disagreementwere reconciled by additional review of videotapes.

Results. BG’s errors were all spatial and/or temporal; there were no recog-nizable gesture substitutions. For example, when asked to pantomime theuse of a hammer with her right hand, she produced a rapid oscillating move-ment of the hand and forearm of low amplitude (approximately 6 inches)with a vertical trajectory and an open, flat palm. Data are shown in Table 2.A Kruskal–Wallis test performed on the 0- to 4-point scores for gestures inthe three conditions revealed a significant effect of condition (Right hand:H 5 12.2, p , .01; Left hand: H 5 12.6, p , .005). Multiple comparisonstesting (see Siegal & Castellan, 1988) demonstrated that for both hands, theUse condition was superior to both Imitation and Command conditions (dif-ferences in mean rank exceed critical value of 12.99); the latter two condi-tions did not differ from one another. As Table 2 indicates, performance wasgenerally superior in the Use condition across all spatial/temporal gesturecomponents (grasp, trajectory, amplitude, timing), with the exception of rela-tively superior left-hand timing scores in the Imitation condition. Perhapsnot surprisingly, the greatest relative improvement in the Use condition oc-curred in the grasp component, but other improvements were substantial aswell.

Discussion. BG’s deficits in both the Command and Imitation conditionsconfirm the clinical impression of a severe IM characterized by spatial andtemporal errors. Her parallel performance in both conditions indicate thaterrors in the Command condition are not attributable to language-compre-hension deficits. If one adopts the two-route model’s assumption that IMresults from deficits in gesture representation access or egress, or damage


to representations themselves, at least two questions arise from these data.First, what is the basis for the relative integrity of BG’s tool use? Second,why does she fail to use the direct route upon provision of a model to beimitated? In the next set of studies, we explore the first question; later, weturn to the second.

Improved gesture production with actual tool use is a common featureof IM, though the underlying reasons for this finding remain unclear. Onepossibility is that tool shape, size, and weight may assist selection from apool of potential gestures by excluding gestures that would be difficult toperform with that tool. A second possibility is that the visual and tactile(structural) characteristics of tools may directly activate otherwise inaccessi-ble gesture representations; i.e., structural information may trigger storedgestures in a ‘‘bottom-up’’ fashion (Pilgrim & Humphreys, 1991). Finally,deficient spatiotemporal positioning of the body (e.g., due to partially de-graded engrams or impairments in intrinsic spatial coding) may benefit fromthe cues to posture/joint angles/trajectory that a tangible object provides. InBG’s case, the substantial improvement in the grasp component of the ges-ture seen in the Use condition is suggestive of this possibility.2 In the case ofeach of these scenarios, the tool-use augments deficient (but not obliterated)gesture-related procedure or representations. In other words, adequate gestur-ing with tool in hand suggests that gesture information is at least partiallyintact.

However, there is another possible explanation for relatively intact tooluse in apraxia. On some accounts, plausible actions upon objects may betriggered directly from objects’ perceptible attributes without invokingstored gestures; i.e., the action may be driven by affordances of the objectfor certain actions (e.g., the handle of a hammer for grasping and swinging,the openings of a scissors for inserting fingers and opening/closing; see Gib-son, 1977; but see also Sirigu, Duhamel, & Poncet, 1991; and Buxbaum,Schwartz, & Carew, 1997, for discussion of the limitations of affordances).If BG’s actions with objects are triggered solely by such affordances, thenshe should perform similar, affordance-driven gestures with objects that havein common a set of affordances. To pursue this possibility, we analyzed BG’sproduction of gestures with sets of objects matched for affordances.

Study 2: Gesturing with Objects Matched for Affordances

Methods. BG was asked to demonstrate gestures with eight pairs of affordance-matchedobjects with objects in her dominant (left) hand. The matched object pairs were rubber band–hair elastic, pencil (unsharpened)–chopstick, foundation makeup (label removed)–mouthwash

2 Sirigu, Cohen, Duhamel, Pillon, Dubois, and Agid (1995) reported a patient with isolatedimpairments in positioning of the hand with respect to objects; when the hand posture wascorrected by the examiner, other aspects of the gesture improved to normal. Unlike that subject,BG’s gesture trajectories and timing were impaired on some trials even when her hand posturewas correct.


(label removed), hairbrush–scrub-brush, birthday candle–cigarette, baseball–orange, decora-tive hair comb–regular comb, magic marker–lipstick, and aftershave (label removed)–nailpol-ish remover (label removed).

Results. BG performed perfectly with 15/16 (94%) of the objects, demon-strating the correct grasp, use, and placement of each. She erred with thecandle, whose wick she pinched repeatedly while saying, ‘‘you light this.’’

Discussion. BG’s nearly perfect performance with objects matched foraffordances indicates that she does not rely solely on information given byobject weight, shape, and texture in producing gesture. Instead, the data sug-gest that the motor system is able to access the specific stored gesture infor-mation relevant to distinct objects. These data do not speak to whether tools‘‘cue’’ gesture selection by narrowing the range of candidate gesture repre-sentations, directly trigger activation of otherwise inaccessible representa-tions via structural object properties (Pilgrim & Humphreys, 1991), or guidespatiotemporal positioning of the body, but we provide additional evidencerelevant to this question below.

On the two-route model of praxis, relatively intact tool use in the contextof severely deficient imitation suggests severe degradation of the input praxi-con or disconnection of praxicons from visual input. In either case, BGshould be severely deficient in gesture recognition. If, on the other hand,the deficit is external to the stored gesture representation system, gesturerecognition should be relatively intact. We assessed these competing possi-bilities next.

Study 3: Gesture Recognition

Methods. In the Tool Match condition, BG performed a modified version of the Gestureto Object Matching task from the Florida Apraxia Battery (Gonzalez Rothi, Raymer, Ochipa,Maher, Greenwald, & Heilman, 1991). She was asked to view 17 pantomimed gestures onvideotape and to match the gesture with a drawing of an appropriate tool from an array offour tools. One of the three tool ‘‘foils’’ in the array was visually and semantically similarto the target (e.g., target: paintbrush; foil: hairbrush), the second was functionally associatedwith the target (e.g., target: paintbrush; foil: paint can), and the third was associated with avisually similar gesture (e.g., target: paintbrush; foil: hammer). In the Tool-Use Decision Con-dition, BG was asked to make ‘‘correct’’ vs ‘‘incorrect’’ decisions for 30 videotaped gesturesperformed with tools, 20 of which were incorrect. Incorrect gestures were performed witherrors of grasp, trajectory, amplitude, and/or timing. Objects were not named by the examinerin this or the preceding condition. In the Pantomime Decision condition, she similarly made‘‘incorrect’’ vs ‘‘correct’’ decisions for videotaped gestures; in this condition, however, thegestures were pantomimed without tools. There were 50 pantomimes, 20 of which were per-formed incorrectly. Incorrect gestures were spatial in nature and were qualitatively similar tothose of the Tool-Use Decision condition.

Results. In the Tool Match condition, BG matched 15/17 (88%) of gesturesto tools. In the Tool-Use Decision condition, she appropriately made 25/30 (83%) ‘‘correct’’ vs ‘‘incorrect’’ decisions about gestures with tools. Incontrast, she performed poorly in the Pantomime Decision condition, makingonly 21/50 (42%) accurate decisions. Nineteen of her 29 errors were failures


to recognize correct gestures and the remaining 10 errors were failures todetect incorrect gestures. Her performance in this condition was at chanceand significantly more impaired than in the other two conditions (Tool Matchvs Pantomime Decision: χ2 5 10.9, Fisher’s Exact p 5 .0015; Tool-UseDecision vs Pantomime Decision: χ2 5 13.1, Fisher’s Exact p 5 .0004).

Discussion. Results of the Tool Match and Tool-Use Decision conditionsindicate that BG can recognize gestures when they are performed with toolsor can be associated with tools through a matching procedure. On the two-route model, these data indicate that BG’s input praxicon, while perhaps notperfectly normal, is largely intact and accessible to visual input. Recall thatthe results of Studies 1 and 2 suggest that the praxicon(s) can access motorsystems (at least when tools are used). Taken together, these data raise ques-tions about the reasons for BG’s failures in gesture pantomime and imitationand in gesture recognition without tool context information.

There are at least two explanations for the pattern of BG’s performance.One possibility is that degradation of the gesture praxicon(s) is sufficientlymild or moderate that it solely affects tasks in which tool context informationis not provided. On this account, one would have to accept the possibilitythat the presence of tool context information explains the striking disparitybetween BG’s severely impaired gesture pantomime and her very mildlyimpaired gesture with tool in hand. Another possibility is that the impairmentis external to the stored gesture representation system. On the latter account,it might be suggested that BG imperfectly codes dynamic body part positionsand that this deficit affects all tasks relevant to the ability to position bodyparts in space over time or to appreciate such positioning in others. We mayspeculate that when tools are used with the gesture to be recognized or imi-tated, knowledge of the characteristic trajectory and amplitude of tool move-ment (e.g., hammers swing up and down in an arc) may provide a form of‘‘top-down’’ feedback to processes encoding the dynamic body positions ofthe actor.

Fortunately, the two accounts make differential predictions about the per-formance expected in meaningful as compared to meaningless gesture tasks.If impairments are due to deficits within the lexical route, performanceshould be superior with meaningless movements, as these are performed viathe direct route and do not engage the putatively damaged system. If impair-ments are external to the lexical system, performance should be superior withmeaningful gesture tasks, as these take advantage of the relative integrity ofstored gesture representations. We assessed these competing possibilities inStudy 4.

Study 4: Imitation of Meaningless Gesture Analogs

Methods. Fifteen meaningless gesturelike movements were created with reference to thegestures assessed in the Imitation condition of Study 1. For each meaningful gesture, the planeof movement (vertical/horizontal), joints moved (shoulder/elbow/wrist/fingers), grip type


(hand open/clenched/partially open), and oscillations (present/absent) were tabulated. As canbe seen in Appendix 1, meaningless analogs preserved the characteristics of the meaningfulgesture with respect to these attributes. For example, the ‘‘hitchhiking’’ gesture assessed inStudy 1 is a vertical motion with greatest movement at the elbow, the hand is partially open(the thumb is extended), and there are oscillations. The meaningless analog of the hitchhikinggesture similarly entailed a vertical motion with greatest movement at the elbow, the handwas partially open (the fifth finger was extended), and there were oscillations. BG viewed avideotape of a model performing each movement with her right hand and was required toreproduce the movement as precisely as possible. She was permitted to perform during herobservation of the model; there was thus no memory requirement. Right- and left-hand perfor-mance was blocked by ABBA design.

A healthy 62-year-old female control subject was also assessed with this procedure as wellas with the procedure used in the Imitation condition of Study 1 above (meaningful gestureimitation). BG’s productions were scored individually by two coders with the 4-point scaleused in Study 1 (see Appendix 2). Percentage agreement averaged across all spatial/temporalgesture components was 76% (grasp 5 84%, trajectory 5 79%, amplitude 5 73%, timing 568%). Gestures about which there was disagreement were reconciled through review of video-tapes. The control data were scored by a single coder.

Results. The control subject was near ceiling in both Meaningful andMeaningless Imitation conditions [Meaningful: R 5 96% (58/60), L 5 94%(56/60); Meaningless: R 5 94% (56/60), L 5 95%(57/60)].

BG was profoundly impaired in imitating meaningless analogs (R 5 42%,L 5 30%) and performed even more poorly than in imitating the meaningfulgestures of Study 1 (Meaningless imitation R hand: grasp 5 53%, trajec-tory 5 20%, amplitude 5 47%, timing 5 47%; Meaningless imitation Lhand: grasp 5 40%, trajectory 5 33%, amplitude 5 33%, timing 5 13%).An ANOVA with the factors Hand (left, right) and Imitation Condition(Meaningful, Meaningless) revealed a significant effect of condition suchthat meaningful gestures were performed better than meaningless gestures[F(1, 56) 5 9.9, p , .005], no effect of hand (p 5 .8), and no condition byhand interaction (p 5 .21).

Discussion. When gesture information is absent, BG is particularly defi-cient in positioning both her left and right hands and arms in space overtime to match the positioning of another person’s body. For BG, but not fora control subject, stored gesture information confers a processing advantagein on-line imitation. The relative superiority of meaningful gestures is moresubtle with the right than left hand, but as judged by the absence of an interac-tion in the ANOVA, is present for both hands. This pattern is entirely incon-sistent with a deficit within the praxicon system, as such a deficit shouldresult in relatively greater impairment for learned gestures dependent upona stored representation. Instead, the findings support the predictions of amodel positing that the deficit(s) causing BG’s apraxia are largely externalto the stored gesture system.

In this context, it is noteworthy that a recent investigation by Goldenberg(1995) demonstrated that nearly half of the left-hemisphere aphasic patientsassessed were impaired on meaningless posture-imitation tasks. Impairedsubjects also performed deficiently when asked to pose a mannequin to match


a given hand posture. Based on this, as well as on subsequent studies (e.g.,1997), Goldenberg has suggested that subjects were deficient in appre-hending the movement and configuration of body parts in general, based ondeficient ‘‘conceptual knowledge’’ of the human body. A different accountis suggested by investigators studying childhood autism, who have proposedthat impairments in novel gesture imitation may reflect difficulty in spatiallytransforming the child’s view of another’s action into a matching action onthe self (Barresi & Moore, 1996; Smith, 1998). The present account appearsto be closely aligned with the latter perspective.

However, it remains possible that the deficient representation is conceptual(i.e., semantic), as Goldenberg (1995) has suggested. Deficits in a semanticor propositional representation of the relationship of body parts to one an-other should not be affected by the spatial attributes of movements that sub-jects are required to recognize or imitate. Thus, for example, the ability toencode the fact that the hand rests ‘‘above’’ the eye in a ‘‘saluting’’ gestureshould not be affected by whether a salute to be recognized or imitated isviewed from a head-on or side view.

Conversely, if the difficulty lies in encoding the precise spatial relation-ships of body parts, then spatial characteristics of the stimuli, such as viewingangle, should affect performance. We assessed this in the next study, inwhich BG was asked to make same/different decisions about gestures whenviewed from differing angles. It should be noted that this task bears resem-blance to the body-position matching task used by Reed and Farah (1995)to assess the body schema.

Study 5: Gesture Matching—Effect of Viewing Angle

Methods. BG was asked to decide whether pairs of pantomimed movements presented onvideotape were the ‘‘same’’ or a ‘‘different’’ gesture. In half the trials, the two movementswere the same meaningful or meaningless gesture; in the remaining trials the second movementof each pair differed in its spatial characteristics (amplitude or trajectory, e.g., key-use panto-mimed with a large vertical rather than circular trajectory of the wrist). There were two condi-tions with 40 pairs each. In the Same View condition, movement pairs were filmed fromidentical viewing angles. In the Rotated View condition, the second movement of each pairwas filmed at an angle 90° from the first. Half the movements in each condition were meaning-ful gestures, and half were the same meaningless gesture analogs assessed in Study 4. Eachgesture was performed for approximately 5 s; there was approximately a 1-second delay be-tween gestures in a pair. For both meaningful and meaningless gestures, Same View andRotated View Conditions were blocked and presented in ABBA order. A 62-year-old femalecontrol subject was assessed on the meaningful conditions only.

Results. BG’s performance in the Same View condition was significantlybetter than in the Rotated View condition (35/40 vs 28/40; χ2 5 3.6, p 5.05). This pattern of results was present for both meaningful gestures (SameView: 18/20, 90%; Rotated View 14/20, 70%) and meaningless gestures(Same View: 17/20, 85%; Rotated View:14/20, 70%). Several errors in theRotated View condition were incorrect rejections of ‘‘same’’ movements,


while others were failure to detect ‘‘different’’ movements. For example,BG failed to detect that pantomimed cutting with scissors in a single lineartrajectory differed from cutting in multiple radial trajectories. The controlsubject performed perfectly in both conditions.

Discussion. BG’s performance in the Same View conditions indicates thatshe was able to comply with the demands of the task, including the require-ment to hold body positions in memory. Her imperfect performance in thiscondition may be suggestive of some degree of difficulty in coding or main-taining body position information. Stronger evidence, however, comes fromBG’s relatively impaired performance in the Rotated View condition, inwhich she had to match gestures across a shift in perspective. The fact thatBG performs particularly poorly when a spatial transformation of the bodyis required suggests that the representation underlying her deficient apprecia-tion of others’ bodies is spatial rather than conceptual (semantic) in nature.Below, in Study 7, we provide further evidence supporting this conclusion.

Although the data to this point are consistent with deficits in a spatiomotorbody representation, an additional possibility is that BG suffers a generaldeficit in spatial rotation or transformation which affects numerous classesof objects, bodies included. We assessed this possibility next.

Study 6: Object Matching—Effect of Viewing Angle

Methods. BG was given our laboratory’s Matching Across View Shifts Test. She was re-quired to match a reference photograph of a familiar object in a standard view to a targetphotograph. The target was presented in an array with two distractors. In 1/3 of the 72 trialsthe reference photo is an object in a standard view, in 1/3 an atypical view, and in 1/3 anodd view. The latter two conditions require a mental rotation. Normal controls perform thistask at ceiling.

Results. BG performed correctly on 24/24 (100%) of standard view, 23/24 (96%) of atypical view, and 22/24 (92%) of odd view trials. Her perfor-mance in the object-matching condition not requiring rotation (standardview) was equivalent to her performance in the Same View condition of thegesture-matching study reported above (χ2 5 2.2, p 5 .2), indicating thatthese baseline matching tasks were approximately equally difficult for BG.In contrast, her performance in the conditions of the object-matching studyrequiring rotation (atypical and odd views) is superior to the Rotated Viewcondition of the gesture-matching study reported above (χ2 . 6.9, p , .01for both comparisons). These data provide support for the hypothesis thatBG has a specific deficit in spatially transforming body (but not object) infor-mation.

It remains possible that BG’s specific deficits in transformation of bodyinformation reflect problems in rotating and manipulating a visual, ratherthan spatiomotor, image of the body. In that case, it would be inaccurate tocharacterize the deficient representation as spatiomotor in the sense impliedby accounts of the body schema. To assess this, we asked BG to perform a


FIG. 3. BG’s performance on the mental hand rotation task of Study 7.

variant of the task developed by Persons and colleagues (1994) mentionedearlier, which demonstrated that decisions about hand laterality are made bymentally rotating one’s own motor hand image. The investigators asked con-trol subjects to make decisions about whether drawings depicted left or righthands while they maintained their own hands, out of sight, in prespecifiedpositions. Subjects’ responses were fastest when there was congruence be-tween their own hand positions and those depicted. Furthermore, the patternof response latencies suggested that subjects were rotating a ‘‘motor image’’of their own hands through the same trajectory that would be used in a realmovement: Systematic discontinuities in latency occurred when subjectswould have had to rotate their own hand-image in a biomechanically impos-sible manner. BG performed an easier variant of this task, assessing accuracy(but not latency) of left/right decisions to hand-stimuli that were congruentor incongruent with her own hand positions.

Study 7: Mental Body Rotation (Motor Imagery)

Methods. BG and a 62-year-old female control were asked to identify whether a photographdepicted a left or right hand. Ninety-six photos of hands were presented, half in palm-up andhalf in palm-down views. All stimuli were in canonical position with fingers pointing awayfrom the subject. The subjects’ own hands, covered with a dark cloth, were positioned palm-up on 48 trials and palm-down on 48 trials. Thus, subjects’ hand positions were congruentwith stimuli on half the trials. Subjects were not permitted to move their hands. Subjects’hand position was blocked, and blocks were performed in ABBA order (see Coslett, 1998,for details of the task).

Results. As shown in Fig. 3, with her own hands positioned palms down,BG was correct on 20/24 (83%) of palm-down and only 7/24 (29%) of palm-up pictures; with her own hands positioned palms up, she was correct on23/24 (95%) of palm-up and only 17/24 (70%) of palm-down pictures (Total


on ‘‘congruent’’ trials 5 89%; Total on ‘‘incongruent’’ trials 5 50%; χ2 517.8, p , .0001). She also tended to be less accurate in discriminating pic-tures of right hands (30/48; 62%) than left hands (37/48; 77%), though thedifference did not reach significance (p 5 .12). The control subject per-formed equally accurately in congruent and incongruent trials [Total on‘‘congruent’’ trials 5 46/48 (96%); Total on ‘‘incongruent’’ trials 5 45/48(94%)].

Discussion. BG, but not a control subject, is significantly more accuratein making left/right decisions about hands in ‘‘congruent’’ trials in whichshe does not have to perform a mental rotation to align her own internalhand-image with the stimuli. Data from the behavioral studies of Parsons etal. (1987, 1994) and the PET study of Kosslyn et al. (1998), described above,suggest that the present task is performed by rotating a motor image of thehand. BG’s inability to perform motor rotations supports the findings ofStudy 6 in suggesting that she is deficient in the dynamic spatiomotor repre-sentation of the body supporting such motor imagery; i.e., the body schema.

There is one final question relevant to the nature of the procedures and/or representations disrupted in BG. Several accounts of the body schemapropose that as it represents information about the position and extent of thehuman body, it underlies the ability to position the body in space to interactwith objects in the environment; that is, to perform so called ‘‘extrinsic’’egocentric spatial coding. Inconsistent with this, clinical observations of BGwere not suggestive of optic ataxia (misreaching under visual guidance). Wefurther explored BG’s ability to position her hand with respect to objects ina final study.

Study 8: Hand-in-Slot Test

Methods. BG was assessed with a variant of a task described by Goodale, Milner, andcolleagues (Goodale, Milner, Jacobson, & Carey, 1991; Milner et al., 1991) in which she wasrequired to position her hand with respect to a large slot displayed in a number of differentorientations. A 12 3 4-cm slot in a round disk 56 cm in diameter was presented 40 cm fromthe chest wall. On each trial, the slot was oriented horizontally, vertically, 45° left, or 45°right. BG was required to begin each trial with her hand palm-down on a tabletop and, upona ‘‘go’’ signal, to reach her hand through the slot as accurately as possible. There were fivetrials with each hand in each of the four slot orientations presented in random order. Handposition relative to the slot was videotaped with a head-on camera and later coded from thevideotape. Any contact of the edges of the slot by the hand was coded as an error.

Results. BG performed perfectly accurately with both hands. There wereno trials on which the hand contacted the edge of the slot.

Discussion. The hand-in-slot task requires coding of an object in the envi-ronment with respect to the body, a form of spatial coding usually referred toas ‘‘egocentric.’’ There is evidence that patients with optic ataxia, a parietaldisorder of misreaching, are impaired in the forms of egocentric codingneeded to direct the hand to object locations (see Buxbaum & Coslett, 1997,1998b). But BG exhibits optic ataxia neither on clinical testing nor in the


present study. This suggests that extrinsic egocentric spatial coding is intact,at least for spatial positions near midline.3 The evidence for impaired intrinsicspatial coding of dynamic body position presented above is of particularinterest in this context, as it suggests that while both intrinsic body-part posi-tion coding and egocentric coding of object location may rely (to a greater orlesser degree) on an implicit internal model of the body, they are neverthelessdissociable.

GENERAL DISCUSSION

We have presented data from a primary progressive apraxic woman whichcannot be accommodated by the ‘‘two-route’’ account of IM (GonzalezRothi et al., 1991) without additional assumptions. BG is unable to gestureto command or imitation, but performs relatively well with tool in hand.Study 2 indicated that her relatively accurate performance with tools can notbe attributed to object affordances, suggesting that gesture representationsare largely intact and accessible to motor output. Study 3 demonstrated thatshe recognizes gestures well when contextual tool information is provided,indicating that (at least under these circumstances) gesture representationscan be accessed by visual input. Study 4 indicated that BG is more deficientin imitating meaningless gesturelike movements than spatially matchedmeaningful gesture analogs, supporting the conclusion that gesture represen-tations are relatively intact and may provide a form of ‘‘top-down’’ supportto deficient processes external to the stored gesture system. Studies 5–7 at-tempted to elucidate the nature of the deficient representations and/orprocesses and showed that BG has difficulty in matching gestures (but notobjects), particularly when a spatial transformation is required, and in per-forming mental motor transformations to assess the positions of body-partstimuli. These suggest that the deficient processes are not conceptual or vi-sual, but spatiomotor in nature.

Proponents of the dual-route model might attempt to suggest that BG (andother similar patients) suffer deficits in both lexical and direct gesture routes.The deficits in gesture pantomime, meaningful imitation, and some recogni-tion tasks, it might be argued, are attributable to some combination of dam-age to input and output gesture representations. The severe deficits in mean-ingless imitation, as well as the other difficulties with body-position encodingdemonstrated in Studies 4–7, are due to an additional severe deficit in theprocedures and representations of the direct route. However, this argumentfails to satisfactorily explain the significant disparity between BG’s severelyimpaired gesture pantomime and near-normal performance on gestures withtool in hand, the integrity of her performance on recognition tasks with tools,

3 Note that on some accounts BG’s mild right neglect is attributable to a deficit in egocentriccoding for positions in the right hemispace (see, e.g., Buxbaum & Coslett, 1994).


FIG. 4. A schematic of the praxis system explicitly incorporating a dynamic body schemawhich participates in both meaningful and meaningless gesture processing.

or the superiority of her meaningful as compared to meaningless imitation.Alternatively, it might be suggested that BG suffers deficits at the level ofthe ‘‘innervatory patterns’’ that form the final common pathway for both thedirect and lexical routes. However, a deficit at this level would not explainBG’s impaired recognition of gestures pantomimed without tools or the rela-tive superiority of meaningful as compared to meaningless gestures. The datafrom BG, then, suggest that the dual-route account requires modification oraugmentation.

Taken together, the evidence suggests that BG’s deficits in gesture panto-mime, recognition, and imitation result primarily not from gesture represen-tation integrity, access, or egress, but from deficits in dynamic coding of theintrinsic positions of the body parts of self and others. Figure 4 provides aschematic of a model of the praxis system incorporating this dynamic repre-sentation. Note that this representation, which we have termed the ‘‘bodyschema’’ in agreement with other contemporary investigators (e.g., Parsons,1994) is the substrate for both the ‘‘lexical’’ and ‘‘direct’’ routes in that itinstantiates the procedures used to calculate and update the dynamic posi-tions of the body parts relative to one another in all contexts; the ‘‘lexical’’route differs only in the availability of augmentative support from storedrepresentations.

We might speculate that the stored portion of the gesture representationcontains only the information critical in distinguishing one particular learnedmovement from another, whereas procedures computed on-line add informa-tion about particular joint angles, hand aperture, and orientation, i.e., thefeatures that render a given gesture precisely appropriate for a particularcontext. For example, the stored portion of a ‘‘hammering’’ gesture might


include a broad oscillating movement at the elbow joint and a hand grip inthe ‘‘clench’’ position, whereas the ‘‘flexible’’ features derived on-line inresponse to the environment might include shoulder angle (appropriate forhammering on a vertical vs horizontal surface), oscillation amplitude andfrequency (appropriate for driving a large vs small nail), and clench size(appropriate for holding a large vs small hammer). The on-line computationsmay constitute the procedures and routines (‘‘schemas’’) that form the build-ing blocks of learned gesture. Note that dynamic information about the posi-tion of body parts relative to one another remains the substrate for both thestored (‘‘lexical’’) and on-line (‘‘nonlexical’’) features of the gesture. Inother words, the critical assumption is that output to the motor system isembedded in intrinsic spatial coordinates defined by the body schema. Inthis model, then, the procedures involved in intrinsic spatial coding of thebody positions of self and others should not be viewed merely as an elabora-tion of the direct route.

In gesture-imitation and -comprehension tasks, specification of the actionsof self and others in a common system of body-centered coordinates de-creases the computational demand on spatial transformation procedures(Mussa Ivaldi, Morasso, & Zaccaria, 1988; Morasso & Sanguineti, 1995).In movement production tasks, accurate specification of the dynamic relativepositions of body parts is essential when extrinsic egocentric coding (i.e.,coding of positions of body parts with respect to objects in the environment)cannot be used, as is the case in gesture pantomime tasks performed withoutobjects. Thus, BG’s deficits in intrinsic spatial coding affect all tasks requir-ing the relative positioning of body parts in space over time or recognizingthe body positions of others. Because the system is interactive, support fromstored tool and/or gestural information may augment the deficient body posi-tion coding, explaining BG’s relatively good performance on production,recognition, and imitation tasks in which such information is available.

The language-based model of two distinct routes to praxis, while clearlyexplaining many forms of IM, cannot readily accommodate the pattern ex-hibited by BG because it does not consider the strong intrinsic relationshipof ‘‘lexical’’ and ‘‘nonlexical’’ gesture representations. Contrary to the pre-dictions of an account positing that deficits in IM necessarily stem from theintegrity or accessibility of input and/or output gesture representations, themodel clearly predicts that at least one subtype of IM patients will performbetter in gesture production and in recognizing others’ gestures with toolsthan without and better in imitating meaningful as compared to meaninglessgestures.4 Because the relationship of meaningful and meaningless gesture

4 We believe that there are indeed IM patients for whom gesture representation integrity oraccessibility is deficient. For such patients, however, there should be diminished evidence of‘‘top-down’’ support from stored representations, such that meaningful gestures are as im-paired as meaningful gestures.


imitation distinguishes apraxia attributable to a deficit in stored gesture ac-cess or integrity from that attributable to impairment in the ‘‘body schema’’as we have used the term here, meaningless gesture imitation is an importantcomponent of the apraxia evaluation.

Finally, given the SPECT scan evidence that the superior posterior parietallobes are involved in patient BG, it is of note that according to Morasso andSanguineti (1995), a likely site for the body schema is the posterior parietalcortex (PPC), and in particular, the superior PPC area 5. Area 5 is an areaof confluence between somatosensory cortex (areas 1, 2, and 3), motor cortex(areas 4 and 6), and other areas of the PPC (area 7) involved in integratingexternal (egocentric) space and subcortical and spinal circuits; thus, it pro-cesses a number of peripheral and centrally generated inputs and is poten-tially able to synthesize these various inputs in active movements. Area 5is also activated in anticipation of movement (Crammond & Kalaska, 1989)and is insensitive to load variations (Kalaska, Cohen, Prud’homme, & Hyde,1990), suggesting that it codes the kinematic aspects of movement. Thesefeatures of area 5 have been characterized as ‘‘ideal’’ for a motor planningsubsystem that relies on a continually updated internal body schema (Mo-rasso & Sanguineti, 1995). Notably, patients with corticobasal degenerationand Pick’s disease, two diagnoses under consideration for BG, have frequentinvolvement of the superior parietal lobes (e.g., Dick, Snowden, Northen,Goulding, & Neary, 1989; Fukui, Sugita, Kawamura, Shiota, & Nakano,1996; Piccirilli, D’Alessandro, & Ferroni, 1990). This predicts that IM pa-tients with superior parietal involvement should exhibit patterns of perfor-mance on meaningful and meaningless gesture tasks consistent with impair-ment of the body schema as we have outlined it here, and thus similar tothe pattern demonstrated by BG.

BODY SCHEMA AND PRAXIS 187A

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APPENDIX 2

Praxis Scoring Guidelines

Gestures are scored dichotomously (correct/incorrect) in five categories:1. Content

Score as ‘‘0’’ only if another recognizable gesture is substituted fortarget gesture (e.g., substitution of hammer for saw). If content is scored‘‘0,’’ remaining four categories are not scored.If subject receives ‘‘1’’ for content, score on the following.

2. Hand PostureScore as ‘‘0’’ if hand posture/grasp is unrecognizable, flagrantly incor-

rect, or only transiently correct (small fragment of total gesture with correctposture or grasp). Score ‘‘0’’ for ‘‘body part as object’’ (BPO) errors.

Score as ‘‘1’’ if posture is correct or subtly incorrect (e.g., hand apertureslightly too big or small; wrist angle slightly incorrect).

3. Arm Posture/TrajectoryScore as ‘‘0’’ if arm posture and/or trajectory [e.g., joint angles, plane

of movement relative to body/environment (e.g., side to side instead of backand forth)], shape of movement (e.g., circular instead of linear) are flagrantlyincorrect or only transiently correct (small fragment of total gesture withcorrect posture).

Score as ‘‘1’’ if both arm posture and trajectory are correct or if armposture and/or trajectory are subtly incorrect (e.g., elbow slightly too bent;trajectory at slight angle relative to what is appropriate; shape of movementslightly distorted.

4. AmplitudeScore as ‘‘0’’ if size of movement is clearly too large or too small (e.g.,

‘‘sawing’’ with small ‘‘scratching’’ movement) or if size is only transientlycorrect (e.g., small fragment of total gesture with correct amplitude).

Score as ‘‘1’’ if size is correct or subtly too large or too small (e.g.,slight ‘‘overshoot’’ or ‘‘undershoot’’ in movement amplitude).

5. Timing/FrequencyScore as ‘‘0’’ if speed of movement is flagrantly too fast or slow and/

or if number of cycles of movement is flagrantly too few or many (e.g.,‘‘flipping’’ coin four times in succession; ‘‘scissoring’’ only once).

Score as ‘‘1’’ if speed of movement is subtly too fast or slow and/orif frequency is subtly inappropriate (e.g., flipping coin twice; scissoring onlytwice).


REFERENCES

Barresi, J., & Moore, C. (1996). Intentional relations and social understanding. Behavioraland Brain Science, 19, 107–154.

Benton, A., & Sivan, A. B. (1993). Disturbances of the body schema. In K. M. Heilman &E. Valenstein (Eds.), Clinical neuropsychology. Oxford: Oxford Univ. Press.

Bonda, E., Frey, S., & Petrides, M. (1996). Evidence for a dorso-medial parietal system in-volved in mental transformations of the body. Journal of Neurophysiology, 76, 2042–2048.

Buxbaum, L. J., & Coslett, H. B. (1994). Neglect of chimeric figures: Two halves are betterthan a whole. Neuropsychologia, 32, 275–288.

Buxbaum, L. J., & Coslett, H. B. (1997). Subtypes of optic ataxia: Reframing the disconnectionaccount. Neurocase, 3, 159–166.

Buxbaum, L. J., & Coslett, H. B. (1998a.) Evidence for selective impairments of body-partstructural descriptions in autotopagnosia. Journal of the International Neuropsychologi-cal Society, 4(1). [abstract]

Buxbaum, L. J., & Coslett, H. B. (1998b). Spatio-motor representations in reaching: Evidencefor subtypes of optic ataxia. Cognitive Neuropsychology, 15(3), 279–312.

Buxbaum, L. J., & Coslett, H. B. (in press). Specialized structural descriptions for humanbody parts: Evidence from autotopagnosia. Cognitive Neuropsychology.

Buxbaum, L. J., Schwartz, M. F., & Carew, T. G. (1997). The role of semantic memory inobject use. Cognitive Neuropsychology, 14, 219–254.

Cloud, B. S., Swenson, R., Malamut, B. L., Kaplan, E., Sands, L. P., Gitlin, H. L., & Libon,D. J. (1994). The Boston revision of the Wechsler Memory Scale—Mental control sub-test. Journal of the International Neuropsychological Society, 1, 354.

Coslett, H. B. (1998). Evidence for a disturbance of the body schema in neglect. Brain andCognition, 37(3), 527–544.

Crammond, D. L., & Kalaska, J. F. (1989). Neuronal activity in primate parietal cortex area 5varies with intended movement direction during an instructed-delay period. ExperimentalBrain Research, 76(2), 458–462.

De Renzi, E., Motti, F., & Nichelli, P. (1980). Imitating gestures: A quantitative approach toideomotor apraxia. Archives of Neurology, 37, 6–10.

Dick, J. P. R., Snowden, J., Northen, B., Goulding, P. J., & Neary, D. (1989). Slowly progres-sive apraxia. Behavioral Neurology, 2, 101–114.

Fukui, T., Sugita, K., Kawamura, M., Shiota, J., & Nakano, I. (1996). Primary progressiveapraxia in Pick’s disease: A clinicopathologic study. Neurology, 47, 467–473.

Gallese, V., Fadiga, L., Fogassi, L., & Rizzolati, G. (1996). Action recognition in the premotorcortex. Brain, 119(2), 593–609.

Gibson, J. J. (1977). The Theory of Affordances. In R. Shaw & J. Bransford (Eds.). Perceiving,acting, and knowing: Toward an ecological psychology. Hillsdale, NJ: Erlbaum.

Gold, M., Adair, J. C., Jacobs, D. H., & Heilman, K. M. (1995). Right–left confusion inGerstmann’s Syndrome: A model of body centered spatial orientation. Cortex, 31, 267–283.

Goldenberg, G. (1995). Imitating gestures and manipulating a mannikin—The representationof the human body in ideomotor apraxia. Neuropsychologia, 33(1), 63–72.

Goldenberg, G., & Hagmann, S. (1997). The meaning of meaningless gestures: A study ofvisuo-imitative apraxia. Neuropsychologia 35, 333–341.


Gonzalez Rothi, L. J., Ochipa, C., & Heilman, K. M. (1991). A cognitive neuropsychologicalmodel of limb apraxia. Cognitive Neuropsychology, 8(6), 443–458.

Gonzalez Rothi, L. J., Raymer, A. M., Ochipa, C., Maher, L. M., Greenwald, M. L., & Heil-man, K. M. (1991). Florida Apraxia Battery: Experimental edition.

Goodale, M. A. (1993). Visual pathways supporting perception and action in the primate cere-bral cortex. Current Opinions in Neurobiology, 3, 578–585.

Goodale, M. A., Milner, A. D., Jakobson, L. S., & Carey, D. P. (1991). A neurological dissocia-tion between perceiving objects and grasping them. Nature, 349, 154–156.

Goodglass, H., & Kaplan, E. (1983). The assessment of aphasia and related disorders, 2nded. Philadelphia, PA: Lea & Febiger.

Gurfinkel, V. S., & Levik, Y. S. (1998). Reference systems and interpretation of proprioceptivesignals. Human Physiology, 24(1), 46–55.

Head, H., & Holmes, G. (1911/1912). Sensory disturbances from cerebral lesions. Brain, 34,102–254.

Heaton, R. K., Grant, I., & Matthews, C. G. (1991). Comprehensive norms for an expandedHalstead-Reitan Battery. Odessa, FL: Psychological Assessment Resources.

Heilman, K. M., & Gonzalez Rothi, L. J. (1993). Apraxia In K. M. Heilman & E. Valenstein(Eds.), Clinical neuropsychology (3rd ed., pp. 141–150). New York: Oxford Univ. Press.

Heilman, K. M., Gonzalez Rothi, L., Mack, L., Feinberg, T., & Watson, R. T. (1986). Apraxiaafter a superior parietal lesion. Cortex, 22, 141–150.

Humphreys, G. W., & Riddoch, M. J. (1984). Routes to object constancy: Implications fromneurological impairments of object constancy. Quarterly Journal of Experimental Psy-chology A, 36, 385–415.

Jeannerod, M. (1999). To act or not to act: Perspectives on the representation of actions.Quarterly Journal of Experimental Psychology A, 52, 1–29.

Jeannerod, M., Arbib, M. A., Rizzolatti, G., & Sakata, H. (1995). Grasping objects-the corticalmechanisms of visuomotor transformation. Trends in Neuroscience, 18, 314–320.

Kalaska, J. F., Cohen, D. A., Prud’homme, M., & Hyde, M. L. (1990). Parietal area 5 neuronalactivity encodes movement kinematics, not movement dynamics. Experimental BrainResearch, 80(2), 351–364.

Kimura, D. (1977). Acquisitions of a motor skill after left-hemisphere brain damage. Brain,100, 527–542.

Kimura, D., & Archibald, Y. (1974). Motor functions of the left hemisphere. Brain, 97, 337–350.

Kosslyn, S. M., Digirolamo, G. J., Thompson, W. L., & Alpert, N. M. (1998). Mental rotationof objects versus hands: Neural mechanisms revealed by positron emission tomography.Psychophysiology, 35, 151–161.

Lezak, M. D. (1995). Neuropsychological assessment, 3rd ed. Oxford: Oxford Univ. Press.

Libon, D. J., Mattson, R. E., Glosser, G., Kaplan, E., Malamut, B. L., Sands, L. P., Swen-son, R., & Cloud, B. S. (1996). A nine word dementia version of the California VerbalLearning Test. The Clinical Neuropsychologist, 10, 237–244.

Liepmann, H., & Maas, O. (1907). Fall von linksseitiger agraphie und apraxis bei rechtsseitigerlahmung. Journal Fur Psychologie Und Neurologie, 10, 214–227.

Mesulam, M. M. (1985). Principles of behavioral neurology. Philadelphia: Davis Press.

Milner, A. D. Perrett, D. I., Johnston, R. S., Benson, P. J., Jordan, T. R., Heeley, D. W.,Bettucci, D., Mortara, F., Mutani, R., Terazzi, E., & Davidson, D. L. W. (1991). Percep-tion and action in ‘visual form agnosia’. Brain, 114, 405–428.


Morasso, P., & Sanguineti, V. (1995). Self-organizing body schema for motor planning. Jour-nal of Motor Behavior, 27(1), 52–66.

Mussa Ivaldi, F. A., Morasso, P., & Zaccaria, R. (1988). Kinematic networks: A distributedmodel for representing and regularizing motor redundancy. Biological Cybernetics, 60(1),1–16.

Nelson, H. E., & O’Connell, A. (1978). Dementia: The estimation of premorbid intelligencelevels using the new adult reading test. Cortex, 14(2), 234–244.

Ochipa, C., Rothi, L. J. G., & Heilman, K. M. (1990). Conduction apraxia. Journal of Clinicaland Experimental Neuropsychology, 12, 89.

Ogden, J. (1985). Autotopagnosia. Brain, 108, 1009–1022.Parsons, L. M. (1994). Temporal and kinematic properties of motor behavior reflected in men-

tally simulated action. Journal of Experimental Psychology: Human Perception and Per-formance. 20(4), 709–730.

Parsons, L. M. (1987). Imagined spatial transformations of one’s hands and feet. CognitivePsychology, 19, 178–241.

Piccirilli, M., D’Alessandro, P., & Ferroni, A. (1990). Slowly progressive apraxia withoutdementia. Dementia, 1, 222–224.

Pieczuro, A., & Vignolo, L. A. (1967). Studio sperimentale sull’aprassia ideomotorica. SistemaNervosa, 19, 131–143.

Pilgrim, E., & Humphries, G. W. (1991). Impairment of action to visual objects in a case ofideomotor apraxia. Cognitive Neuropsychology, 8, 459–473.

Rapczak, S. Z., Ochipa, C., Anderson, K. C., & Poizner, H. (1995). Progressive ideomotorapraxia: Evidence for a selective impairment of the action production system. Brain andCognition, 27(2), 213–236.

Reed, C. L., & Farah, M. J. (1995). The psychological reality of the body schema: A testwith normal participants. Journal of Experimental Psychology: Human Perception andPerformance, 21(2), 334–343.

Rizzolatti, G., Camarda, R., Fogassi, L., Gentilucci, M., Luppino, G., & Matelli, M. (1988).Functional organization of area 6 in the macaque monkey. II. Area F5 and the controlof distal movements. Experimental Brain Research, 71, 491–507.

Rizzolatti, G., Fadiga, L., Gallese, V., & Fogassi, L., (1996). Premotor cortex and the recogni-tion of motor actions. Cognitive Brain Research, 3, 131–141.

Russell, D. G. (1976). Spatial location cues and movement production. In G. E. Stelmach(Ed.), Motor control. New York: Academic Press.

Sakata, H., Takaoka, Y., Kawarasaki, A., & Shibutani, H. (1973). Somatosensory propertiesof neurons in superior parietal cortex (area 5) of the rhesus monkey. Brain Research,64, 85–102.

Siegel, S., & Castellan, N. J. (1988). Nonparametric statistics for the behavioral sciences,2nd ed. Boston, MA: McGraw-Hill.

Sirigu, A., Duhamel, J. R., & Poncet, M. (1991). The role of sensorimotor experience in objectrecognition. Brain, 114, 2555–2573.

Sirigu, A., Cohen, L., Duhamel, J. R., Pillon, B., Dubois, B., & Agid, Y. (1995). A selectiveimpairment of hand posture for object utilization in apraxia. Cortex, 31, 41–55.

Smith, I. M. (1998). Gesture imitation in autism. I. Nonsymbolic postures and sequences.Cognitive Neuropsychology, 15, 747–770.

Snyder, L. H., Grieve, K. L., Brotchie, P. & Andersen, R. A. (1998). Separate body- andworld-referenced representations of visual space in parietal cortex. Nature, 394, 887–891.

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