Age-Dependent Sexually-Dimorphic Asymmetric Development of the Ferret Cerebellar Cortex

Kazuhiko Sawada,Ichio Aoki

doi:10.3390/sym9030040

Abstract

A three-dimensional (3D) T1-weighted Magnetic Resonance Imaging (MRI) at 7-Tesla system was acquired with a high spatial resolution from fixed brains of male and female ferrets at postnatal days (PDs) 4 to 90, and their age-related sexual difference and laterality were evaluated by MRI-based ex vivo volumetry. The volume of both left and right sides of cerebellar cortex was larger in males than in females on PD 10 and thereafter. When the cerebellar cortex was divided into four transverse domains, i.e., anterior zone (AZ; lobules I–V), central zone (CZ; lobules VI and VII), posterior zone (PZ; lobules VIII–IXa), and nodular zone (NZ; lobules IXb and X), an age-related significantly greater volume in males than in females was detected on either side of all four domains on PD 42 and of the AZ on PD 90, but only on the left side of the PZ on PD 90. Regarding the volume laterality, significant leftward asymmetry was obtained in the CZ and PZ volumes in males, but not in females on PD 90. From asymmetry quotient (AQ) analysis, AQ scores were rightward in the AZ in both sexes already on PD 21, but gradually left-lateralized only in males in the CZ, PZ, and NZ during PDs 42 to 90. The present study suggests that a characteristic counterclockwise torque asymmetry (rostrally right-biased, and caudally left-biased or symmetrical) is acquired in both sexes of ferrets during PDs 42 to 90, although the leftward laterality of the posterior half of the cerebellum was more enhanced in males.

Highlights

Morphological and functional asymmetry is reported in brain regions related to preference of hand/paw use [1,2,3], cognition [2,4], emotion [5], and so on
The cerebellar torque asymmetry was reportedly clockwise in primates such as humans [13] and chimpanzees [14], but counterclockwise torque asymmetry was observed in carnivores, such as ferrets [15]
Anteriorly left-biased and posterior right-biased absolute volumes of the cerebellum were reported as an intrinsic cerebellar asymmetry [13,34], indicating a clockwise cerebellar torque

Summary

Introduction

Morphological and functional asymmetry is reported in brain regions related to preference of hand/paw use [1,2,3], cognition [2,4], emotion [5], and so on. It is well known that large-scale fiber connectivity, such as cerebro-cerebellar connections, is involved in the morphological lateralization [6,7,8]. Environmental variables may be involved in the asymmetric morphology of the brain. Some mammalian species, including primates and carnivores, have a distinctive asymmetric feature of the cerebellar morphology, called “torque asymmetry”. The cerebellar torque asymmetry was reportedly clockwise in primates such as humans [13] and chimpanzees [14], but counterclockwise torque asymmetry was observed in carnivores, such as ferrets [15]

Methods

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Discussion

Conclusion