Dissertation

Sex differences in the anatomy of human perisylvian regions: Frontal and temporal cortical language areas

Knaus, Tracey Ann

2003

Overview

The left hemisphere plays a predominant role in speech-language functions. Anatomical asymmetries of perisylvian speech-language regions have been found with evidence that leftward asymmetries are associated with language dominance. There is also evidence that sex-linked differences in the functional organization of language exist, although sex-linked anatomical differences have not been extensively studied and results have been conflicting. For example, developmental language disorders are male predominate, and women may have more bilaterally represented language functions. Given the controversy in the literature and the need to learn more about sex-linked anatomical differences in healthy adults, a series of experiments were designed to study the anatomy and function of perisylvian language related cortex. Volumetric MRI was used to measure gray matter volumes of posterior language areas, including Heschl's gyrus (HG), planum temporale (PT), and posterior superior temporal gyrus (pSTG) in 48 right-handed men and women, matched for age and education and frontal regions, including the pars triangularis (PTR), pars opercularis (POP), and diagonal sulcus (DS) in 60 right-handed men and women, matched for age and education. Language tests were administered to a subsample of subjects. There were no consistent HG asymmetries and no sex differences. There was a leftward PT asymmetry (L > R), but no sex differences. For the pSTG, men had rightward asymmetry (R > L), while women were as likely to have R > L as L > R. For the temporal areas together, in men about equal numbers had L > R as R > L, whereas women had L > R. There were no asymmetries or sex differences for any frontal language areas. When a measure of listening comprehension was examined, there was a trend for a significant PT asymmetry direction-by-sex interaction. Women with rightward PT asymmetry performed better, whereas men with leftward PT scored better. These results are interesting because the PT mediates auditory processing and atypical (R > L) PT anatomy has been found in individuals with dyslexia. Although speculative, it may be that atypical PT anatomy in women is not associated with aberrant function, whereas in men atypical anatomy may be a neural risk for dysfunctional language development. Future studies should explore these important relationships in neurodevelopmental and acquired language disorders.

• Publisher: ProQuest Dissertations & Theses
• Subject: Neurology / Neurosciences
• ISBN: 0496319256, 9780496319251