Deep Dyslexic Patient Research Articles

The multiple-lemma representation of Italian compound nouns: A single case study of deep dyslexia

It is not clear how compound words are represented within the influential framework of the lemma-lexeme theory. Theoretically, compounds could be structured through a multiple lemma architecture, in which the lemma nodes of both the compound and its constituents are involved in lexical processing. If this were the case, syntactic properties of both the compound and its constituents should play a role when performing tasks involving compound processing, e.g., compound-word reading. This issue is investigated in the present study through an assessment of the performance of a deep dyslexic patient (GR) in three compound-reading experiments. In the first experiment, verb–noun (VN) compound nouns (e.g., lavapiatti, “dishwasher”, lit. wash-dishes) were employed as stimuli, while in the second, VN compound stimuli were embedded in sentences, and were compared to paired verb phrases (e.g., lui lava piatti, “he washes dishes”). Position-specific effects were ruled out by means of a third experiment, which investigated the retrieval of noun-noun compounds (e.g., pescespada, “swordfish”, lit. fishsword). In experiment 1, GR made errors on the verb constituent more frequently than on the noun, an effect that did not emerge in Experiment 2: when embedded in sentences, VN compounds were read significantly better than verb-phrases and no grammatical-class effect emerged. In Experiment 3, the first and the second constituent were read with the same level of accuracy. The disproportionate impairment, which emerged in reading the verb component of nominal VN compounds, indicates that the grammatical properties of constituents are being retrieved, and thus confirms access to the constituent lemma-nodes. However, the results suggested a whole-word representation when compounds are embedded in sentences; since the sentence context affects the access to compounds through syntactic constraints, whole-word representation is arguably at the lemma level as well (multiple-lemma representation). Experiment 3 indicates that these effects cannot be accounted for by a position-specific impairment.

Qualitatively Different Semantic Representations for Abstract and Concrete Words: Further Evidence from the Semantic Reading Errors of Deep Dyslexic Patients

This paper presents an investigation of the hypothesis that conceptual knowledge for abstract and concrete items is underpinned by qualitatively different representational frameworks (Crutch and Warrington, 2005a). A re-analysis of the semantic reading errors of four deep dyslexic patients is presented, examining the incidence of semantically associated and semantically similar errors in response to abstract and concrete target words. The results demonstrate that abstract target words elicit a greater proportion of associative than similar errors, while concrete words show the reverse pattern. These findings provide evidence which converges with that previously documented for a semantic refractory access dysphasic to suggest that abstract concepts are represented in an associative network while concrete concepts are represented in a categorical framework. The author would like to express his gratitude to Professor Elizabeth Warrington and Professor Max Coltheart for their helpful comments on an earlier version of this paper. He is also indebted to Mr. Chris Frost for his advice on the statistical analysis of the data, and to Professor Martin Rossor for his support of this work. The author is an Alzheimer's Research Trust Fellow.

Toward a frontal lobe disconnection model of deep dyslexia: The role of semantic feedback in phonological false memories

We use a false memory paradigm to investigate the extent to which phonologically relations of a target word may be implicated in semantically driven access of that target word. We are specifically interested in understanding how access to orthography may limit the scope of this implication. Our interest in these questions is directly motivated by the claim that the probability of deep dyslexics making a semantic error in reading a word is affected by the number of close phonological relations of the word (Buchanan, L., Hildebrandt, N., & MacKinnon, G. E. (1994). Phonological processing of non-words by a deep dyslexic patient: A rowse is implicitly a rose. Journal of Neurolinguistics, 8, 163–181; Buchanan, L., Hildebrandt, N., & MacKinnon, G. E. (1996). Phonological processing of non-words in deep dyslexia: Typical and independent? Journal of Neurolinguistics, 9, 113–133). We use the study list in a false memory paradigm to semantically prime words. We look for false recognition effects among phonological relations of the semantically primed words in both modalities, with and without simultaneous orthographic overlap. The critical lures of interest in the experiments are words that are related by orthographic or phonological overlap to the unseen semantic target. We found increased false recognition rates for phonological associates of the unseen semantically-primed target in the auditory modality, only among words with no orthographic overlap with the unseen semantically-primed target. The locus of overlap and the phonological neighborhood size of the phonological relation also plays a role in the false memory rate. In a related experiment, we showed that the phonological neighborhood and concreteness of critical lures also mediates the probability of a semantic false memory. These results are discussed with respect to a frontal lobe disconnection theory of deep dyslexia, which posits that semantic errors in deep dyslexia are result from impoverished constraints to prefrontal regions that are implicated in semantic and phonological access of written words.

New evidence for morphological errors in deep dyslexia

Morphological errors in reading aloud (e.g., sexist → sexy) are a central feature of the symptom-complex known as deep dyslexia, and have historically been viewed as evidence that representations at some level of the reading system are morphologically structured. However, it has been proposed ( Funnell, 1987) that morphological errors in deep dyslexia are not morphological in nature but are actually a type of visual error that arises when a target word that cannot be read aloud (by virtue of its low imageability and/or frequency) is modified to form a visually similar word that can be read aloud (by virtue of its higher imageability and/or frequency). In the work reported here, the deep dyslexic patient DE read aloud lists of genuinely suffixed words (e.g., killer), pseudosuffixed words (e.g., corner), and words with non-morphological embeddings (e.g., cornea). Results revealed that the morphological status of a word had a significant influence on the production of stem errors (i.e., errors that include the stem or pseudostem of the target): genuinely suffixed words yielded more stem errors than pseudosuffixed words or words with non-morphological embeddings. This effect of morphological status could not be attributed to the relative levels of target and stem imageability and/or frequency. We argue that this pattern of data indicates that apparent morphological errors in deep dyslexic reading are genuinely morphological, and discuss the implications of these errors for theories of deep dyslexia.

Semantic ambiguity and the failure of inhibition hypothesis as an explanation for reading errors in deep dyslexia

We report evidence for dissociation between explicit and implicit access to word representations in a deep dyslexic patient (JO). JO read aloud a series of ambiguous (e.g., bank) and unambiguous (e.g., food) words and performed a lexical decision task using these same items. When required to explicitly access the items (i.e., naming), JO showed relative impairment for ambiguous compared with unambiguous words. In contrast, the same stimuli produced an advantage for ambiguous words in lexical decision. The results are discussed within a framework of deep dyslexia that considers errors in production to arise through a failure to inhibit spuriously activated candidate representations.

Semantics and semantic errors: Implicit access to semantic information from words and nonwords in deep dyslexia

In this paper we describe dissociations of implicit versus explicit access to semantic information in a patient with deep dyslexia. This acquired reading disorder is characterized by the production of morphological (e.g., SLEEP read as SLEEPING) and semantic errors (e.g., HEART read as BLOOD) and consequently provides a potential window into the operation of both aspects of the language system. The deep dyslexic patient in this study (JO) demonstrated implicit semantic access to items in a number of tasks despite the fact that she was unable to correctly read these items aloud. The findings from this study are consistent with a model of lexical deficits that distinguishes between explicit and implicit access to lexical representations on the basis of inhibitory processes.

Both concreteness and age-of-acquisition affect reading accuracy but only concreteness affects comprehension in a deep dyslexic patient

As concreteness correlates very highly with the age-of-acquisition (AoA) of words, we attempted to disentangle the effects of these two variables in the oral reading and comprehension performance of the deep dyslexic patient LW. The results of a multiple regression analysis of LW’s reading of 217 words showed that both AoA and concreteness affect reading accuracy, with the AoA effect being most apparent for her reading of concrete words. However, concreteness and not AoA affected LW’s performance in matching spoken definitions to printed words, both when the distractors were semantically unrelated and when they were related. These data are interpreted in terms of a model of reading in deep dyslexia in which concreteness affects the ease with which semantics are accessed and can activate lexical representations, and AoA affects the ease with which lexical phonology becomes available for spoken word production.

Representation and processing of idioms: evidence from aphasia

Idiomatic expressions are often considered ‘automatic speech’ that need not be syntactically or morphologically parsed. However, there is a great structural variation within idioms, which could imply that not all idioms are processed alike. In the present case study with a deep dyslexic patient we compare reading of Finnish verb phrase idioms and noun phrase idioms. On the basis of the present experiments, we conclude that noun phrase idioms are processed more holistically than verb phrase idioms. Moreover, it seems that in verb phrase idioms, processing of inflected complement nouns is context-sensitive: our patient showed improved performance on these items as long as they were primed with sentence context (be it semantically adequate or not). This suggests that idiomatic inflected nouns may be stored as parts of their syntactic constructions.

¿Por qué cometen errores semánticos los pacientes afásicos?

One of the most striking and surprising symptoms of the aphasic patients is the production of semantic errors. This kind of errors, which consists of replacing a word by another with a different but similar meaning, may appear when speaking, as it happens when a patient say dog in reference to a cat (semantic paraphasia), when reading as it happens when a patient reads dog where is writing cat (semantic paralexia), as well as in repetition or in writing. Some patients make these errors only in a specific linguistic modality (deep dyslexic patients make semantic errors in reading, deep dysphasic patients in repetition, etc.), but some patients make semantic errors in several modalities or even in all of them. Why these differences and what are the causes of these errors? Nowadays, models of linguistic processing built up from experiments with normal subjects provide us an answer to most of the above questions. From these models, by using appropriate tasks, it is possible to examine the reasons because of a patient makes certain errors. In fact, the results in different tasks help us to locate the deficit of each patient more than errors per se. It has been shown that sometimes the same type of error (e.g. a semantic paraphasia) can be caused by different processes in different patients. In this paper we will try to analyze which are the cognitive processes underlying semantic errors in each of the linguistic activities, when such processes are altered by injury, as well as to determine the best procedures to know what mechanisms are generating semantic errors in each aphasic patient.

When Does a Deep Dyslexic Make a Semantic Error? The Roles of Age-of-Acquisition, Concreteness, and Frequency

Semantic reading errors are the central and defining feature of deep dyslexia. This study compared the words the deep dyslexic patient LW read correctly with those she omitted and those to which she produced semantic errors in terms of their concreteness, age-of-acquisition, frequency, and length. Semantic errors were made to less concrete, later-acquired, and shorter words than were read correctly; there was no reliable effect of word frequency. More importantly, the actual semantic errors produced were later-acquired than the stimulus words, but they were not more concrete or reliably more frequent. These results implicate age-of-acquisition in the process that produces semantic errors. It is proposed that concreteness determines the specificity of the semantic system to activate a set of candidate responses and that age-of-acquisition biases the ease with which certain words can be selected from this set to be produced as reading responses.

Phonological processing of non-words by a deep dyslexic patient: a rowse is implicitly a rose

Phonological processing of non-words by a deep dyslexic patient: a rowse is implicitly a rose

A functional neuroimaging description of two deep dyslexic patients

A functional neuroimaging description of two deep dyslexic patients

The autocue? Self-generated phonemic cues in the treatment of a disorder of reading and naming

Abstract This study describes a therapy programme that aimed to improve oral reading and spoken naming in a deep dyslexic patient by teaching the patient grapheme-phoneme correspondences. This aim was achieved and the improvement could be attributed to the specific effects of the therapy. However, the pattern of results obtained was very different to that predicted. The patient proved unable to perform or to relearn one of the processes necessary for successful reading by a sublexical routine (blending of individual phonemes to form a word). It is concluded that the improvement had been achieved not by a learned mechanism for sublexical reading but instead by enabling the use of patient-generated phonemic cues. The therapy had enabled the patient to produce successfully the phoneme associated with the initial letter of the word, which then acted as a phonemic cue facilitating reading of that word. Spoken naming was also facilitated as information on the written form of the word could similarly be used to ...

Modality-independent impairments in word processing in a deep dyslexic patient

Modality-independent impairments in word processing in a deep dyslexic patient

Attractor dynamics in word recognition: converging evidence from errors by normal subjects, dyslexic patients and a connectionist model

People make both semantic and visual errors when trying to recognise the meaning of degraded words. This result mirrors the finding that deep dyslexic patients make both semantic and visual errors when reading aloud. We link the results with the demonstration that a recurrent connectionist network which produces the meaning of words in response to their spelling pattern produces this distinctive combination of errors both when its input is degraded and when it is lesioned. The reason why the network can simulate the errors of both normal subjects and patients lies in the nature of the attractors which it develops as it learns to map orthography to semantics. The key role of attractor structure in the successful simulation suggests that the normal adult semantic reading route may involve attractor dynamics.

Finnish Compound Structure: Experiments with a Morphologically Impaired Patient

The present study addresses two major aspects of compound processing, namely the issues of access code and structural effects (headedness), with an extensively studied deep dyslexic patient, HH, who has previously been shown to suffer from morphological impairment. In oral reading of compounds, HH preserves their morphological structure and, at the same time, shows additional processing load in increased errors compared to monomorphemic and derived words. Our data suggest that semantically transparent Finnish compounds are decomposed into their constituents at the level of lexical access. Furthermore, there is a processing asymmetry between the constituents, since several qualitative features of HH's reading performance suggest that it is the first constituent which primarily serves as the initial access code.

A functional neuroimaging description of two deep dyslexic patients.

Deep dyslexia is a striking reading disorder that results from left-hemisphere brain damage and is characterized by semantic errors in reading single words aloud (e.g., reading 'spirit' as 'whisky'). Two types of explanation for this syndrome have been advanced. One is that deep dyslexia results from a residual left-hemisphere reading system that has lost the ability to pronounce a printed word without reference to meaning. The second is that deep dyslexia reflects right-hemisphere word processing. Although previous attempts to adjudicate between these hypotheses have been inconclusive, the controversy can now be addressed by mapping functional anatomy. In this study, we demonstrate that reading by two deep dyslexic patients (CJ and JG) involves normal or enhanced activity in spared left-hemisphere regions associated with naming (Broca's area and the left posterior inferior temporal cortex) and with the meanings of words (the left posterior temporo-parietal cortex and the left anterior temporal cortex). In the right-hemisphere homologues of these regions, there was inconsistent activation within the normal group and between the deep dyslexic patients. One (CJ) showed enhanced activity (relative to the normals) in the right anterior inferior temporal cortex, the other (JG) in the right Broca's area, and both in the right frontal operculum. Although these differential right-hemisphere activations may have influenced the reading behavior of the patients, their activation patterns primarily reflect semantic and phonological systems in spared regions of the left hemisphere. These results preclude an explanation of deep dyslexia in terms of purely right-hemisphere word processing.

Deep dyslexia and right hemisphere reading-a regional cerebral blood flow study

Deep dyslexia is an acquired reading disorder that is characterized by the production of semantic reading errors, greater success when reading aloud concrete and highly imageable words, frequent visual and visual-semantic errors, morphological errors and very poor reading of nonwords. The right hemisphere hypothesis proposes that in deep dylsexia the patient is not reading with an impaired version of the normal left hemisphere reading system, and cannot use that system for reading at all. Instead, a different reading system, located in the right hemisphere is used. The right hemisphere hypothesis was examined in this study by investigating the amount of cortical activation in the left and right cerebral hemispheres of a deep dyslexic patient (L.H.) during visual word recognition. Three experimental tasks were devised to isolate a Visual Word Recognition process and a Spoken Word Production process and these tasks were administered to the deep dyslexic patient as well as another patient with left-hemisphere-damage but a different form of acquired dyslexia (surface dyslexia) and two matched control subjects. Regional cerebral blood flow (rCBF) was monitored during performance on each of the tasks. For L.H., but not the other three subjects, rCBF in the right hemisphere was greater than in the left hemisphere during Visual Word Recognition. By contrast, there was greater activation of the left hemisphere than the right hemisphere for L.H. during Spoken Word Production: this was also true of the other three subjects, but the effect was statistically significant only for L.H. These results support the right-hemisphere hypothesis of deep dyslexia.

Activation of the Phonological Lexicon for Reading and Object Naming in Deep Dyslexia

Poor oral reading in some cases of deep dyslexia could be due to difficulty in inhibiting the phonological lexical entries of words semantically related to the correct reading responses. If this is the case, then additional activation of the correct phonological entries should improve reading performance, whereas additional activation of competing entries should lead to errors. This should hold true for object naming as well as for reading, since both depend on a semantically mediated lexical route. These predictions were borne out with an “output” deep dyslexic patient, who made many semantic errors in both reading and naming. Providing phonetic cues (the initial portions of the correct responses) increased his reading and naming accuracy, and providing miscues (the initial portions of words related semantically to the correct responses) led to errors. Furthermore, when the patient was shown a printed word or pictured object and the examiner spoke a correct reading or naming response in isolation, the patient almost always accepted the response as correct, but he also judged that many semantically related foils were correct. Finally, a comparison of reading and naming errors suggested that “visual” errors may sometimes have a phonological basis.

Phonological processing of nonwords in deep dyslexia: Typical and independent?

Patients with acquired deep dyslexia are unable to read nonwords aloud. The deficit has therefore been attributed to damage in nonlexical phonological processing. Buchanan, Hildebrandt and MacKinnon [5 Journal of Neurolingistics 8, 163–182, 1994] demonstrated that a deep dyslexic patient could process nonword phonology in two implicit tests. The generality of this claim is examined by replicating the Buchanan et al. experiments with two other deep dyslexic patients. Dissociations between lexical and nonlexical processing are examined by manipulating nonword phonology in a task that does not require lexical analysis. The results suggest that sensitivity to nonword phonology in deep dyslexia is common and is distinct from a purely lexical analysis.