Effects of gender, digit ratio, and menstrual cycle on intrinsic brain functional connectivity: A whole‐brain, voxel‐wise exploratory study using simultaneous local and global functional connectivity mapping

Abstract

IntroductionGender and sex hormones influence brain function, but their effects on functional network organization within the brain are not yet understood.MethodsWe investigated the influence of gender, prenatal sex hormones (estimated by the 2D:4D digit ratio), and the menstrual cycle on the intrinsic functional network organization of the brain (as measured by 3T resting‐state functional MRI (rs‐fMRI)) using right‐handed, age‐matched university students (100 males and 100 females). The mean (±SD) age was 20.9 ± 1.5 (range: 18–24) years and 20.8 ± 1.3 (range: 18–24) years for males and females, respectively. Using two parameters derived from the normalized alpha centrality analysis (one for local and another for global connectivity strength), we created mean functional connectivity strength maps.ResultsThere was a significant difference between the male mean map and female mean map in the distributions of network properties in almost all cortical regions and the basal ganglia but not in the medial parietal, limbic, and temporal regions and the thalamus. A comparison between the mean map for the low 2D:4D digit ratio group (indicative of high exposure to testosterone during the prenatal period) and that for the high 2D:4D digit ratio group revealed a significant difference in the network properties of the medial parietal region for males and in the temporal region for females. The menstrual cycle affected network organization in the brain, which varied with the 2D:4D digit ratio. Most of these findings were reproduced with our other datasets created with different preprocessing steps.ConclusionsThe results suggest that differences in gender, prenatal sex hormone exposure, and the menstrual cycle are useful for understanding the normal brain and investigating the mechanisms underlying the variable prevalence and symptoms of neurological and psychiatric diseases.

Increased large-scale inter-network connectivity in relation to impulsivity in Parkinson’s disease

“…Since Iat and Inp are regarded as ‘cognitive’ impulsivity 24 , this study could successfully detect the difference in the pathophysiology between cognitive and motor impulsivity in PD. Although no study to date reported the association between ‘cognitive’ impulsivity and right FPN, the FPN plays an important role in instantiating and flexibly modulating cognitive control 25 , 26 . Therefore, our findings suggest that abnormal cognitive control due to dysfunction of FPN is related to ‘cognitive’ impulsivity in PD.…”

“…Three runs, each with 105 volumes, were performed for each participant. In total, data were acquired over approximately 15 min during a resting state for each participant, as this duration was deemed the most appropriate to obtain reliable data 26,62 . The participants were asked to remain awake but keep their eyes closed during the acquisition.…”

“…Although there are many limitations to the in vivo assessment of human brain, remarkable progress has been made in resting-state functional magnetic resonance imaging (rs-fMRI), which has become more popular than conventional event-related fMRI. Metabolic changes in brain due to stimulation are < 5%, and almost all forms of brain dysfunction can be detected at a resting state 25 , 26 . Furthermore, rs-fMRI can reduce noise compared to event-related fMRI, particularly in elderly patients with PD characterised by bradykinesia or bradyphrenia.…”

Effects of perinatal blood pressure on maternal brain functional connectivity

“…We used CompCor [ 31 , 32 ], six head motion time-course parameters regression [ 33 ], and global signal regression (mean time course of the functional brain image voxels) to exclude signal artefact unrelated to brain activity [ 34 – 36 ]. Temporal filtering (from 0.01 to 0.1 Hz) was then applied to remove constant offset and linear trends over each run.…”

Regional abnormality of functional connectivity is associated with clinical manifestations in individuals with intractable focal epilepsy

“…Centrality analysis using rs-fMRI has detected alterations in the network in several epilepsy types 10 , 20 , 21 , and initial observations suggested a network disruption in epilepsy and disease progression as well as postsurgical seizure outcome, which emphasizes that graph theoretical analysis may lend markers for disease staging and prognostics. In this present study, we employed normalized α-centrality (nAC) on rs-fMRI 22 , 23 to quantify the brain regional network organization to compare different centralities. The nAC measures the strength of a node in a network from the local viewpoint to the global viewpoint by changing the parameter (that is, α) from zero to 1/λ; thereby, λ is the maximum eigenvalue of the adjacency matrix of the network.…”