Turid Helland

Executive Functions in Dyslexia

This study focused on executive functions in dyslexia. A group of 43 heavily-affected young dyslexics, divided into two groups based on the results of a receptive language test, and 20 non-dyslexic controls, were tested with a Dichotic Listening Test, the Stroop Color Word Test and the Wisconsin Card Sorting Test. The dyslexic subjects demonstrated significant impairment on all tasks, but with different patterns of impairment according to the subgrouping. The subgroups were equally impaired on the Dichotic Listening Test, but differed on the Stroop and the Wisconsin Tests. The data support a hypothesis suggesting executive problems in dyslexia, depending on receptive language skills.

Digit Span in Dyslexia: Variations According to Language Comprehension and Mathematics Skills

The aim of this study was to investigate digit span performance in dyslexia. It was hypothesised that differences would be found in accordance with subgrouping by language comprehension and mathematic skills, and by analyses of how the digit span scores were attained. Two digit span tasks were given to a group of dyslexic children and controls (n = 57), mean age 12.62 (SD = 1.43). The tasks were “Digit Span” of the WISC-R, and “Digit Span 2,” where the use of back-up strategies like finger counting and lip reading were restricted. As expected, the digit span scores were significantly lower in the dyslexia group than in the control group. Restrictions of back-up strategies did not alter the scores in the control group, while the scores were lowered in the dyslexia group. Further analyses of longest digit span, serial recall, and serial position indicated different retrieval patterns in the subgroups. The subgroup with good language comprehension and mathematic skills (n = 12), showed impaired serial recall especially in backward recall. The subgroup with good language comprehension skills, but with mathematics impairment (n = 9), showed impaired serial recall in both forward and backward recall. The subgroup with language impairments (n = 16), recalled fewer digits than the two other subgroups. The findings were discussed in relation to the “Phonological loop” of the Multi Component Model ofWorking Memory, and implications for intervention were discussed.

Neuroanatomical precursors of dyslexia identified from pre-reading through to age 11

Developmental dyslexia is a common reading disorder that negatively impacts an individuals ability to achieve literacy. Although the brain network involved in reading and its dysfunction in dyslexia has been well studied, it is unknown whether dyslexia is caused by structural abnormalities in the reading network itself or in the lower-level networks that provide input to the reading network. In this study, we acquired structural magnetic resonance imaging scans longitudinally from 27 Norwegian children from before formal literacy training began until after dyslexia was diagnosed. Thus, we were able to determine that the primary neuroanatomical abnormalities that precede dyslexia are not in the reading network itself, but rather in lower-level areas responsible for auditory and visual processing and core executive functions. Abnormalities in the reading network itself were only observed at age 11, after children had learned how to read. The findings suggest that abnormalities in the reading network are the consequence of having different reading experiences, rather than dyslexia per se, whereas the neuroanatomical precursors are predominantly in primary sensory cortices.

Absence of Ear advantage on the consonant-vowel dichotic listening test in adolescent and adult dyslexics: Specific auditory-phonetic dysfunction

The present study investigated auditory-phonetic processing in a group of adolescent and adult reading disabled subjects. Right- and left-handed dyslexic subjects were compared with an age, sex, and handedness matched control group. All subjects were studied with a consonant-vowel version of the dichotic listening task with repeated presentations of dichotically presented pairs of CV-syllables. Left and right ear correct scores were compared for ear advantage in each of the different subgroups of subjects. The main finding was the absence of an expected right-ear advantage (REA) in the right-handed dyslexic group as compared to the right-handed normal readers. Both the dyslexic and normal left-handed groups did not show a REA. The findings are discussed within a theoretical framework that focuses on a basic auditory-phonetic processing dysfunction in developmental dyslexia that persists into adulthood.

Structural and Functional Reorganization of the Corpus Callosum between the Age of 6 and 8 Years

The establishment of an efficient exchange of information between the cerebral hemispheres is of crucial importance in the developing functionally lateralized brain. The corpus callosum, the major connection between the cerebral hemispheres, grows constantly throughout childhood and adolescence. However, behavioral studies suggest the existence of a critical time period for callosal functional development starting around the age of 6 years. In the present longitudinal study, examining a cohort of 20 children at the age of 6 and 8 years, we assessed the relationship between structural and functional callosal development during this time period. The structural development was quantified by calculating the increase in callosal thickness using a shape-based computational analysis of the mid-sagittal corpus callosum as obtained with magnetic resonance imaging. The functional development was assessed with a speech discrimination task based on the dichotic presentation of consonant-vowel syllables. The statistical analysis revealed that children whose callosal isthmus increased in thickness over the course of 2 years showed a decrease in interhemispheric information transfer. However, children exhibiting a decrease in isthmus thickness revealed an increase in information transfer. These results might indicate a refinement process of the callosal connections to optimize the neuronal communication between the developing cerebral hemispheres.

Exploring Language Profiles for Children With ADHD and Children With Asperger Syndrome

Objective: The aims of the present study was to investigate communication impairments in a Norwegian sample of children with ADHD and children with Asperger syndrome (AS) and to explore whether children with ADHD can be differentiated from children with AS in terms of their language profiles on the Norwegian adaptation of the Children’s Communication Checklist Second Edition (CCC-2). Method: The CCC-2 was completed by the parents, and altogether, 77 children aged between 6 and 15 years participated in the study. Results: Communication impairments were as common in a group of children with ADHD as in a group of children with AS. Although a similar pattern appeared on most CCC-2 scales, children with ADHD and children with AS could be distinguished from each other in terms of their language profiles on the subscales assessing stereotyped language and nonverbal communication. Conclusion: Language abilities should be taken into account when standard assessments of ADHD and AS are performed and before therapies are initiated.

Effects of Bottom-Up and Top-Down Intervention Principles in Emergent Literacy in Children at Risk of Developmental Dyslexia: A Longitudinal Study

This longitudinal study focused on the effects of two different principles of intervention in children at risk of developing dyslexia from 5 to 8 years old. The children were selected on the basis of a background questionnaire given to parents and preschool teachers, with cognitive and functional magnetic resonance imaging results substantiating group differences in neuropsychological processes associated with phonology, orthography, and phoneme—grapheme correspondence (i.e., alphabetic principle). The two principles of intervention were bottom-up (BU), “from sound to meaning”, and top-down (TD), “from meaning to sound.” Thus, four subgroups were established: risk/BU, risk/TD, control/BU, and control/TD. Computer-based training took place for 2 months every spring, and cognitive assessments were performed each fall of the project period. Measures of preliteracy skills for reading and spelling were phonological awareness, working memory, verbal learning, and letter knowledge. Literacy skills were assessed by word reading and spelling. At project end the control group scored significantly above age norm, whereas the risk group scored within the norm. In the at-risk group, training based on the BU principle had the strongest effects on phonological awareness and working memory scores, whereas training based on the TD principle had the strongest effects on verbal learning, letter knowledge, and literacy scores. It was concluded that appropriate, specific, data-based intervention starting in preschool can mitigate literacy impairment and that interventions should contain BU training for preliteracy skills and TD training for literacy training.

Attentional functions in speech fluency disorders.

This study focused on attentional functions in fluency disorders. Nine persons who stuttered, eight persons who cluttered, and nine fluent controls, executed a set of attention tasks while psychophysiological indices of activation (heart rate variability and skin conductance) were recorded. The results indicated that the stutter group had a significantly longer response time on the Posner Test of Covert Attention Shifts than the other two groups, and the effect was most obvious when the target appeared in the right visual field. There were no significant differences between groups in the physiological activation as measured by heart rate, skin conductance and heart rate variability. The present results support the hypotheses that stuttering may be associated with impaired skills to focus attention, while cluttering did not seem to be associated with impaired focused attentional skills. However, the sample available within the study period was limited, and due to small samples care should be taken before making firm conclusions.

Visual-Sequential and Visuo-Spatial Skills in Dyslexia: Variations According to Language Comprehension and Mathematics Skills

This study focused on visual-sequential and visuo-spatial functions in a group of 39 heavily dyslexic children, compared to a Control group. Mean age was 12.72 (SD 1.71). The dyslexia group was divided into three subgroups by language comprehension and mathematics skills. Only on a visual-sequential task was no difference seen between the groups. The main differences occurred between the two dyslexic subgroups with no language comprehension impairment, but with varying mathematics skills. Whereas the subgroup with good mathematics skills scored within the upper ranges, the mathematics-impaired subgroup showed significantly lower scores. The third dyslexic subgroup, with both language comprehension and mathematics impairments, performed within the norm. The study indicates a dissociation between language comprehension and visuo-spatial skills in dyslexia, which has implications for how variations in dyslexia should be understood. The results also show that the visuo-spatial impairments seen in one of the dyslexia subgroups lead to two ways of understanding mathematics impairment when it co-occurs with dyslexia: (1) as a visuo-spatial problem; (2) as a linguistic problem. These distinctions should imply different intervention strategies in dyslexia.

Brain asymmetry for language in dyslexic children

Studies of brain asymmetry in dyslexia have yielded mixed results both with respect to patterns of asymmetry and their cognitive correlates. This paper assessed language lateralisation inferred from dichotic listening with forced attention in a clinical group of young dyslexic subjects. As a whole the dyslexic group showed a deviant asymmetry pattern compared to a control group. Subdivision into two subgroups by receptive language abilities yielded differential patterns within the dyslexia group. Both subgroups exhibited a weaker response pattern to right ear stimuli than the control group. In addition, the subgroup with no language impairment showed bilateral language representation, whereas the subgroup with impaired receptive language abilities showed reversed dominance patterns.