Semantic Memory Impairment Does Not Impact on Phonological and Orthographic Processing in a Case of Developmental Hyperlexia

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1 BRAIN AND LANGUAGE 56, (1997) ARTICLE NO. BL Semantic Memory Impairment Does Not Impact on Phonological and Orthographic Processing in a Case of Developmental Hyperlexia GUILA GLOSSER,*, PATRICK GRUGAN, AND RHONDA B. FRIEDMAN *Department of Neurology, The Graduate Hospital, Philadelphia, Pennsylvania; Department of Neurology, University of Pennsylvania, Philadelphia, Pennsylvania; and GICCS, Department of Neurology, Georgetown University, Washington, DC Recent evidence from patients with progressive language disorders and dementia has been used to suggest that phonological and orthographic processing depend on intact semantic memory. These claims challenge the traditional view that there are functionally separate modules in the language system. The effect of a severe, but nonprogressive, semantic impairment on phonological and orthographic processing was evaluated in LA, a mentally retarded child with hyperlexia. Knowledge of a word s meaning did not affect LA s word repetition, a measure of phonological processing, or his acquisition and retention of orthographic patterns for writing to dictation low-frequency words with exceptional spellings. These findings support the assertion that both orthographic and phonological whole-word representations can be acquired, stored, and retrieved in the absence of a functional link to semantic memory Academic Press Most language processing models assume separability of at least some of the cognitive components involved in this processing. More specifically, current models of single word reading and spelling postulate at least three functionally distinct mechanisms, one specialized for processing orthographic attributes of letter strings, one for processing phonological attributes, and one for processing semantic information (Caplan, 1995). Recently data from studies of neurological patients with progressive language and cognitive impairments have been used to challenge the assumed separability of language processing components. Patterson and Hodges (1992) described patients with progressive focal dementia or progressive Address correspondence and reprint requests to Guila Glosser, Department of Neurology Gates 3 West, University of Pennsylvania Medical Center, 3400 Spruce Street, Philadelphia, PA Fax: (215) This research was supported by Research Grant DC from the National Institute of Deafness and Other Communication Disorders, National Institutes of Health X/97 $25.00 Copyright 1997 by Academic Press All rights of reproduction in any form reserved.

2 SEMANTIC MEMORY IMPAIRMENT 235 aphasia who showed a selective deficit in reading words with exceptional spelling-to-sound correspondence. These authors hypothesized that the apparent disruption in accessing orthographic representations required for reading exception words was a consequence of these patients semantic impairments. Citing the ease with which words onset and rime come apart in normal phonemic speech errors, Patterson and Hodges assume that words are stored phonologically at a subword level. They further postulate that access to semantic knowledge provides the glue that binds these subword elements into full words. In the absence of the link to semantics, the translation from orthography to phonology occurs at a subword level. Words processed in sublexical segments are vulnerable to regularization errors (e.g., pronouncing the word pint to rhyme with mint ). Therefore, it is claimed that deterioration of semantic knowledge will necessarily produce a surface alexic pattern of reading manifested in difficulties decoding words with exceptional spelling to sound correspondence and the production of phonologically regular errors for these words. Patterson, Graham, and Hodges (1994a) subsequently studied patients with the presumptive diagnosis of Alzheimer s Disease (AD) and found that impaired reading of low frequency words with exception spellings was directly related to dementia severity and the degree of semantic impairment. The investigators concluded that when semantic memory is disrupted, its link to the orthographic processing mechanism necessarily breaks down. This, in turn, impacts on the stability of the representations of whole-word patterns in the orthographic lexicon. In effect, the link to semantic memory is what makes the whole word whole. When this breaks down, words are translated from orthography to phonology using the most frequently occurring patterns of spelling-to-sound correspondence, which compromises the ability to read exception words, although words with regular spelling-to-sound correspondence continue to be decoded adequately. Patterson, Graham, and Hodges (1994b) extended this analysis to assess the impact of semantic memory impairment on phonological lexical processing. Patients with semantic dementia were found to show an advantage for repeating short lists of words whose meanings they knew versus words whose meanings they did not know. Errors on the semantically unknown strings were generally incorrect combinations of correct phonemes that frequently showed a separation of onset and rime of the target words. The authors argued that semantic information is one of the glues that bind phonemes in lexical phonological representations. When semantic processing is impaired, a major source of the coherence of a word s phonological representation is lost, and then phonological information in memory is more likely to be accessed in units smaller than the whole word, leading to phonological distortion. Patterson and colleagues have interpreted their findings as a challenge to the traditional view of the functional independence of the modules that make

3 236 GLOSSER, GRUGAN, AND FRIEDMAN up language processing. Hodges, Patterson, and Tyler (1994) made this challenge explicit, claiming that phonological and orthographic representations of whole words, as well as structural descriptions used to recognize familiar objects, are dependent on semantic memory. In this analysis, the cognitive computations that allow the activation of a representation at one level (orthographic or phonological as the case may be) and the eventual response (in this case the reading or repetition of a word) occur through interaction with other levels (in this case semantic knowledge). When this interaction is compromised, the subword constituents of the representation may not be sufficiently bound to allow the production of a correct response. In short, the various levels cannot function independently. The challenge to the thesis that processing components in the language system are functionally discrete rests on the interpretation that when semantic knowledge is impaired, it results in disturbed coherence of phonological and orthographic lexical representations, leading to deficits in spelling and reading aloud exception words and impaired repetition of multiword lists. We had the opportunity to examine these claims using data obtained from the study of a mentally retarded hyperlexic child, LA. Glosser, Friedman, and Roeltgen (1996) described LA s semantic deficits and his single word processing abilities as being similar to those reported in patients with probable AD. However, unlike the dementing patients examined by Patterson and colleagues, whose deficits are progressive and ultimately generalize to affect all areas of cognitive functioning, LA s semantic deficits are stable and relatively circumscribed. These conditions afforded us the opportunity to study and clarify the impact of semantic impairment on the acquisition, retention, and retrieval of lexical phonological and orthographic knowledge. CASE REPORT LA s medical history is significant for premature birth at 25 weeks, with a rupture of membranes, prolapsed cord, and emergency Cesarean section. His birth weight was 2.2 pounds. At age 1 week, his EEG was abnormal, and at age 2 years, 9 months, he suffered his first seizure. Since that time he has had regular complex partial seizures with secondarily generalized convulsions. On anticonvulsant medication (Tegretol), seizures are controlled to 2 4 per year. LA s neurological examinations have been significant for mild paraparesis. EEGs have shown bilateral spikes and slow waves, right greater than left, and on CT scan there are enlarged ventricles, again right greater than left. When first evaluated at age 6, Full Scale IQ was 51 on the Wechsler Preschool and Primary Scale of Intelligence (WPPSI; Wechsler, 1967). LA showed severe attention deficit disorder with hyperactivity, and marked neuromotor, cognitive, and behavioral delays. Despite his cognitive deficits, single word oral reading was assessed to be at an early third grade level on the

4 SEMANTIC MEMORY IMPAIRMENT 237 Wide Range Achievement Test Revised (WRAT-R; Jastak et al., 1984). Without any formal education or reading training at home, he had reportedly begun to read spontaneously at age 3 1 /2. LA s cognitive profile matches that described for hyperlexia, which has been defined as precocious oral reading abilities in young children who manifest otherwise significantly delayed language, cognitive, and behavioral development (Aram & Healy, 1988). Extensive assessments of LA s reading and spelling abilities between the ages of six and eight are detailed in Glosser, Friedman, and Roeltgen (1996). Briefly, the assessments revealed the following patterns: At age six, LA was reading at the early third grade level, but was unable to write or spell. Qualitatively, LA s oral reading showed normal effects of part-of-speech, imageability, word length, and regularity, and normal performance on standardized pseudoword reading tests compared to healthy children matched for reading grade level. This performance suggested intact orthographic and phonological processing. At the same time, LA demonstrated profound impairments in semantic processing of single words presented orally and in writing. Comprehension of word meanings was assessed to be at a three-year-old level. By age seven his reading had progressed to the mid-third-grade level, and without having had any formal training in the interim, he had acquired spelling skills at the mid-second-grade level. A detailed assessment of spelling at age eight revealed neither part-of-speech nor regularity effects in writing to dictation when compared to healthy children matched in oral reading level. Irregularly spelled words and functor words were spelled normally, as were pseudowords. Despite his abilities to write from sound, LA was unable to write from meaning, performing poorly on tests of written naming and homophone disambiguation. These results provided further evidence of intact orthographic and phonological processing, in the context of severely impaired semantic processing abilities. The following two experiments were conducted to evaluate relationships between LA s semantic impairment and his abilities to process lexical information orthographically and phonologically. EXPERIMENT 1 The first experiment addressed the issue of the impact of semantic memory impairment on orthographic processing. One method often used to assess the integrity of orthographic processing mechanisms is to test spelling for words with exceptional sound-to-letter correspondence (Glosser and Friedman, 1995). Unlike words with regular orthographic patterns, the spellings for exception words cannot be derived directly from the sound of the word. Spelling exception words requires one to draw on preexisting representations of the orthographic word forms. According to the traditional view of the written language processing system, disruption in the semantic system should not impact on the ability to

5 238 GLOSSER, GRUGAN, AND FRIEDMAN acquire or access unique spelling patterns in the orthographic lexicon. This account predicts that a cognitive defect within the semantic system, such as the one described for LA, should not affect his ability to learn the spellings for words whose meanings he does not know. His knowledge of word spellings should not be related to semantic knowledge; rather, it should be only a function of his exposure to the orthographic forms. The alternative view, espoused by Patterson and colleagues, predicts that LA s acquisition of orthographic patterns for words with exceptional spellings will be directly related to his knowledge of the meanings of these words. By this view, LA would be expected to have great difficulty acquiring and retaining memories of irregular orthographic patterns in the absence of semantic information that helps to bind together these unique orthographic lexical representations. To test this hypothesis we evaluated LA s ability to learn the spellings of low-frequency words with exceptional spellings. A multiple baseline method was used to assess the effectiveness of mere exposure to new orthographic patterns of words whose meaning he did not know. Methods At the time of this study LA was 10 years old. As in previous assessments he showed severe semantic impairment (standard score 56) on the Peabody Picture Vocabulary Test Revised (Dunn and Dunn, 1981), a measure of word meaning knowledge that demonstrated abilities at about a 6:1-year-old level. On the WRAT-R standard scores for single word oral reading and spelling to dictation were 122 and 120, respectively, indicating abilities at approximately an eighth-grade level. To test spelling of irregular semantically known and unknown words, two matched lists of 16 low-frequency picturable nouns of exceptional sound-to-spelling correspondence were created (e.g., hearth, brooch, trough). The two lists were matched for Francis and Kucera (1982) word frequency (List A mean 10.7; List B mean 11.9) and letter length (List A mean 5.31; List B mean 5.31). On an initial test of spelling to dictation (Test 1), LA performed equally on both lists. LA was then trained to spell the words he had misspelled from List A. While the experimenter pronounced each word out loud, LA was shown the word and asked to copy it. After all the training words were presented in this manner, spelling to dictation was assessed. This procedure of alternately training by copy and testing spelling to dictation was repeated until LA wrote 100% of the words to dictation correctly on two consecutive trials. LA learned all the words in List A to criterion in five trials. After six weeks, savings of List A training was assessed by testing spelling to dictation of both Lists A and B (Test 2). Using the same procedure described above, LA was then trained to spell the words he had misspelled from List B. Again, criterion was achieved in five training trials. After three weeks, LA was tested on spelling of both full lists (Test 3). Comprehension of the words on the spelling test was assessed using a word picture matching task. Each word was simultaneously shown and pronounced, and LA was asked to point to its corresponding picture. Each picture was presented with three distractors: a semantically related object, an object related to the target either by the phonology of its name or by its picture s visual characteristics, and an unrelated item. Comprehension was tested twice using

6 SEMANTIC MEMORY IMPAIRMENT 239 FIG. 1. Results of a program to train spelling of low-frequency exception words in a hyperlexic child. Performance of a group of age-matched healthy children on the two matched word lists is represented by dashed lines. this method, once after training the spellings of List A words, and once after the completion of Test 3. 1 Results Results of the training program are presented in Fig. 1. Spelling to dictation at Test 1 was the same for both List A and B (43.8% correct). This performance is similar to that of 10 healthy age-matched children (five girls and five boys, mean age 9:11) who spelled 35% of the items correctly on each of the lists. After training of List A words, at Test 2, LA spelled 75% of the words on List A correctly, while his performance on List B was unchanged, at 43.8% correct. After training of List B words, without additional 1 Comprehension was not tested prior to training to minimize LA s exposure to the meanings of the word spellings that he was being taught.

7 240 GLOSSER, GRUGAN, AND FRIEDMAN TABLE 1 Percentage of Low-Frequency Words with Exceptional Sound Spelling Correspondence Spelled Correctly to Dictation: Comparison of Words Whose Meaning Was Known and Words Whose Meaning Was Unknown Test 1 Test 3 Semantically known words N 18 Semantically unknown words N 14 reinforcement of List A training, at Test 3, LA spelled 88% of the words on List A correctly, and 75% of those on List B. Low-frequency words were chosen for this experiment on the assumption that LA would not know their meanings. When tested after the first training session, LA correctly identified 68.8% of the items on the word picture matching task, and after Test 3 he identified 59.4% of the items, a nonsignificant difference. Of those items missed, LA chose the phonological/visual distractor 59% of the time, an unrelated item 18% of the time, and the semantic distractor only 23% of the time, indicating that LA had little if any semantic knowledge about many of the words on this test. Ten healthy age-matched children correctly identified 86.7% of the items (range 79% 97%). In contrast to LA, the majority (62.9%) of the healthy children s errors were semantically related distractors. They made many fewer phonological/visual (22.2%) and unrelated (14.2%) errors. Given the relative stability of the comprehension performances on Test 1 and Test 3, data from the two assessments were combined to constitute a more reliable index of LA s knowledge of the meanings for the words on the spelling tests. The meaning for a word was considered to be known if its corresponding picture was correctly identified on both Tests 1 and 3. Otherwise the meaning for the word was considered to be unknown. Using these criteria 43.75% of the spelling words were semantically unknown. The relationship between word meaning knowledge and spelling to dictation is shown in Table 1. At Test 1, prior to training, LA spelled known words, with which he must have had prior experience, significantly better than unknown words, some of which he may have never encountered (χ ; p.05). At Test 3, however, there was no significant advantage for spelling known versus unknown words (χ 2.003; p.90). Without learning the meanings of the words, LA acquired and retained new orthographic patterns for words without apparent semantic representation. These results are consistent with the view that semantic influence is not required for orthographic processing.

8 SEMANTIC MEMORY IMPAIRMENT 241 EXPERIMENT 2 To assess the impact of semantic memory impairment on phonological processing, we employed tests of word repetition similar to those often used in studies of patients with phonological deficits (Caplan et al., 1986; Friedman & Kohn, 1990). The ability to repeat words of increasing length, especially the capacity to repeat multisyllable pseudowords, is generally considered to be a stringent assessment of the intactness of phonological processing. Warrington (1975) developed a method, subsequently used by Patterson et al. (1994b), that compares repetition for words whose meanings are known, words whose meanings are unknown but whose phonology may be familiar, and pseudowords without meaning that are composed of totally new phonological combinations. Traditional views of language processing (e.g., Ellis & Young, 1988; Kremin, 1987; Morton & Patterson, 1980; Patterson & Shewell, 1987) predict that word meaning knowledge should not impact on repetition. Repetition should not differ for words whose meaning is known compared to words whose meaning is unknown. Since repetition is facilitated for words whose phonological form is already represented in memory (Caplan et al., 1986), repetition of both known and unknown real words is expected to be superior to pseudowords. According to the alternative view, proposed by Patterson and colleagues, repetition of words whose meaning is known should be superior to repetition of words whose meanings are unknown. It is argued that for unknown words there is no semantic glue to bind the subword components. The absence of the link to semantics would be expected to cause the words to be retrieved in their subword components, which increases the likelihood of phonological errors in repetition. This view does not make direct predictions regarding pseudowords. It can be inferred, however, that when the phonological system is stressed by a sequence of pseudowords containing many semantically unbound phonological segments, errors similar to those seen with unknown words should occur. Methods To assess LA s capacity to process phonological information at the single word level, he was administered a test of repetition of 30 orally presented single words and 30 pseudowords of 1 5 syllables in length (e.g., investigation and torrelliative ). LA was tested using these lists at ages 6 and 7. His performance was compared to that of a group of 10 healthy children (seven girls and three boys, mean age 8:2) matched to LA in reading grade level. Because LA performed at ceiling levels when repeating single words and word pairs and he failed to respond to most four-word lists, a three-item repetition test was developed to evaluate the effect of semantic knowledge on repetition. The test included semantically known words (cow-ladder-whale), semantically unknown words (jaw-faucet-sieve), and pseudowords (loy-pellen-chipe). Known words were chosen either from nouns that LA used correctly in spontaneous speech or from those for which he showed consistent comprehen-

9 242 GLOSSER, GRUGAN, AND FRIEDMAN TABLE 2 Percentage of Correct Repetition of 30 Single Words and 30 Pseudowords One to Five Syllables in Length Real words Pseudowords LA age LA age Healthy children 97 (SD 2.7) 94 (SD 6.7) (mean age 8:1) sion on standardized and experimental word picture matching tests. Unknown words were defined as nouns that LA failed to identify correctly on the same word picture comprehension tests. Each unknown word was matched with a known word for number of phonemes and number of syllables. Although the known and unknown words were matched in terms of phonological features and part-of-speech, it was not possible to completely match the lists in terms of word frequency. Word frequency was significantly higher (t (94) 2.06; p.05) for known (mean frequency 48.2; SD 106.3) as compared to unknown words (mean word frequency 13.9; SD 44.8). This is most likely because of the inherent relationship between word frequency and semantic knowledge. A list of pseudowords matched to the real words in number of phonemes and syllables was created. In the final version of the test 23 known, 23 unknown, and 23 pseudoword triplets were interspersed and presented for immediate recall. Results LA s repetition of single words and pseudowords up to five syllables in length was comparable to that of healthy children matched for reading level (Table 2). LA also performed perfectly in repeating the semantically known and unknown single words used in Experiment 1 (18/18 known words correct and 14/14 unknown correct). Thus, there were no indications of apparent impairments in LA s ability to repeat isolated known words, unknown words, or pseudowords. The triplet repetition task provides a more rigorous test of the effect of semantic knowledge on the ability to reproduce phonological lexical forms. Results presented in Table 3 indicate no significant differences in the total TABLE 3 Repetition of Triplet Words Whose Meaning Was Known, Words Whose Meaning Was Unknown, and Pseudowords Correct words (N 69) Known words 60 Unknown words 60 Pseudowords 47

10 SEMANTIC MEMORY IMPAIRMENT 243 number of semantically known and unknown words repeated correctly. By contrast, both known and unknown words were repeated significantly better than pseudowords (χ ; p.05). These results indicate that the semantic status of a word (whether its meaning is known or not) does not affect the accuracy of its repetition. On the other hand, lexicality status, whether or not the stimulus is a real word that has been heard before, does enhance repetition of the item. Together the findings are supportive of the claim that LA s processing of lexical phonological information occurs independently of his semantic knowledge. DISCUSSION The performances of this hyperlexic child indicate that phonological and orthographic processing can be accomplished successfully despite impairment in semantic processing. The results are consistent with the claimed independence among semantic, phonological, and orthographic processing components in the language system and do not support recent challenges to this claim. Experiment 1 showed that orthographic word forms could be learned in the absence of semantic mediation, even for items with exceptional spelling-to-sound correspondence. Despite markedly impaired comprehension of word meanings LA acquired and retained the orthographic patterns for new words with exceptional spellings. LA s spelling capacities paralleled his precocious abilities to read aloud all types of words, including those with exceptional spellings (Glosser, Friedman, & Roeltgen, 1996). LA s repetition performances in Experiment 2 showed further that semantic knowledge is not necessary for the processing of complex lexical phonological information. LA s repetition of single words and pseudowords up to five syllables in length was normal, though his word meaning comprehension was defective in comparison to healthy children. The apparent dissociation between semantic and phonological processing capabilities is even more apparent in LA s repetition of triplet word strings. LA repeated strings of words whose meaning he did not know as well as words whose meaning he did know. Furthermore, he showed an advantage for repeating real words as compared to pseudowords, regardless of the semantic status of the words. The presence of a lexicality effect suggests that, even in the context of impaired access to semantic knowledge, whole word phonological patterns can be accessed to provide an advantage for real words compared to pseudowords. LA s performance profile suggests that repetition for known and unknown real words utilizes the same mechanism, presumably activation of whole-word phonological representations, a process that works less well for repeating pseudowords (Friedman & Kohn, 1990). The findings from this pair of experiments have theoretical relevance in terms of models of language processing. They suggest that both orthographic and phonological processing can be accomplished without requiring input

11 244 GLOSSER, GRUGAN, AND FRIEDMAN from the semantic system. While it seems plausible that these components interact in normal language processing, our findings suggest that they can also work separately. 2 Ours are not the only findings that conflict with the recent challenge to the modularity thesis. Raymer and Berndt (1994) described two women with probable AD who could read exception words that they did not understand. Cipolotti and Warrington (1995) present the case of a patient with probable Pick s disease who also demonstrated preserved oral reading in the context of impaired semantic memory. They found that reading of words of exceptional spelling-to-sound correspondence was not impaired, even when the meanings for these words was unknown. Schwartz, Saffran & Marin (1980), in one of the earliest investigations of a patient with profound semantic impairment, also found preserved reading of exceptional words. All of these reports dispute the claim that a loss of semantic memory inevitably causes a surface alexic pattern of reading. How, then, can we understand some of the recent findings from dementia patients that seem to show a relationship between semantic impairment and lexical phonological and orthographic processing deficits? One possible explanation of dementia patients impaired reading of exception words is that these patients have concomitant disorders in language processing components other than the semantic lexicon. These patients have multifocal cerebral dysfunction that can impact different aspects of linguistic processing. As the disease progresses it may spread to simultaneously disrupt function in areas believed to be critical for semantic processing in the anterior left temporal lobe (Hodges et al., 1992) and in proximal regions in the posterior left temporal lobe considered necessary for orthographic lexical processing (Friedman, Ween, & Albert, 1993; Roeltgen, 1993). If orthographic processing is disrupted in a progressive manner with the advancing disease, then exception word reading would be expected to correlate with dementia severity. Assuming that orthographic processing relies on activation of a network of items (Plaut et al., 1996), words with fewer lexical neighbors (exception words) should be more vulnerable to breakdown. Since many cognitive mechanisms are disintegrating concurrently in AD, it is not surprising to find correlation between two separately deteriorating processing mechanisms, for semantics and orthography. The presence of a letter-by-letter reading strategy in the semantic dementia patient, PP (Hodges, Patterson, & Tyler, 1994), upon whom Patterson and colleagues base many of their conclusions, is also consistent with the inter- 2 The assumed separability of language processing components into discrete modules has no bearing on the manner in which information is assumed to be processed within the modules. Although the different language processing components may be computationally autonomous and informationally encapsulated, it is quite possible that information processing within the modules takes place in a highly interactive manner.

12 SEMANTIC MEMORY IMPAIRMENT 245 pretation that impaired access to semantic knowledge is not the only cause for the observed deficits in phonological and structural description representations in dementia patients. Letter-by-letter reading (pure alexia) is understood as a disruption of the processing of information between the visual system and the language system (Friedman, Ween, & Albert, 1993). The presence of this type of reading disorder indicates that disruption in components other than the semantic system is contributing to the reading problem in some dementia patients. It is just as plausible to suppose that the pattern of surface alexia seen in some of the reported dementia cases results from disrupted orthographic processing. As for the findings regarding repetition, it seems noteworthy that even the dementia patients presented by Patterson, Graham, and Hodges (1994a) show perfect repetition at the single word level. This may be taken as evidence for relatively intact phonological representations (Caplan et al., 1986; Friedman & Kohn, 1990). Since multiword repetition most likely engages cognitive mechanisms outside of the language system (Warrington, 1975; McCarthy & Warrington, 1987), impaired performance on such tasks can not be used as evidence of disruption within modular components of the language system. The fact that dementia patients show deficits in repeating three- and four-word strings is more likely explained by the fact that this activity engages short-term or working memory systems that are known to be impaired in patients with AD (Morris & Baddley, 1988). Since working memory is believed to draw on both phonological and semantic processes (Shelton, Martin, & Yaffee, 1992), it is reasonable to expect that a semantic deficit might impact negatively on tests of auditory verbal span. This, however, does not constitute evidence for the claim that semantic knowledge is necessary for phonological processing at the single word level. We have suggested that dementia patients cognitive impairments in nonsemantic and nonlinguistic domains may account for the observed phonological and orthographic processing deficits reported by Patterson, Hodges, and others (e.g., Rapscak et al., 1989) in these patients. Another way to understand the apparent discrepancy between our findings in the case of developmental hyperlexia and those obtained with some cases of acquired dementia is to consider that disruption to the semantic system may have different effects in a developing nervous system compared with a mature nervous system. In the course of normal development it is likely that associations among semantics, phonology and orthography become established and reinforced over many years. The removal of semantic influences from a system that has learned to process language in this interactive manner might have an effect on phonological and orthographic processing in certain adult dementia patients (Plaut et al., 1996). This does not mean that phonological and orthographic processing can not develop or function competently without semantic knowledge. In some adult dementia patients semantic impairment does not appear to influence orthographic or phonological processing (e.g., Cipo-

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