title: MRI-based morphometric characterizations of sexual dimorphism of the cerebrum of ferrets (Mustela putorius).
abstract: The present study aimed to characterize cerebral morphology in young adult ferrets and its sexual dimorphism using high-field MRI and MRI-based morphometry. Ex vivo short TR/TE (typical T1-weighted parameter setting for conventional MRI) and T2W (long TR/TE) MRI with high spatial resolution at 7-tesla could visualize major subcortical and archicortical structures, i.e., the caudate nucleus, lentiform nucleus, amygdala and hippocampus. In particular, laminar organization of the olfactory bulb was identifiable by short TR/TE-MRI. The primary and secondary sulci observable in the adult ferret were distinguishable on either short TR/TE- or T2W-MRI, and the cortical surface morphology was reproduced well by 3D-rendered images obtained by short TR/TE-MRI. The cerebrum had a significantly lower volume in females than in males, which was attributed to region-specific volume reduction in the cerebral cortex and subcortical white matter in females. A sexual difference was also detected, manifested by an overall reduction in normalized signal ratios of short TR/TE-MRI in all cerebral structures examined in females than in males. On the other hand, an alternating array of higher and lower short TR/TE-MRI intensity transverse zones throughout the cortex, which was reminiscent of the functional cortical areas, was revealed by maximum intensity projection (MIP) in 3D. The normalized signal ratio of short TR/TE-MRI, but not T2W-MRI in the cortex, was negatively correlated with the density of myelin-basic protein immunoreactive fibers (males, r=-0.440; females, r=-0.481). The present results suggest that sexual differences in the adult ferret cerebrum are characterized by reduced volumes of the cerebral cortex and subcortical white matter in females, and by overall reductions in physiochemical characteristics, as obtained by short TR/TE-MRI, in females. It should be noted that short TR/TE-MRI-based MIP delineated functional cortical areas related to myeloarchitecture in 3D. Such an approach makes possible conventional investigation of the functional organization of the cerebral cortex and its abnormalities using high-field MRI.
authors.affiliation: Department of Physical Therapy, Faculty of Medical and Health Sciences, Tsukuba International University, Tsuchiura, Ibaraki 300-0051, Japan. Electronic address: k-sawada@tius-hs.jp.
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Sawada
authors.forename: Miwa
authors.initials: M
authors.lastname: Horiuchi-Hirose
authors.forename: Shigeyoshi
authors.initials: S
authors.lastname: Saito
authors.forename: Ichio
authors.initials: I
authors.lastname: Aoki
mesh_terms: D000818:Animals; D002540:Cerebral Cortex / Q000166:cytology*; D054022:Cerebrum / Q000166:cytology*; D056324:Diffusion Tensor Imaging / Q000379:methods*; D005260:Female; D005289:Ferrets / Q000502:physiology*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008297:Male; D009413:Nerve Fibers, Myelinated / Q000648:ultrastructure*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012727:Sex Characteristics
keywords: A1; AAF; ADF; AEG; ASG; AVF; Amg; Brain; CNG; Cd; EPI; Evolution; Gl; Hip; IPI; LG; Ln; M1; MBP; MIP; Mi; Neurodevelopmental disorders; OBG; OD; Ob; Obc; PEG; PFA; PPF; PPr; PSF; PSG; Phylogeny; S1; SII; SIII; SSG; Sexual dimorphism; Th; VCA; aad; ac; aci; amygdala; ancinate sulcus; anterior ancinate dimple; anterior auditory field; anterior commissure; anterior dorsal field; anterior ectosylvian gyrus; anterior sigmoid gyrus; anterior ventral field; as; caudal suprasylvian sulcus; caudate nucleus; cc; cg; cingulum; cns; coronal gyrus; coronal sulcus; corpus callosum; crs; cruciate sulcus; csss; ec; external capsule; external plexiform layer; glomerular layer; hippocampus; ic; internal capsule; internal plexiform layers; intrabulbar anterior commissure; lateral gyrus; lateral sulcus; lentiform nucleus; ls; maximum intensity projection; mitral layer; myelin basic protein; oSVZ; occipitotemporal sulcus; olfactory bulb; olfactory bulb core; opr; optic radiation; optical density; orbital gyrus; ots; outer subventricular zone; paraformaldehyde; posterior ectosylvian gyrus; posterior pseudosylvian field; posterior sigmoid gyrus; posterior suprasylvian field; presylvian sulcus; primary auditory cortex; primary motor cortex; primary somatosensory cortex; prs; pseudosylvian sulcus; pss; rf; rhinal fissure; rhinal sulcus; rostral posterior parietal cortex; rostral suprasylvian sulcus; rs; rsss; secondary somatosensory cortex; septum; splenial sulcus; spt; ss; subWM; subcortical matter; suprasylvian gyrus; thalamus; third somatosensory cortex; visual cortical area