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F E Tønnessen

Publications and source records attributed to F E Tønnessen.

5 recordsLinked to original sources
PubMed1999

A new gene (DYX3) for dyslexia is located on chromosome 2.

Developmental dyslexia is a specific reading disability affecting children and adults who otherwise possess normal intelligence, cognitive skills, and adequate schooling. Difficulties in spelling and reading may persist through adult life. Possible localisations of genes for dyslexia have been reported on chromosomes 15 (DYX1), 6p21.3-23 (DYX2), and 1p over the last 15 years. Only the localisation to 6p21.3-23 has been clearly confirmed and a genome search has not previously been carried out. We have investigated a large Norwegian family in which dyslexia is inherited as an autosomal dominant trait. A genome wide search for linkage with an average 20 cM marker density was initiated in 36 of the 80 family members. The linkage analysis was performed under three different diagnostic models. Linkage analysis in the family identified a region in 2p15-p16 which cosegregated with dyslexia. Maximum lod scores of 3.54, 2.92, and 4.32 for the three different diagnostic models were obtained. These results were confirmed by a non-parametric multipoint GENEHUNTER analysis in which the most likely placement of the gene was in a 4 cM interval between markers D2S2352 and D2S1337. Localisation of a gene for dyslexia to 2p15-16, together with the confirmed linkage to 6p21.3-23, constitute strong evidence for genetic heterogeneity in dyslexia. Since no gene for dyslexia has been isolated, little is known about the molecular processes involved. The isolation and molecular characterisation of this newly reported gene on chromosome 2 (DYX3) and DYX1 will thus provide new and exciting insights into the processes involved in reading and spelling.

Adult↗
PubMed1993

Dyslexia, left-handedness, and immune disorders.

OBJECTIVE: To illuminate a possible three-way association between dyslexia, immune disorders, and left-handedness. Geschwind's, Behan's, and Galaburda's hypotheses have been of special interest in this connection. DESIGN: Statistical analysis based on general assessment of the prevalence of the three aforementioned conditions. PARTICIPANTS: There were 734 children included from a total of 1165 in grade 6 (about 12 years of age) in the municipality of Stavanger, Norway. SETTING: Educational and demographic statistics indicate that the municipality of Stavanger is representative of the national population at large regarding the three conditions examined. MAIN OUTCOME MEASURES: A screening test with high reliability and validity was used to assess reading ability. It measured word recognition and phonological decoding. The questionnaires that recorded the students' handedness and immune disorders were filled in by the parents. Handedness was assessed by a Norwegian version of the Oldfield Inventory. A questionnaire concerning allergies and asthma was used to assess the prevalence of immune disorders. RESULTS: The bivariate analyses disclosed a significant association between handedness and dyslexia and a significant but weak association between handedness and immune disorders. No significant association was found between dyslexia and immune disorders. A triadic analysis yielded the following: 66.7% of the left-handed dyslexic children had immune disorders (P > .05); 42.1% of the left-handed children with immune disorders had dyslexia (P < .01); and 32% of the dyslexic children with immune disorders were left-handed (P < .05). CONCLUSIONS: There seems to be some association between dyslexia, left-handedness, and immune disorders. Of the three factors, handedness seems to be the most important association. The findings lend some support to the one interpretation of the hypotheses of Geschwind, Behan, and Galaburda.

Adolescent↗
PubMedDate not supplied

Options and limitations of the cognitive psychological approach to the treatment of dyslexia.

If the field of cognitive psychology is to avoid the use of introspective methods, it must focus on the objective norms or rules for correct performance of cognitive tasks and not on subjective processes. In this manner, the cognitive approach will be more logical than empirical. Cognitive psychology alone is not able to answer the question "Why is it that some people have difficulty following some of the cognitive norms or rules?" Behaviorism and connectionism can make more important contributions here. In the treatment of dyslexia, emphasis must be placed on the fact that reading is a skill that requires both automatization and awareness. To have a flexible and functional combination of these, we must borrow from cognitive psychology, connectionism, and behaviorism.

Child↗
PubMedDate not supplied

Testosterone and dyslexia.

Geschwind, Behan and Galaburda have presented empirical research which indicates an association between left-handedness, immune disorders, and learning difficulties. Moreover, they have presented an hypothesis that purports to explain these associations, i.e. the 'testosterone hypothesis'. This article seeks to show that their hypothesis cannot explain: (a) which types and degrees of the conditions will appear, (b) why these conditions appear more often in males than in females, and (c) why these conditions seem to run in families. Moreover, this article attempts to show (d) that the hypothesis does not make clear the distinction between genetic and environmental factors, and that environmental factors are of greater importance. In addition, the hypothesis leads to great importance being given to purely random factors, because random factors alone determine whether or not a person with hemispherical symmetry will develop abnormal dominance Furthermore, this article argues that an hypothesis of this type should be based on a clear dividing line between latent and manifest symptoms, particularly when these are used to define research samples. Finally, (e) this article seeks to raise doubt as to the possible verification or falsification of the hypothesis by means of empirical studies.

Brain↗