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Sex steroids and connectivity in the human brain: A review of neuroimaging studies

Institute of Psychology, Brain and Development Laboratory, Leiden University, Leiden, The Netherlands.
Psychoneuroendocrinology (Impact Factor: 5.59). 06/2011; 36(8):1101-13. DOI: 10.1016/j.psyneuen.2011.05.004
Source: PubMed

ABSTRACT Our brain operates by the way of interconnected networks. Connections between brain regions have been extensively studied at a functional and structural level, and impaired connectivity has been postulated as an important pathophysiological mechanism underlying several neuropsychiatric disorders. Yet the neurobiological mechanisms contributing to the development of functional and structural brain connections remain to be poorly understood. Interestingly, animal research has convincingly shown that sex steroid hormones (estrogens, progesterone and testosterone) are critically involved in myelination, forming the basis of white matter connectivity in the central nervous system. To get insights, we reviewed studies into the relation between sex steroid hormones, white matter and functional connectivity in the human brain, measured with neuroimaging. Results suggest that sex hormones organize structural connections, and activate the brain areas they connect. These processes could underlie a better integration of structural and functional communication between brain regions with age. Specifically, ovarian hormones (estradiol and progesterone) may enhance both cortico-cortical and subcortico-cortical functional connectivity, whereas androgens (testosterone) may decrease subcortico-cortical functional connectivity but increase functional connectivity between subcortical brain areas. Therefore, when examining healthy brain development and aging or when investigating possible biological mechanisms of 'brain connectivity' diseases, the contribution of sex steroids should not be ignored.

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    • "The present sample was mostly female (Table 1). Myelination of the CC is an on-going process until adulthood and is influenced by hormonal status (Peper et al. 2011). However, controls were matched for sex and PDS scores, and these variables were used as covariates in between-group comparisons. "
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    • "Finally, there is evidence that hormonal changes that occur during puberty can affect both structural and functional connectivity (Peper et al. 2011). Hormonal changes, in particular, may help to explain the timing of the changes that we observed here. "
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    • "In addition to these structural effects, the amount of circulating ovarian hormones influenced functional abilities in humans, specifically, verbal memory (Peper et al., 2011) and explicit memory recall (Gooren, 2007). Moreover, estrogen administration was found to protect against neurodegeneration only in cognitively intact women for whom degeneration had not yet started (Siegfried, 2007). "
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Jiska S Peper