word meaning blindness revisited

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WORD MEANING BLINDNESS REVISITED Matthew A. Lambon , Ralph Andrew W. Ellis & Karen Sage Published online: 09 Sep 2010.

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COGNITIVE NEU ROPSYCHOLOGY, 1998, 15 (4), 389- 400

WORD M EANING B LINDNESS R EVISITED Matthew A. Lambon Ralph MRC Cognition and Brain Sciences Unit, Cambridge, UK


Andrew W. Ellis University of York, UK

Karen Sage University of Manchester, UK

Lam bon Ralp h, Sag e, and Ellis (1996) d escribed a patient, JO, w ho had im p aired u nderstand ing of w ritten w ord s in the presence of norm al com p rehension of objects and spoken w ord s. She w as able to recognise letters and cou ld d ifferentiate w ritten w ord s from nonw ords in lexica l d ecision tasks. JO’s ability to read alou d all typ es of w ord s and non w ord s w as also intact. Although JO’s und erstan d ing w ith silent reading w as com prom ised, her com prehension w as d ram aticall y im prov ed w hen she w as perm itted to read w ord s alou d. Lam bon Ralph et al. interp reted this d isord er as d ue to a p artial d isconnection of the v isu al inpu t lexico n from the sem antic sy stem and labelled the d isorder “w ord m eaning blindness”. JO’s w ord m eaning blind ness resu lted from a progressiv e illness that p rovid ed us w ith an opportunity to inv estig ate the pattern of d eterioratio n in this app arently rare form of d y slexia. Over a period of one year w e tested her on three occasions w ith a battery of neu rop sycholog ical tasks d esig ned to asses s her com prehension across m odalities and her ability to read aloud variou s w ord s, inclu ding w ord s w ith excep tional sp elling-to-sound corres pond ences. The m ain find ing of this longitu d inal assess m ent w as a fu rther red u ction in her u nd erstand ing of w ritten w ord s read silently w ith a p reserv ation of spoken w ord com p rehension. Throu ghout the period there w as little or no chang e in JO’s ability to read alou d w ord s and nonw ord s, inclu d ing exception w ord s. The im plications of this p attern for theories that em p hasise the role of sem antics in reading alou d are d iscu ssed .

Requests for reprints should be ad d ressed to Dr. M. A. Lam bon Ralph, MRC Cognition and Brain Sciences Unit, 15 Chaucer Road, Cam bridg e CB2 2EF, UK. (Tel: 01223 335294; Fax: 01223 359062; E-m ail: m att.lam bon-ralph@m rcap u.cam .ac.uk). This study was conducted w hile the first au thor w as in receipt of a studen tship from the Eng ineerin g and Physical Sciences Research Council. We would like to than k JO for her continued patience in com pleting our long itudinal stud y. We are g rateful to Rita Berndt and two anonym ous referees for their useful com m ents on a prev ious draft of this pap er.

Ó 1998 Psy cholog y Press Ltd

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INTRODUCTION

terms of a traditional m odel of visual word

In 1996 we reported a case of “ word m eaning

recognition. Errorless letter recognition and lexical d ecision im plied that the visual analysis


blindness” (Lambon Ralph et al., 1996). Patient JO was able to read aloud all types of word s and differentiate them from non words. Access to m eaning was normal for spoken words and from picture input. In contrast, when JO was required to read silently, her understand ing of written words was im paired. She was poor at defining written words, matching words to target pictures, and completing written synonym jud gem ent tasks. In word-to-picture matching and word association tasks JO typically chose either the correct target or a sem antically related foil, suggesting that the access disord er was only partial. It would appear that, in general, only an impoverished sem antic representation could be accessed from written words. If, howev er, JO read words aloud, her com prehension was normal. Presumably when JO listened to herself read aloud she could use her intact auditory com prehension processes to understand the words. This recod ing of orthographic inform ation v ia phonology for com prehension is reminiscent of an observ ation made by Bram well (1897). He reported a patient with word meaning deafness whose com prehension of spoken words improv ed when she first wrote do wn spoken sentences. JO’s pattern was, in effect, the rev erse of word meaning d eafness, and the term “ word m eaning blindness” was proposed for her perform ance. Lambon Ralph et al. (1996) offered the following interpretation for JO’s performance in

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COGNITIVE NEU ROPSYCHOLOGY, 1998, 15 (4)

system and visual input lexicon were intact. N ormal com prehension of spoken words and pictures suggested that the recognition systems for those input m odalities were intact, as was the sem antic system . It was suggested that the m ost likely cau se of her word meaning blind ness was a partial disconnection between the (intact) visual input lexicon and the (intact) sem antic system. In add ition, a separate inner speech impairm ent was dem onstrated. This left her unable to recycle the sound s of written words internally, so she could only understand written words by first reading them aloud. JO’s word meaning blindness arose as a result of a progressive brain d isorder similar in som e way s to the focal atrophy seen in sem antic dem entia (Hodges, Patterson, Oxbury, & Funnell, 1992; Snowden, Gou lding, & N eary , 1989). Like those patients, JO’s episodic mem ory (both present and past) seemed to be intact. She was able to complete m any nonverbal reasoning tasks, and although she was anomic, her phonology and syntax were norm al. Unlike cases of sem antic dem entia, JO’s central sem antics were intact and com prehension d ifficulties were apparent for written words only. JO was originally tested in a period from March to July 1995. The data gathered at that time form ed the basis of our previous report (Lam bon Ralph et al., 1996). JO was revisited on a regular basis to follow the decline in her cognitive abilities. This allowed t wo questions (noted by Lambon Ralph et al., 1996) to be addressed:


WORD MEANING BLINDNESS REVISITED

1. How would her comprehension with re-

sion on other systems such as read ing aloud

spect to each m od ality (pictures, spoken and written words) change over time?

(see following). On the second question, Lambon Ralph et

2. If written word comp rehension declined further, would surface d yslexia result?

al. (1996) noted that a semantic access im pairm ent for written words might, according to som e theories, lead to surface d yslexia; that is, a tendency to m ispronounce word s with

Our first question could be considered to be rather trivial. If a progressiv e brain disorder impaired a specific function then continued atrophy should lead to an accentuated deficit within the sam e process. This presum es, ho wev er, that the apparent dissociation was not d ue to a generalised decrement in cognitiv e perform ance that appears initially to affect a single function becau se the

irregular or exceptional spellings (e.g. colonel ® “kollonel”) while showing a preserv ed ability to read aloud regular or consistent words, and non word s. Recent theories have stressed the importance of word m eaning in reading aloud, particularly for the successful pronunciation of lo w-frequency words with exceptional spelling-to-sound correspon-

process is a com plex one and, thus, is sensitiv e to a nonspecific im pairm ent (Ellis & Young, 1988; Shallice, 1988). In fact this possi-

d ences (Patterson & Hod ges, 1992; Patterson, Graham, & Hodges, 1994; Plaut, McClelland, Seidenberg, & Patterson, 1996). In these theo-

bility has been noted and discussed with reference to em pirical data for the sim ilar but

ries there is a “direct”, nonsemantic route for the com putation of phonology from orthography that is accurate for regular words, non-

reversed pattern of com prehension seen in cases of word meaning d eafness, where im paired com prehension of spoken word s dissociates from intact und erstanding of written words (Ellis, 1984; Franklin, Howard, & Patterson, 1994; Franklin & Lambon Ralph, submitted; Franklin, Turner, Lam bon Ralph, Morris, & Bailey, 1996; Tyler & Moss, 1997). Howev er, the pattern of word meaning deafness has only been reported for nonprogressiv e aphasics, which is analogous to single “snap-shot” testing in progressiv e cases. As JO’s word meaning blindness arose from a progressiv e disease, longitud inal assessm ent can help to differentiate between the specific versus generalised hypothesis and m ight highlight the impact of im paired com prehen-

words, and high-frequency irregular words. This route is relativ ely inefficient at reading lo w-frequency irregular words correctly. Such word s are held to rely on support from the sem antic system for their correct pronunciation. On this view, the m eaning of a target word prov ides a deg ree of constraint on output phonology. If, for any reason, the contribution of sem antics to reading aloud is red uced sufficiently, the patient should begin to m ispronounce lo w-frequency exception words; that is, the patient should becom e surface d yslexic. Work within this framework has focused on im pairm ent to the sem antic system itself as a cause of red uced sem antic contribution to reading, and hence surface


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LAMBON RALPH ET AL.

dyslexia (e.g. Patterson & Hod ges, 1992), or

CASEREPORT

on a reduction in the strength of the links bet ween the sem antic system and phonology,

JO’s personal and medical history is giv en in


which causes a patient to become both anom ic and surface dyslexic (Graham , Patterson, & Hod ges, 1995). Howev er, weakening of the links from orthography to semantics, of the sort we have suggested was responsible for JO’s word m eaning blindness, should also reduce the contribution of sem antics to reading aloud , and should therefore result in a patient misread ing lo w-

Lam bon Ralph et al. (1996). She was v isited on a regular basis from March 1995 until April 1996. Ov er this period a num ber of tests were repeated. The first ad ministration was in March –July 1995. During that time a wide selection of assessm ents was giv en, which form ed the basis of our prev ious paper. A subset was re-adm inistered in October 1995 and ag ain in March –April 1996.

frequency exception words she no longer understands (cf. Ellis, Lambon Ralph, Morris, & Hunter, in press).

Over the course of the year JO’s condition was subject to a significant decline. A num ber of clinical observ ations are worthy of report.

JO was not surface dyslexic when tested in early 1995. It was possible, howev er, that sufficient semantic activation rem ained to sus-

JO, a wido w, rem ained at hom e and continued her busy social life. Although unable to use a d iary (becau se she couldn’t understand the

tain errorless reading aloud. We have alread y discussed the notion that two processes might hav e different susceptibility to a single

written word s), she m anaged to keep her appointments with those people who v isited

deficit. This applies equally here: com prehension will be v ery sensitiv e to the impairm ent bet ween orthography and sem antics but read ing aloud will be less so. The relativ e insensitivity of exception word reading accuracy to sem antic impairm ent could be due to the contribution of the direct or nonlexical route, which can prov ide the pronunciation of m any words withou t assistance from the sem antic-lexical route (Hillis & Caram azza, 1995; Patterson et al., in press; Plaut et al., 1996). Consequently, surface dyslexia m ight arise when the sem antic activ ation reduced further during the course of JO’s progressiv e disease. We ad dress that possibility in the present paper.

392


her. She was able to recall ev ents that had occurred in both the recent and remote past. Although not tested in any form al way , her episodic mem ory seemed to rem ain fairly stable. JO’s spontaneous speech becam e simpler in content and the word -finding d ifficulties present in March 1995 increased at a rapid rate to a point where she was unable to com plete the m ajority of sentences successfully. This m ade general conversation v ery difficult. In addition, she produced a num ber of overt (and uncorrected ) sem antic errors in her spontaneous speech, for instance referring to the pears in her garden as “plum s”. The longitud inal data is reported in the next three sections.


Comprehension

target picture together with four category co-

JO was giv en t wo tests longitud inally that re-

ordinate items (e.g. a goat is presented with donkey, deer, horse and cow). On the spoken

quire access to m eaning from either spoken or written words (the written word v ersions were completed with silent reading). The results are


sho wn in Table 1. The PALPA word –picture matching test (Kay, Lesser, & Coltheart, 1992) contains 40 trials in which each target picture is presented with a “close” sem antic, a “distant” sem antic, a visually related, and an unrelated foil. JO’s perform ance on the spoken version remained within the published norm al range while her score on the written version declined from 22/ 40 (55%) in March 1995 to 14/ 40 (35%) in April 1996 (a score which is only just significantly better than chance: chance cut-off = 13/ 40 and above). The drop in perform ance is significant (Binomial: P = .004), as is the d ifference bet ween her performance on written and spoken versions in both 1995 and 1996 (1995: McNem ar

c 2 = 10.6, P < .005; 1996:

c = 22.0, P < .005). In March 1995, JO’s errors on written word –picture matching McN em ar

2

were to pick nine close semantic foils, four distant sem antic foils, four v isually related foils and one unrelated foil. By 1996 this pattern had changed slightly to ten no responses, nine close sem antic, four distant sem antic, and three visual errors. It is interesting to note that although her ov erall score had dropped significantly, 50% of her errors were semantic suggesting that, at least for a subset of item s, an im pov erished semantic representation was still activ ated by the written word input. The within-category word –picture m atching tests inv olv e 100 trials, each containing the

v ersion her score rem ained stable (the drop from 96/ 100 to 93/ 100 is not statistically significant: Binom ial, P = .23), although in March 1996 it was just outsid e the range collected from six eld erly subjects. On the written version her perform ance dropped d ramatically 2 from 83/ 100 to 37/ 100 (McNem ar, c = 34.9, P < .005; chance cut-off = 28/ 100 and above). For each of the three testing sessions the difference between the scores in spoken and written versions was significant (March 1995: McNem ar 2 2 c = 8.5, P < .005; October 1995: McNem ar c = 15.4, P < .005; March 1996: McNem ar c = 48.8, P < .005). It was d em onstrated in 1995 that JO’s per2

form ance on written word com prehension tasks im proved to a norm al lev el when she was perm itted to read the words aloud (Lambon Ralph et al., 1996). This recoding effect was assessed longitudinally using the PALPA word association task. In this test the patient is required to pick which of four words is closest in meaning to a target item (e.g. fog). The correct response (e.g. mist ) is accom panied with a sem antically related foil (e.g. steam) and t wo unrelated items (which are sem antically related to each other: e.g. bolt and lock). Half the items relate to concrete items and the other half to abstract concepts. The results are sho wn in Table 1. In the silent condition, JO’s performance for the concrete items rem ained unchanged (but outside the normal range) while her score for the abstract item s reduced to just 2/ 15 (13%: a


393

LAMBON RALPH ET AL.

Table 1. Jo’s Comprehensi on of Spoken Words, Written Words, and Pictures


Task/Stimulus Types PALPA spoken word –picture m atching PALPA w ritten word –picture m atching Within-categ ory spoken w ord picture m atching Within-categ ory w ritten word –pictu re m atching PALPA w ord-association Hig h im ag eability Low im ag eability Hig h im ag eability Low im ag eability Pyram id s & Palm Trees Test Pictu res

Reading Condition

No. of Items

March 1995

October 1995

March 1996

Normal Control

40

90%

NT

95%

88 –100

a

40

55%

NT

35%

88 –100

a

100

96%

96%

93%

96 –100

b

100

83%

77%

37%

96 –100

b

Silent Silent Aloud Aloud

15 15 15 15

33% 47% 66% 80%

40% 47% 73% 53%

40% 13% 66% 53%

73 –100 a 60 –100 a 73 –100 a 60 –100

–

52

92%

75%

81%

94 –100

Silent

Silent

a

a

a

Published norm s (2 SD cut-off). b Collected from six elderly control subjects. N T = not tested.

score no better than chance). When permitted to read the item s aloud, her perform ance in-

March 1996 fell further belo w the normal range. The d ifference bet ween her scores in

creased significantly on all three occasions (March 1995: Binom ial, P = .001; October 1995: Binom ial, P = .02; March, 1996: Binom ial, P =

March 1995 and October 1996 is significant 2 (McNem ar c = 4.3, P < .05), although the d ifference bet ween her scores in March 1995 and

.006). Her understand ing of written word s read aloud (an ind irect test of spoken word

March 1996 d oes not achiev e significance 2 (McNem ar c = 2.1, n.s.).

comprehension) was only one point outsid e the normal range both for concrete and abstract item s.

Reading Aloud

The all-pictu re version of the Pyramids and Palm Trees Test (Ho ward & Patterson, 1992) requires the patient to chose which of two

JO’s longitudinal reading perform ance is shown in Table 2. Her read ing accuracy changed little ov er the intervening year. The

pictures (e.g. a palm tree or a fir tree) is associativ ely linked to a target picture (e.g. a pyramid ). In March 1995, JO’s performance on this

words used by Strain, Patterson, and Seidenberg (1995) orthogonally m anipulate regularity, imag eability, and frequency in List 1, and

test was one point outside the normal range (see Table 1). Her scores in October 1995 and

im ag eability and regularity for a set of lo w-frequency words in List 2. JO was able to read

394



Table 2. JO’s Reading Aloud


Task Strain et al.: List 1 Strain et al.: List 2 Levels of regularity PALPA non w ords 3 letters 4 letters 5 letters 6 letters a

No. of Items

March 1995

October 1995

March 1996

Normal Cont rols

96 64 120

100% 95% 97%

99% 97% 98%

99% 97% 93%

98 –100 b 92 –98 b 95 –100

6 6 6 6

67% 67% 83% 100%

83% 100% 100% 100%

100% 100% 83% 83%

67 –100 a 83 –100 a 67 –100 a 67 –100

a

a

Published norm s (2 SD cut-off). b Collected from 10 elderly control subjects.

these words as well as norm al control subjects. The sam e pattern was found for non word

d om inant nam ing errors were either failures to

read ing (PALPA Test No. 36: Kay et al., 1992). Only on the “Levels of Regularity” list

nate or superordinate nam es). Her decline in

(Shallice, Warrington, & McCarthy, 1983) was there a very sm all (and nonsignificant) d rop in read ing accuracy.

N am ing Test (Kaplan, Goodglass, & Wein-

respond or sem antic errors (category co-ordiperformance was most apparent for the Boston traub, 1976), her score red ucing from 40/ 60 to 2 28/ 60 (66% ® 47%: McNem ar c = 7.6, P < .01) and on a nam ing-to-d efinition task (50 com m on object and anim al targets given sim ple

Naming

d ictionary-style definition s containing percep-

The clinical indications of increasing anom ia were confirm ed by three tests of naming and a category fluency task (see Table 3). JO’s pre-

tual and associativ e/ functional information; e.g . dog, “a domesticated, four-legged mam m al which has fur and barks”), her accuracy

Table 3. JO’s Naming and Category Fluency

Task Boston Nam in g Test N am ing 240 line dra wing s N am ing to definition Category fluency (8 categories )

No. of Items

March 1995

October 1995

March 1996

60 240 50

66% 77% NT 40

63% 71% 74% 28

47% 69% 46% 18

–

Normal Controls a

82 –98 b 95 –100 b 94 –100 Mean 113.7 a SD 19.4

a

Pu blished norm s. b Collected from six elderly control su bjects. NT = not tested .


395

LAMBON RALPH ET AL.

dropped from 37/ 50 to 23/ 50 (74% ®

46%;

JO’s word m eaning blind ness was not only

McN em ar c = 9.4, P < .005). On the set of 240 sim ple line d ra wings, her nam ing deteriorated slightly from 184/ 240 to 166/ 240 (77% ® 69%:

a stable but also an increasing feature of her progressive illness. This finding allows us to

2

McN em ar c = 14.5, P < .005). JO’s progressiv e anom ia also lead to a d ecline in performance on a test of category fluency (Hodges et al.,

reject the possibility noted by Lambon Ralph et al. (1996) that JO’s pattern of perform ance m ight have becom e m ore like that seen in sem antic dem entia, where und erstanding from

1992). The notable d ifferential between JO’s increasing anom ia and her intact spoken

all modalities is equally comprom ised. The accentuated dissociation bet ween written and spoken word comp rehension allo wed us to

word –picture m atching perform ance is very sim ilar to the pattern described by Graham ,

address the alternative hypothesis, suggested in the Introduction, that the difference was in

Patterson, and Hodges (1995) for their patient FM (albeit FM’s anom ia was consid erably deeper). Although FM was first described as a

fact due to a relative sensitiv ity of written word com prehension to a more general cognitive impairm ent. We can now argue ag ainst

sem antic dem entia patient with im paired com prehension and naming (see Hod ges et al., 1992), over tim e Graham et al. were able to

this on two grounds. First, JO and patients with word meaning deafness form a d ouble d issociation between written and spoken com -

dem onstrate a pattern of “progressiv e pure anom ia” — increasing word -finding d ifficulties for picture naming and category fluency

prehension , thus implying t wo quite separate routes into conceptual knowledge. Second , JO’s progressive illness led to a dram atic re-

without a corresponding change in her com prehension scores.

d uction in her comprehension of written words with no apparent change to her com -


2

DISCUSSION The most obvious change in JO’s data was a dram atic reduction in her ability to und erstand written words. There was no corresponding change in her und erstanding of spoken word s and only a small d ecline for picture comprehension. There was, in addition a substantial increase in JO’s anomia. The recoding effect (increased com prehension of written word s when read aloud) remained ap parent in 1996.

396


prehension of the sam e words when they were presented orally. A subset of tasks was included in the longitudinal battery to test the theory that a sem antic impairm ent would lead to surface dyslexia. In v ariants of this theory (cf. Patterson & Hod ges, 1992; Patterson et al., 1994; Plaut et al., 1996) the influence of sem antic representation s on phonological com putation from orthography can be reduced in three different way s: as a result of an impairm ent to sem antic kno wledge itself, as a consequence of d am ag e to the link bet ween orthographic and sem antic representations, or to the link bet ween sem antics



and output phonology. Between 1995 and

Caram azza, 1995). This could suggest that the

1996, JO’s sem antic route had been com promised ev en further: both her word m eaning

relationsh ip between sem antics and reading aloud v aries from indiv idual to indiv idual (cf.

blindness and anomia had increased. Despite these consid erable changes, JO’s reading aloud had not declined from its 1995 levels. This notable difference can be seen clearly if JO’s

Plaut, 1997), so that some subjects require relatively intact com prehension (and regularise words when they make close-semantic com prehension errors) whereas others need v ery

percentage scores for the assessm ents are plotted on the same axes (see Fig. 1). In this regard, JO’s data ad d to the sm all num ber of patients

little (e.g. EP) or perhaps none at all. Although the indiv idual d ifferences hypothesis fits this pattern of results, it is not clear that there is any

for whom exception word read ing remains intact despite relativ ely poor comp rehension

existing or potential d ata which could falsify the theory (see Lambon Ralph et al., 1995).

(Cipolotti & Warrington, 1995; Lam bon Ralph, Ellis, & Franklin, 1995; Raymer & Berndt, 1996; Sch wartz, Saffran Marin, 1980).

Despite very poor word –picture m atching performance, 50% of JO’s errors were sem antically related to the target item s. This indicates

In its current formulations (even in comp utational form : Plaut et al., 1996), the theory that sem antics contributes to the reading aloud of

that for a num ber of written words an im pov erished sem antic representation was still being activated that might hav e provid ed sufficient

low-frequency exception words does not make any clear predictions regarding the quantity or quality of sem antic activation re-

support for the “direct” orthography-to-phonology route. Hence JO’s data sho w that accurate exception word read ing can occur in the

quired for a giv en level of read ing perform ance (Lambon Ralph et al., 1995). Funnell

presence of impaired sem antic access but do not address the question of whether exception

(1996) argued that her patient EP regularised an exception word only when no m eaning remained av ailable. Reading accuracy was significantly associated with comp rehension

word reading can surv ive a com plete block to sem antics from orthography. It is possible that in tim e, when JO’s written word com prehension had declined ev en further, a surface d ys-

when assessed by a word –picture matching task containing the target and an unrelated foil; there was no association if the foil was

lexia pattern m ay have em erged. Such a result could arise if a d ecline in conceptual kno wledge is paired with a much slower, non-linear

replaced with a close sem antic d istractor. To make matters m ore com plicated, it should be

d ecrement in reading accuracy (see Plaut et al., 1996, Fig. 25). We would suggest that future

noted that other patients have dem onstrated a significant association bet ween reading accuracy and word –picture m atching in which the foils are all within the sam e category

longitud inal studies, which continue beyond the stage we were able to assess JO, should be able to estim ate the relative gradients of reading and com prehension deterioration and to

(Graham, Hodges, & Patterson, 1994; Hillis &

confirm whether the rate of decline varies from


397


LAMBON RALPH ET AL.

Fig. 1. JO’s reading aloud vs. written word comprehension and picture naming.

398



individual to indiv idual (Plaut, 1997) or if, in fact, that the two processes can classically dissociate (Shallice, 1988) from each other, giv en


the prediction that the relationsh ip between them is a subtle one. Manuscript receiv ed 3 March 1997 Rev ised m anuscript receiv ed 14 January 1998 Manuscript accepted 14 January 1998

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