The relationship between perisylvian morphology and verbal short-term memory functioning in children with neurodevelopmental disorders.

Although children with neurodevelopmental disorders frequently present with reduced short-term memory functioning, the relationship between perisylvian morphology and verbal short-term memory functioning has received limited attention. Thus, examining this relationship in children with neurodevelopmental disorders was the focus of this exploratory study. Results suggested leftward asymmetry in the temporal bank of the planum temporale is related to better coding and storage of semantic material. In contrast, parietal bank morphology is related to coding and storage of phonological material, and presence of an extra gyrus in the parietal region is associated with reduced phonological working memory. Data also supported a relationship between pars triangularis morphology and verbal short-term memory functioning, but this is not material-specific.

Planum temporale asymmetry and ear advantage in dichotic listening in Developmental Dyslexia and Attention-Deficit/Hyperactivity Disorder (ADHD).

The planum temporale is clearly involved in language processing, for it serves as the auditory association cortex. Research has consistently demonstrated that 60 to 70% of the population has leftward asymmetry of the planum temporale. Research has also suggested that dyslexic individuals tend to have either rightward asymmetry or symmetrical plana. Moreover, many studies have found a relationship between the presence of dyslexia and/or language impairment and deficits in the normal right ear advantage found in dichotic listening paradigms. In this context, this study examined the relationship between planum temporale asymmetry and ear preference in dichotic listening performance in children with Developmental Dyslexia and Attention-Deficit/Hyperactivity Disorder (ADHD). Subjects included 19 children with dyslexia (10 of whom had a comorbid diagnosis of ADHD), 23 children with ADHD, and 12 diagnosed normal control children. Dichotic listening data were not collected for 8 of the 12 normal control children and for 3 of the 23 ADHD children. Results revealed no significant difference between ADHD and dyslexic subjects in regard to ear advantage on the free recall dichotic listening task. In addition, although the directed dichotic listening tasks were not related to degree of planum asymmetry, as predicted, results indicated that subjects who consistently displayed an atypical left ear advantage tended to have larger right bank lengths than those who consistently displayed a typical right ear advantage. These findings support the notion that some individuals with dyslexia or language deficits tend to have a larger right planum temporale and that performance on dichotic listening tasks may reflect this relatively unusual pattern.