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To know what it is for, but not how it is: Semanticdissociations in a case of visual agnosiaAndrea Peru a b & Renato Avesani ca Dipartimento di Scienze Neurologiche e della Visione, Università di Verona, Italyb Dipartimento di Scienze dell'Educazione, Università di Firenze, Italyc SRRF, Ospedale ‘Sacro Cuore’, Negrar, Italy

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To cite this article: Andrea Peru & Renato Avesani (2008): To know what it is for, but not how it is: Semanticdissociations in a case of visual agnosia, Neurocase: The Neural Basis of Cognition, 14:3, 249-263

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NEUROCASE2008, 14 (3), 249–263

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NNCS To know what it is for, but not how it is: Semantic dissociations in a case of visual agnosia

DISSOCIATIONS IN VISUAL AGNOSIA Andrea Peru1,2 and Renato Avesani3

1Dipartimento di Scienze Neurologiche e della Visione, Università di Verona, Italy2Dipartimento di Scienze dell’Educazione, Università di Firenze, Italy3SRRF, Ospedale ‘Sacro Cuore’, Negrar, Italy

We report the case of a woman who displayed impaired object recognition following a severe head injury. Herelementary visual functions were substantially preserved, allowing her a coherent percept. On the other hand, shewas impaired in accessing stored knowledge from both visual and verbal input. In particular, she showed adramatic dissociation between fully preserved access to functional knowledge, and severely impaired access toperceptual knowledge so that she could describe what objects are for, but not how they are. Our findings from thiscase suggest that different categories of object knowledge are represented independently in separate units within thesemantic system.

Keywords: Visual agnosia; Object recognition; Semantic memory; Traumatic brain injury; Stored knowledge.

INTRODUCTION

Visual object recognition is a hierarchical processin which low-level brain areas accomplish the anal-ysis of primary sensory attributes (e.g., form, size,colour, motion, orientation), while high-level,associative brain areas integrate information aboutthe stimulus into semantic memory, and assign it ameaning. It follows that cerebral lesions centredupon different brain areas may lead to an impair-ment of object recognition. Classically, cases ofimpaired recognition due to the failure to achieve afull percept from visual information, in spite ofsubstantially preserved elementary sensory abili-ties, have been labelled as apperceptive agnosia,while the term associative agnosia has been appliedto cases in which – provided the absence of a general

intellectual decline – the stimulus is correctly per-ceived, and yet recognition does not occur (Lissauer,1890). Even if over the last decades it has becomeincreasingly clear that it is difficult to draw theboundary at which apperceptive agnosia ends andassociative agnosia begins (De Renzi & Lucchelli,1993; Humphreys & Riddoch, 2006), and most ofthe cases of visual agnosia are the result of a com-bination of two difficulties mainly concerningvision and semantic memory, respectively, thebasic Lissauer dichotomy is still appropriate for abroad classification of most of the cases of impairedobject recognition.

This paper reports on a case of a patient who,following a severe brain injury, showed an impair-ment in object recognition matching the classicaldefinition of associative agnosia. Then, in the rest

We wish to thank FB for her patience and cheerful participation; her friend NZ for her generous cooperation; G. Berlucchi for hishelpful comments on the manuscript; A. Beltramello for reviewing the magnetic resonance images, and M. Veronese for his help withpreparing the figures.

This work was supported by grants from the M.U.R.S.T. and from the Consiglio Nazionale delle Ricerche, Italy.Address correspondence to Andrea Peru, Dipartimento di Scienze Neurologiche e della Visione, Sezione di Fisiologia, Università di

Verona, Strada le Grazie 8, I-37134 Verona, Italy (E-mail: andrea.peru@medicina.univr.it).

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of the paper we focus just on the condition inwhich sufficiently well preserved visual functionsgive rise to a correct perception, but recognitionstill does not occur, clearly indicating difficultiesconcerning semantic memory (i.e., stored knowl-edge of perceptual and functional attributes whichconfer meaning to objects).

In these cases, the first question that arises iswhether the impairment of semantic memory wasdue to a block of access rather than to storage deg-radation. Theoretically speaking, it should not bedifficult to disentangle the two conditions: a blockof access manifests itself as a selective impairmentof information conveyed through one (i.e., visual,in our case) sensory channel; so a patient who failsto recognize a visually presented stimulus, can rec-ognize it when the appropriate channel is used. Bycontrast, storage degradation implies that knowl-edge of objects is definitively lost, so that it remainsinaccessible regardless of how the input is transmit-ted. As a consequence, such patients should bediagnosed as affected by semantic amnesia (oftenleading to dementia) rather than associative agno-sia. However, symptoms for the two conditionsmay overlap, making diagnosis difficult.

Another complication stems from the fact thatsemantic memory seems far from being a unitarysystem. A large corpus of evidence already existsdocumenting different patterns of selective seman-tic impairment, thus suggesting that differentattributes of objects are represented independentlyin separate units within the semantic system.Indeed, several cases of category-specific (e.g.,abstract vs. concrete words, and animate vs. inani-mate concepts), and input-modality (e.g., picturesvs. spoken words) have been so far reported (seeColtheart et al., 1998; Saffran & Schwartz, 1994,for a review). Perhaps, the most documented selec-tive semantic impairment refers to the categoricaldistinction between animate vs. inanimate con-cepts. For instance, both the patientsMichelangelo, described by Sartori, Miozzo, andJob (1993), and LA, described by Gainotti andSilveri (1986) who suffered from a herpes simplexencephalitis, performed much worse when thestimuli referred to animate than inanimateconcepts, while others (Saffran & Schwartz, 1994;Riddoch & Humphreys, 2004) were much worsewhen the stimuli referred to inanimate concepts.Strictly related (but not co-incident, see Discussion)to the animate vs. inanimate distinction, is thedistinction between the type of semantic attributebeing probed, with several patients showing a

selective impairment of semantic information aboutvisual attributes with preservation of semantic infor-mation about non-perceptual attributes (Basso,Capitani, & Laiacona, 1988; De Renzi & Lucchelli,1994; Farah, Hammond, Mehta, & Ratcliff, 1989;Hart & Gordon, 1992; Gainotti & Silveri, 1986;Sartori et al., 1993). Finally, another distinctionwhich has yielded selectivity is input-modality.There are reports of patients whose ability to per-form semantic tasks depended upon the modalityof stimulus input: typically, pictures or seen objectsversus spoken or written words (McCarthy & War-rington, 1988).

Caution must be used before accepting this doc-umentation as evidence of a categorical organiza-tion of semantic knowledge, a concept whichimplies that specific brain areas are committed tothe knowledge of different attributes of differentcategories. In fact, it is not easy on theoreticalgrounds to establish a priori which semantic cate-gories actually exist and then which classes ofselective semantic impairments can be expected(Coltheart et al., 1998).

Further clinical evidence is necessary to clarifythis issue. Here, we report a detailed investigationon a patient who showed a very peculiar pattern ofsemantic dissociations. Findings from this casemay shed light on the organization of semanticmemory, and the ways in which we access it.

CASE REPORT

FB is a right-handed female who was born inLondon, and lived in England until she was 13 yearsold. She went to an English school and was immersedin an English-speaking environment, whereas shespoke Italian within her family. Moving to Italywhen she was 13 years old, she graduated fromhigh school and then worked in a travel agency.

FB was always healthy, she had never smoked,drunk nor made use of other toxic substances. Atthe age of 34, she suffered a very severe head andchest injury from a skiing accident. Radiologicalinvestigation showed a closed pneumothorax and askullcap fracture with multiple focal cortical contu-sions mainly involving the right frontal region andthe left posterior temporal lobe. After the accidentFB was unconscious in Intensive Care for 10 days,then consciousness gradually recovered and thepatient was referred to the Neurological Depart-ment. On admission, neurological examinationrevealed a marked ataxia and difficult gait, but no

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other signs of motor and sensory impairment.Cranial nerves were intact; in particular, visual fieldwas normal to confrontation and visual acuity was6/10 in both eyes with optical correction.

The main cognitive symptoms included a diffi-culty recognizing objects and a severe loss ofmemory for recent events. A control CT scan car-ried out 3 months after the accident demonstratedthe presence of a severe communicating hydro-cephalus, which required the implantation of aventriculo-peritoneal shunt. Over the next monthsFB gradually improved in mobility and self careskills so, approximately 6 months after the acci-dent, she was admitted to a Rehabilitation Unitwhere all the investigations reported below tookplace in several separate sessions throughout thepost-acute period between 14 and 16 months afterthe injury.

At that time, an MRI scan showed a severe dila-tion ex vacuo of the ventricles, with a moderate sulcalwidening, and several areas of altered signal intensityregarded as sequelae of multiple deep contusionsinvolving Broadman’s areas 10 bilaterally, 11 and 47on the right, and 19 and 37 on the left (see Figure 1).

In the following, we will first report findingsfrom neuropsychological assessment, then detail anexperimental investigation aimed at better evaluat-ing the patient’s impairment of visual recognition.

NEUROPSYCHOLOGICAL EXAMINATION

When our observation began, FB did not showany behavioural disturbances, but her relativesnoticed that her mood had changed substantially:having been gregarious and outgoing before,she became apathetic and increasingly dependenton her family. Throughout testing, however, FBwas very cooperative and maintained a goodlevel of alertness as well as a remarkable ability toconcentrate.

She was completely autonomous as regardsdeambulation, dressing, and self care skills. Shewas disoriented in time, but well oriented in spaceand personal information. Spontaneous speechwas fluent without any evidence of aphasic impair-ment, but her dialogue was perseverative, and lack-ing insight, even though when requested why shewas an in-patient she promptly reported her visualproblems resulting from a head injury. Her wellwithin normal range performance on the Informa-tion, Analogies, Comprehension, and VocabularyWAIS-R verbal subtests (scaled score = 10 in each

subtest) demonstrated a substantial preservationof general semantic knowledge and intellectualfunctioning. By contrast, verbal perseverations,and her failure to make a progressive subtractionof 3 digits starting from 20, as well as her perform-ance on the Corsi Block Tapping Test (FB failed tomeet requirements at least partially because shewas unable to develop an effective strategy to solvethe problem) suggested a certain impairment ofexecutive functions.

The major cognitive symptoms, however,involved memory abilities: FB displayed a mildamnesia for the events of her recent past, and amore severe anterograde amnesia. In addition, herdigit and spatial span were in the below-averagerange (i.e., = 3) so that – in spite of well-preservedcomprehension and knowledge of arithmetic rulesand the numbering system – on both the TokenTest and the WAIS-R arithmetic subtest, FB failedin all those trials requiring a memory span beyondher capabilities.

EXPERIMENTAL INVESTIGATION

The patient’s impairment of visual recognitionwas assessed by means of the Birmingham ObjectRecognition Battery (BORB), as well as otherclassical neuropsychological tests, and other testsspecifically constructed for the present study. Adetailed list of the stimuli used in these tests isreported in the Appendices. Five women,matched for age and educational level, served asthe control group on those tests for which cut-offscores were not available. Consistent with thecriteria adopted by BORB, also in these teststwo standard deviations from the control meanscore were taken as a cut-off index for normalperformance.

As mentioned above, visual field and correctedvisual acuity were normal. FB was also able totrace the routes of Ishara tables, and performedflawlessly when asked to find a coloured tokenamong several distractors. Moreover, she had noproblem tracing the contours of a shape, andcopying drawings of common objects and simplegeometric shapes.

With the aim to demonstrate the preservation ofan effective perception by means of a quantitativerather qualitative approach, we presented FB withvarious BORB tests of early visual processing.First, she was administered the BORB perceptualmatching tests requiring the unidimensional

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discrimination of length, size, orientation, andposition of gap, respectively. In all of these tests, thesubject has to judge two items in a pair as being thesame or different. There are an equal number of‘same’ and ‘different’ pairs; in turn, based on themagnitude of the difference between the items, ‘dif-ferent’ pairs are sorted into three categories: large,intermediate, and small. In all the same/differentmatching task runs. FB scored at or above the

cut-off (see Table 1), and her performance corre-sponded to the varying levels of difficulty with noerrors on the ‘large’ and ‘intermediate different’trials, but several errors on ‘small different’ and‘same’ trials. Then FB was presented with twotests designed to assess the observer’s ability tojudge that an object remains invariant across dif-ferent viewpoints. The Minimal Feature View Taskrequires the identification of the critical features

Figure 1. Series of selected axial MRI scans. The left hemisphere is represented on the right. See text for details.

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DISSOCIATIONS IN VISUAL AGNOSIA 253

of the object, the Foreshortened View Taskinvolves a holistic coding of the relationshipbetween the different axes of an object. As shownin Table 1, FB scored above the cut-off on boththese tests, thus demonstrating the integrity ofthe so-called intermediate vision (Humphreys &Riddoch, 2006).

After having demonstrated the substantial integ-rity of the early, pre-categorical, stages of visualprocessing, we focussed on the access to storedknowledge.

Access to stored knowledge from vision (and other sensory modalities)

Knowledge of real life

Four different subtests of increasing difficultywere administered in a fixed order. Stimuli con-sisted of black-and-white line drawings of animals(87.5% of the cases) and tools (12.5% of the cases).In each subtest, 50% of the stimuli were real items,and the remaining 50% were chimerical itemsobtained by juxtaposing the complementary halvesof two different drawings. For each stimulus dis-played, the patient was asked to judge if it wasreal or unreal. Although unable to identify almostall the items presented to her, FB scored at orabove the cut-off on all the 4 subtests. Once again,however, her accuracy decreased as difficultyincreased with 15.6% of errors on the easy versionsof the test and 29.7% of errors on the hard versions(see Table 2).

Object identification: black-and-white line drawings

FB was unable to identify any of the 15 black-and-white line drawings from the BORB subtestno. 13. It is noteworthy that all the stimuli belongto animate categories, and have names that occur

TABLE 1 Pre-categorical stages of visual processing

FB’s score Max Mean SD Cut-off

Perceptual Matching TestsLenght Match Test 24 30 26,9 1,6 24Size Match Test 23 30 27,3 2,4 23Orientation Match

Test24 30 24,8 2,6 20

Position of Gap Match Test

34 40 35,1 4 27

Object Constancy TestsMinimal Feature

View Test22 25 23,3 2 19

Foreshortened View Test

19 25 21,6 2,6 16

TABLE 2 Access to stored knowledge from vision (and touch)

Test form FB’s score Max Mean SD Cut-off

Knowledge of Real-Life ObjectsBORB Object-Non Object Decision Test A: Hard 23 32 27 2,2 23

B: Easy 28 32 30,5 1,4 28A: Easy 26 32 28,9 2,4 24B: Hard 22 32 25,4 4,7 16

Object IdentificationPicture Naming

BORB Test 13: Animate Items b/w 0 15 12,7 2,2 8BORB Test 14: Animate Items b/w 0 6 n/a n/a n/aBORB Test 14: Inanimate Items b/w 2 6 n/a n/a n/aBingo: Animate Items colour 0 8 8 0 8Bingo: Inanimate Items colour 7 10 10 0 10Real Items: Visual Test 17 30 30 0 10Real Items: Haptic Test 26 30 29,2 0,8 28

Knowledge of CategoryBORB Item Match Test 22 32 30 2,2 26BORB Associative Match Test 19 30 27,5 2,4 22Odd-One-Out Test no cue 3 10 10 0 10

cue 10 10 10 0 10

In bold scores below the cut-off.Legenda: n/a = not available; b/w = black and white drawings; colour = coloured pictures; no cue = no cue provided; cue =semantic cue provided.

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with low frequency. Then we presented FB withthe subtest no. 14 that consists of 76 items, half ofwhich belong to animate (e.g., animals, fruits, veg-etables, etc.) categories, and the remaining half toinanimate (e.g., clothing, furniture, vehicles, etc.)categories. Within each of the two categories, halfof the items have names that occur with low fre-quency and the other half have names that occurwith high frequency. On the first 12 (i.e., six ani-mate and six inanimate) items, FB correctly namedonly two inanimate objects whose names have highfrequency (i.e., television and bed), but failed torecognize all the remaining items, and refused tocontinue. Such a pronounced floor effect made sta-tistical analysis meaningless. Therefore, we furtheraddressed the issue of category specificity of thedisorder by presenting the patient with coloured,more vivid, stimuli.

Object identification: coloured pictures

FB was asked to name 18 coloured pictures froma children’s bingo, displayed one by one in apseudo-random order (see Appendix 1 for details).Eight of them represented inanimate, non-livingitems (i.e., things existing in nature or commonobjects), and 10 represented animate, living items(i.e., fruits or vegetables). FB scored 0 out of 8 onliving items and 7 out of 10 on non-living items,and this difference in naming across categories wassignificant (χ2[1] = 6.10, p < .05). It is noteworthy,however, that although all the items were selectedas easily recognizeable by 6-year-old children, thetwo lists were not matched a priori for perceptualvividness and word frequency. It follows that theerrorless performance of our control subjects onboth the series of pictures cannot be taken as directevidence of the fact that the two stimulus sets wereequally demanding in terms of both word-findingdifficulty and perceptual salience. To ensure this,two precautions were taken: First, we checked theword frequency of this set of names in spoken andwritten usage by means of Corpus and FrequencyLexicon of Spoken (i.e., Corpus LIP, De Mauro,Mancini, Vedovelli, & Voghera, 1993) and Written(i.e., CoLFIS, Laudanna, Thornton, Brown,Burani, & Marconi, 1995) Italian, respectively. Asshown in Appendix 1, names with low and highfrequency seem to be equally distributed betweenthe two lists. We subsequently ranked the percep-tual salience of each picture by asking 10 naïveobservers to rate how easily they were able to iden-tify it. Ratings were on a 10-point scale with the

end values of ‘absolutely impossible to recognize it’and ‘absolutely impossible to miss it’. As expected,all the items were judged very easy to recognize(overall mean = 8.97, range = 8–10), and, moreimportantly, observers found living items as easyto recognize than non-living ones.

Object identification: haptic test

With the aim of examining whether the patient’simpairment of object recognition depended on themodality of input, we presented FB with a series of30 every-day-life objects, and asked her for an identi-fication, first by vision and then by palpating themwhile blindfolded. As in previous naming tests, cir-cumlocutory responses clearly demonstrating thepatient’s knowledge about each item, were scored ascorrect. On the visual task FB scored 17 out of 30(corresponding to 56.6% of the cases), while pro-duced ‘don’t know’ responses in the other cases. Herperformance significantly (χ2[1] = 5.17, p < .05)improved to 26 out of 30 (86.7%) correct on the hap-tic task (see Appendix 2 for details). In particular,FB continued to miss four items; namely the pencil-sharpener, the ruler, the torch, and the nail-vanish.Again, all the errors were ‘don’t know’ responses. Torule out the possibility that the improvement ofperformance observed in the haptic task simplyreflected a practice effect, we re-administered thesame test at a 1-month interval, presenting thepatient first with the haptic and then with the visualtask. Results were absolutely consistent across thedifferent sessions: All the items not known on thefirst occasion were also not known on the second.

Knowledge of associative properties of the objects

When asked to choose which one of two picturespresented in separate boxes at the bottom of thepage, belongs to the same category as the targetpicture presented in a box at the top of the page(e.g., two types of lamp or squirrel), FB scored bet-ter than chance, but below the cut-off (see Table 2,BORB Item Match test). Even worse, she scored atthe chance level (see Table 2, BORB AssociativeMatch test), when she was asked to associate itemsnot belonging to the same category, but simplylinked by a functional relationship (e.g., car/roador clown/circus tent). A similar, very poor, resultwas observed when FB was presented with a series offour coloured pictures from the above-mentionedchildren’s bingo, three of which belonging to the samecategory, and the remaining to another (e.g., three

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DISSOCIATIONS IN VISUAL AGNOSIA 255

fruits and one object), and requested to indicatethe odd one out (see Table 2, Odd-One-Out Test).A dramatic improvement was observed, however,with the patient’s performance now reaching ceil-ing level, when the examiner provided her with thesemantic category of related items (e.g., ‘All butone of these items is a fruit. Find the odd one out’).

Access to stored knowledge from verbal input

Drawing from memory

FB had no problem drawing simple two-dimen-sional geometric shapes (e.g., triangle, square, cir-cle) as well as different types of common inanimateobjects (e.g., clock, ship, flower). She also depicteda flower and a recognizable human face, but whenasked to draw animals from BORB subtest no. 9(i.e., a giraffe, a kangaroo, and a tiger) she perse-vered in drawing a quadruped with a long neck. Itis noteworthy that FB was unable to recognize herown drawings. Moreover, when asked to verballyreport the most salient feature of these stimuli, inall cases she gave a ‘don’t know’ response, beingunable to report even the giraffe’s long neck shehad drawn a few minutes before (see Table 3).

Perceptual differences between pairs of stimuli

We assessed FB’s ability to verbally describe theperceptual differences between pairs of itemsbelonging to the same semantic category, byadministering her a partially modified version ofthe test used by De Renzi and Lucchelli (1994). FB

was orally presented with 25 pairs of items andasked to say how they differ as regards their visualappearance. Fifteen pairs were inanimate, artificialobjects, five were animals, and the remaining fivefruits and vegetables. FB was almost totally unableto describe any perceptual difference betweenpairs: indeed, only when presented with the pairincluding the tail of a pig and the tail of a horse,did she refer to a perceptual property, although ina wrong way (i.e., ‘The pig’s tail is longer’). By con-trast, she was quite accurate describing functionaldifferences and only in three out of 25 trials pro-duced ‘don’t know’ responses (see Appendix 3 fordetails). In this vein, it is worth noting that thepatient’s almost absolute inability to refer to anyproperties other than functional ones produced insome cases notably confabulatory responses (e.g.,‘What’s the difference between horse’s ears andsheep’s ears? Horses hear better’).

Object-colour knowledge

According to the observation that retrievingonly one, perhaps the most salient, feature underthe guidance of direct questions (e.g., what colouris the lemon?) can be easier than searching for gen-eral attributes on his/her own initiative (De Renzi &Lucchelli, 1994), we further assessed the patient’sknowledge of perceptual attributes by asking herto recall the colour of 45 orally presented itemsthat are known to have a typical colour (seeAppendix 4 for details). Of 45 items, 23 were ani-mate objects (i.e., seven animals, and 16 fruits andvegetables), while of the remaining 22 items, mostwere things existing in nature (e.g., blood, snow,grass, gold), and a couple of them were objects

TABLE 3 Access to stored knowledge from verbal input

FB’s score Max Mean SD Cut - off

Verbal Access to the Visual StoreDrawing from Memory

Geometric Shapes and Inanimate Objects 10 11 n/a n/a n/aBORB Test 9: Animate Items 1 3 n/a n/a n/a

Verbal Description of Visual DifferencesPerceptual Differences between Pairs Test objects 0 15 30 2,2 26

fruits 0 5 27,5 2,4 22animals 0 5 10 0 10

Object-Colour KnowledgeColour Recall Test 30 45 44,6 0,5 44

In bold scores below the cut-off.Legenda: n/a = not available.

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conventionally painted with a given colour (i.e.,male and female newborn baby clothes). Beforeanalysing FB’s performance, however, we wantedto establish firmly that all the items in the list havean absolutely typical colour, namely that there wasonly one possible solution for each item. To dothis, we analysed the control subjects’ responses,and found that they were absolutely consistent,with the only exception of the item ‘coffee’ the col-our of which was declared black by three of thecontrol subjects and brown by the remaining two.Compared to the control data, FB’s score was verypoor. Indeed, she correctly reported the colour of30 out of 45 items. More interestingly, however,her performance strictly depended on the colour ofthe item, irrespective of its nature (i.e., animate vs.inanimate). That is, FB performed flawlessly onitems having a certain colour (i.e., white, yellow,red, blue, and green), but failed to report the col-our of all the black, grey, brown, pink, and orangeitems. Moreover, her pattern of errors was abso-lutely consistent: In fact, she labelled as blue all theblack items, as green all the grey, as red all thebrown and the orange, and as yellow all the pinkones (see Appendix 4). To rule out the possibilitythat such a pattern of errors simply reflected a par-ticular form of anomia for colour words, we pre-sented FB with two control experiments. First, weasked her to produce as many colour words as shecould within a time limit of 1 min: FB producedthe following seven colour words: black, white,red, yellow, green, blue, and brown. Then, weasked her to name the colour of 10 tokens dis-played one by one in a pseudo-random order: FBmade only two errors out of 10 trials (i.e., ‘red’ forboth ‘violet’ and ‘orange’). Taken together, thesefindings clearly demonstrate that the patient’serrors on the colour recall test could not be due toanomia.

DISCUSSION

Following a severe brain injury, patient FB showedimpaired object recognition, along with a mildimpairment of executive functions, and memorydeficits. Neurological examination documented asubstantial preservation of her elementary visualfunctions, and the successful performance on copy-ing, matching, and object constancy tasks, con-firmed that she was able to achieve a coherentpercept. A condition in which the stimulus iscorrectly perceived, but recognition does not

occur, clearly indicates difficulties concerningstored knowledge (i.e., semantic memory). Giventhat the patient’s failure in object recognition wasnot evident with all the concepts, on all the sensorymodalities, and on all the types of tasks, it seemsreasonable to ascribe such an impairment to a dif-ficulty accessing stored knowledge rather than adisruption of it. Here, we will try and reconcile thevery peculiar pattern of dissociations exhibited bypatient FB within the frames of the organization ofsemantic memory, and the ways we access it.

Sensory modality

When requested to identify a series of 30 every-day-life objects by palpating them while blindfolded, FBmade 4 errors. Theoretically speaking, a patientwho fails to recognize objects either by vision or byhaptic modality, should be diagnosed as havingsemantic amnesia rather than visual agnosia. Asargued by De Renzi (1999), however, ‘the unimodalnature of the deficit is sometimes not as strict as thedefinition of agnosia would imply’; that is, an error-less recognition when exploring objects by othersensory modalities (i.e., ear or hand) is not a man-datory condition for the diagnosis of visual agno-sia. Given that FB’s performance was much betterin the haptic (86.7% of correct responses) than inthe visual (56.6% of correct responses) domain, wesuggest that the very few errors made in the haptictest, far from disconfirming the diagnosis of visualagnosia, also simply reflected a slight impairment inaccessing stored knowledge by haptic input.

Level of knowledge

One of the most intriguing dissociations showed bypatient FB concerns the distinction between explicit(conscious) and implicit (unconscious) level ofknowledge. In spite of a marked inability to namemost of the items presented to her, FB performedabove the cut-off on all the four subtests aimed atevaluating her knowledge of real life. Moreover,provided with the appropriate semantic cue, shereached ceiling level on the associative match test inwhich she was asked to find the odd one out from aset of four pictures. Successful performance onthese tasks clearly indicate a deep, albeit implicit,processing of visual information leading FB toaccess knowledge of the appropriate shape of reallife objects as well as supra-ordinate categoricalknowledge. From a more general perspective, these

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findings further support the notion that even ifexplicit knowledge of sensory stimuli seems to belost, information gleaned unconsciously about suchstimuli can still drive brain-damaged patients’behaviour (Berlucchi, 2004).

Output required

FB made relatively appropriate drawings of two-dimensional geometric shapes, and common inani-mate objects. She could also depict a flower, a humanface, and a giraffe. When presented with her owndrawings, however, she was unable to identify anyof them. Analogously, on verbal input, she wasunable to report any salient features of the stimulishe had correctly drawn a few minutes before (e.g.,giraffe’s long neck). At least two different interpre-tations, not mutually exclusive, can be put forwardto explain this behaviour. First, in line with the dualpathways model of extrastriate visual cortex(Goodale & Milner 1992; Goodale & Westwood2004), separate neural networks can be assumed foraction and perception: A plausible, although some-what speculative interpretation of FB’s behaviourposits a preservation of the neural substratesinvolved in visually guided actions, alongside aselective derangement of the neural network sub-serving retrieval of perceptual attributes fromstored knowledge (see below). Alternatively, a morecautious interpretation posits that this behaviourcan be viewed as further evidence of the above men-tioned dissociation between implicit and explicitlevels of knowledge: Spared implicit knowledgeallows a correct motor behaviour, while impairedexplicit knowledge prevents a correct verbal report.

Perceptual vividness

FB failed to name most of the black-and-white linedrawings, but correctly named several colouredpictures presented to her. Consistent with the ideathat the more vivid the stimulus, the more likelythe access to the stored knowledge, FB scoredmuch better when she was presented with col-oured, vivid pictures rather than black-and-whiteline drawings.

Semantic selectivity

More interestingly, FB’s performance on colouredpictures was at floor for living items, but relatively

spared for non-living (70%) items. Based on theresults of our control experiments, we rule out thepossibility that these differences in performancedepended on the fact that the two stimulus setswere not matched a priori for perceptual salienceand word frequency. Rather, it seems likely thatFB’s inability to identify living things reflects aselective loss of knowledge about that specific,semantic category of objects. As correctly arguedby Coltheart et al. (1998), semantic categories arefar from being well defined and several classifica-tions are, at least, ambiguous (e.g., musical instru-ments are usually taken as animate objects, whilebody parts are often considered to belong to theinanimate category), so that the living–nonlivingdichotomy can seem somewhat artificial. A lot ofclinical evidence supports, however, the distinctionbetween animate vs. inanimate objects (Saffran &Schwartz, 1994). For instance, a very recent studyon patients in the early stages of Alzheimer’s dis-ease showed a clear category dissociation so that,even when variables such as imageability, percent-age of name agreement, and number of targetalternatives were factored out, patients were moreimpaired in naming non-living than living things(Albanese, 2007, but see also Tippet, Meyer,Blackwood, & Diaz-Asper, 2007 for a contrastingresult). Moreover, studies with positron emissiontomography have demonstrated that, besidesthe bilateral activation of the ventral temporallobes and Broca’s area, naming animals and toolsactivate selective brain areas (i.e., the left medialoccipital lobe, and the left premotor area, respec-tively), thus providing reliable anatomical supportto such an intriguing dissociation (Martin, Wiggs,Ungerlaider, & Haxby, 1996).

Type of attribute

FB demonstrated a dramatic dissociation betweenfully preserved access to functional knowledge andseverely impaired access to perceptual knowledge.Indeed, when requested to verbally describe thedifferences between pairs of items belonging to thesame semantic category, even though she wasexplicitly asked to report only perceptual, visualattributes, our patient always referred to func-tional, non-perceptual ones, sometimes giving con-fabulatory responses. A dissociation between animpaired knowledge of visual attributes vs. a pre-served knowledge of functional, non-perceptualattributes has often been reported in the literature

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(e.g., Basso et al., 1988; De Renzi & Lucchelli, 1994;Gainotti & Silveri, 1996; Hart & Gordon, 1992;Sartori et al., 1993). Analogously, evidence of thesymmetrical dissociation (i.e., a preserved knowl-edge of perceptual attributes vs. an impairedknowledge of functional, non-perceptual attributesin absence of a general intellectual decline) has alsobeen provided (e.g., Riddoch & Humphreys, 1987;Sheridan & Humphreys, 1993). This dissociationhas been questioned by Caramazza and Shelton(1998), who argued that such asymmetrical evi-dence is the result of a greater difficulty retrievingperceptual rather than functional attributes. In thisvein, Farah and McClelland (1991) noticed that inmost of the cases the dissociation betweenimpaired knowledge of perceptual attributes vs.preserved knowledge of functional attributes isaccompanied by a selective impairment for ani-mate objects. Based on this observation, theyargued that the selective impairment of perceptualattributes is artefactual, due to the fact that percep-tual attributes are critical for identifying animateobjects while inanimate objects mainly depend onfunctional attributes. There is reliable clinical evi-dence, however, supporting the notion that withinsemantic memory, the knowledge about perceptualattributes can be distinguished from the knowledgeabout functional properties, and can then be selec-tively affected by it (Riddoch & Humphreys, 1987).For instance, probed with animate objects withcareful matching of difficulty level, patient NBshowed better knowledge for functional attributesthan for visual properties of objects (Powell & Dav-idoff, 1995). In turn, patient AC describedby Coltheart et al. (1998), showed a selectiveimpairment of semantic information about visualattributes with preservation of olfactory semanticattributes; moreover, such an impairment equallyaffected animate and non-animate objects. Find-ings from our case provide further support for anattribute-specific selective impairment. Indeed,irrespective of the semantic category (i.e., animatevs. non-animate) of the item presented to her,patient FB provided a fairly accurate descriptionof non-perceptual, functional attributes, but wascompletely unable to retrieve perceptual (visual)attributes. Such a deep impairment in accessingstored knowledge of perceptual attributes can beeasily accounted for when considering the involve-ment of BA 19 and 37 of the left hemisphere, asclearly revealed by MRI scans. Indeed, recent func-tional magnetic resonance imaging (fMRI) evi-dence suggests that BA 19 and 37 of the left

hemisphere – which belong to the ventral stream ofprojections from the striate cortex to the infero-temporal cortex, and are originally involved inobject perception – are also engaged duringretrieval of those memories (Vaidya, Zhao, Des-mond, & Gabrieli, 2002).

Colour selectivity

FB’s difficulty accessing perceptual knowledgefrom verbal input, however, was not absolute.Indeed, she was better able to name the most sali-ent perceptual feature, namely the colour,although with some specific exceptions. Whencompared with her performance on the other testsaimed at assessing the access to stored knowledgeof perceptual attributes from verbal input, FB’sperformance on the colour retrieval test –although impaired – seems to suggest an impairedknowledge of object form, but (relatively) sparedobject colour knowledge. That is, a condition mir-roring the case of an impaired object colourknowledge, but spared knowledge of object formand function (Miceli et al., 2001; Price &Humphreys, 1989). Caution must be used beforedrawing such a conclusion, however, since it isevident that searching for perceptual attributes onhis/her own initiative is much more difficult thanretrieving a well-defined feature under the guid-ance of direct questions (De Renzi & Lucchelli,1994). This can be particularly true for a patientlike FB who has suffered a lesion of BA 10 whichhas been demonstrated to be activated duringencoding and retrieval (Beason-Held, Golski,Kraut, & Esposito, 2005). Further support for thehypothesis of a retrieval impairment stems from adeeper analysis of FB’s performance on the col-our recall test. Indeed, when asked to recall thecolour of items known to have a typical colour,FB scored at ceiling on items having a certain col-our (i.e., white, yellow, red, blue, and green), butfailed to report the colour of all the black, grey,brown, pink, and orange items, regardless ofwhether they were living or non-living things.Even more curiously, the analysis of errorsrevealed an absolutely consistent pattern, with allthe black items labelled as blue, all the grey asgreen, all the pink as yellow, and all the brownand the orange as red (see Appendix 4). That is,while in the other cases of impairment in object-colour retrieval (Beauvois & Saillant, 1985; DeVreese, 1991; Farah, Levine, & Calvanio, 1988;

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Luzzati & Davidoff, 1994; Miceli et al., 2001; Sch-nider, Landis, Regard, and Benson, 1992), mostof incorrect responses were of dark or achromaticcolours, all FB’s errors were with ‘primary’ col-ours, namely colours which maximised the physi-ological responses of the double-opponents (i.e.,red–green and blue–yellow) ganglionar cells andvisual cortex neurons (Schiller, 1994), and thefirst colours to be learned by children (Kowalsky& Zimiles, 2006). To the best of our knowledge,no similar, consistent pattern of errors has beenso far described. One could argue that such a pat-tern of errors reflects a particular form of anomiafor colour words. On the basis of the patient’sfairly good performance on both naming and flu-ency task, however, we can certainly rule out thepossibility that these errors were due to interfer-ence from colour anomia. Therefore, we assumethat these errors do reflect a genuine, selectiveimpairment in object-colour retrieval.

CONCLUSIONS

We have reported the case of a patient, FB, with amodality specific impairment in object recognitionmatching the classical definition of an associativeagnosic patient. The main findings of the in-depthinvestigation were as follows:

1. FB’s primary visual functions are substantiallypreserved and allow her to achieve a coherentpercept. That is, FB suffers no major deficit inthe early, pre-categorical, stages of visualprocessing.

2. By contrast, FB is severely impaired in access-ing stored knowledge. Such an impairment,however, far from being absolute, varies as afunction of several factors including the levelof knowledge (i.e., explicit vs. implicit)assessed, the perceptual vividness of the stimu-lus (e.g., coloured stimuli vs. black-and-whiteline drawings), its semantic category (i.e., livingvs. non-living), the type of attribute (i.e., per-ceptual vs. functional) tested, the way ofretrieval (i.e., free search vs. direct question)adopted, and the output (i.e., verbal report vs.drawing) required.

3. In particular, the pattern of performanceexhibited by FB clearly suggests that the coredeficit is the difficulty achieving an explicitknowledge of the perceptual features either byvisual or spoken input.

With the necessary caution that must be used ininterpreting data from a single case study, we con-sider that the findings from our case stand againstthe idea of semantic memory as a unitary system. Onthe other hand, they strongly support the notion thatsemantic memory is subserved by discrete neuronalnetworks so that perceptual and associative proper-ties as well as different categories of objects are rep-resented independently in separate units within thesemantic system (Humphreys & Riddoch, 2006).

Original manuscript received 24 May 2007Revised manuscript accepted 26 May 2008

First published online 8 August 2008

REFERENCES

Albanese, E. (2007). The ‘hidden’ semantic category dis-sociation in mild-moderate Alzhimer’s diseasepatients. Neuropsychologia, 45, 639–643.

Basso, A., Capitani, E., & Laiacona, M. (1988). Progres-sive language impairment without dementia: A casewith isolated category specific semantic defect. Jour-nal of Neurology Neurosurgery and Psychiatry, 51,1201–1207.

Beauvois, M. F., & Saillant, B. (1985). Optic aphasiafor colours and colour agnosia: A distinctionbetween visual and visuo-verbal impairments in theprocessing of colours. Cognitive Neuropsychology,2, 1–48.

Beason-Held, L. L., Golski, S., Kraut, M. A.,Esposito, G., & Resnick, S. M. (2005). Brain activationduring encoding and recognition of verbal and figuralinformation in older adults. Neurobiological Aging,26, 237–250.

Berlucchi, G. (2004). Some effects of cortical and cal-losal damage on conscious and unconscious process-ing of visual information and other sensory inputs.Progress in Brain Research, 144, 79–93.

Caramazza, A., & Shelton, J. R. (1998). Domain-specificknowledge systems in the brain: The animate-inani-mate distinction. Journal of Cognitive Neuroscience,10, 1–34.

Coltheart, M., Inglis, L., Cupples, L., Michie, P.,Bates, A., & Budd, B. (1998). A semantic subsystemof visual attributes. Neurocase, 4, 353–370.

De Mauro, T., Mancini, F., Vedovelli, M., & Voghera, M.(1993). Lessico di frequenza dell’italiano parlato(Corpus LIP). Milano: ETAS Libri.

De Renzi, E. (1999). Agnosia. In G. Denes, &L. Pizzamiglio (Eds), Handbook of clinical and experi-mental neuropsychology. Hove, UK: Psychology Press.

De Renzi, E., & Lucchelli, F. (1993). The fuzzy bounda-ries of appercettive agnosia. Cortex, 29, 187–215.

De Renzi, E., & Lucchelli, F. (1994). Are the semanticsystems separately represented in the brain? Cortex,30, 3–25.

De Vreese, L. P. (1991). Two systems for colour-namingdefects. Verbal disconnection vs colour imagerydisorder. Neuropsychologia, 29, 1–18.

Dow

nloa

ded

by [

Uni

vers

ita D

egli

Stud

i di F

iren

ze],

[an

drea

per

u] a

t 03:

14 1

8 A

pril

2012

260 PERU AND AVESANI

Farah, M., & McClelland, J. L. (1991). A computationalmodel of semantic memory impairment: Modalityspecificity and emergent category specificity. Journalof Experimental Psychology General, 120, 339–357.

Farah, M. J., Levine, D. N., & Calvanio, R. (1988). Acase study of mental imagery deficit. Brain Cognition,8, 147–164.

Farah, M. J., Hammond, K. M., Mehta, Z., & Ratcliff, G.(1989). Category-specificity and modality-specificityin semantic memory. Neuropsychologia, 27, 193–200.

Gainotti, G., & Silveri, M. C. (1996). Cognitive andanatomical locur of lesion in a patient with a category-specific semantic impairment. Cognitive Neuropsy-chology, 13, 357–389.

Goodale, M. A., & Milner, A.D (1992). Separate visualpathways for perception and action. Trends in Neuro-science, 15, 20–25.

Goodale, M. A., & Westwood, D. A. (2004). An evolv-ing view of duplex vision: Separate but interactingcortical pathways for perception and action. CurrentOpinion in Neurobiology, 14, 203–211.

Hart, J., & Gordon, B. (1992). Neural subsystems forobject knowledge. Nature, 359, 60–64.

Humphreys, G. W., & Riddoch, M. J. (2006). Features,objects actions: The cognitive neuropsychology ofvisual object processing, 1984–2004. Cognitive Neu-ropsychology, 23(1), 156–183.

Kowalsky, K., & Zimiles, H. (2006). The relationbetween children’s conceptual functioning with colorand color term acquisition. Journal of ExperimentalChild Psychology, 94, 301–321.

Laudanna, A., Thornton, A. M., Brown, G., Burani, C., &Marconi, L. (1995). Un corpus dell’italiano scrittocontemporaneo dalla parte del ricevente. InS. Bolasco, L. Lebart, & A. Salem (Eds), III GiornateInternazionali di Analisi Statistica dei Dati Testuali(Vol. I, pp. 103–109). Roma: Cisu.

Lissauer, H. (1890). Ein Fall von Seelenblindheit nebsteinem Beitrag zur Theorie derselben. Archiv fur Psy-chiatrye, 21, 222–270.

Luzzati, C., & Davidoff, J. (1994). Impaired retrieval ofobject-colour knowledge with preserved colour nam-ing. Neuropsychologia, 32, 933–950.

Martin, A., Wiggs, C. L., Ungerlaider, L. G., & Haxby,J. V. (1996). Neural correlates of category-specificknowledge. Nature, 379, 649–652.

McCarthy, R. A., & Warrington, E. K. (1988). Evidencefor modality-specific meaning systems in the brain.Nature, 334, 428–430.

Miceli, G., Fouch, E., Papasso, R., Shelton, J. R.,Tomaiuolo, F., & Caramazza, A. (2001). The dissoci-ation of color from form and function knowledge.Nature Neuroscience, 4, 662–667.

Powell, J., & Davidoff, J. (1995). Selective impairmentsof object knowledge in a case of acquired corticalblindness. Memory, 3, 435–461.

Price, C. J., & Humphreys, G. W. (1989). The effects ofsurface detail on object categorization and naming.Quarterly Journal of Experimental Psychology, 41A,797–828.

Riddoch, M. J., & Humphreys, G. W. (1987). Visualobject processing in optic aphasia: A case of semanticaccess agnosia. Cognitive Neuropsychology, 4, 131–185.

Riddoch, M. J., & Humphreys, G. W. (2004). Objectidentification in simultanagnosia: When wholes arenot the sum of their parts. Cognitive Neuropsychol-ogy, 11, 423–442.

Saffran, E. M., & Schwartz, M. F. (1994). Of cabbagesand things: Semantic memory from a neuropsycho-logical perspective – A tutorial review. In C. Umiltà, &M. Moscovitch (Eds), Attention and performance 15:Conscious and nonconscious information processing.Cambridge MA: MIT Press.

Sartori, G., Miozzo, M., & Job, R. (1993). Category-specific naming impairment? Yes. Quarterly Journalof Experimental Psychology, 46(3), 489–509.

Schiller, P. H. (1994). Area V4 of the primate visual cortex.Current Directions in Psychological Science, 3, 89–92.

Schnider, A., Landis, T., Regard, M., & Benson, F.(1992). Dissociation of color from object in amnesia.Archives of Neurology, 49, 982–985.

Sheridan, J., & Humphreys, G. W. (1993). A verbal-semantic category-specific recognition deficit. Cogni-tive Neuropsychology, 10, 143–184.

Tippet, L. J., Meyer, S. L., Blackwood, K., & Diaz-Asper,C. (2007). Category-specific deficits in Alzheimer’s dis-ease: Fact or artefact? Cortex, 43, 907–920.

Vaidya, C. J., Zhao, M., Desmond, J. E., & Gabrieli,J. D. (2002). Evidence for cortical encoding specificityin episodic memory: Memory-induced re-activationof picture processing areas. Neuropsychologia, 40,2136–2143.

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APPENDIX 1

Pictures naming

CoLFIS Corpus LIP Salience FB’s responses

Living Items(listed in alphabetical order)1 Cock 38 4 8,4 ?2 Fish 318 13 8,9 ?3 Hand 1595 134 8,6 ?4 Heart 672 42 9,4 ?5 Horse 251 37 9,3 ?6 Flower 410 8 9,1 ?7 Lemon 103 7 8,3 ?8 Chestnut 30 1 9,4 ?

median 284,5 10,5 9,0Non-Living Items(listed in alphabetical order)

Handbag 25 25 8,9 handbagCandle 61 1 9,6 you light it up when the electric

light is out of orderHouse 2954 471 9,4 houseLamp 24 1 8,7 lampPipe 18 1 8,2 ?Boat 171 14 9,4 boatStar 261 4 9,5 you see it as a light in the night

skyTrain 230 29 8,5 trainUmbrella 31 6 8,7 ?Flag 153 5 9,1 ?

median 107,0 5,5 9,0

? = don’t know response.Corpus LIP = Corpus and Frequency Lexicon of Spoken Italian (De Mauro et al., 1993).CoLFIS = Corpus and Frequency Lexicon of Written Italian (Laudanna et al., 1995).Salience = Perceptual salience as ranked by ten naive observes (mean value).

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APPENDIX 2

Object identification: real items

FB’s responses

Items(listed in alphabetical order) Visual Test Haptic Test

1 Battery ? battery2 Chalk ? to write on the blackboard3 Clothes-pin to hang clothes to hang clothes4 Coffe-cup coffee-cup coffee-cup5 Coin coin coin6 Comb comb comb7 Diary diary diary8 Eraser ? to erase errors9 Fork fork fork10 Glasses glasses glasses11 Hammer hammer hammer12 Key key key13 Measuring tape a tape with numbers . . . to measure a tape with numbers . . . to measure14 Nail-varnish ? ?15 Padlock ? to lock16 Paper clip ? to clip papers17 Pen ? pen18 Pencil pencil pencil19 Pencil sharpener ? ?20 Ruler ? ?21 Scissors ? scissors22 Screw ? screw23 Screwdriver screwdriver screwdriver24 Slide a frame with photo inside a frame with photo inside25 Tape tape tape26 Teaspoon teaspoon teaspoon27 Tennis ball ball ball28 Toothpick ? toothpick29 Torch ? ?30 Watch watch watch

? = don’t know response.

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APPENDIX 3

Perceptual differences between pairs of stimuli

APPENDIX 4

Colour recall test

Items (listed in alphabetical order) FB’s responses

Inanimate objects1 knife blade - blade of a saw knife is to cut meat, saw is to cut wood2 fork - spoon fork is to eat pasta, spoon is to eat soup3 button - coin button is for clothes, coin is for shopping4 match - toothpick the top of the match is to light fire5 pot - frying pan both of them are for cooking6 clothes brush - toothbrush clothes brush is for clothes, toothbrush is for teeth7 telephone token - coin telephone token is to phone, coin is to buy8 pot - colander ?9 needle - pin to sew you must use a needle not a pin10 wheel of a bicycle - wheel of a car the wheel of a car is faster11 tie - scarf tie is for men, you wear a scarf around the neck12 spaghetti - noodles you can eat both of them . . . two kinds of pasta13 cigar - cigarette cigar smells bad and is more dangerous14 spoon - ladle ladle is to serve soup, spoon is to eat soup15 nail - screw ?

Animals1 snail shell - turtle shell ?2 pig’s tail - horse’s tail pig’s tail is longer3 fly - bee bee can sting4 horse’s ears - sheep’s ears horses hear better5 peacock’s tail feathers - turkey’s tail feathers both are birds

Fruits and Vegetables1 artichoke - fennel you can eat both of them2 cherry - strawberry both are fruits … you can eat both of them3 almond - hazelnut you can eat both of them4 pear - apple both are fruits and grow up on trees5 bean - pea beans are for pasta e fagioli*, peas are for risi e bisi*

? = don’t know response.*typical Italian dishes.

Items(listed in alphabetical order)

HitsColour

Blue male newborn clothes, sapphire, sea, skyGreen artichocke, basil, crocodile, emerald, frog, grass, lizardRed blood, cherry, hearth, ruby, strawberry, tomato, watermelon (inside)White albumen, chalk, salt, sea-gull, snow, sugarYellow banana, corn, gold, lemon, sun

ErrorsColour FB’s responses

Black blackboard, coffee, panther, petroleum, tar BlueBrown chestnut, tobacco, walnut RedGray elephant GreenOrange carrot, lobster, orange, tangerine RedRed female newborn clothes, pig Yellow

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