Sex Differences in the Complexity of Healthy Older Adults' Magnetoencephalograms.

Elizabeth Shumbayawonda,David López-Sanz,Daniel Abásolo,Ricardo Bruña,Alberto Fernández,Fernando Maestu

doi:10.3390/e21080798

Abstract

The analysis of resting-state brain activity recording in magnetoencephalograms (MEGs) with new algorithms of symbolic dynamics analysis could help obtain a deeper insight into the functioning of the brain and identify potential differences between males and females. Permutation Lempel-Ziv complexity (PLZC), a recently introduced non-linear signal processing algorithm based on symbolic dynamics, was used to evaluate the complexity of MEG signals in source space. PLZC was estimated in a broad band of frequencies (2–45 Hz), as well as in narrow bands (i.e., theta (4–8 Hz), alpha (8–12 Hz), low beta (12–20 Hz), high beta (20–30 Hz), and gamma (30–45 Hz)) in a sample of 98 healthy elderly subjects (49 males, 49 female) aged 65–80 (average age of 72.71 ± 4.22 for males and 72.67 ± 4.21 for females). PLZC was significantly higher for females than males in the high beta band at posterior brain regions including the precuneus, and the parietal and occipital cortices. Further statistical analyses showed that higher complexity values over highly overlapping regions than the ones mentioned above were associated with larger hippocampal volumes only in females. These results suggest that sex differences in healthy aging can be identified from the analysis of magnetoencephalograms with novel signal processing methods.

Highlights

Sex differences in brain structure and functioning are a matter of crucial importance, they remain relatively unexplored [1]
These results suggest that sex differences in healthy aging can be identified from the analysis of magnetoencephalograms with novel signal processing methods
Following the sensor space broadband analysis, a source space complexity analysis was performed to investigate these differences further, both in broadband and narrow bands, after which a source-by-source statistical comparison, using cluster-based permutation tests (CBPT) to control for multiple comparisons, was carried out to identify the exact location of the cluster containing the significant differences between

Summary

Introduction

Sex differences in brain structure and functioning are a matter of crucial importance, they remain relatively unexplored [1]. Personality/behavioral traits such as physical aggression appear more frequently in males, whereas neuroticism and agreeableness are more common in females [9,10,11]. The authors reported significant differences in volume and tissue density that affected regions such as the amygdala, hippocampus, putamen, insula, cingulate gyrus, frontal pole, posterior cingulate/precuneus, planum temporale, etc. Males tended to show larger volumes in limbic regions and posterior cingulate/precuneus, whereas females exhibited larger volumes in language regions and anterior cingulate. In addition to structural measures, functional investigations by means of MRI (i.e., fMRI), such as those assessing brain connectivity, showed significant differences. The strength of the connectivity within the default mode network (DMN) was higher in females, while the connectivity within the sensorimotor and visual cortices was stronger in males [13]

Methods

Results

Discussion

Conclusion