Brain Responses Difference between Sexes for Strong Desire to Void: A Functional Magnetic Resonance Imaging Study in Adults Based on Graph Theory

Abstract

Background: The alternations of brain responses to a strong desire to void were unclear, and the gender differences under the strong desire to void remain controversial. The present study aims to identify the functional brain network's topologic property changes evoked by a strong desire to void in healthy male and female adults with synchronous urodynamics using a graph theory analysis. Methods: The bladders of eleven healthy males and eleven females were filled via a catheter using a specific infusion and withdrawal pattern. A resting-state functional magnetic resonance imaging (fMRI) was performed on the enrolled subjects, scanning under both the empty bladder and strong desire to void states. An automated anatomical labeling (AAL) atlas was used to identify the ninety cortical and subcortical regions. Pearson's correlation calculations were performed to establish a brain connection matrix. A paired t-test (p < 0.05) and Bonferroni correction were applied to identify the significant statistical differences in topological properties between the two states, including small-world network property parameters [gamma (γ) and lambda (λ)], characteristic path length (L_p), clustering coefficient (C_p), global efficiency (E_glob), local efficiency (E_loc), and regional nodal efficiency (E_nodal). Results: The final data suggested that females and males had different brain response patterns to a strong desire to void, compared with an empty bladder state. Conclusions: More brain regions involving emotion, cognition, and social work were active in females, and males might obtain a better urinary continence via a compensatory mechanism.

Keywords: brain–bladder control; desire to void; graph theory; resting-state functional magnetic resonance imaging; small-world network; topologic properties.

Figure 1

Bladder filling and fMRI protocol.

Figure 2

Brain functional connection matrix of healthy female and male subjects under both of the states.

Figure 3

The C_p, L_p, E_g, and E_loc in healthy female subjects between both of the states. Legend: It showed that the significantly increased C_p, L_p, E_glob and decreased E_loc in these females. C_p, clustering coefficient; L_p, characteristic path length; E_glob, global efficiency; E_loc, local efficiency (p < 0.05) (y axis label is the σ value; * represents statistically significant data).

Figure 4

The C_p, L_p, E_g and E_loc in healthy male subjects between both of the states. Legend: It showed that the significantly decreased C_p in the female subjects, without significant changes in C_p L_p, E_glob. C_p, clustering coefficient; L_p, characteristic path length; E_g, global efficiency; E_loc, local efficiency (p < 0.05) (y axis label is the σ value; * represents statistically significant data).

Figure 5

The brain regions with an alternated E_nodal in the healthy male subjects between both of the states. Legend: (a) For female subjects, a larger E_nodal in bilateral calcarine fissure and surrounding cortex, lingual gyrus, and fusiform gyrus were detected under the empty bladder state. (b) Under the strong desire to void state, a larger E_nodal in the left inferior frontal gyrus and the orbital part of middle frontal gyrus, right median cingulate, middle occipital gyrus and middle temporal gyrus, and bilateral gyrus rectus, inferior parietal gyrus and supramarginal gyrus was detected in healthy females. (c) The larger E_nodal in the right inferior occipital gyrus and thalamus of male subjects under the empty bladder state. (d) The significantly increased E_nodal of healthy male subjects presented in right frontal operculum and medial superior frontal gyrus, left supplementary motor area and the bilateral supramarginal gyrus (p < 0.05).