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Biomedical subjects

A J Fawcett

Publications and source records attributed to A J Fawcett.

18 recordsLinked to original sources
PubMed2005

Developmental dyslexia, learning and the cerebellum.

Theoretical frameworks for dyslexia must explain how the well-established phonological deficits and the literacy deficits arise. Our longstanding research programme has led to a distinctive 'twin level' framework that proposes, first, that the core deficits are well described in terms of poor skill automaticity. Second, these 'cognitive level' symptoms are attributed to abnormal cerebellar function--a 'brain-level' analysis. The evidence includes data from behavioural, imaging, neuroanatomical and learning studies. The frame-work leads to an 'ontogenetic' analysis that links cerebellar deficit at birth, via problems in articulation and working memory, to the known phonological, speed and literacy difficulties. Differences in locus of cerebellar impairment, experience and/or links to other brain regions may account for subtypes of dyslexia and possibly other developmental disorders. The automaticity/ cerebellar deficit framework provides an explicit demonstration that it is possible to explain motor, speed and phonological deficits within a unified account, integrating previously opposed approaches.

Cerebellar Diseases↗
PubMed2001

Developmental dyslexia: the cerebellar deficit hypothesis.

Surprisingly, the problems faced by many dyslexic children are by no means confined to reading and spelling. There appears to be a general impairment in the ability to perform skills automatically, an ability thought to be dependent upon the cerebellum. Specific behavioural and neuroimaging tests reviewed here indicate that dyslexia is indeed associated with cerebellar impairment in about 80% of cases. We propose that disorders of cerebellar development can in fact cause the impairments in reading and writing characteristic of dyslexia, a view consistent with the recently appreciated role of the cerebellum in language-related skills. This proposal has implications for early remedial treatment.

Animals↗
PubMed1999

Association of abnormal cerebellar activation with motor learning difficulties in dyslexic adults.

BACKGROUND: In addition to their impairments in literacy-related skills, dyslexic children show characteristic difficulties in phonological skill, motor skill, and balance. There is behavioural and biochemical evidence that these difficulties may be attributable to mild cerebellar dysfunction. We wanted to find out whether there was abnormal brain activation when dyslexic adults undertook tasks known normally to involve cerebellar activation. METHODS: Brain activation was monitored by positron emission tomography in matched groups of six dyslexic adults and six control adults as they carried out either a prelearned sequence or learned a novel sequence of finger movements. FINDINGS: Brain activation was significantly lower (p<0.01) for the dyslexic adults than for the controls in the right cerebellar cortex and the left cingulate gyrus when executing the prelearned sequence, and in the right cerebellar cortex when learning the new sequence. INTERPRETATION: The results provided direct evidence that, for this group of dyslexic adults, the behavioural signs of cerebellar abnormality reflect underlying abnormalities in cerebellar activation.

Adult↗
PubMed1995

Time estimation deficits in developmental dyslexia: evidence of cerebellar involvement.

In addition to their language-related difficulties, dyslexic children suffer problems in motor skill, balance, automatization and speeded performance. Given the recent evidence for cerebellar involvement in the acquisition of language fluency, these problems suggest cerebellar deficit. To test the hypothesis of cerebellar dysfunction in dyslexia, a time estimation task considered to be a sensitive index of cerebellar function was administered to matched groups of dyslexic and control children. The dyslexic children showed the predicted deficit on time estimation (among the most severe obtained in our research programme) but not on a control, loudness estimation, task. Cerebellar dysfunction, therefore, provides a parsimonious account of otherwise disparate data on deficits in dyslexia.

Acoustic Stimulation↗
PubMed1995

Impaired recognition of traffic signs in adults with dyslexia.

Ten adults with dyslexia (4 women and 6 men, mean age: 26.8 years, range: 19-43 years) and 11 controls (5 women and 6 men, mean age: 20.5 years, range: 18-29 years) were tested on their ability to differentiate between real and false traffic signs. The stimuli, computer-presented color pictures, were chosen to minimize the applicability of verbal or written linguistic skills to the task. The adults with dyslexia recognized the traffic signs significantly less well than did the controls. Furthermore, whereas for the controls there was a significant correlation between traffic sign recognition and driving experience, no such correlation was found for the adults with dyslexia. The results are interpreted in terms of a deficit in implicit learning.

Adolescent↗
PubMed1994

Reaction times and dyslexia.

Five groups of children, including two groups of dyslexics (aged 15 and 11 years), were tested on simple reaction, selective choice reaction, and lexical decision tasks. In simple reactions to a pure tone, the dyslexic children responded as quickly as their chronological age controls and significantly faster than their reading age controls. In selective choice reactions to pure tones, the dyslexic children were significantly impaired compared with their chronological age controls and no faster than their reading age controls. This speed impairment obtained even though a selective choice reaction task has only one positive response. In "by-item" analyses of lexical decisions to spoken words, the dyslexic children were significantly impaired compared even with their reading age controls. The pattern of results suggests that at least two factors contribute to slowness of dyslexic children: a general deficit reflected in slower stimulus classification speed and a linguistic deficit reflected in slower lexical access speed.

Adolescent↗
PubMed1994

Naming speed in children with dyslexia.

A series of tests of naming speed in discrete reaction time format were undertaken by seven groups of children: three groups with dyslexia with mean ages 8, 13, and 17 years; three groups of normally achieving children matched for age and IQ with the dyslexic groups; and a group of 10-year-old children with mild learning difficulties (slow learners) matched for reading age with the youngest dyslexic group. The children with dyslexia were significantly slower than even their chronological age-matched controls, and equivalent to their reading age-matched controls, on naming colors, digits, and letters, and significantly slower than even their reading age-matched controls on naming pictures of common objects. Overall, performance of the 17-year-old children with dyslexia was closest to that of the 8-year-old controls. Performance of the slow learners was equivalent to that of the youngest children with dyslexia. The results show that children with dyslexia have persistent-and unexpectedly severe-problems in naming speed for all stimuli, regardless of whether or not the stimulus requires grapheme-phoneme decoding.

Adolescent↗
PubMed1994

Adults with dyslexia have a deficit in voice recognition.

A group of 7 dyslexic students and 8 nondyslexic students matched for age and IQ were tested on recognition of computer-presented voices and faces. Although face recognition showed a ceiling effect which prevented any solid conclusions being drawn from this task, the dyslexic group were significantly impaired on the recognition of voices.

Adult↗
PubMed1992

Automatisation deficits in balance for dyslexic children.

Traditional theories of dyslexia have focused on components of the reading process. The Dyslexic Automatisation Deficit hypothesis takes a broader view, attributing deficits to an inability to become completely fluent in cognitive and motor skills. A series of experiments compared the balance of 15-yr.-old and 11-yr.-old groups of dyslexic children and normal children matched for age and IQ under single-task and dual-task conditions. There were no group differences in the single-task conditions. However, introduction of a concurrent secondary task led to a dissociation in that, whereas the balance of normal children was unaffected, the dyslexic children's balance was significantly impaired. It was concluded that the normal children balanced automatically whereas the dyslexic children did not. These results directly support the proposed framework.

Achievement↗
PubMed1990

Automaticity: a new framework for dyslexia research?

The performance of a group of 23 13-year-old dyslexic children was compared with that of same-age controls on a battery of tests of motor balance. A dual-task paradigm was used--subjects performed each test twice, once as a single task, and once as a dual task concurrently with a secondary task. Two alternative secondary tasks were used, the classic counting-backwards task and an auditory choice reaction task. Both secondary tasks were calibrated for each subject to ensure that their performance on the secondary task alone fell between pre-specified performance criteria. In all single-task conditions there was no difference between the performance of the two groups. By contrast, in 19 out of the 20 tests performed under dual-task conditions, the dyslexic group were significantly impaired, whereas the controls showed no impairment, thus resulting in significantly better performance by the control group than the dyslexic group. The sole exception was that the dyslexic children were not impaired on the easiest balance condition with the choice reaction task. Under the dual-task conditions the dyslexic children also performed worse than the controls on the secondary task. It is very hard to accommodate the findings within the traditional framework of a deficit specific to lexical skills. One plausible explanation of the results is that, unlike the controls, the dyslexic children need to invest significant conscious resources for monitoring balance, and thus their performance is adversely affected by any secondary task which serves to distract attention from the primary task. This need for "conscious compensation" suggests that for dyslexic children the skill of motor balance is poorly automatized. It is possible, therefore, that many of the reading deficits of dyslexic children are merely symptoms of a more general learning deficit--the failure to fully automatize skills.

Adolescent↗
PubMedDate not supplied

Systematic identification and intervention for reading difficulty: case studies of children with EAL.

Literacy underpins education. There is now very widespread concern over standards of literacy for children from multi-cultural backgrounds, who are learning English as a second or subsequent language, and who may have special educational needs. Research evidence suggests that the earlier children's difficulties can be identified, the more effective (and cost-effective) intervention will be, provided that the intervention is tailored to the child's abilities and skills. Nicolson and Fawcett have developed systematic procedures for identifying children at risk for reading difficulty, together with systematic teaching strategies to overcome reading difficulty. In this paper we present case studies of children with EAL (English as an additional language) drawn from a controlled study using computer interventions with secondary school children. Our findings indicate that children with EAL may be more resistant to remediation than some children with learning difficulties. The prognosis is more problematic for children with both EAL and dyslexia.

Adolescent↗
PubMedDate not supplied

Cerebellar tests differentiate between groups of poor readers with and without IQ discrepancy.

A comprehensive test battery, including phonological, speed, motor and cerebellar tasks, was administered to the entire cohort of two schools for children with learning disabilities. Testing was undertaken blind without accessing the psychometric data on the children. Children were then allocated to a discrepancy group on the basis of their IQ, with the majority (n = 29) classified as nondiscrepant (IQ < 90) and a smaller set (n = 7), with IQ of at least 90, classified as discrepant (with dyslexia). Both groups showed significant deficits relative to age-matched controls on almost all the tests. On phonological, speed, and motor tasks, the nondiscrepant group were at least as severely impaired as the discrepant group. By contrast, on the cerebellar tests of postural stability and muscle tone, the nondiscrepant group performed significantly better than the children with dyslexia and close to the level of the controls. The findings indicate that cerebellar tests may prove a valuable method of differentiating between poor readers with and without IQ discrepancy. The findings are interpreted in terms of the cerebellar deficit hypothesis for dyslexia.

Cerebellum↗
PubMedDate not supplied

Vocabulary training for children with dyslexia.

A vocabulary training program, using the parents as sole instructors, led to significant and lasting improvements in word knowledge and lexical access speed for 13 adolescents with dyslexia. Furthermore, when the trained words matched the current vocabulary age of the child, the improvement generalized to untrained words.

Adolescent↗