Gender and cytoarchitecture differences: Functional connectivity of the hippocampal sub-regions

Adnan A S Alahmadi; Nada O Alotaibi; Norah Y Hakami; Raghad S Almutairi; Afnan M F Darwesh; Rawan Abdeen; Jamaan Alghamdi; Osamah M Abdulaal; Walaa Alsharif; Salahaden R Sultan; Ibrahem H Kanbayti

doi:10.1016/j.heliyon.2023.e20389

Gender and cytoarchitecture differences: Functional connectivity of the hippocampal sub-regions

Heliyon. 2023 Sep 21;9(10):e20389. doi: 10.1016/j.heliyon.2023.e20389. eCollection 2023 Oct.

Affiliations

¹ Radiologic Sciences, Faculty of Applied Medical Sciences, King Abdulaziz University, Jeddah, Saudi Arabia.
² NMR Research Unit, Department of Neuroinflammation, Queen Square MS Centre, UCL Queen Square Institute of Neurology, London, United Kingdom.
³ Diagnostic Radiology Technology, College of Applied Medical Sciences, Taibah University, Madina, Saudi Arabia.

Abstract

Introduction: The hippocampus plays a significant role in learning, memory encoding, and spatial navigation. Typically, the hippocampus is investigated as a whole region of interest. However, recent work has developed fully detailed atlases based on cytoarchitecture properties of brain regions, and the hippocampus has been sub-divided into seven sub-areas that have structural differences in terms of distinct numbers of cells, neurons, and other structural and chemical properties. Moreover, gender differences are of increasing concern in neuroscience research. Several neuroscience studies have found structural and functional variations between the brain regions of females and males, and the hippocampus is one of these regions.

Aim: The aim of this study to explore whether the cytoarchitecturally distinct sub-regions of the hippocampus have varying patterns of functional connectivity with different networks of the brain and how these functional connections differ in terms of gender differences.

Method: This study investigated 200 healthy participants using seed-based resting-state functional magnetic resonance imaging (rsfMRI). The primary aim of this study was to explore the resting connectivity and gender distinctions associated with specific sub-regions of the hippocampus and their relationship with major functional brain networks.

Results: The findings revealed that the majority of the seven hippocampal sub-regions displayed functional connections with key brain networks, and distinct patterns of functional connectivity were observed between the hippocampal sub-regions and various functional networks within the brain. Notably, the default and visual networks exhibited the most consistent functional connections. Additionally, gender-based analysis highlighted evident functional resemblances and disparities, particularly concerning the anterior section of the hippocampus.

Conclusion: This study highlighted the functional connectivity patterns and involvement of the hippocampal sub-regions in major brain functional networks, indicating that the hippocampus should be investigated as a region of multiple distinct functions and should always be examined as sub-regions of interest. The results also revealed clear gender differences in functional connectivity.

Keywords: Functional connectivity; Functional magnetic resonance imaging (fMRI); Gender differences; Hippocampal sub-fields; Hippocampus; Resting state functional magnetic resonance imaging (rsfMRI).