Brain Morphology in Developmental Dyslexia and Attention Deficit Disorder/Hyperactivity

Specific reading disability (dyslexia): what have we learned in the past four decades?

“…This finding implies lack of specificity with regard to children with reading disability, but Leonard et al (2001) failed to replicate the finding. Other studies report that the temporoparietal brain areas are smaller (Duara et al, 1991;Kushch et al, 1993), or not different in those with or without reading difficulties (Hynd et al, 1990;Jernigan, Hesselink, Sowell, & Tallal, 1991). Consistent with this theme, studies that measure the corpus callosum find differences in its size (Duara et al, 1991;Hynd et al, 1990) as well as no differences in its size (Larsen et al, 1990;Schultz et al, 1994) between groups with and without dyslexia.…”

Atomoxetine Increases Extracellular Levels of Norepinephrine and Dopamine in Prefrontal Cortex of Rat A Potential Mechanism for Efficacy in Attention Deficit/Hyperactivity Disorder

“…In support of the role for frontal cortex in ADHDlike behaviors, lesions of the frontal lobes cause a breakdown of goal directed activity, executive function, attention and produce hyperactivity (Benson and Stuss 1982;Petrides and Milner 1982). In imaging studies, the right frontal lobes including PFC (Hynd et al 1990;Castellanos et al 1996b) and the caudate nucleus of children with ADHD were smaller in volume than controls, possibly suggesting a neurodevelopmental lag in the maturation of the associated neuronal pathways and their connectivity (Castellanos et al 1996b). Thus, increasing catecholaminergic neurotransmission in cortical areas may be involved in the efficacy of psychostimulants and atomoxetine in ADHD.…”

Enhancement of brain event-related potentials to speech sounds is associated with compensated reading skills in dyslexic children with familial risk for dyslexia

“…It has been stated that probably deviation in both directions from average on a symmetry-asymmetry scale can lead to deficient reading skills: small symmetrical brain structures would be associated with deficits in multiple domains of language and larger asymmetrical structures with more isolated phonological deficits that are compensated for until adulthood . Across studies, reduced or reversed asymmetry has been seen systematically in dyslexics and thought to be related to deviations in normal patterns of corticogenesis (Hynd, Semrud-Clikeman, Lorys, Novey, & Eliopulos, 1990;Shapleske, Rossell, Woodruff, & David, 1999). The brain symmetry in dyslexics suggests anatomical differences in areas relevant for speech and language Petersen, Fox, Posner, Mintun, & Raichle, 1988).…”