Executive functioning in adults and children with developmental dyslexia.
The performance of developmentally dyslexic children and adults was studied upon a range of tasks that involved executive functioning. Both adult and child samples of dyslexics were found to under-perform on the group-embedded figures test. This test required the identification of constituent parts from within complex visual arrays, with good performance necessitating the inhibition of the processing of the surrounding context. A general deficit on visual-spatial tasks was eliminated as an explanation as dyslexics performed normally upon a range of other non-verbal assessments. The dyslexics consistently demonstrated a deficit in digit span tasks, a decrement that was increased with distractors, again suggesting difficulties in inhibiting the processing of the surrounding context. A deficit was also identified upon a verbal fluency task without a deficit in vocabulary level. Additionally, a specific deficit in the recollection of the temporal order of the presentation of items was in evidence, without a deficit in the recognition of the items themselves. The findings taken as a whole suggest that dyslexic individuals show deficiencies in executive functions relating to inhibition of distractors and to sequencing of events, a set of tasks associated with left prefrontal cortex functioning in the acquired neuropsychology literature.
Department of Psychology, School of Social Sciences and Law, University of Greenwich, London SE9 2UG, UK. m.j.brosnan@greenwich.ac.uk
Mark
M
Brosnan
James
J
Demetre
Stephen
S
Hamill
Kate
K
Robson
Haidee
H
Shepherd
Gerard
G
Cody
D000293:Adolescent; D000328:Adult; D002648:Child; D004410:Dyslexia / Q000523:psychology*; D005260:Female; D006801:Humans; D008297:Male; D008568:Memory / Q000502:physiology; D009483:Neuropsychological Tests; D010364:Pattern Recognition, Visual / Q000502:physiology; D011597:Psychomotor Performance / Q000502:physiology*; D011932:Reading; D013028:Space Perception / Q000502:physiology; D014705:Verbal Behavior / Q000502:physiology