In ancient Sanskrit texts, the word ‘Rtu’ refers to a woman’s menstrual cycle as well as cosmic order and ritual (Gadon, 1989).
Yet, through the centuries the menstrual cycle came to be regarded through the lens of stigma and taboo (Schroeder, 1976). Most people are aware of the hormonal fluctuations throughout the female menstrual cycle. Low estradiol at menstruation, high estradiol pre-ovulation at the end of the follicular phase, and high progesterone and estradiol during the second half of the cycle following ovulation, the luteal phase: are considered to have cyclic modulation of mood (Philips & Sherwin, 1992) and some cognitive effects (Hampson, 1990). Previous animal models have shown that cognitive abilities, affective state, drug-abuse vulnerability, and pain sensitivity are influenced as such (Farage et al., 2008). Further, estrogen depletion in natural or surgical menopause is thought to be linked with cognitive decline (Weber et al., 2014). New findings have confirmed that there are functional and structural changes in the female brain throughout the menstrual cycle (Hageman et al., 2011; Hidalgo-Lopez et al., 2020). A woman’s menstrual cycle is divided into the four phases- the menstrual phase, follicular phase, ovulation phase and the luteal phase.
The Menstrual Phase
The menstrual phase is characterised by menses, low levels of estrogen and progesterone. During this phase, larger grey matter volumes have been detected in the right fusiform gyrus and parahippocampal gyrus (Pletzer et al., 2018). The parahippocampal gyrus has been found to support spatial memory and navigation (Lew & Semendeferi, 2017). Therefore, females may experience improved navigation and spatial awareness during menstruation, and so perform better in activities like dancing. Furthermore, the default mode network, which is most active when a person is daydreaming or mind wandering, has shown significantly increased connectivity with the left middle frontal area of the brain during the menstrual phase as opposed to the follicular phase after (Weis et al., 2019). While studies have highlighted that default mode network deactivation leads to more successful task performance, this could explain why some women feel distracted and find difficulty focusing during their period (Weis et al., 2019).
The Follicular Phase
This phase is characterised by a peak in estrogen as an egg is prepared to be released (Lisofsky et al., 2015). Increased grey matter volumes in the hippocampal and parahippocampal structures during the follicular phase have been established, as well as increased functional connectivity of the left and right hippocampus (Lisofsky et al., 2015). In addition, a decrease in activity of the default mode network was detected in a different study (Weis et al., 2019). Thus, suggesting that tasks may be most successfully conducted, as women may be more focused in this phase. Pletzer and colleagues (2018) suggested that the increase in grey matter volumes during this phase is related to high levels of estradiol (the strongest of the three estrogens and most common in fertile women). Rising levels of estradiol have also been thought to reduce the effects of stress hormones, which contributes to the preservation of happy moods (Scott, 2012). Many women report feeling positive and energetic during this time. Overall, increased grey matter volume in the hippocampal and parahippocampal structures are a consequence of the rising estradiol, suggesting that estradiol can assist with neuroplasticity during this phase of the menstrual cycle.
Ovulation
At the time of ovulation, females typically report feeling most positive, in flow, with the strongest libido (Sumner et al., 2018). The luteinising hormone increases to prompt the release of an egg from the ovaries, which may interact with other present hormones to increase the female libido. Studies have indicated that women have a greater tolerance for pain, display more addictive behaviours, may spend more money on items to enhance feelings of attractiveness and are generally more attractive to the opposite sex. Ovulation normally occurs around day 14 of the menstrual cycle. A study found that brain activation in the hippocampus peaks during the ovulation phase (Pletzer et al., 2018) with a peak in grey matter volume of around 1.8% (Franke et al., 2015)- which magnitude is subject to individual differences (Lisofsky et al., 2015). A peak in grey matter volume has been explained by fast modulation of synaptic plasticity due to high levels of estrogen (Lisofsky et al., 2015).
Luteal
In the final phase of the menstrual cycle, progesterone levels rise, and one may begin to feel more irritable and experience pre-menstrual symptoms aka ‘PMS’. Progesterone helps the body make cortisol, which is associated with stress. Women might seek comforting foods and behaviours during this time, like binge eating chocolate or having a duvet day watching Netflix. Improving nutrition, sleep and exercise during this time, can ease unwanted symptoms of the luteal phase. While pre-menstrual symptoms are very common, they are not ‘normal’ and can be a sign that something is off balance. There may be cognitive deficits in executive functioning in symptomatic women experiencing PMS, confirming that sex hormones influence higher cognitive processes (Le et al., 2020). The rise of progesterone has been associated with significantly reduced activity in the left hippocampus compared to the follicular phase, which supports episodic verbal memory (Pletzer et al., 2018). However, increased activity has been found in the right hemisphere fronto-striatal circuit during this phase of the cycle, which is a circuit of the brain that supports motor, cognitive and emotional processes (Alkhasli et al., 2019).
Conclusion
Overall, emerging evidence in the field of neuroscience is unveiling ways women may be able to work with their cycle to enhance their lives. It is important to recognise that females may thrive at different points during their cycle and may need more rest than usual at other points. Thus, improving understanding about the phases of the menstrual cycle, the abnormal nature of PMS, and resulting neuroplasticity from hormonal fluctuations can enhance the lives of many females. For example, the changing hormones during the menstrual phase can cause your brain to have difficulty focusing during tasks, therefore women should be more patient with themselves during this time where the default mode network is most negative. Meditation practises have been suggested to improve interference of the default mode network and therefore women on their period may benefit from practises such as a ten-minute meditation in the morning to improve focus for the day (Garrison et al., 2015).
References
Alkhasli, I., Sakrida, K., Mottaghy, F. M., Binkofski, F. (2019). Modulation of Fronto-Striatal Functional Connectivity Using Transcranial Magnetic Stimulation. Frontiers in Human Neuroscience. https://www.frontiersin.org/articles/10.3389/fnhum.2019.00190/full
Dubol, M., Epperson, C.N., Sacher, J., Pletzer, B., Derntl, B., Lanzenberger, R., Sundström-Poromaa, I. and Comasco, E. (2021). Neuroimaging the menstrual cycle: A multimodal systematic review. Frontiers in Neuroendocrinology, 60, p.100878.
Feinberg D , Jones B , LawSmith M , Moore F , DeBruine L , Cornwell R , Hillier S , Perrett D (2006) Horm Behav 49:215–222. https://doi.org/10.1016/j.yhbeh.2005.07.004
Franke, K., Hagemann, G., Schleussner, E. and Gaser, C. (2015). Changes of individual BrainAGE during the course of the menstrual cycle. NeuroImage, 115, pp.1–6.
Gadon, Elinor W. (1989). The once and future goddess. San Francisco: Harper.
Garrison, K. A., Zeffiro, T. A., Scheinost, D., Constable, R. T., & Brewer, J. A. (2015). Meditation leads to reduced default mode network activity beyond an active task. Cognitive, affective & behavioral neuroscience, 15(3), 712–720. https://doi.org/10.3758/s13415-015-0358-3
Gorvett, Z. (2018). How the menstrual cycle changes women’s brains – for better. [online] www.bbc.com. Available at: https://www.bbc.com/future/article/20180806-how-the-menstrual-cycle-changes-womens-brains-every-month.
Hagemann, G., Ugur, T., Schleussner, E., Mentzel, H.-J., Fitzek, C., Witte, O.W. and Gaser, C. (2011). Changes in Brain Size during the Menstrual Cycle. PLoS ONE, 6(2), p.e14655.
Hampson, E (1990). Estrogen-related variations in human spatial and articulatory-motor skills. Psychoneuroendocrinology 1990, 15, 97–111. https://doi.org/10.1016/0306-4530(90)90018-5
Hidalgo-Lopez, E., Mueller, K., Harris, T., Aichhorn, M., Sacher, J. and Pletzer, B. (2020). Human menstrual cycle variation in subcortical functional brain connectivity: a multimodal analysis approach. Brain Structure and Function, 225(2), pp.591–605.
Le, J., Thomas, N., & Gurvich, C. (2020). Cognition, The Menstrual Cycle, and Premenstrual Disorders: A Review. Brain sciences, 10(4), 198. https://doi.org/10.3390/brainsci10040198
Lew, C.H. and Semendeferi, K. (2017). Evolutionary Specializations of the Human Limbic System. Evolution of Nervous Systems, 4, pp.277–291.
Lisofsky, N., Mårtensson, J., Eckert, A., Lindenberger, U., Gallinat, J. and Kühn, S. (2015). Hippocampal volume and functional connectivity changes during the female menstrual cycle. NeuroImage, 118, pp.154–162.
McEwen, B.S. and Milner, T.A. (2016). Understanding the broad influence of sex hormones and sex differences in the brain. Journal of Neuroscience Research, [online] 95(1-2), pp.24 –39. Available at: https://onlinelibrary.wiley.com/doi/abs/10.1002/jnr.23809.
Phillips, S.M & Sherwin, B.B. (1992) Variations in memory function and sex steroid hormones across the menstrual cycle. Psychoneuroendocrinology. 17, 497–506. DOI: 10.1016/0306-4530(92)90008-u
Pletzer, B., Harris, T. and Hidalgo-Lopez, E. (2018). Subcortical structural changes along the menstrual cycle: beyond the hippocampus. Scientific Reports, 8(1).
Protopopescu, X., Butler, T., Pan, H., Root, J., Altemus, M., Polanecsky, M., McEwen, B., Silbersweig, D. and Stern, E. (2008). Hippocampal structural changes across the menstrual cycle. Hippocampus, [online] 18(10), pp.985–988. Available at: https://onlinelibrary.wiley.com/doi/full/10.1002/hipo.20468 [Accessed 4 Jul. 2019].
Ray, L. (2019). The Menstrual Cycle More Than Just the Period. [online] Helloclue.com. Available at: https://helloclue.com/articles/cycle-a-z/the-menstrual-cycle-more-than-just-the-period.
Schroeder, F. (1976). Feminine hygiene, fashion and the emancipation of american women. American Studies, 17(2), 101-110. http://www.jstor.org/stable/40641221
Sumner, R.L., Spriggs, M.J., McMillan, R.L., Sundram, F., Kirk, I.J. and Muthukumaraswamy, S.D. (2018). Neural plasticity is modified over the human menstrual cycle: Combined insight from sensory evoked potential LTP and repetition suppression. Neurobiology of Learning and Memory, 155, pp.422–434.
The Women’s Centre (2022). A Woman’s Brain Actually Changes Size During Menstrual Cycles. [online] www.wcorlando.com. Available at: https://www.wcorlando.com/contents/news/news-from-dr-gearity/a-womans-brain-actually-changes-size-during-menstrual-cycles#:~:text=A%20Woman
Thiyagarajan, D.K., Basit, H. and Jeanmonod, R. (2019). Physiology, Menstrual Cycle. [online] Nih.gov. Available at: https://www.ncbi.nlm.nih.gov/books/NBK500020/.
Weber, M.T.; Maki, P.M. & McDermott, M.P (2014). Cognition and mood in perimenopause: A systematic review and meta-analysis. J. Steroid Biochem. Mol. Biol. 142, 90–98 DOI: 10.1016/j.jsbmb.2013.06.001
Weis, S., Hodgetts, S. and Hausmann, M. (2019). Sex differences and menstrual cycle effects in cognitive and sensory resting state networks. Brain and Cognition, 131, pp.66–73.