The Structural and Functional Connectivity of the Pineal Gland, and its Age and Gender Associations

Abstract

Purpose: The pineal gland (PG) is a structure located in the midline of the brain, and is considered the main part of the epithalamus. There are reports on the role of this area for brain function by hormone secretion, as well as few reports on its role in brain cognition. However, little knowledge is available on the structural and functional connectivity of the PG with other brain regions, as well as its age and gender associations.

Materials and Methods: In this work, we used the diffusion and resting-functional MRI data of 282 individuals, in the age range of 19 to 76 years old. All participants were checked for their medical and mental health by a general practitioner, and the MRI data were collected using a 3 Tesla scanner. The diffusion data were analyzed using the Explore DTI software (version 8.3), and the fMRI data were analyzed using the CONN toolbox (version 18.0).

Results: Two white matter tracts connecting the PG Body to PG Roots and PG to Pons were extracted in this study. The mean FA of the two tracts were 0.26 ± 0.06 and 0.24 ± 0.08, respectively. Neither the FA values of the tracts nor their lengths, showed any associations with age and gender; However, with increasing age, the likelihood of successfully identifying the PG-Pons tract decreased. In functional connectivity analysis, five brain regions showed positive connectivity with the PG, including the superior temporal gyrus, middle temporal gyrus, brain stem, vermis, and the subcallosal cortex, and 25 regions showed negative connectivity. These connectivities did not show an association with gender, but some associations with age were observed.

Conclusion: This study is novel in estimating the functional and structural connectivity of the PG with other brain areas, and also in assessing the association of these connections with age and gender, which could help to increase our knowledge on the functional neuroanatomy of the pineal gland.