Effects of sex and age on regional prefrontal brain volume in two human cohorts.

This study examined interactive effects of sex and age on prefrontal brain anatomy in humans. It specifically targeted ranges of the adult life span and regions of cortex that previously showed male-female differences. Participants were 68 healthy human males and females aged 20-72 years. Data collection and analysis were conducted in parallel across two cohorts (laboratories) to investigate reproducibility of effects in relation to sex and age. Volumes for four regional prefrontal subfields per hemisphere were obtained from high-resolution MRI. Regional sex by age interactions were replicated across cohorts. In men, age effects were greatest in medial prefrontal volume, with decreases in dorsal medial and orbital medial regions. In women, age-related changes in medial prefrontal regions were limited to the dorsal volume, with additional decreases observed in lateral subfields. Cohort and Cohort x Age effects in total brain and total prefrontal volume were linked to a combination of methodological and sampling-related factors. Findings indicated that neuroanatomical changes throughout adulthood unfold along different time scales in men and women. Results also showed that sex differences in ageing localized to medial prefrontal regions were particularly robust to variation across cohorts.

Comparison of standard and optimized voxel-based morphometry for analysis of brain changes associated with temporal lobe epilepsy.

We compared statistical parametric maps (SPMs) of group-wise regional gray matter differences between temporal lobe epilepsy (TLE) patients with unilateral hippocampal atrophy (HA) determined by manual volumetric analysis relative to a healthy control population using standard and optimized voxel-based morphometry (VBM). We also investigated the impact of customized neuroanatomical templates on SPMs. Standard and optimized VBM analyses of gray matter concentration (GMC) and gray matter volume (GMV) correctly identified HA, regardless of the template used for normalization. The distribution of hippocampal and extrahippocampal abnormalities differed according to the technique (standard v optimized; GMC v GMV), but was not dependent on template type (default v customized) within each technique. In particular, hippocampal GMC reduction was confined to subregions of hippocampus, whereas GMV reduction was observed in the hippocampal head, body, and tail. Unlike standard and optimized GMC reduction, symmetrical GMV reduction was observed in bilateral thalamus, lenticular nuclei, cerebellum, and ipsilateral entorhinal cortex, perirhinal cortex, and fusiform gyrus in both left and right HA patients. These results show that group-wise SPMs of GMC (i.e., regional distribution of gray matter) and GMV (i.e., volume per se) reduction can identify focal atrophy that has been quantified with manual region of interest techniques, although effects are attenuated in analyses of GMC. Unlike SPMs of GMC, analyses of GMV revealed similar extrahippocampal abnormalities as previous region-of-interest volumetric and histopathological studies of intractable TLE. We suggest that in studies of neurological disorders, optimized VBM analyses of GMV may reveal subtle neuroanatomical changes that are not identified in analyses of GMC.