Elsevier

Sleep Medicine

Volume 13, Issue 6, June 2012, Pages 720-727
Sleep Medicine

Original Article
Gender differences in brain regional homogeneity of healthy subjects after normal sleep and after sleep deprivation: A resting-state fMRI study

https://doi.org/10.1016/j.sleep.2011.09.019Get rights and content

Abstract

Objective

To explore the gender differences of brain regional homogeneity (ReHo) in healthy subjects during the resting-state, after normal sleep, and after sleep deprivation (SD) using functional magnetic resonance imaging (fMRI) and the ReHo method.

Methods

Sixteen healthy subjects (eight males and eight females) each underwent the resting-state fMRI exams twice, i.e., once after normal sleep and again after 24 h’s SD. According to the gender and sleep, 16 subjects were all measured twice and divided into four groups: the male control group (MC), female control group (FC), male SD group (MSD), and female SD group (FSD). The ReHo method was used to calculate and analyze the data, SPM5 software was used to perform a two-sample T-test and a two-pair T-test with a P value <0.001, and cluster volume ⩾270 mm3 was used to determine statistical significance.

Results

Compared with the MC, the MSD showed significantly higher ReHo in the right paracentral lobule (BA3/6), but in no obviously lower regions. Compared with the FC, the FSD showed significantly higher ReHo in bilateral parietal lobes (BA2/3), bilateral vision-related regions of occipital lobes (BA17/18/19), right frontal lobe (BA4/6), and lower ReHo in the right frontal lobe. Compared with the FC, the MC showed significantly higher ReHo in the left occipital lobe (BA18/19), and left temporal lobe (BA21), left frontal lobe, and lower ReHo in the right insula and in the left parietal lobe. Compared with the FSD, the MSD showed significantly higher ReHo in the left cerebellum posterior lobe (uvula/declive of vermis), left parietal lobe, and bilateral frontal lobes, and lower ReHo in the right occipital lobe (BA17) and right frontal lobe (BA4).

Conclusions

The differences of brain activity in the resting state can be widely found not only between the control and SD group in a same gender group, but also between the male group and female group. Thus, we should take the gender differences into consideration in future fMRI studies, especially the treatment of brain-related diseases (e.g., depression).

Introduction

Prior to the 1990s, few studies examined gender differences in symptoms, disease progression, or the treatment of psychiatric disorders. In the last twenty years, however, research efforts have begun to include the examination of gender differences in studies on brain function using animal models and human subjects. Gender difference is investigated in studies including micturition control, cognitive control of emotion, and drug uses [1], [2], [3]. Referred to a great quantity of literatures, Cosgrove noted that while there were many similarities in brain structure, function, and neurotransmission in healthy males and females, there are important differences that distinguish the male from the female brain [4]. Overall, brain volume is greater in males than in females; yet, when controlling for total volume, global cerebral blood flow was higher in females than in males. Females have a higher percentage of gray matter and males a higher percentage of white matter. The concept of gender differences and Regional volume differences are less consistent, with there being an opinion that there is greater gray matter volume as a percentage of total intracranial volume in the male versus the female gender [5] or no gender differences [6]; Some scholars have shown no gender differences when controlling for brain volume in total gray matter volume and the activation of the frontal lobe and the temporal lobe [2], some have considered more activated regions [7] or stronger signals of extensive regions in females versus males despite no gender differences in carrying out tasks [8].

Sleep Deprivation (SD) is a sleep loss status and generally caused by personal or environmental reasons. It can lead to a series of changes in emotional balance, cognitive function, learning and memory, immune function, and the central nervous system [9], and is accompanied by increased fatigue. SD duration is associated with maladaptive emotional regulation, leading to exaggerated neural reactivity, aversive experiences, psychological and physiological, or even behavioral, reactivity to negative. SD targets the biological mechanisms which are responsible for the possibility, unique to mood disorders, of rapid switching between depression, euthymia, and mania. The rapidity of action of SD enables the study of the correlates of antidepressant response at close time points, providing a good model to study the biological basis of the antidepressant response and of the pathophysiology of affective illness. It’s widely applied in studies including attentional networks [10], interindividual variability [11], and working memory [12]. It’s generally acknowledged that brain activity appears in the form of a mass or region made up of many cluster volumes. On the basis of this hypothesis, Zang [13] proposed to analyze the characteristics of the regional brain activity and to evaluate the similarity between the adjacent cluster volumes’ brain activity using the Regional Homogeneity (ReHo) method. The ReHo method has been widely applied in studies, including studies on depression [14], pediatric epilepsy [15], Parkinson’s disease [16], and Alzheimer’s disease [17]. Using functional magnetic resonance imaging (fMRI) and the ReHo method, the current study looked at the brain gender differences of healthy volunteers after normal sleep and after SD.

Section snippets

Subjects

Sixteen healthy subjects (eight males, eight females), ranged in age from 21 to 25 yrs (mean: 22 yrs), were recruited for this study. All sixteen subjects met the following criteria: (1) right-handed; (2) had a good sleeping habit; (3) had a regular dietary habit and did not smoke; (4) did not consume any stimulants, alcohol, tea or coffee for at least 24 h prior to the study; (5) had no inborn or other acquired diseases; (6) had no foreign implants in the body; (7) had an IQ > 100 when assessed by

Subjects

All subjects completed the whole study well. None of the subjects had more than 1 mm maximum displacement in x, y, or z and 1° of angular motion. All subjects’ data were used in this study.

MSD versus MC

Compared with the MC, the MSD showed significantly higher ReHo in the right paracentral lobule (V = 351mm3), but there were no lower ReHo regions (Table 1, Fig. 1).

FSD versus FC

Compared with the FC, the FSD showed significantly higher ReHo in the left occipital lobe (cuneus, middle occipital gyrus, inferior occipital gyrus,

ReHo analysis under SD

The MSD showed significantly higher ReHo in the right paracentral lobule (BA3/6, V = 351 mm3) as compared with the MC, but there were no lower regions (P < 0.001, V  270 mm3; Table 1, Fig. 1). This suggested that the time consistency of spontaneous neuron activity in the right frontal lobe was higher in the MSD than in the MC. However, this higher ReHo in the frontal lobe was small, suggesting it was likely a mild compensatory reaction and might not lead to functional disorders or corresponding mental

Conclusions

There are wide gender differences between the brain activity of the subjects in the control and in the SD groups during the resting state in this study, and the differences are not the same for males and females. Therefore, the gender differences should be taken into consideration for future fMRI studies, particularly for studies on diseases, such as depression, that differ in prevalence and symptoms between males and females.

In short, the study of gender differences could possibly be a hot

Conflict of interest

The ICMJE Uniform Disclosure Form for Potential Conflicts of Interest associated with this article can be viewed by clicking on the following link: doi:10.1016/j.sleep.2011.09.019.

. ICMJE Form for Disclosure of Potential Conflicts of Interest form.

Acknowledgments

The authors are highly grateful to the sixteen subjects who participated in this research. This work was supported by the national innovation experiment program for university students of China (grant No. 091040307).

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