Abstract
The present study quantitatively assessed sexual dimorphism of cortical convolution and sulcal morphology in young adult ferrets by MRI-based sulcal surface morphometry. Ex vivo T1-weighted (short TR/TE) MRI of the ferret cerebrum was acquired with high spatial resolution at 7-tesla. The degree of cortical convolution, evaluated quantitatively based on 3D MRI data by sulcation index (SI), was significantly greater in males (0.553 ± 0.036) than in females (0.502 ± 0.043) (p < 0.001). The rostrocaudal distribution of the cortical convolution revealed a greater convolution in the frontal region of the cortex in males than in females and by a posterior extension of the convolution in the temporo-parieto-occipital region of males. Although the cerebral width in the frontal region was not different between sexes, the rhinal fissure and rostral region of splenial sulcus were more infolded in males than in females. On the contrary, the cerebral width was greater in males in the temporo-parieto-occipital region, and male-prominent posterior extension of infolding was noted in the lateral sulcus, caudal suprasylvian sulcus, pesudosylvian sulcus, hippocampal sulcus, and the caudal region of splenial sulcus. Notably, the caudal descending region of lateral sulcus was clearly infolded in males, but obscured in females. The present results suggest a region-related sexual dimorphism of the sulcal infolding, which is reflected by local cortical expansion in the ferret cerebrum. In particular, male-favored sulcal infolding with expansion of the temporo-parieto-occipital neocortex may be relevant to the human cerebral cortex regarding visuo-spatial and emotion processing, which are known to differ between sexes. The present results will provide fundamental information assessing sex-related changes in the regional sulcal infolding, when ferrets with experimentally-induced gyrification abnormality will be used as models for male-prevalent or male-earlier-onset neurodevelopmental disorders.
Highlights
In some mammalian species, the cerebral cortex forms a gyrencephalic morphology with phylogenetically-conserved patterns of sulci and gyri (Chi et al, 1977; Sawada et al, 2012a, 2014).Sexual dimorphism of sulcal morphologyWhile sexual dimorphism of the sulcal morphology has not been fully addressed, an asymmetric pattern of the primary sulcal length is known to differ between sexes in humans (Liu et al, 2010) and cynomolgus monkeys (Imai et al, 2011)
Sulcal Infolding in Temporo-Parieto-Occipital Region The present study revealed that male-favored posterior extension of primary sulci in the temporo-parieto-occipital region was involved in an expansion of the cortical region in the ferret cerebrum
Sexual dimorphism of the cortical convolution of young adult ferrets was characterized by malefavored sulcal infolding in the frontal region, and by maleprominent posterior extension of primary sulci with cortical expansion of the temporo-parieto-occipital region
Summary
While sexual dimorphism of the sulcal morphology has not been fully addressed, an asymmetric pattern of the primary sulcal length is known to differ between sexes in humans (Liu et al, 2010) and cynomolgus monkeys (Imai et al, 2011). Abnormal development of the primary sulci is reportedly involved in pathological changes in human psychological and neurodevelopmental disorders such as schizophrenia, obsessive-compulsive disorder and autism (Levitt et al, 2003; Boddaert et al, 2004; Wobrock et al, 2010; White and Hilgetag, 2011). Sexual differences in the sulcal morphology and gyrification in the male-prevalent neurodevelopmental disorders have not been documented
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