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Biomedical subjects

M Coltheart

Publications and source records attributed to M Coltheart.

At least 19 recordsLinked to original sources
PubMed2002

Disturbed communication in schizophrenia: the role of poor pragmatics and poor mind-reading.

BACKGROUND: Disturbed speech in schizophrenia may reflect pragmatic deficits of expressive language. Pragmatic comprehension deficits also occur in schizophrenia. This study investigated whether poor 'mind-reading' (i.e. a general difficulty with inferring and monitoring other people's thoughts) causes pragmatic language impairments of both expression and comprehension in patients with schizophrenia. METHOD: Mind-reading (or theory of mind) was tested in patients with schizophrenia and in healthy controls using a false-belief picture-sequencing task. Pragmatic comprehension skills were assessed using a test of non-literal speech interpretation. Clinical ratings of formal thought disorder (FTD) indexed the expressive language deficits of patients. To control for possible contributory effects of executive dysfunction, inhibitory control was tested using capture picture-sequences and executive-planning was tested using the Tower of London task. RESULTS: False-belief picture-sequencing, understanding of irony and understanding of metaphors were all selectively impaired in the patients. Poor mind-reading (indexed by high error rate in sequencing false-belief stories) was associated with poor understanding of irony, but was unrelated to poor understanding of metaphors. Whereas poor appreciation of irony and poor mind-reading were associated with high ratings of positive formal thought disorder, high ratings of negative formal thought disorder were associated with poor understanding of metaphors and executive dysfunction. CONCLUSIONS: Whereas poor mind-reading may contribute to positive aspects of formal thought disorder and impaired appreciation of irony in patients with schizophrenia; negative features of formal thought disorder and poor understanding of metaphors appear better explained by abnormal semantics. Overall, the findings of this study support the view that the functional basis of formal thought disorder in schizophrenia is not unitary.

Adolescent↗
PubMed2001

Visual perspective-taking and schizotypy: evidence for a simulation-based account of mentalizing in normal adults.

Modular theory-of-mind accounts attribute poor mentalizing to disruption of a cognitive module dedicated to computing higher-order representations of primary representations (metarepresentations). Since metarepresentational capacity is needed to mentalize about other people's beliefs but is not needed to judge visual perspectives (which can be done by mentally rotating primary representations of seen objects), this view predicts that visual perspective-taking will be intact in individuals with selective mentalizing impairments. Counter to that prediction, this study found evidence of disturbed visual perspective-taking in normal adults who score higher on the personality variable of schizotypy and who are known to be relatively poor mentalizers (despite intact ability to inhibit salient inappropriate information in order to reason consequentially on the basis of hypothetical states, other than mental states). Whereas high-schizotypal adults and low-schizotypal adults did not differ in their ability to judge item questions (asking the relative location of array features), high-schizotypal adults performed more poorly than low-schizotypal adults in judging appearance questions (asking how an array would appear from another perspective) under viewer-rotation instructions (asking subjects to imagine moving themselves relative to a fixed array) and performed better than low-schizotypal adults in judging appearance questions under array-rotation instructions (asking subjects to imagine rotating an array relative to their own fixed viewer position). Based on these and other findings we conclude that poor mentalizing in normal adults is better understood as an impairment of perspective-taking (visual and/or cognitive) and introduce the concept of allocentric simulation to explain the functional basis of this perspective-taking impairment.

Adult↗
PubMed2001

DRC: a dual route cascaded model of visual word recognition and reading aloud.

This article describes the Dual Route Cascaded (DRC) model, a computational model of visual word recognition and reading aloud. The DRC is a computational realization of the dual-route theory of reading, and is the only computational model of reading that can perform the 2 tasks most commonly used to study reading: lexical decision and reading aloud. For both tasks, the authors show that a wide variety of variables that influence human latencies influence the DRC model's latencies in exactly the same way. The DRC model simulates a number of such effects that other computational models of reading do not, but there appear to be no effects that any other current computational model of reading can simulate but that the DRC model cannot. The authors conclude that the DRC model is the most successful of the existing computational models of reading.

Dyslexia↗
PubMed2001

'I know your name but not your face': explaining modality-based differences in access to biographical knowledge in a patient with retrograde amnesia.

In current functional models of person recognition it is proposed that there exists a single common body of semantic information concerning people accessible from all modalities (e.g. names, faces). In this paper, we present evidence that challenges this view. Two experiments are discussed investigating residual autobiographical and public knowledge in a patient suffering from retrograde amnesia. Knowledge about people was investigated in each case by asking a series of questions, ranging from the very general to the very specific. Experiment 1 examined knowledge about famous people. The results showed that the patient accessed more information about famous people when cued with names than when cued with faces. Experiment 2 examined knowledge about people known personally to the patient. Again, the same pattern of results emerged. While the patient responded accurately to all questions posed with name cues, her ability to recall the same information when prompted with face cues was clearly inferior. This modality-based difference in accessing biographical knowledge is discussed in relation to models of person recognition.

Adolescent↗
PubMed2001

Mirrored-self misidentification: two cases of focal onset dementia.

We present two patients in whom the mirror sign, the inability to recognize one's own reflected image, was a stable and persisting symptom signalling the onset of a progressive dementing illness. Extensive neuropsychological testing was conducted with both patients, with particular emphasis on face processing and the understanding of reflected space. Both patients were also investigated with structural imaging techniques (computed tomography and magnetic resonance imaging). Although the neuroimaging results were not strongly lateralizing for either patient, neuropsychological testing revealed striking right hemisphere dysfunction with relatively intact left hemisphere cognitive function in both patients. Of particular interest was the patients' dissociation on tests of face processing; one patient, FE, had significant face processing deficits while the other patient, TH, had relatively intact face processing. Further testing with TH revealed striking deficits in his ability to interpret reflected space. The results of the face processing tests are discussed in the context of current models of normal face processing, with particular emphasis on the affective component in face recognition. We propose that a combination of cognitive deficits underlie the mirror sign delusion, including perceptual, affective and reasoning impairments, and also discuss the contributions of cortical and subcortical lesions in these two patients and in delusions in general.

Aged↗
PubMed2000

Deep dyslexia is right-hemisphere reading.

Two views exist concerning the proper interpretation of the form of acquired dyslexia known as deep dyslexia: (a) that it represents reading by a multiply damaged left hemisphere reading system; (b) that it represents reading which relies extensively on right-hemisphere orthographic and semantic processing. Price, Howard, Patterson, Warburton, Friston, and Frackowiak (1998) have recently reported a brain-imaging study whose results, they claim, "preclude an explanation of deep dyslexia in terms of purely right-hemisphere word processing." Their claim conflicts with the conclusions of previous published work, which strongly supports the RH hypothesis, work which they do not mention. Furthermore, I argue that their own results also favor the RH hypothesis (even though they claim otherwise); indeed, their results permit the formulation of a much more detailed version of the RH hypothesis than has hitherto been possible. Hence I conclude that the right-hemisphere interpretation of deep dyslexic reading remains the preferred explanation of deep dyslexia.

Brain↗
PubMed2000

Reading aloud begins when the computation of phonology is complete.

Naming latency experiments in which monosyllabic items are read aloud are based on the assumption that the vocal response is not initiated until the phonology of the entire syllable has been computed. Recently, this assumption has been challenged by A. H. Kawamoto, C. T. Kello, R. Jones, and K. Bame (1998), who argued instead that the reading-aloud response begins as soon as the initial phoneme is computed. This view would be refuted by evidence of anticipatory coarticulation effects on the initial phoneme due to the nature of the following vowel in the speeded reading-aloud task. The authors provide such evidence.

Humans↗
PubMed2000

Serial processing in reading aloud: reply to Zorzi (2000).

K. Rastle and M. Coltheart (1999; see also M. Coltheart & K. Rastle, 1994) reported data demonstrating that the cost of irregularity in reading aloud low-frequency exception words is modulated by the position of the irregularity in the word. They argued that these data implicated a serial process and falsified all models of reading aloud that operate solely in parallel, a conclusion that M. Zorzi (2000) challenged by successfully simulating the position of irregularity effect with such a model. Zorzi (2000) further claimed that a reanalysis of K. Rastle and M. Coltheart's (1999) data demonstrates sensitivity to grapheme-phoneme consistency (which he claimed was confounded across the position of irregularity manipulation) rather than the use of a serial process. Here, the authors argue that M. Zorzi's (2000) reanalyses were inappropriate and reassert that K. Rastle and M. Coltheart's (1999) findings are evidence for serial processing.

Humans↗
PubMed2000

Dissociable cognitive impairments in problem drinkers.

Patients in a treatment programme for severe alcohol dependence were tested on a battery of tests designed to examine organizational and visuo-spatial abilities. Analysis using a case-study approach indicated independent organizational and visuo-spatial impairments. An understanding of aetiological factors underlying these cognitive deficits and implications for treatment are discussed.

Adult↗
PubMed1999

The relationship between language-processing and visual-processing deficits in developmental dyslexia.

Some research on developmental dyslexia focuses on linguistic abnormalities such as poor reading of nonwords or poor reading of exception words. Other research focuses on visual abnormalities such as poor performance on psychophysical tasks believed to assess the functioning of the magnocellular and parvocellular layers of the lateral geniculate nucleus (LGN). Little is known about what the relationships are between these two types of abnormalities. We measured nonword reading, exception word reading, and performance with Ternus apparent movement displays (the perception of which is believed to depend upon the magnocellular and parvocellular pathways) in dyslexic children and children without reading difficulties. Our results indicate that performance on the Ternus task is related to nonword reading ability but not to exception word reading ability. We offer two alternative interpretations of these findings. According to the first of these, nonword reading requires a serial left-to-right allocation of covert attention across the letter string being read and the neural systems involved in this attentional process also play a part in responses to the Ternus display. According to the second, poor nonword reading and abnormal Ternus performance are not directly related: perinatal/neurodevelopmental insult has affected the LGN (influencing Ternus performance) and the adjacent medial geniculate nucleus (MGN; affecting phonological ability) and the MGN abnormalities may be more functionally related to poor nonword reading.

Attention↗
PubMed1999

Mentalising, schizotypy, and schizophrenia.

Despite accumulating evidence that patients with schizophrenia perform poorly in mentalising tasks, doubts remain about the primacy of the role played by defective mentalising in schizophrenia. This study investigated the relationship between mentalising ability and self-reported schizotypal traits in non-clinical adults who reported no history of psychiatric illness in order to test two counter-proposals: (1) defective mentalising is a primary cause of psychotic symptoms in schizophrenia; and (2) defective mentalising in schizophrenia is a secondary consequence of the chronic asociality that is typical of general psychiatric illness. Mentalising ability was tested using a false-belief picture sequencing task that has been used elsewhere to demonstrate poor mentalising in patients with schizophrenia. Evidence of selective mentalising deficits in high schizotypal non-clinical subjects discounted the view that defective mentalising is restricted to psychiatric illness and strengthened the case for continuity models of psychosis-proneness. Furthermore, evidence that poor mentalisers in the normal population are more likely to self-report psychotic-like traits, as well as asocial or idiosyncratic behaviours, refuted suggestions that defective mentalising is linked solely to asocial symptomatology and supported the view that defective mentalising may have a fundamental role to play in the explanation of psychotic symptoms. In order to specify what that role might be, alternative theoretical accounts of defective mentalising were tested. Neither executive planning deficits nor failure to inhibit cognitively salient inappropriate information could adequately explain the pattern of selective mentalising deficits found in high schizotypal non-clinical subjects. Our findings suggest that there exists a domain-specific cognitive module that is dedicated to inferring and representing mental states which, when dysfunctional, causes defective mentalising that manifests phenomenologically in psychotic-like traits and impoverished social awareness of variable expression and ranging severity.

Adult↗
PubMed1999

Modularity and cognition.

Modularity is a concept central to cognitive science, and Fodor's analysis of cognitive modularity in his book The Modularity Of Mind has been widely influential - but also widely misunderstood. It is often claimed that the possession of some or other system-property is a necessary condition for that system to be modular in Fodor's sense, but Fodor made it clear that he was not proposing a definition of modularity, nor proposing any necessary conditions for the applicability of the term. He was simply suggesting a number of system properties that are typical of modular systems. I argue that it is nevertheless possible to derive a useful definition of modularity from the kinds of arguments put forward by Fodor: A cognitive system is modular when and only when it is domain-specific. Given any such proposed module, the other features of modularity discussed by Fodor should be dealt with as empirical issues: for each feature (innateness, for example), it is an empirical question whether or not the proposed module has that feature.

Journal Article↗
PubMed1999

A position-sensitive Stroop effect: further evidence for a left-to-right component in print-to-speech conversion.

In the classical Stroop effect, response times for naming the color in which a word is printed are affected by the presence of semantic, phonological, or orthographic relationships between the stimulus word and the response word. We show that color naming responses are faster when the printed word shares a phoneme with the color name to be produced than when it does not, in conditions where there is no semantic relationship between the printed word and the color name. This result is compatible with a variety of computational models of reading. However, we also found that these effects are much larger when it is the first phoneme that the stimulus and response share than when it is the last. Our data are incompatible with computational models of reading in which the computation of phonology from print is purely parallel. The dual route cascaded model computational model of reading, which has a lexical route that operates in parallel and a nonlexical route that operates serially letter by letter, successfully simulates this position-sensitive Stroop effect. The model also successfully simulates the "onset effect" in masked priming (Forster & Davis, 1991) and the interaction between the regularity effect and the position in a word of a grapheme-phoneme irregularity (Rastle & Coltheart, 1999b)--effects which, we argue, arise for the same reason as the position-sensitive Stroop effect we report.

Analysis of Variance↗
PubMed1998

Interpreting ambiguous advertisements: the effect of frontal lobe damage.

Despite intact primary language processes patients with frontal lobe deficits often have impaired communication skills including impaired capacity to understand conversational inference. This study examined the ability of three patients with demonstrated frontal lobe pathology to interpret lexically ambiguous advertisements. When compared to a nonbrain-damaged control group it was found that the frontal lobe patients were poorer at comprehending the abstract or inferred meanings inherent in the advertisements. The pattern of performance across the patients did, nevertheless, differ despite a similar end result. These findings are discussed in relation to theories concerning the contribution of the frontal lobes to language function.

Adult↗
PubMed1995

Memory functioning in social drinkers: a study of event-related potentials.

Verbal memory functioning was assessed in light and heavy social drinkers by recording event-related potentials in subjects instructed to memorize lists of words using either repetition or elaborative learning strategies. Although overall performance did not differ significantly between light and heavy drinkers, heavy drinkers showed reduced within-list organization compared with light drinkers. There were statistically significant differences in the event-related potential indices of memory functioning elicited during complex elaborative processing which were consistent with decreased within-list organization in heavy drinkers.

Adult↗
PubMed1993

Varieties of developmental dyslexia.

This paper reviews and evaluates the evidence for the existence of distinct varieties of developmental dyslexia, analogous to those found in the acquired dyslexic population. Models of the normal adult reading process and of the development of reading in children are used to provide a framework for considering the issues. Data from a large-sample study of the reading patterns of developmental dyslexics are then reported. The lexical and sublexical reading skills of 56 developmental dyslexics were assessed through close comparison with the skills of 56 normally developing readers. The results indicate that there are at least two varieties of developmental dyslexia, the first of which is characterised by a specific difficulty using the lexical procedure, and the second by a difficulty using the sublexical procedure. These subtypes are apparently not rare, but are relatively prevalent in the developmental dyslexic population. The results of a second experiment, which suggest that neither of these reading patterns can be accounted for in terms of a general language disorder, are then reported.

Age Factors↗
PubMed1989

Cerebral hemisphere function and migraine.

An hypothesis that migraine is the experience of a protective vascular response to cerebral information overload has been explored to a limited extent by examining the association between laterality of the attack and verbal and spatial performances under standard symptom-free conditions. The study was restricted to individuals with unilateral symptoms always presenting on the same side. It emerged that those with classical migraine do not always have prodromata referable to the same side as the pain. Indeed, in the present study, prodromata were almost exclusively referable to the left (dominant) cerebral hemisphere. A subgroup of those with speech disturbances as a feature of the prodromal symptoms was also found to have relatively impaired language abilities on routine testing. It is this finding that lends some support to the hypothesis. The findings also invite the refining proposition that information overload, as defined in the hypothesis, is almost always borne by the dominant (verbal) hemisphere in our species. Such overload might concurrently or sequentially also overtax a suggested limited right hemisphere language capacity, in terms of the hypothesis, accounting for the right-sided pain sometimes presenting in these cases. Otherwise, pain appears to be predominantly left-sided or midline. Perhaps the frequency of this particular syndrome is an indictment of the limitations of language as a basis for communication, as well as reflecting the possibility that most of our stressful transactions and their cerebral processing use a verbal substrate. The results also reveal the need for agreement on rules for classification of laterality in migraine.

Adolescent↗