Functional Aspects of Hypothalamic Asymmetry

Abstract

Anatomically, the brain is a symmetric structure. However, growing evidence suggests that certain higher brain functions are regulated by only one of the otherwise duplicated (and symmetric) brain halves. Hemispheric specialization correlates with phylogeny supporting intellectual evolution by providing an ergonomic way of brain processing. The more complex the task, the higher are the benefits of the functional lateralization (all higher functions show some degree of lateralized task sharing). Functional asymmetry has been broadly studied in several brain areas with mirrored halves, such as the telencephalon, hippocampus, etc. Despite its paired structure, the hypothalamus has been generally considered as a functionally unpaired unit, nonetheless the regulation of a vast number of strongly interrelated homeostatic processes are attributed to this relatively small brain region. In this review, we collected all available knowledge supporting the hypothesis that a functional lateralization of the hypothalamus exists. We collected and discussed findings from previous studies that have demonstrated lateralized hypothalamic control of the reproductive functions and energy expenditure. Also, sporadic data claims the existence of a partial functional asymmetry in the regulation of the circadian rhythm, body temperature and circulatory functions. This hitherto neglected data highlights the likely high-level ergonomics provided by such functional asymmetry.

Lower hypothalamus subunit volumes link with impaired long-term body weight gain after preterm birth

“…In our case this link was also valid for the PVN.DM.LH + and the INF.VM + , but not the LH + subunit, namely for the FT as well as for the VP/VLBW cohort. For literature describing the asymmetrically representation of certain hypothalamic functions and transmitters compare (e.g., 21 , 62 , 63 ). In total, the last results further confirm the representative character of our sample with respect to hypothalamic volumes.…”

Left-right side-specific endocrine signaling complements neural pathways to mediate acute asymmetric effects of brain injury

“…Top-down control of the hypothalamic-pituitary-adrenal and hypothalamic-pituitary-gonadal axes, as well as the immune system, is left-right hemisphere specific ( Bakalkin et al, 1984 ; Inase and Machida, 1992 ; Kiss et al, 2020 ; Lueken et al, 2009 ; Madsen et al, 2012 ; Meador et al, 2004 ; Sullivan and Gratton, 2002 ; Xavier et al, 2013 ). The right-sided injuries to the brain or spinal nerves compared to those on the left side produce stronger effects on the neuroendocrine systems, including hormonal levels in the peripheral circulation ( Hussain et al, 2012 ; Inase and Machida, 1992 ; Kononenko et al, 2017 ; Lueken et al, 2009 ).…”

Research Progress on the Effect of Epilepsy and Antiseizure Medications on PCOS Through HPO Axis

“…The contents of GnRH in the hypothalamus on both sides are different, and it is much more abundant on the right side than on the left side (45). The laterality of epilepsy is an important factor affecting reproductive endocrine disorders in WWE (38,46).…”