Impairment in processing meaningless verbal ...

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Impairment in processing meaningless verbal material in several modalities: The relationship between short-term memory and phonological skills a

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Patrizia S. Bisiacchi , Lisa Cipolotti & Gianfranco Denes

b

a

Dipartimento di Psicologia Generale, Padova, Italy b

Clinica Neurologica, Padova, Italy

Available online: 29 May 2007

To cite this article: Patrizia S. Bisiacchi, Lisa Cipolotti & Gianfranco Denes (1989): Impairment in processing meaningless verbal material in several modalities: The relationship between short-term memory and phonological skills, The Quarterly Journal of Experimental Psychology Section A, 41:2, 293-319 To link to this article: http://dx.doi.org/10.1080/14640748908402367

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THE QUARTERLY JOURNAL OF EXPERIMENTAL PSYCHOLOGY, 1989,41A (2) 293-319


Impairment in Processing Meaningless Verbal Material in Several Modalities: The Relationship between Short-term Memory and Phonological Skills Patrizia S . Bisiacchi Dipartimento di Psicologia Generale, Padova, Italy

Lisa Cipolotti and Gianfranco Denes Clinica Neurologica, Padova, Italy Phonological processing abilities were studied in a patient who, following focal brain damage, showed selective impairment in non-word reading, writing, and repetition and also a severe short-term memory (STM) deficit specific for auditorily presented verbal material. The patient could execute tasks involving phonemic manipulation and awareness perfectly. Our data, in contrast with earlier observations in a case of developmental phonological dyslexia, show that acquired impairment in non-word reading, writing, repetition, and immediate memory may occur despite good phonological processing abilities. The role of STM in processing meaningless verbal material is discussed.

The processing of meaningless verbal material may be selectively impaired following brain damage and interpreted as a consequence of the loss of a specific cognitive procedure. This procedure may be viewed either within the framework of a dual-route model (Morton, 1980;Coltheart, 1981; Patterson, 1981) according to which a non-word is processed by a computational component that converts information from one code to another (e.g. printto-sound component converting graphemes into phonemes), or in that of a lexical analogy model of language processing (Marcel, 1980; Kay & Marcel, 1981) according to which non-word processing can be achieved by analogy with existing words having matching segments. Requests for reprints should be sent to P. S. Bisiacchi, Dipartimento di Psicologia Generale, Piazza Capitaniato 3, 35139 Padova, Italy. Authors’ names are listed in alphabetical order. This research was supported in part by grants MPI to G. Denes and P. S. Bisiacchi.

0 1989 The Experimental Psychology Society


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BISIACCHI, CIPOLOTTI, DENES

Following Beauvois and Derouesnk’s (1979) seminal work, cases have been described of patients whose ability to read words was almost perfect, whereas their performance in reading non-words was severely impaired (Beauvois & Derouesne, 1979; Shallice & Warrington, 1980; Beauvois, Derouesne, & Saillant, 1980; Patterson, 1982; Funnell, 1983; Job & Sartori, 1984; Derouesne & Beauvois, 1985; Denes, Cipolotti, & Semenza, 1987).This clinical picture, called phonological dyslexia, is currently interpreted by most authors as reflecting disruption of the non-lexical procedure that permits orthography to be converted into phonology by means of a print-to-sound conversion system. This system seems to be independent of that which converts phonemes into graphemes: Beauvois and Derouesne’s (1979) phonological dyslexic patient showed intact ability in writing nonsense words on dictation. Similarly, in the writing domain, patients have been reported (Shallice, 1981; Beauvois & Derouesne, 1981; Baxter & Warrington, 1985; Patterson, 1988) with specific impairment in writing non-words to dictation but preserved ability in writing real words (phonological dysgraphia). In these patients non-word reading is markedly superior to writing of the same items. Phonological dysgraphia has been interpreted as the consequence of disruption of the non-lexical route in writing, so that it is impossible for such patients to map the phonemes of non-words on to corresponding graphemes or sublexical units. An auditory parallel to phonological dysgraphia and dyslexia has been described by Beauvois, Derouesne, & Bastard (1980) and McCarthy & Warrington (1984), who reported patients with severe difficulty in the production of non-words in repetition tasks; this pattern contrasted with significantly superior ability in word repetition tasks. The nature of these patients’ deficit could not primarily be ascribed to a verbal short-term memory (STM) deficit (Warrington & Shallice, 1969) but, according to Beauvois, Derouesne, and Bastard (1980) and McCarthy and Warrington (1984), to selective difficulty at the level of the phonological processing necessary to translate speech perception into articulation. In fact, although McCarthy and Warrington’s patients showed associated impairment in their auditory verbal STM, they showed an improvement in tasks that “made greater rather than lesser demands on ST storage”. Similarly, the performance of Beauvois, Derouesne, and Bastard’s (1980) patient in repeating nonwords improved in relation to the time allowed to the subject to process the stimuli. According to the above authors, this fact suggests slowing down of the phonological processing rather than any STM impairment. Considering the single route impairment hypothesis, some cases have been described in which disorders of reading, writing and/or repetition could be explained by the deficit of a cognitive mechanism involved in all these tasks; if a patient shows a similar pattern of errors and good performance in


STM AND PHONOLOGICAL SKILLS

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different tasks, the co-occurring symptoms may reasonably be functionally related and due to damage to a common underlying mechanism. Most theoretical models of language processing include computational components and buffer systems (Caramazza, Miceli, & Villa, 1986). Computational components convert information from one code to another, whereas buffer systems store information of some kind in preparation for further processing. Particularly relevant to knowledge of the role of buffer systems in processing non-words in different modalities are the cases reported by Bub, Black, Howell, and Kertesz (1987) and Caramazza et al. (1986). Bub et al. (1987) describe a patient with selective impairment in non-word reading and repetition. They ascribe this symptom complex to specific impairment at the level of the response buffer, whose role is assumed to be the active maintenance of phonemic information required for non-word reading and repetition. However, these authors did not explore non-word writing. Caramazza et al. (1986) describe an adult patient with a selective deficit in non-word reading, writing, and repetition. Types of errors were similar in all three tasks and could be explained in terms of phonological principles. The authors argued that this constellation of symptoms could be due to impairment of a phonological (output) buffer, specific for processing non-words. This system is said to hold phonological representation of non-words temporarily for further conversion into articulatory representations for speech production. Following the same line of reasoning, the writing of nonwords implies the maintenance of phonological representation while phoneme-grapheme conversion takes place. According to Caramazza et al. (1986), this proposed mechanism is specific for processing of non-words, as words can address lexical articulatory representations directly from the phonological output lexicon for speech production. Similarly, word writing can be accomplished by means of direct access to orthographic representation from the lexical semantic system. Caramazza et al. (1986) argued that failure in processing meaningless verbal material may be due to impairment of a buffer system the role of which is unspecified in STM tasks. In contrast to previous cases in which the deficit was interpreted on the basis of dual-access models proposed for language processing, the impaired non-word reading and writing case described by Campbell and Butterworth (1985) was interpreted as being due to a phonological processing deficit affecting performance in all tasks requiring generation of a phonological code. These authors described the case of a college student without any clinical language impairment who showed a selective deficit in reading and writing non-words. Their subject, a developmental case without any neurological impairment, did not suffer from any other cognitive deficit except for a €PA 41/2-F


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reduced verbal STM. In a series of tasks aimed at revealing her ability in phonological manipulation and awareness, the subject turned out to be impaired in all tasks requiring awareness of phonemic structure (rhyme judgement, homophone matching) and phonemic manipulation (phonological and orthographic segmentation). The authors concluded that impairment of phonological processing and awareness probably underlay both phonological dyslexia and dysgraphia. Whether her STM impairment was a consequence and/or a cause of her difficulties in phonemic manipulation and awareness was left undetermined. It seems therefore that a failure in processing meaningless verbal material could in a developmental context be due to loss of a central operation: phonological manipulation. One would expect a verbal STM deficit to be associated with this symptom complex, as a number of studies (Allport, 1984) have clearly shown the importance of intact phonological processing for normal auditory verbal STM. Finally, patients with specific impairment of auditory verbal STM have been described (Warrington & Shallice, 1969; Vallar & Baddeley, 1984). Although no specific investigation of non-word processing was carried out, it must be noted that the patient described by Vallar and Baddeley (1984) was able to read non-words, whereas in a personal communication the authors claimed that the patient was completely unable to repeat and write twosyllable non-words. In this paper we describe an Italian patient affected by acquired lefthemisphere focal damage, whose performance on a non-word processing task was similar to the cases reported. We were interested in verifying whether in an acquired case a supramodal deficit in processing meaningless verbal material would be associated with impairment of phonemic processing and awareness and reduced memory span.

CASE REPORT RR is a 24-year-old right-handed woman. She attended school for a total of 8 years. In November 1984, at the age of 23, she suddenly developed right hemiparesis and language disturbances. A CT scan showed an area of hypodensity in the vascular territory of the left middle cerebral artery, most prominent in the temporo-parietal region. The patient improved over the following days and months, with the complete disappearance of motor impairment. Her aphasic pattern, initially of global type, showed marked though incomplete recovery. The patient was first seen in our unit in April 1985. five months after the stroke.


297

The data reported here were collected between April 1985 and February 1986.

Neurological Examination Apart from neuropsychological signs (see below), this was entirely within normal limits.


Neuropsyc hologicaI Eva1uation The patient was oriented in time and space. Her co-operation was excellent and her mood appropriate. Buccofacial and limb praxis were unimpaired, both on verbal command and on imitation. Her drawing ability, both on command and on copy, was normal. No visual, auditory or tactile agnosia was present. No calculation disturbances were noted. She scored 27/36 on the Raven Coloured Progressive Matrices 47. She obtained a verbal IQ of 84, a performance IQ of 89, and a full-scale IQ of 86 on the WAIS. RR did not show any gross memory impairment in everyday life. However, she was able to repeat correctly only 3 digits forwards and 3 backwards. Her visuo-spatial span (as assessed by the block tapping test [Milner, 19711) was 4 items forwards and 4 backwards. On the recognition memory face test (Warrington, 1984) her score was within normal limits (40; average is 43, with SD= 3.09). In long-term verbal memory tests such as the word learning test (De Renzi, Faglioni, & Ruggerini, 1977), paired-associate learning test, and memory of short stories, the patient’s performance was within the normal range. In word-learning tests she could correctly recall all 10 words after 5 presentations but could not learn the correct order of the words (after 10 more presentations she refused to continue the task).

Language Examination The patient was given an Italian version of the BDAE (Goodglass & Kaplan, 1972). Her spontaneous speech was fluent, without any articulatory disturbance. Phrase length was normal, and informational content was proportional to fluency. Mild anomic disturbances, which the patient tended to bypass with circumlocutions, were present, and some elements of paragrammatism (mostly functor substitutions) were also noted. Her language comprehension of everyday life was good. On the BDAE comprehension subtests she scored as follows: flawless in “word discrimina-


298


tion” and “body part identification” and on “commands”; however, she scored only 6/12 on “complex material”. On the shortened version of the Token Test (De Renzi & Faglioni, 1978) she scored 21.5/36, errors being concentrated in the last part. Repetition was good for short sentences, but omissions were noted in long sentences. Naming was good, apart from some hesitations. On category naming tests she was able to produce 9 animal nouns in 90 sec. On reading subtests her performance was flawless in reading aloud and reading comprehension. She scored 3 1.5/36 on a written version of the Token Test (untimed presentation). On writing subtests she performed well on writing single letters (to dictation), numbers up to 4 digits, words, and short sentences.

EXPERIMENTAL EVALUATION Lexical Decision Task The patient was presented in the vocal and written modality with a list of 80 items of random intermixed words and non-words; non-words were derived by changing 1 or 2 letters from the corresponding real word, giving rise to pronounceable strings. In the written modality the items were printed on index cards and the patient’s task consisted in sorting out the non-words. Her performance was flawless, as she could correctly detect 40/40 non-words. The same stimuli were auditorily presented, one every two seconds. Her performance was again flawless (40/40).

Auditory/Visual Matching In this task our patient was required to decide whether a spoken stimulus such as /brin/ and a written stimulus brin or prin were the same or different. The test material consisted of 80 pairs of stimuli. Half the auditory and visual items were the same, the other half were different. The phonemes explored were stop consonants and could be contrasted for voice, place of articulation, or both. RR’s performance in this task was flawless.

Reading, Writing and Repetition Reading Performance

RR was a good reader: before her illness she used to read daily newspapers, novels, and books. After her stroke she complained that reading was very difficult.


299

Letter Naming. Letter naming was correct for all the letters in the Italian alphabet (21). Letter Sounding. RR was able to give the appropriate sound to every letter of the Italian alphabet.


Syllable Reading. The patient was asked to read aloud 15 nonsense syllables composed of CV(5), VC(5) or CCV(5). She read 14/15 syllables correctly, the single error being on CV (Gi /@i/ was read as Gli /Ai/). Word Reading. The patient was asked to read a list of 139 words. Stimulus features varied in the list, which included: word class (nouns, verbs, adjectives, and function words) frequency, concreteness, and length. RR read 135 words correctly (97.1%); they were read promptly, and no relationship was found between stimulus length and reading time. The noun list was composed of 62 items including high- and low-frequency concrete nouns, nouns with unusual stress position, and abstract nouns. She read 59 nouns correctly, making 3 visual errors giving rise to 2 neologisms (eresia-teseria, fama-tnoma) and 1 abstract word not related semantically (realru-tlealtu). She read 20/20 adjectives correctly. Her performance on reading functors was again flawless (27/27). She made only one error in reading 30 verbs, limited to the affixed part (chiamano-rchiamiamo).

TABLE 1 Summary of RR's Reading of Italian Words

N

Concrete nouns H.F. Concrete nouns L.F. Nouns with unusual stress position H.F. Nouns with unusual stress position L.F. Abstract nouns H.F. Abstract nouns L.F. Functors H.F. Functors L.F. Adjectives H.F. Adjectives L.F. Affixed verbs H.F. Affixed verbs L.F. Total H.F. = high frequency; L.F. = low frequency.

10 10 10 10 10 12 15 12 10 10

Number correct

% Correct

10

100

I0

I00

15 15

10 10 9 10 15 12 10 10 14 15

100 100 90 83 100 100 100 100 93.3 100

139

135

97.12


300


Non-word Reading The patient was asked to read a list of 130 pronounceable non-words of different lengths ( 4 1 0 letters). The non-words were obtained by changing a single letter in the initial, medial, or final position of high- or low-frequency words. All these non-words were thus visually similar to existing Italian words. RR was able to read 82 non-words correctly (63%). All errors were visually related to the non-word target and dealt mainly with substitution of a single letter of the target non-word (pentando-+pertando), omission of a letter (rilcuote-rilcute), or addition of one letter to the nonword target (carpagna+carapagna) (see Table 2 for further details). Some of these errors resulted in real Italian words (18 cases, corresponding to 39% of total errors, e.g. aiulla+aiuola; awntihaventi). The remaining 28 errors (61 "/o) were other non-words. Summary RR could read words essentially normally, but she was less proficient in reading non-words. It should be stressed that most of her incorrect responses to non-words were off-target by one or two letters only. Writing Performance

Letters. RR could correctly write all the letters of the Italian alphabet to dictation, given either the alphabetic name (21/21 correct) or the syllabic sound (1 5/15 correct). Syllables. The patient was asked to write to dictation the same syllables used in the reading test. She wrote 14/15 syllables correctly, the only error being of CCVs type (spo+sguo).

TABLE 2 Errors in Reading Non-words: Distribution of Error Types

Response

Single letter errors Substitutions Insertions Deletions Unawareness of the stress in the last syllables Multiple letter errors Multiple substitutions Multiple deletions Substitution & insertion Transpositions

Worh

Non-worh

Total

16 0 I 0

9

2 6 4

25 2 7 4

0 0 I 0

2 1 3 1

2 1 4 1



301

Words. The same list of stimuli used in the reading test was administered as a writing-to-dictation test; 1191139 words (85.6%) were written correctly. RR's word writing was not affected by length. No frequency effect was noted. She wrote 56/62 nouns correctly. Her 6 errors were: 1 multi-letter error (perdita-tpredica); 1 letter added (esito-+esisto) and 4 single-letter substitutions giving rise to neologisms (i.e. eresia+esesia). She could write 17/20 adjectives, making 3 errors consisting of letter substitutions giving rise to neologisms (i.e. ostile-tortile; banale-tmadale; ignobile+indobile). Her performance in writing functors was 24/21. One error was a function word substitution (percih-per;); the other 2 were letter substitutions giving rise to neologisms (i.e. invano-imano; pertunto+pentanto). She made 8 errors in writing 30 verbs: 6 of these were concentrated in the root of the verb (i.e. dara-ttara; arde-tarte; ideh-tuteb; urto-tutto; ergeva-temergeva; sbuchi-sbicchi); 2 were omissions. Non-word Writing. The patient was asked to write to dictation the 130 non-words used in the reading tests. She could correctly write only 52 out of 130 non-words (40%). In only 4 cases could she not produce any written response at all. In 13 cases, errors consisted of words differing from the target non-word by only 1 letter (e.g. pentunto-tpensando; quosszkquassz2). In 61 cases, the errors consisted of other non-words, mainly differing from the target by only one letter. The distribution of error types is shown in Table 4.

TABLE 3 Summary of RR's Writing of Italian Words

N

Concrete nouns H.F. Concrete nouns L.F. Nouns with unusual stress position H.F. Nouns with unusual stress position L.F. Abstract nouns H.F. Abstract nouns L.F. Functors H.F. Functors L.F. Adjectives H.F. Adjectives L.F. Affixed verbs H.F. Affixed verbs L.F. Total H.F. = high frequency, L.F. = low frequency.

Number correct

YOcorrect

10 10 10 10 10 12 15 12 10 10 15 15

10

100

10 9 10 10 10 14 10 10 7 14 8

100

139

119

90 100

100 83.3 93.3 83.3 100 70 93.3 53.3

85.6

302

BISIACCHI, CIPOLOTTI, DENES TABLE 4 Errors in Writing Non-words: Distribution of Error Types

Response


Single letter errors Substitutions Insertions Deletions Accent

Words

Non-words

Total

10

24 3 4 2

34 3 4 2

6 2 5 6 3 1 1 3 1 1 2

6

0 0 0

Multiple letter errors Multiple substitutions Multiple deletions Substitution & insertion Substitution & deletion Substitution & transposition Deletion & transposition Deletion & insertion Fragments Substitution & accent Deletion & accent Neologisms

0 0 0 1

0 0 0 0

0 0 0

2 5

I 3 1 1 3 1 1 2

-

Summary. RR wrote most words correctly but was able to write only 40% of non-words. Most of the errors in writing non-words involved only one letter of the dictated item. Repetition Performance

Phonemes. The patient correctly repeated all the phonemes of the Italian alphabet. Syllables. The patient was asked to repeat the same syllable used in the reading and writing tests. Her performance was flawless (1 5/15 correct). Words. The same list used in the reading tests was administered as a repetition test. RR could correctly repeat 137/139 words (98.5%). She made one error on verbs (chiamano+chiamammo) and one error on abstract nouns uama+noma). Non-words. The same list of non-words used in the reading and writing tests was administered. The examiner read each item once, and the patient


303


was asked to repeat the stimulus immediately after the examiner had finished. She could repeat 1 13/l 30 non-words correctly (87%). Repetition errors were concentrated mainly in non-words of 7-10 letters, without any tendency to voiced/unvoiced confusion (this kind of confusion was present in only 2/17 errors). The distribution of error types made in non-word repetition is shown in Table 5. As in reading and writing non-words, most errors were substitutions of one phoneme (12/17). Summary. RR’s repetition of words was almost perfect (98.5%), but her performance on non-word repetition was mildly impaired (87%). Once again, her errors were substitutions of single letters, as in reading and writing. Summary of Reading, Writing, and Repetition Tasks

Word Processing. The patient correctly processed most of the stimuli (97% in reading, 85.6% in writing, and 98.5% in repetition). No semantic errors were made. The few errors in all tasks involved letter or phoneme substitutions or deletions. Non-word Processing. Performance on these tasks was significantly inferior to word processing, with writing more impaired (40% correct) than reading (63% correct) and repeating (87% correct). A similar pattern of errors emerged in the three tasks: incorrect answers were usually one or two letters or phonemes off-target. A more detailed TABLE 5 Errors in Repetition of Nonwords: Distribution of Error Types

Error types Single phoneme errors Substitutions Insertions Deletions Transpositions Accent Muliiple phoneme errors Multiple substitutions Multiple insertions Substitution & insertion Substitution & deletion Fragments

No

12

0 2 1

I


304


analysis was carried out in order to assess the stimulus/error relationship in terms of phonological relatedness. Each error was counted separately when more than one error was present in any item. The analysis was carried out on 43 incorrectly produced target letters in reading, 80 in writing, and 15 in repetition. The confusion matrices were then made out for reading, writing, and repetition. The confusion matrices report the phonological relationship between stimuli and errors. For example, in reading, when the error involved a stop consonant or a vowel, 76.4% of the patient’s responses consisted of another stop consonant or another vowel, respectively. In writing, the values were 75%, and in repetition 100%. From this pattern of errors it seems that, in the three modalities, a phonological relationship to the stimulus is maintained at least as regards errors in the phonological categories of stop consonants and vowels. The same pattern occurs, but it is weaker, if all the phonological categories are included: in this case the percentages are 57 in reading, 42 in writing, and 7 1.4 in repetition. In order to rule out the possibility that RR’s impaired performance in processing meaningless verbal material could be due to a combination of low educational level and low IQ (86), 10 normal subjects matched for age, education, and IQ were submitted to reading, writing, and repetition of the same list of non-words used for our patient. The results are reported in Table 6, in which it is evident that normal subjects were able to process almost perfectly meaningless verbal material. RR’s scores are also reported in Table 6.

Phonological Processing A selective difficulty in repeating and writing non-words to dictation may be TABLE 6 Mean Errors and Standard Deviations for a Group of 10 Control Subjects and RR, for Reading, Writing, and Repetition of 130 Non-words

Reading

Writing

Repetition

-

X SD

-

X SD

-

X SD

Controls N = 10

RR

4.4 1.98

481 130

2.8

781I30

1.4

1.7

1.3

171130


305

due to a subtle phonemic perception deficit affecting linguistic tasks where lexical-semantic mediation is impossible (Blumstein, Baker, & Goodglass, 1977). We therefore tested RR’s ability in discrimination and identification tasks involving synthetic speech sounds varying in Voice Onset Time (VOT).


Auditory Phoneme Discrimination and Categorization Tests

Blumstein, Cooper, Zurif, and Caramazza (1977) have shown in a series of studies that the speech perception deficit of aphasics may be successfully analysed by exploring their ability to process the acoustic feature VOT. VOT may be defined as the timing relation between release of the burst in a stop consonant and onset of glottal pulsing. It is one of the acoustic dimensions of a speech sound and is an important parameter for distinguishing between the voiced and voiceless forms of the stop consonants.

A total of 1 1 stimuli signalling the phonetic categories [du] and in the Haskins laboratories was used. Two test tapes (one identification and one discrimination) were used. The identification tape gave random presentation of 10 occurrences of each stimulus with an inter-trial interval (ITI) of 4 sec. The discrimination tape gave random presentation of stimulus pairs in which the members of each pair were either the same or differed from each other by a VOT of 20 msec. The members of each pair were separated by 1 sec of silence; the IT1 was 3.5 sec. The discrimination test consisted of 3 separate random-order parts, each containing a total of 47 discrimination trials, 36 different and 1 1 the same. Stimuli.

[tu] synthesized

Procedure. The subject was tested in a quiet but not soundproofed room. The test tape was played on a Revox tape recorder, and the signal was presented through headphones. In the identification test the patient was required to identify each stimulus presented auditorily by pointing to the appropriate card printed with du or tu. In the discrimination task the patient was required to determine whether the stimulus pair was the same or different by pointing to the appropriate card on which the words “uguule = ” [same] and “diverso # ” [different] were written. Results

RR’s identification and discrimination tests were in the normal range, as assessed by comparing her performance with that of a group of age-matched normal Italian subjects (Celia, 1974). RR thus showed normal ability in processing speech signals at the phonetic level. The fact that RR performs in the normal range on this sensitive test of

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EISIACCHI, CIPOLOTTI, DENES


speech perception makes it unlikely that her problems in repeating and writing non-words on auditory presentation are due to a subtle problem in auditory discrimination.

Phonemic Manipulation In analogy with the hypothesis that difficulty in non-word repeating and writing may reflect a phonetic discrimination deficit, poor non-word reading may be due to failure in manipulating letter sounds effectively. In order to test this hypothesis, we determined the patient’s ability in handling phonemes in spoken words by means of a series of tests requiring conscious manipulation of single phonemes within word sounds. A modified version of Campbell and Butterworth’s (1985) tests was used, adapted for the Italian language. Spoonerizing Task

The task consisted of exchanging initial sounds from pairs of spoken words (e.g. “Sandro Pertini” becomes “Pandro Sertini”). At the level of oral phonetic segmentation, this task reflects the basic phonemic parsing ability necessary for good spelling. The patient performed well, with 18 correct answers out of 20 pairs. It is interesting to note that in seven pairs the correct solution could not be obtained by only mentally exchanging the first letters of the couple-that is, if RR simply exchanged letters and mentally read the new word, she made a mistake (e.g. “Silvia Chiri” “[KJilvia Siri”). By comparison, the mean score of 10 normals on this task was 19.2. The two errors made by the patient were omissions. Counting Phonemes

This task consisted of counting the “number of sounds” in a spoken word or non-word. In Italian there are few instances of lack of correspondence between number of sounds and number of letters, and because of this very high correspondence between graphemes and phonemes it is reasonable to assume that orthographic strategies may be used in counting phonemes. If this were the case, we would expect a high number of errors in all items in which number of sounds does not correspond to number of letters (e.g. in Italian “gl”, “ch”, “sc”, “gn” correspond to only one phoneme /a/, /k/,/J/, /q/,respectively). RR’s performance was as follows:

Nun- words

Words

NL = NS 14/15 (NL

=

NL > NS 13/15

NL=NS 14/15

number of letters; NS = number of sounds.)

NL>NS 14/15


307


Auditory Acronyms

This task requires phonological parsing and assembly. The patient’s task was to take the first sound of 2 or 3 spoken words and combine them in order to form a new word (e.g., “io nuoto” should give “in”; “Giovanni lavorava ieri” should give “gli” (/Li/). The patient was given 20 items in which the correct response could be achieved by both Orthographic and phonemic strategies because the sound of the letters is identical to the sound of the corresponding grapheme (i.e. ‘‘io nuoto” = “in”), and 10 items in which the sound of the first letter did not correspond to the sound of the grapheme (i.e. “sciabola in” = “sci”(/Ji/) and not “si” (/si/). RR made 17/20 correct responses in the first list and 8/10 in the second.

Orthographic Segmentation Tasks

Some authors (e.g., Kay and Marcel, 1981) have suggested that non-word reading and writing is achieved by analogy with segments of known words. This operation must rely on efficient orthographic and phonological segmentation abilities. RR’s ability in this respect was therefore tested by using a modified version of Funnell’s (1983) tests, adapted for the Italian sample. The stimuli in the three experimental conditions were presented separately on index cards, no time limit being imposed.

Task 1. Words in this task could be orthographically segmented into two further words (e.g. “infatti“-+“in” “$atti”). The patient was first asked to read the complete word aloud (“infattl“’)and then the two individual words forming it (“in” “jiatti”). Out of 15 words, we calculated how many complete words she could read and how many component words she could compare, (in this case the maximum score was 30). She scored 15 in the first part and 30 in the second. Task 2. The second task differed from the first in that two component words changed their stress or voice/voiceless dimension (e.g. “malizia” is composed of “mal?’ and “[zlia”; in the whole word “malizia” the “z” is voiced, whereas in the compound word “zia” the “z” is voiceless, at least in the north of Italy). We again found the same kind of score: a perfect 15/15 for the first part, and 28/30 for the second. Task 3. The patient was asked to find a word hidden among various letters forming a non-word. For example, the non-word “scocata” concealed the word “oca”. The maximum score was 15. RR scored 15.

308


Phonological Segmentation Tasks


Tasks 1 and 2 were similar to Tasks 1 and 2 of the orthographic segmentation test, the only difference being that the words were administered auditorily. The patient was asked to repeat back the two words forming the item separately, with a pause between them (e.g., “infutti” was repeated “in”‘yutti”).She scored 30130 when the two component words did not change stress or voice/voiceless dimension and 28/30 when they did.

Tusk 3. The patient was asked to segment the initial sound from a short spoken word and to pronounce it in isolation; 15 words were presented and she correctly reported all 15 sounds. Summary of Phonological and Orthographic Tests

RR did not show any difficulty in any task requiring orthographic or phonological segmentation. Similarly, she could correctly perform tests requiring phonological manipulation and processing abilities. Her difficulty in non-word processing was therefore independent of her ability to generate or manipulate phonemic segmentation. Memory Experiments Vallar and Baddeley (1984) have fractionated the process of verbal STM into several subsystems: 1. a phonological non-articulatory short-term store where auditorily presented verbal items have obligatory access (the phonological similarity effect reflects the activity of this system); 2. an articulatory rehearsal initial process whose function is to recode visually presented verbal material phonologically and to refresh information already in the phonological store. Continuous repetition of an irrelevant speech sound (articulatory suppression) abolishes the similarity effect for visually presented material (Murray, 1968; Levy, 1971; Baddeley, Thomson, & Buchanan, 1975).

Neuropsychological examination of our patient showed that she had selective impairment in verbal STM, whereas LTM was within normal limits. Further dissociation was evident in the STM system, as visual STM was better than auditory STM. On this basis a series of memory experiments was planned in order to verify the nature of RR’s STM impairment. Phonological Similarity Effect and Articulatory Suppression Effect

Following Conrad and Hull’s (1 964) seminal work, it has been abundantly shown that, in terms of the articulatory code in which they are stored


309


phonologically, similar items are more difficult to remember than dissimilar ones. The effect of phonological confusability (i.e., more errors in lists of phonologically similar syllables) is a demonstration of phonological input buffer functioning. With auditory presentation it is assumed that access to this store is obligatory (Salamt & Baddeley, 1982), whereas with visual presentation the effect only occurs if subvocal rehearsal is prevented by articulatory suppression (Murray, 1968; Levy, 1971; Estes, 1973). We tested whether RR’s recall of phonologically similar and phonologically dissimilar letters showed the phonological similarity effect. Procedure. Two pools of letters were used: a phonologically dissimilar set (F, K, Q,R,X , L and 2)and a phonologically similar set (B, P,C, G, T and D). From each set 10 sequences of either 2,3, or 4 letters were generated at random. No letter was repeated within a sequence. Both auditory and visual modalities were tested. RR was asked to report orally the items of the presented sequence in the correct order after 10 sec. There were two recall conditions:

1. RR kept silent during both presentation and the 10 sec preceding recall (serial recall). 2. RR was instructed to repeat the word “il” during both presentation of the material and during the 10 sec preceding recall. This concurrent task was required in order to determine whether RR showed the articulatory suppression effect. Results. Control data were taken from Vallar and Baddeley (1 984) who showed that normal Italian subjects are able to remember up to 75% correct sequences of 6 letters auditorily presented, whereas in visual presentation reached 78%. With articulatory suppression the percentage of correctly recalled sequences (for visual presentation) dropped to 2 1. Furthermore, control subjects showed the phonological similarity effect. Table 7 shows RR’s performance on auditory and visual presentation in the first condition (serial recall). Table 8 shows RR’s performance on auditory and visual presentation in the second condition (articulatory suppression). Summary.

The patient showed the following:

1. Items presented visually were recalled better than those presented auditor-

ily. 2. The phonological similarity effect for visually presented stimuli was not shown, but this effect did occur in the auditory modality. 3. Concurrent tasks did not influence recall.

310

BISIACCHI, CIPOLOTTI. DENES TABLE 7 Phonological Similarity Effect: Serial Recall, Percentage of Correct Answers

Auditory presentation


Item phonologically similar Item phonologically dissimilar

,

Visual presentation

2-letter

3-letter

4-letter

2-letter

34etter

4-letter

80 80

0 50

0 0

100

60 60

30

90

10

TABLE 8 Phonological Similarity Effect: Articulatory Suppression, Percentage of Correct Responses

Auditory presentation

Item phonologically similar Item phonologically dissimilar

Visual presentation

2-letter

3-letter

4-letter

2-letter

34etter

4-letter

80 50

0 20

0 0

100 100

60 60

20 10

It seems therefore that RR did have access to the phonological store, as for auditory presented items she did show a phonological similarity effect, although the capacity of her auditory store is below normal limits. On visual presentation, however, she did not show any similarity effect, suggesting that visually presented letters were not phonologically encoded. Further evidence for this interpretation came from the absence of the suppression effect, in that prevention of subvocal rehearsal by a concurrent articulatory task did not impair her performance. Recency Effect

The better recall of the last items of a superspan sequence has been interpreted (Miller, 1956) as proof of normal phonological buffer functioning. Figure 1 shows the patient’s serial recall for letters presented visually (data for auditory presentation were not plotted because of her poor performance). The serial position curve showed no recency effect, indicating that recall from the phonological buffer (responsiblefor the better recall of the last items) was not used in the normal way.

RECENCY EFFECT:VISUAL PRESENTATION

x 100


80

60

40

20

0 1

2

3

4

S.P.

S.P. =Serial position

s

Free recall

b - 4 articulatory suppression FIG. 1 . Percentages of correct recall for letters presented visually.

€PA 41/2-6

31 1

31 2


As previous tasks had revealed some evidence that RR was not using the strategy of subvocal rehearsal (i.e. no evidence of phonological encoding for visually presented material, no articulatory suppression effect, no recency effect) we decided to investigate this issue further by means of the following task:


Word Length Effect

The signature of the subvocal articulation process in immediate memory is the word length effect. Baddeley et al. (1975) showed that short words are easier to remember than longer words in span tasks. The effect of word length upon immediate memory span was examined by using auditory and visual presentation of sequences of words of two and four syllables. RR was given two lists of proper names to recall. One list was composed of short names (e.g. Pino, Zole, Lisa, Luca, etc.) and the other of long names (e.g. Sebastiano, Annibale, Agostino, etc.). The percentage of correct recall was determined for each list. In auditory presentation the names were presented at the rate of one item per sec. In visual presentation they were written on index cards and presented at a rate of 1 every 2 sec. RR’s task was to repeat the sequences 10 sec after presentation, in the correct order. The percentage of correct recall was determined for each list. Control data for auditory presentation were collected from 10 normal subjects matched for age and educational level. They showed a clear word length effect. Table 9 shows control data and RR’s performance on both visual and auditory presentation. RR’s pattern of results shows that: 1. There was no word length effect, as no difference was observed in the recall of short versus long items in either presentation modality. 2. RR showed slightly better performance when presentation was visual. In conclusion, analysis of her memory clearly revealed that she had a grossly defective immediate memory. The lack of a word length effect suggests that she either could not rehearse subvocally or that she did not use this ability, probably because it was of no help to her. In agreement with Hitch and Halliday (1983), who demonstrated that subvocal rehearsal and vocal fluency are closely related, we are tempted to argue that RR’s performance was due to a strategic choice more than to the impossibility of using rehearsal given her fluent spontaneous speech. Moreover, given the lack of visual recency, phonological similarity, and articulatory suppression effects, coupled with better recall for visually presented material, it is tempting to conclude that RR had a defective phonological ST store.


31 3

TABLE 9 Word Length Effect: Percentage of Correct Responses

RR


Visual list 2-items 3-items 4-items Auditory list 2-items 3-items 4-items 5-items

Controls

Short names

Long names

100

90 60 0

50 0 90 40 0 -

100

40 0 -

Shori names

Long names

100 100 100 81

100 100

95 41

The presence of this impairment may explain why RR did not use subvocal rehearsal in verbal STM. In normal subjects this strategy is used for refreshing traces stored in the phonological buffer and for phonological coding of visually presented material, which may thus converge at the phonological buffer. In RR this strategy, although available, was not used, as the phonological buffer to which rehearsed information must be sent was impaired.

DISCUSSION There is no doubt that, considering her reading pattern, R R s impairment could be classified as phonological dyslexia-that is, she showed the following: I . Reading of words was practically flawless, whereas reading of non-words was significantly impaired. 2. No semantic paralexias were noted. 3. Word length did not affect her performance on reading words.

Like other phonological dyslexic patients (described by Derouesnt & Beauvois, 1985; Funnell, 1983; Denes et al., 1987), RR did not show any clear grammatical class effect. However, in spite of her poor non-word reading, it should be noted that she was perfectly capable of sounding single graphemes and reading single syllables correctly. Again, this pattern is not uncommon in phonological dyslexic patients, as shown by Funnell (1983), Coltheart (1985), and Denes et al. (1987).


314


In the writing domain a similar pattern of performance emerged. Spontaneous writing, as well as writing words to dictation, was good and markedly superior to ability in non-word writing. No length effect in writing words was observed. Only a few errors in word writing were concentrated on verbs. This pattern is very suggestive of phonological dysgraphia as described by Shallice (1981) and Baxter and Warrington (1985). Lastly, selective impairment in non-word processing emerged in repetition, although it was less evident than in reading and writing. Although she was able to repeat all types of words correctly, RR showed significant difficulty in repeating non-words. A similar pattern emerged in the analysis of RR’s errors on the above tasks. No length effect was present in reading, writing, and repetition of nonwords composed of 4-10 letters. Processing of meaningless syllables (CV; VC; CCV) was, however, markedly superior to lengthier meaningless words, irrespective of the modality of presentation. All errors were characterized by substitution of a single letter or phoneme. A qualitative analysis showed that the kind of substitution errors made by RR in non-word reading, writing, and repetition was explicable in terms of a specific phonological principle, giving rise to off-target errors within the same phonological category. Summing up the characteristics of RR’s impairment in processing meaningless verbal material, the following pattern emerges: 1. Impairment was selective for non-word reading, writing, and repetition. 2. The pattern of errors in these tasks, although quantitatively different (writing performance was worse than reading, which, in turn, was worse than repetition), was qualitatively similar and explicable in phonological terms. In the light of a dual model of language processing, it therefore seems as though our patient has lost the use of a non-lexical strategy for non-word processing, leading to similar patterns of errors. This forces us to look for an internal causal structure at the basis of her complex of symptoms. In a developmental case, Campbell and Butterworth (1985) showed that the deficit of their subject extended beyond phonological manipulation out of a lexical context and consisted in impaired phonological awareness and manipulation. This is not like our case: not only were RR’s phoneme discrimination and identification ability normal, as shown by her flawless performance on VOT, auditory lexical decision, and visual-auditory matching tasks, but her performance was also within normal limits on all tasks requiring written and auditory material segmented into phonemic terms and/or manipulating such segmentations. It can therefore be suggested from the analysis of this acquired case that, for successful performance on reading, writing, and repetition of new



31 5

material, good phonological awareness and manipulation are not suficient processes. It seems that processing meaningless verbal material not only requires the generation of phonological representations, but probably involves a further step, consisting in the possibility of maintaining the processed material in a buffer system holding segmented phonological information, in order to build a composite blend sound that can be explicitly articulated or further processed (e.g. phoneme-grapheme correspondence) so that a non-word can be written. The role of this buffer system is well described in Caramazza et al. (1986). In the light of our data, we can say that this buffer is not the locus of phonemic parsing; in other words, it seems that segmented phonemic information is structurally represented within this buffer. Following Caramazza et al. (1986), we still cannot distinguish between an output or an input phonological buffer, or know whether it is possible to assume that a single phonological buffer is used in both input and output processing. Further interest lies in the co-occurrence of the STM deficit. RR’s STM deficit was characterized by impaired digit span, absence of a phonological similarity effect for consonant sequences on visual presentation, no effect of articulatory suppression, and no effect of word length on span. She also showed better recall for visually presented material. Again, it must be recalled that this STM impairment was completely dissociated from her phonological abilities. Therefore it can be claimed that, at least in acquired cases, good phonological awareness and manipulation are not sufficient processes for a normal STM. These data could be interpreted in the framework of the working memory system (Baddeley, 1983) as being due to a selective deficit in the (input) phonological store, while subvocal rehearsal, although available, is not used. The association of non-word processing impairment and STM impairment shown by RR is not exceptional: most phonological dyslexic and dysgraphic patients show a reduced digit span (Patterson, 1981). Moreover, as shown in Table 10, most patients described with impairment in non-word processing in several modalities show a similar STM deficit. At this point the question naturally arises as to whether the deficits observed in non-word processing and STM are due to impairment of different functional systems or to a common or partially overlapping system. In the light of our data and on those of the literature, we suggest that the phonological buffer system occupies space within the short-term phonological store. We cannot conclude in favour of the coincidence of the 2 systems or their partial overlapping, as at least one patient PV (Vallar & Baddeley, 1984), described as having a specific impairment within the phonological store, could read non-words correctly although she was unable to repeat and write them (Vallar, personal communication). Our data show that the buffer system probably does not support phonemic parsing as RR did not have any

31 6

BISIACCHI, CIPOLOTTI, DENES TABLE 10 Performance of Reading, Writing, Repetition Tasks, Digit Span, and Phonological Tasks of RR and Patients in the Present Paper Reading

Writing

Repetition

Words Non-

Words Non-

Words Non-

words

words

words

Digit span Phonological processing


~

~

~~

IGR"

+

-

+

-

+

-

3

Auditorydiscr. of phones Auditory visual matching

+ +

MVb

+

-

agraphia

+

-

?

Auditory phonological discrimination

+

REc

+

-

+

+

-

3

Phonological parsing skills Counting phonemes Orthographic parsing skills Phonological segmentation

-

-

PVd

+

+

+

-

+

-

2

RR

+

-

+

-

+

-

2 V O T Auditory ident. & discr. Spoonerizing task Counting phonemes Aud. acronyms Phonological segmentation

Phonological discrimination Assignment of stress Rhyme judgement

-

-

+ + + +

+ + + + +

+ = correct - = impaired ? = not reported "Caramazza et al., 1986. bBub et al., 1987. 'Campbell & Butterworth, 1985. dVallar & Baddeley, 1984.

difficulty in tasks requiring phonemic segmentation or analysis. We therefore suggest that the buffer system holds phonemic information structurally represented in a segmental way. Our patient's results showed that an acquired deficit of auditory-verbal STM is neither a consequence nor a cause of phonological manipulation or awareness difficulties. The analysis of the present case also clarifies some results reported by Campbell and Butterworth (1985). The difficulties shown by their subject,



31 7

RE, may be explained in at least two ways. The development of non-word processing skills may depend on intact phonological processing abilities, such as segmentation; alternatively, the operations involved in skilled phonological processing may overlap with those of non-word processing. However, if the latter explanation is correct, then we should always find that impaired non-wurd processing is associated with impairment in tasks such as segmentation. This was not the case in our patient. An analogy between reading and writing skills in developmental versus acquired deafness can be made at this point. Pre-lingual and post-lingual deaf children are impaired in reading aloud (Swisher, 1976; Bishop, 1982; Denes, Balliello, Volterra, & Pellegrini, 1986), whereas those who become deaf in adult life do not have any difficulty in reading aloud. Similarly, in writing, a selective difficulty in treating morpho-syntactic elements is evident in developmental but not in acquired deafness. This fact suggests that auditory skills are important for the correct acquisition of reading aloud and writing morpho-syntactic elements, but, once learned, these abilities may proceed independently of auditory skills. Similarly, the operations involved in non-word processing and phonological processing might be interdependent in development but then function independently once acquired.

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