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Dorothy V M Bishop

Publications and source records attributed to Dorothy V M Bishop.

At least 19 recordsLinked to original sources
PubMed2006

Auditory event-related potentials differ in dyslexics even when auditory psychophysical performance is normal.

Developmental dyslexia is characterized by a phonological processing deficit and impaired low-level auditory processing may contribute to this problem. However, this remains controversial because not all dyslexic individuals show psychophysical deficits on auditory processing tasks; hence it has been argued that auditory processing deficits are not a causal factor in dyslexia. Because behavioral psychophysical tasks include both bottom-up processing and top-down strategies, dyslexics' successful coping strategies may positively influence their performance on auditory behavioral measures. Therefore we have studied whether dyslexics who perform adequately on auditory psychophysical tasks nevertheless show electrophysiological evidence of impaired auditory processing. We compared auditory event-related mismatch negativity (MMN) potentials to frequency modulated (FM) tones at 5, 20 and 240 Hz between dyslexic adults and controls. Groups were matched for age, cognitive ability and psychophysical FM detection thresholds. The dyslexic group showed significantly smaller MMNs in the 20 Hz FM condition in both the early (150-300 ms, P=0.010) and late (300-500 ms, P=0.049) time frames. A 2-way ANOVA showed a significant group by FM rate interaction (P=0.012). There were no significant differences between the groups in the 5 Hz or 240 Hz conditions. The magnitude of the 20 Hz FM MMN correlated with the degree of discrepancy between cognitive and literacy skills (0.66, P=0.003) in the entire group. Thus, even among compensated dyslexics with above-average cognitive abilities and adequate performance on auditory psychophysical tasks, the MMN responses of some dyslexic adults were found to be abnormal.

Adult↗
PubMed2006

Characteristics of the broader phenotype in autism: a study of siblings using the children's communication checklist-2.

Non-autistic relatives of people with autistic disorder have an increased risk of social and communicative difficulties: this is known as the "broad phenotype." Better methods for characterizing the broad phenotype are needed to facilitate identification of risk genes for autism. 29 siblings of 20 children with autistic disorder, 13 siblings of 9 children with PDDNOS, and 46 typically developing control children from 26 families were assessed by parental report using the Children's Communication Checklist-2 (CCC-2). Groups were matched on age and IQ and siblings with autism were excluded. Group mean scores on the CCC-2 differed on only one subscale, syntax. However, siblings of children with autism or PDDNOS were over-represented in the tails of the distributions of several scales, and 10 (24%) scored more than 2 SD below the control mean on a total score based on all 10 subscales. Only two of these 10 children scored above threshold on one or more scales of the Autism Diagnostic Interview-Revised (ADI-R). Children with abnormal scores on the CCC-2 total were characterized by low-verbal IQ and their fathers tended to score high on the social and communication scales of the Autism Quotient, a measure of the broad phenotype in adults. The CCC-2 shows promise as a quick screening device for the broad phenotype in non-autistic siblings of children with autism.

Adolescent↗
PubMed2006

High heritability of speech and language impairments in 6-year-old twins demonstrated using parent and teacher report.

Previous twin studies have demonstrated high heritability of specific language impairment (SLI) when the diagnosis is based on psychometric testing. The current study measured the effectiveness of parent and teacher ratings of communication skills in identifying heritable language impairment. The Children's Communication Checklist was completed by parents and teachers of 6-year-old twins recruited from a general population sample. One hundred and thirty twin pairs (65 MZ) were selected because at least one twin had low language skills at 4 years of age; a further 66 pairs (37 MZ) were a low risk group with no indication of language difficulties at 4 years. Internal consistency, inter-rater reliability, and validity in identifying language impairment were assessed for all CCC scales. CCC scales, especially those assessing structural language skills, were highly effective in identifying cases of language impairment, but agreement between parent and teacher ratings was modest. Genetic analysis revealed negligible environmental influence and substantial genetic influence on most scales. A rater-specific effects model was fit to the data to assess how far parents and teachers assess a common genetic factor on the CCC. Ratings of parents and teachers were influenced to some extent by the same child characteristics, but rater-specific effects were also evident, especially on scales measuring pragmatic aspects of communication. This study shows that there are strong genetic influences on both structural and pragmatic language impairments in children, and these can be detected using a simple checklist completed by parents or teachers.

Child↗
PubMed2006

Common aetiology for diverse language skills in 4 1/2-year-old twins.

Multivariate genetic analysis was used to examine the genetic and environmental aetiology of the interrelationships of diverse linguistic skills. This study used data from a large sample of 4 1/2-year-old twins who were tested on measures assessing articulation, phonology, grammar, vocabulary, and verbal memory. Phenotypic analysis suggested two latent factors: articulation (2 measures) and general language (the remaining 7), and a genetic model incorporating these factors provided a good fit to the data. Almost all genetic and shared environmental influences on the 9 measures acted through the two latent factors. There was also substantial aetiological overlap between the two latent factors, with a genetic correlation of 0.64 and shared environment correlation of 1.00. We conclude that to a large extent, the same genetic and environmental factors underlie the development of individual differences in a wide range of linguistic skills.

Chi-Square Distribution↗
PubMed2006

Effect of attentional state on frequency discrimination: a comparison of children with ADHD on and off medication.

Debate continues over the hypothesis that children with language or literacy difficulties have a genuine auditory processing deficit. Several recent studies have reported deficits in frequency discrimination (FD), but it is unclear whether these are genuine perceptual impairments or reflective of the comorbid attentional problems that exist in many children with language and literacy difficulties. The present study investigated FD in children with attention deficit hyperactivity disorder (ADHD) when their attentional state was altered with stimulant medication. Auditory thresholds were obtained using FD and frequency modulation detection (FM) tasks. In the FD task, participants judged which of 2 pairs contained a high-low frequency sound, and in the FM task, children judged which of two tones "wobbled" (i.e., modulated). Children with ADHD had significantly poorer and more variable FD performance when off compared to on stimulant medication, and did significantly worse than controls on all FD runs when off but not on stimulant medication. However, children with ADHD did not differ from controls on the FM task. These findings demonstrate that certain auditory discrimination tasks are influenced by the child's attentional status. In addition, significant relationships between FD and measures of language and reading were abolished when comorbid attentional difficulties were taken into account. The study has implications for design and interpretation of studies investigating links between auditory discrimination and difficulties in language and literacy.

Age Factors↗
PubMed2006

Developmental cognitive genetics: how psychology can inform genetics and vice versa.

Developmental neuropsychology is concerned with uncovering the underlying basis of developmental disorders such as specific language impairment (SLI), developmental dyslexia, and autistic disorder. Twin and family studies indicate that genetic influences play an important part in the aetiology of all of these disorders, yet progress in identifying genes has been slow. One way forward is to cut loose from conventional clinical criteria for diagnosing disorders and to focus instead on measures of underlying cognitive mechanisms. Psychology can inform genetics by clarifying what the key dimensions are for heritable phenotypes. However, it is not a one-way street. By using genetically informative designs, one can gain insights about causal relationships between different cognitive deficits. For instance, it has been suggested that low-level auditory deficits cause phonological problems in SLI. However, a twin study showed that, although both types of deficit occur in SLI, they have quite different origins, with environmental factors more important for auditory deficit, and genes more important for deficient phonological short-term memory. Another study found that morphosyntactic deficits in SLI are also highly heritable, but have different genetic origins from impairments of phonological short-term memory. A genetic perspective shows that a search for the underlying cause of developmental disorders may be misguided, because they are complex and heterogeneous and are associated with multiple risk factors that only cause serious disability when they occur in combination.

Child↗
PubMed2005

Hemispheric specialization for processing auditory nonspeech stimuli.

The left hemisphere specialization for speech perception might arise from asymmetries at more basic levels of auditory processing. In particular, it has been suggested that differences in "temporal" and "spectral" processing exist between the hemispheres. Here we used functional magnetic resonance imaging to test this hypothesis further. Fourteen healthy volunteers listened to sequences of alternating pure tones that varied in the temporal and spectral domains. Increased temporal variation was associated with activation in Heschl's gyrus (HG) bilaterally, whereas increased spectral variation activated the superior temporal gyrus (STG) bilaterally and right posterior superior temporal sulcus (STS). Responses to increased temporal variation were lateralized to the left hemisphere; this left lateralization was greater in posteromedial HG, which is presumed to correspond to the primary auditory cortex. Responses to increased spectral variation were lateralized to the right hemisphere specifically in the anterior STG and posterior STS. These findings are consistent with the notion that the hemispheres are differentially specialized for processing auditory stimuli even in the absence of linguistic information.

Acoustic Stimulation↗
PubMed2005

Is discrimination training necessary to cause changes in the P2 auditory event-related brain potential to speech sounds?

Previous studies have found that the P2 component of the auditory event-related potential (ERP) increases after speech discrimination training. We compared electrophysiological and behavioral outcomes of individuals undergoing speech discrimination training (N = 8) with an untrained control group (N = 9). Significant improvements on the behavioral speech discrimination task were found only in the trained group; however, there were similar increases in P2 amplitude in both groups. Simple exposure to repeated instances of a speech sound during the ERP recording seems sufficient lead to enhancement of P2. This interpretation was bolstered by the finding of significant change in P2 during the first and second halves of the initial ERP recording, when listeners were not required to make any discriminative response. However, the largest change in P2 occurred between rather than within recording sessions, suggesting that the effects of exposure to a speech stimulus on ERPs may have a slow time-course and are most evident after a delay. Our data challenge the view that increased P2 amplitude reflects enhanced perceptual discrimination by auditory cortex.

Acoustic Stimulation↗
PubMed2005

Genetic influences on language impairment and phonological short-term memory.

It has been known for some years that specific language impairment (SLI), an unexpected failure to acquire age-appropriate language skills, is highly heritable. However, molecular genetic studies have been hampered by the heterogeneity of the disorder and the predominant lack of clear genotype-phenotype relationships. We review recent studies suggesting that a better understanding of the genetics of SLI might emerge if we move away from clinical criteria for diagnosis to look instead at a theoretically based quantitative and cognitive measure of the phenotype: a test of phonological short-term memory (STM). Deficient phonological STM has been linked to specific genetic loci, and might play a role in determining some types of reading impairment as well as SLI. Identifying those cognitive deficits that work best as indices of heritable phenotypes will help us to uncover the aetiology of developmental disorders.

Adolescent↗
PubMed2005

Poor frequency discrimination is related to oral language disorder in children: a psychoacoustic study.

Some children have difficulty in perceiving differences between sounds, even though they have normal hearing sensitivity, and it has been suggested that such problems could lead to difficulties in language and literacy development. Poor ability to distinguish sounds on the basis of frequency (perceived as pitch) has been described in poor readers on a variety of auditory processing tasks. The aim of the present study was three-fold: to determine whether children with specific language impairment (SLI) have difficulty discriminating frequency, whether this deficit is specific to the frequency domain, or part of a more general auditory impairment, and whether it is linked to reading or oral language ability. The performance of a SLI group (N = 15) and a control group with normally developing oral language matched for age and intelligence (N = 18) was compared on a frequency discrimination task and a control task testing intensity discrimination. The children with SLI consistently demonstrated significantly poorer performance on the frequency discrimination task, but not on the intensity discrimination task. Frequency discrimination thresholds were not related to reading ability in either group. This study provides evidence for a basic auditory deficit in children with SLI, regardless of their reading ability.

Auditory Perceptual Disorders↗
PubMed2005

Individual differences in auditory processing in specific language impairment: a follow-up study using event-related potentials and behavioural thresholds.

It has frequently been claimed that children with specific language impairment (SLI) have impaired auditory perception, but there is much controversy about the role of such deficits in causing their language problems, and it has been difficult to establish solid, replicable findings in this area. Discrepancies in this field may arise because (a) a focus on mean results obscures the heterogeneity in the population and (b) insufficient attention has been paid to maturational aspects of auditory processing. We conducted a study of 16 young people with specific language impairment (SLI) and 16 control participants, 24 of whom had had auditory event-related potentials (ERPs) and frequency discrimination thresholds assessed 18 months previously. When originally assessed, around one third of the listeners with SLI had poor behavioural frequency discrimination thresholds, and these tended to be the younger participants. However, most of the SLI group had age-inappropriate late components of the auditory ERP, regardless of their frequency discrimination. At follow-up, the behavioural thresholds of those with poor frequency discrimination improved, though some remained outside the control range. At follow-up, ERPs for many of the individuals in the SLI group were still not age-appropriate. In several cases, waveforms of individuals in the SLI group resembled those of younger typically-developing children, though in other cases the waveform was unlike that of control cases at any age. Electrophysiological methods may reveal underlying immaturity or other abnormality of auditory processing even when behavioural thresholds look normal. This study emphasises the variability seen in SLI, and the importance of studying individual cases rather than focusing on group means.

Adolescent↗
PubMed2005

Executive functions in children with communication impairments, in relation to autistic symptomatology. 1: Generativity.

Previous research has found that people with autism generate few novel responses in ideational fluency tasks, and it has been suggested this deficit is a specific correlate of stereotyped/repetitive behavior. We assessed generativity in children with pragmatic language impairment (PLI) who showed communicative abnormalities resembling those seen in autism. We compared four groups: high-functioning autism; PLI; specific language impairment; and control. Generativity was measured using two fluency tasks previously shown to be sensitive to autistic disorder. Correlational analysis revealed a significant relationship between the percentage of correct responses on the fluency tasks and measures of communicative abnormality. It is often assumed that pragmatic difficulties are caused by limitations of social cognition. This study suggests that difficulties in generating relevant ideas can be another cause of autistic-like communicative abnormalities.

Autistic Disorder↗
PubMed2005

Executive functions in children with communication impairments, in relation to autistic symptomatology. 2: Response inhibition.

Although impairment in executive functions has been described in autism, there has been debate as to whether response inhibition is specifically affected. We compared four groups: high-functioning autism; pragmatic language impairment; specific language impairment; and control. Inhibition was assessed using two subtests from the Test of Everyday Attention for Children, one requiring a verbal response and the other a non-verbal response. Although we found evidence of inhibitory deficits, these were neither specific to autism, nor linked to particular aspects of autistic symptomatology. Rather, they appeared to be associated with poor verbal skills and inattention. It is suggested that future studies need to control for structural language skills and attention deficit when evaluating cognitive deficits in autism. Reliance on control groups matched solely on vocabulary level or nonverbal mental age may obscure the important role played by language skills in executive functions.

Attention↗
PubMed2004

Phonological categorization of vowels: a mismatch negativity study.

There is electrophysiological evidence that phonological categorization has occurred within 100-200 ms post stimulus onset for the syllables /tae/ and /dae/, which vary in voice onset time. Using a similar paradigm, this study investigated when phonological categorization occurred for the contrast between /I/ and /epsilon/, using synthesized speech tokens that differed in the frequency of the first formant. Here we show that phonological categorization of these tokens has not occurred 100-200 ms after stimulus onset. However, the presence of a late mismatch negativity (350 ms after stimulus onset) indicated that phonological categorization had taken place by this time.

Acoustic Stimulation↗
PubMed2004

Using nonword repetition to distinguish genetic and environmental influences on early literacy development: a study of 6-year-old twins.

This study considered whether cognitive profile could distinguish groups of children where genes or environment played a major role in influencing reading level. Same-sex twin pairs from an epidemiological study were categorized according to parental report at 4 years of age into those with low language skills and a typically developing group. A total of 132 same-sex twin pairs from the low language group and 66 from the control group were assessed at 6 years of age, to investigate heritability of reading ability adjusted for nonverbal IQ. For pairs where both twins had normal scores on a nonword repetition test, heritability was zero, with environmental influences explaining all the variance. For pairs where one or both twins had low nonword repetition, the heritability estimate was 0.79 and the variance due to shared environment was zero. Future studies of genetics of reading development should treat those with poor nonword repetition skills as a separate subgroup.

Child↗
PubMed2004

Are phonological processing deficits part of the broad autism phenotype?

Two tests of phonological processing, nonword repetition, and nonsense passage reading, were administered to 80 probands with autistic disorder or PDDNOS (index cases) and 59 typically developing controls, together with their parents and siblings. In addition, parents completed a questionnaire about history of language and literacy problems, and all participants were given tests of verbal (VIQ) and performance IQ (PIQ). Parents also completed the Autism-Spectrum Quotient, which was used to index the broad autism phenotype. Index probands scored well below control probands on the two phonological tests. However, on neither phonological measure did index relatives differ from control relatives. Within the index group, there was no relationship between the proband's level of VIQ, or age at achieving phrase speech, and phonological score of relatives. VIQ was the only measure to show any familiality within the index group. Reported history of language and literacy problems did not differentiate index parents from control parents overall, but those who were categorized as cases of the broad phenotype reported more history of language and literacy problems than did other index parents. However, they did not have poorer scores on the phonological measures. It is concluded that phonological processing deficits are not part of the broad autism phenotype.

Articulation Disorders↗
PubMed2004

Developmental dyslexia and specific language impairment: same or different?

Developmental dyslexia and specific language impairment (SLI) were for many years treated as distinct disorders but are now often regarded as different manifestations of the same underlying problem, differing only in severity or developmental stage. The merging of these categories has been motivated by the reconceptualization of dyslexia as a language disorder in which phonological processing is deficient. The authors argue that this focus underestimates the independent influence of semantic and syntactic deficits, which are widespread in SLI and which affect reading comprehension and impair attainment of fluent reading in adolescence. The authors suggest that 2 dimensions of impairment are needed to conceptualize the relationship between these disorders and to capture phenotypic features that are important for identifying neurobiologically and etiologically coherent subgroups.

Child↗