Biomedical subjects

Catherine J Stoodley

Publications and source records attributed to Catherine J Stoodley.

7 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

A processing speed deficit in dyslexic adults? Evidence from a peg-moving task.

Developmental dyslexia is diagnosed when literacy skills are not commensurate with a person's general cognitive ability and education. While the most common difficulty found in dyslexia is poor phonological processing, many dyslexics are reported to be clumsy, with poor handwriting, suggesting that there may be a motor deficit in dyslexia. To establish whether the motor difficulties described in dyslexic children persist into adulthood, we tested 18 dyslexic adults and 22 control participants on Annett's peg-moving task. The dyslexic participants performed significantly slower than control adults on the peg-moving task with their dominant hands (p=0.004). Furthermore, response times (RTs) during tasks testing component literacy skills correlated with peg-moving ability in the dominant hand in the entire group (orthographic r=0.448, p=0.005; phonological r=0.383, p=0.025). These results indicate that a motor speed deficit in dyslexia may not be simply a sign of developmental delay, but may persist into adulthood. Furthermore, motor speed may be related to the speed at which literacy information is processed.

Adult↗

PubMed2006

Balancing and pointing tasks in dyslexic and control adults.

Developmental dyslexia may affect as much as 15% of the population, but the aetiology of the disorder is still being debated. The cerebellar theory of dyslexia proposes that cerebellar dysfunction could lead to the myriad of symptoms seen in dyslexic individuals, both in literacy and non-literacy domains. The cerebellum is crucial to the fluent performance of motor skills. Previous studies have found that dyslexic children are worse than control children on certain motor and balancing tasks. Here the performance of 28 dyslexic compared to 26 control adults on rapid pointing and balancing measures, tasks which are thought to reflect cerebellar function, was investigated. There were no significant differences between the dyslexic and control participants on the balancing tasks or when the speed and accuracy of pointing were analysed separately. However, when the speed and accuracy of pointing were combined, the dyslexic participants showed poorer performance than the controls (p = 0.045). Furthermore, there were significant relationships between performance on the pointing task and literacy skills, and regression analysis showed that the error and speed of pointing contributed significantly to the variance in literacy skill. The implications for the role of the cerebellum and processing speed in dyslexia are discussed.

Adolescent↗

PubMed2005

Implicit motor learning deficits in dyslexic adults.

Children with developmental dyslexia fail to develop age-appropriate reading skills despite adequate intelligence and education. It has been suggested that dyslexics' various literacy, sensory and motor difficulties may be related to impaired cerebellar function. As the cerebellum is involved in motor learning, we measured serial reaction time performance in 40 adults (21 controls, 19 dyslexics). Dyslexic subjects performed comparably to controls during the randomly-ordered reaction time blocks, indicating that the dyslexics were as able as controls to make appropriate stimulus-response associations. However, the dyslexics failed to show the reaction time reduction that the control group showed during the repeated sequences (p = 0.018) and there was a significant group by condition effect when comparing the last two blocks of the sequence condition with the first two blocks of the final random condition (p = 0.008). Furthermore, there was a significant difference between good and poor readers on the degree of learning during the task (p = 0.015). This suggests that some dyslexics may suffer from an implicit motor learning deficit, which could generalize to non-motor learning.

Adult↗

PubMed2005

Impaired balancing ability in dyslexic children.

Children with developmental dyslexia struggle to learn to read and spell despite adequate intelligence and educational opportunity. Several lines of research are attempting to establish the neurobiological basis of dyslexia, and low-level sensory and motor deficits have been found in dyslexic populations; furthermore, behavioural and imaging data point to cerebellar dysfunction in dyslexia. To investigate this, normal readers (n=19) and children with developmental dyslexia (n=16) were asked to perform various cognitive, literacy, and balancing tasks. Children balanced on the left or right foot, with eyes open or closed, for a period of 10 s during which their movements were recorded with a motion-tracking system. Dyslexic children were less stable than the control children in both eyes-open conditions (left foot P=0.02, right foot P=0.012). While there were no group differences during the eyes-closed conditions, the dyslexic children dropped a foot to correct balance significantly more often than control children (P<0.05). Incidence analysis showed that 50% of the dyslexic group fell into the 'impaired' category on the eyes-open balancing tasks; when the mean balancing scores and the foot drops were considered, only three of our dyslexic children showed no evidence of balancing difficulties. There were strong correlations between reading and spelling scores and the mean eyes-open balancing score (r=0.52 and 0.44, respectively). Thus, while not all children with developmental dyslexia show impaired balancing skills, low-level motor dysfunction may be associated with impaired literacy development. This could be due to several factors, including the involvement of the cerebellum, the magnocellular system, or more general developmental immaturity.

Cerebellum↗

PubMed2002

Separate influences of acoustic AM and FM sensitivity on the phonological decoding skills of impaired and normal readers.

Developmental dyslexia is associated with deficits in the processing of basic auditory stimuli. Yet it is unclear how these sensory impairments might contribute to poor reading skills. This study better characterizes the relationship between phonological decoding skills, the lack of which is generally accepted to comprise the core deficit in reading disabilities, and auditory sensitivity to amplitude modulation (AM) and frequency modulation (FM). Thirty-eight adult subjects, 17 of whom had a history of developmental dyslexia, completed a battery of psychophysical measures of sensitivity to FM and AM at different modulation rates, along with a measure of pseudoword reading accuracy and standardized assessments of literacy and cognitive skills. The subjects with a history of dyslexia were significantly less sensitive than controls to 2-Hz FM and 20-Hz AM only. The absence of a significant group difference for 2-Hz AM shows that the dyslexics do not have a general deficit in detecting all slow modulations. Thresholds for detecting 2-Hz and 240-Hz FM and 20-Hz AM correlated significantly with pseudoword reading accuracy. After accounting for various cognitive skills, however, multiple regression analyses showed that detection thresholds for both 2-Hz FM and 20-Hz AM were significant and independent predictors of pseudoword reading ability in the entire sample. Thresholds for 2-Hz AM and 240-Hz FM did not explain significant additional variance in pseudoword reading skill. It is therefore possible that certain components of auditory processing of modulations are related to phonological decoding skills, whereas others are not.

Acoustic Stimulation↗

PubMedDate not supplied

On the relationship between dynamic visual and auditory processing and literacy skills; results from a large primary-school study.

Three hundred and fifty randomly selected primary school children completed a psychometric and psychophysical test battery to ascertain relationships between reading ability and sensitivity to dynamic visual and auditory stimuli. The first analysis examined whether sensitivity to visual coherent motion and auditory frequency resolution differed between groups of children with different literacy and cognitive skills. For both tasks, a main effect of literacy group was found in the absence of a main effect for intelligence or an interaction between these factors. To assess the potential confounding effects of attention, a second analysis of the frequency discrimination data was conducted with performance on catch trials entered as a covariate. Significant effects for both the covariate and literacy skill was found, but again there was no main effect of intelligence, nor was there an interaction between intelligence and literacy skill. Regression analyses were conducted to determine the magnitude of the relationship between sensory and literacy skills in the entire sample. Both visual motion sensitivity and auditory sensitivity to frequency differences were robust predictors of children's literacy skills and their orthographic and phonological skills.

Auditory Perception↗