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Biomedical subjects

Elizabeth K Warrington

Publications and source records attributed to Elizabeth K Warrington.

16 recordsLinked to original sources
PubMed2007

Word form access dyslexia: understanding the basis of visual reading errors.

We report the case of a patient V.E.M. who exhibits the infrequently described syndrome of visual dyslexia. V.E.M. read many single words accurately and rapidly; however, when words were read inaccurately, the majority of responses were alternate real words bearing a strong visual relationship to the target items. A series of observational and experimental investigations of her reading skills revealed that response accuracy was strongly affected by word frequency and mildly affected by concreteness but not influenced by word length, orthographic neighbourhood size, or semantic priming. It is argued that V.E.M.'s visual dyslexia results from a deficit of the visual word form system. More specifically, we propose that this deficit has an "access" quality, with visual word form representations remaining relatively intact despite an impairment in the processes by which these representations are activated. Taking the results of this study together with previous reports of dyslexic patients who make a high proportion of visual paralexic errors, we also suggest that visual dyslexia represents a multicomponent dyslexic syndrome for which phonological impairment and not semantic impairment may be a necessary condition.

Brain↗
PubMed2006

Partial knowledge of abstract words in patients with cortical degenerative conditions.

Partial knowledge is a common but rarely studied consequence of damage to conceptual representations and is characterized by the retained ability to retrieve crude, superordinate information but not specific, detailed information about a conceptual entity. Previous studies have described partial knowledge for concrete items particularly following semantic dementia (SD). The present study was designed to investigate the occurrence of partial knowledge effects in the conceptual domain of abstract words. A novel 3-level synonym comprehension test was administered to 9 patients with SD, 20 patients with probable Alzheimer's disease (AD), and 40 healthy control subjects. All subject groups showed weaker performance on tasks requiring a fine specification of word meaning compared with those for which a broad sense of meaning or valence was necessary. However, this gradient of partial knowledge was significantly greater for SD and AD subjects than for controls. These results demonstrate that partial knowledge is a general property of a degraded knowledge base and is not restricted to the concrete word domain. It constitutes a normal phenomenon that is exacerbated in the context of neurodegenerative disease.

Aged↗
PubMed2006

The different frameworks underlying abstract and concrete knowledge: evidence from a bilingual patient with a semantic refractory access dysphasia.

We report the case of a bilingual patient (IRQ) who acquired a semantic refractory access dysphasia following a middle cerebral artery stroke. In a series of spoken word-written word matching tasks, the degree of semantic similarity between target and distractor items was found to affect the accuracy of IRQ's identification of concrete but not abstract words. By contrast, the degree of semantic association between target and distractor items was found to affect response accuracy when identifying abstract but not concrete words. These results provide further corroboration for the notion that abstract concepts are supported by an associative representational network whereas concrete concepts are supported by a categorical representational framework. We also demonstrate an equivalent refractory deficit of comprehension in both English and Arabic. In addition, we provide the first documented evidence of a category-specific refractory deficit of knowledge for abstract words.

Aged↗
PubMed2005

Sporadic and familial dementia with ubiquitin-positive tau-negative inclusions: clinical features of one histopathological abnormality underlying frontotemporal lobar degeneration.

BACKGROUND: Frontotemporal lobar degeneration comprises a group of diseases with clinical presentations and underlying histopathologies that overlap. Familial disease occurs in up to 50% of frontotemporal lobar degeneration cases. One of several underlying histopathological abnormalities is of ubiquitin-positive tau-negative inclusions, similar to those in motor neuron disease. OBJECTIVE: To compare clinical features of familial and sporadic cases in this pathological subgroup. DESIGN AND PATIENTS: Case note review of dementia patients with ubiquitin-positive tau-negative inclusion pathological abnormalities proven by autopsy. SETTING: United Kingdom tertiary referral center. MAIN OUTCOME MEASURES: Analysis of clinical features. RESULTS: Eleven familial cases (autosomal dominant) and 18 sporadic cases were identified. Most familial case patients presented with behavioral disturbances similar to those seen in sporadic behavioral cases. Semantic dementia was only seen in sporadic cases. Atypical features occurred in a minority. Sporadic and familial behavioral cases showed no differences in age at onset or disease duration. Neuropsychological test results revealed frontal or temporal deficits in most, but unexpected early parietal deficits in 1. CONCLUSIONS: Behavioral features in familial and sporadic cases were similar, but semantic dementia only occurred in sporadic cases. Diagnostic confusion with Alzheimer disease and corticobasal degeneration occurred in some cases.

Age of Onset↗
PubMed2005

Computation of tactile object properties requires the integrity of praxic skills.

We describe a series of experiments to examine the tactile identification of objects over the course of neurological recovery in a patient with an intracerebral haemorrhage involving the left inferior and superior parietal lobe. Tactile agnosia in this case involved the ipsilesional as well as the contralesional hand, allowing us to observe the effects of dominant parietal lobe damage without the confounding effects of hemiparesis. The findings demonstrate that both apraxia and tactile apperceptive agnosia may result from a unilateral lesion involving the left parietal lobe. The findings further suggest that the computation of macro-geometrical and micro-geometrical tactile object properties is dissociable. Macro-geometrical tactile analysis depends on intact programming of exploratory hand movements, while the role of such movements in micro-geometrical analysis is less clear.

Adult↗
PubMed2005

Jargon dyslexia in an individual with semantic dementia: further evidence for task-specificity in phonological output.

We report a patient with semantic dementia who demonstrated a very unusual dyslexia. He had a global loss of conceptual knowledge in the context of a fluent dysphasia and intact syntax. However, he did not have the surface dyslexia which is typical of semantic dementia; rather his reading impairment was characterized by speech production errors resulting in multiple neologisms. In a series of experiments it was established that input phonological and input orthographical processing were intact as was output phonology for naming and propositional speech. We demonstrate that our patient has a task-specific phonological deficit and we argue that reading and propositional speech rely upon dissociable phonological output systems. Thus we corroborate our earlier evidence of task-specific phonological output stores (Crutch and Warrington, 2001). We also document a greater difficulty with comprehending the written than the spoken word. We account for this pattern of performance in terms of our patient's attempting to read by the indirect phonological route, as with other semantic dementia patients, but suggest that this process is overridden by the task-specific speech production deficit.

Aged↗
PubMed2004

Abstract and concrete concepts have structurally different representational frameworks.

The architecture supporting our conceptual knowledge of abstract words has remained almost entirely unexplored. By contrast, a vast neuropsychological, neurolinguistic and neuroimaging literature has addressed questions relating to the structure of the semantic system underpinning our knowledge of concrete items (e.g. artefacts and animals). In the context of semantic refractory access dysphasia, a series of experiments exploring and comparing abstract and concrete word comprehension are described. We demonstrate that semantically associated abstract words reliably interfere with one another significantly more than semantically synonymous abstract words, while concrete words show the reverse pattern. We report the first evidence that abstract and concrete word meanings are based in representational systems that have qualitatively different properties. More specifically, we show that abstract concepts, but not concrete concepts, are represented in an associative neural network. Furthermore, our patient was found to have significantly greater difficulty in identifying high frequency than low frequency abstract words. This observation constitutes the first evidence of an inverse word frequency effect. Our results challenge the generality of many existing models of human conceptual knowledge, which derive their structure from experimental findings in the concrete domain alone.

Aged↗
PubMed2004

Remembering and forgetting of semantic knowledge in amnesia: a 16-year follow-up investigation of RFR.

We report our long-term follow-up investigations of RFR, a post-encephalitic case of very grave anterograde and retrograde amnesia. We also describe the results of quantitative neuroimaging of his brain injury that showed bilateral and severe reduction in the hippocampal formation and medial temporal structures with sparing of left lateral/posterior and right posterior temporal cortex. We established that RFR had a persistent severe anterograde and retrograde amnesia for personal and public events. His personal semantic knowledge was relatively spared for the retrograde period. There was a modest and global reduction in RFR's vocabulary for words acquired in adulthood before he became amnesic but there was no evidence of any retrograde gradient. His retrograde knowledge of people was also without any gradient. Remarkably, there had been no change in the extent of his semantic knowledge across a prolonged re-test interval indicating that the loss of semantic knowledge was stable and likely to have arisen at the time of his initial lesion. RFR also showed evidence of a limited but significant ability to acquire new word meanings and a more restricted capacity for learning about new celebrities. While he was able to demonstrate face and name familiarity for newly famous people, he was unable to provide much semantic detail. RFR's amnesia can be partially explained by contemporary theories that allow for parallel cortical and hippocampal memory systems but is difficult to reconcile in detail with any extant view.

Aged↗
PubMed2004

The semantic organisation of proper nouns: the case of people and brand names.

We describe the performance of a patient (AZ) with a semantic refractory access disorder on a series of experiments probing comprehension of two broad proper noun categories, namely person names and brand names. By inducing and manipulating the semantic relatedness effects which are commonly observed in semantic refractory access patients, we demonstrate that famous person knowledge is primarily organised by occupation, whilst knowledge of brands is organised by product type. For instance, we show that AZ has significantly greater difficulty identifying a famous person from among distractor personalities who have the same occupation (e.g. composers: Beethoven, Mozart, Handel, and Bach) than those who have different occupations (e.g. Beethoven, Picasso, Shakespeare, and Jefferson). We also show that such semantic relatedness effects do not occur when stimuli are grouped by another variable such as nationality. We argue that these semantic distance effects reflect the greater build-up of refractoriness among concepts which are supported by shared neural circuitry. In psychological space, it seems natural that these individuals should be classified in this way. The strength of our findings lie in the fact that this organisation of psychological space is mirrored by neural organisation. Thus, we report a previously undocumented degree of fine-grain organisation within conceptual knowledge of these classes of proper nouns. We also interpret our data as providing the strongest empirical support to date for the semantic module of cognitive models of person recognition.

Aged↗
PubMed2003

Spatial coding of semantic information: knowledge of country and city names depends on their geographical proximity.

We report the case of a patient, A.Z., with a refractory disorder of semantic processing. Using a number of spoken word-written word matching paradigms, her comprehension of the broad proper nouns category of place names was investigated. In addition to being sensitive to temporal factors, A.Z.'s ability to identify country or city names accurately was significantly worse when selecting a target from an array of geographically close rather than distant places. The influence of geographical proximity and location was observed even when identifying proximal and distal English towns, but not with less well-known American states. These close and distant effects are attributed to the build-up of refractoriness in representations with shared neural circuitry. Our findings reveal a previously undocumented level of fine-grain organization in this domain of semantic space. It is argued that information about geographical proximity cannot be encoded in purely verbal or visual terms. Consequently, we propose the existence of a separate module of spatially encoded information within conceptual knowledge.

Acoustic Stimulation↗
PubMed2003

Nothing to say, something to sing: primary progressive dynamic aphasia.

We describe a 76-year-old man (ADY) with dynamic aphasia in the setting of a degenerative frontal lobe dementia: primary progressive dynamic aphasia. He displayed a striking paucity of propositional speech despite intact speech production, and preserved singing and prosody. Vocal expression in the verbal and musical domains was investigated in a series of neuropsychological experiments based on novel language and musical tasks that were designed to establish the nature and specificity of the verbal output deficit. The features of the language disorder indicated that the speech output pathway was disrupted at the early stage of generation of a new pre-verbal message. In contrast, tests of musical output demonstrated that the generation of new musical ideas was unimpaired. The domain-specificity of dynamic aphasia may result from the disruption of specific cognitive processes necessary for the creation of verbal messages, as well as selective damage of brain regions involved in language production.

Aged↗
PubMed2003

Preservation of propositional speech in a pure anomic: the importance of an abstract vocabulary.

We describe a detailed quantitative analysis of the propositional speech of a patient, FAV, who became severely anomic following a left occipito-temporal infarction. FAV showed a selective noun retrieval deficit in naming to confrontation and from verbal description. Nonetheless, his propositional speech was fluent and content-rich. To quantify this observation, three picture description-based tasks were designed to elicit spontaneous speech. These were pictures of professional occupations, real world scenes and stylised object scenes. FAV's performance was compared and contrasted with that of 5 age- and sex-matched control subjects on a number of variables including speech production rate, volume of output, pause frequency and duration, word frequency, word concreteness and diversity of vocabulary used. FAV's propositional speech fell within the range of normal control performance on the majority of measurements of quality, quantity and fluency. Only in the narrative tasks which relied more heavily upon a concrete vocabulary, did FAV become less voluble and resort to summarising the scenes in an manner. This dissociation between virtually intact propositional speech and a severe naming deficit represents the purest case of anomia currently on record. We attribute this dissociation in part to the preservation of his ability to retrieve his abstract word vocabulary. Our account demonstrates that poor performance on standard naming tasks may be indicative of only a narrowly defined word retrieval deficit. However, we also propose the existence of a feedback circuit which guides sentence construction by providing information regarding lexical availability.

Aged↗
PubMed2002

Preserved calculation skills in a case of semantic dementia.

We present the case of a patient, BET, with a profound semantic dementia who shows a selective preservation of many aspects of number knowledge. In the context of an otherwise global loss of visual and verbal semantic knowledge, our patient demonstrates relatively intact number processing and numerical calculation in both the verbal and visual domain. More remarkably, BET is able to harness her intact calculation skills to number problem solving tasks. Our report provides further evidence that high-level non-verbal reasoning may persist in the absence of any viable language skills.

Aged↗
PubMed2002

The homophone meaning generation test: psychometric properties and a method for estimating premorbid performance.

The Homophone Meaning Generation Test (HMGT; Warrington, 2000) is a new measure of verbal fluency that has been demonstrated to be sensitive to the presence of anterior lesions. In the present study we used the HMGT healthy standardization sample (N = 170) and demonstrate that scores on the HMGT do not differ significantly from a normal distribution and that the test has adequate reliability (alpha = .82). A table for obtaining confidence limits on an individual's score is presented. A regression equation for the estimation of premorbid HMGT performance was constructed using the National Adult Reading Test as the predictor variable. In a sample of 36 cases with anterior lesions estimated premorbid scores were significantly higher than obtained scores (p < .001). Premorbid ability acted to suppress group differences on the HMGT; the partial correlation between neurological status (healthy vs. anterior lesion) and HMGT performance controlling for premorbid ability (.53) was significantly higher than the raw correlation (.44). In addition, hierarchical discriminant function analysis demonstrated that the inclusion of premorbid ability improved classification over that achieved by HMGT scores alone. These results support both the underlying rationale and the clinical utility of controlling for premorbid performance when interpreting verbal fluency scores.

Adult↗
PubMed2002

Does the spelling dyslexic read by recognizing orally spelled words? An investigation of a letter-by-letter reader.

In this single case report we describe our further observations of a patient (ROC) with a classical spelling dyslexia. A word length effect and a script effect were demonstrated. No evidence of semantic processing was obtained with brief tachistoscopic presentations. Single letter identification was unimpaired. In a series of experiments it was shown that her letter-by-letter reading strategy was mediated by explicit letter naming. In particular, it was observed that with successive presentation of the individual letters there was a stepwise function relating her whole word reading to the single letter presentation times. These durations permitted explicit letter naming. When explicit letter naming was prevented by a simultaneous articulatory suppression task, her letter-by-letter reading was significantly impaired. Her performance was compared with a second patient (MRF) who could read but could not spell. His reading was unaffected by articulatory suppression and significantly impaired by a successive presentation of the individual letters of a word. It is argued that explicit letter naming provides an input to the spelling system and thus can be recognized as orally spelled words. We conclude that in the reading-impaired patient there was a lexical deficit compensated for by the operation of a component of her intact spelling system.

Dyslexia, Acquired↗