The Turning, Post Three: The Second Remaking
How, and why, perimenopause changes the brain.
The traditions I named in post two of this series were describing something real—something of spirit, but also of flesh. (I’d recommend reading post one and post two before you continue here.) Something changes after becoming mother—something substantive in the way a woman perceives and processes and inhabits the world. You can feel it happening, a faint hum in the mind that reroutes thinking and often makes placing words difficult. A mother is no longer quite here, but also not quite there. Modern neurological scanning helps us see what the wisdom traditions understood intuitively: the turning from one life stage to another is the crossing of a genuine threshold, one mapped in our cells.
Motherhood changes the brain.
In 2017, a team led by researcher Elseline Hoekzema found what every mother knows: pregnancy changes the brain. Specifically, significant, lasting changes occur in the structure of gray matter in the female brain¹ associated with social cognition, i.e. reading other people’s mental states, perceiving subtle signals of need and threat, and navigating complex relational landscapes. These gray matter areas are pruned and specialized during pregnancy in ways that persist for at least two years after birth—probably longer, and possibly permanently. From brain scans alone, Hoekzema could tell which women in her study cohort had undergone pregnancy.
A 2022 follow-up study by Hoekzema and colleagues mapped additional dimensions of this restructuring¹ᵇ, finding that grey matter changes are widespread, though largely recovered by six months postpartum. In particular, the Default Mode Network undergoes what researchers termed “strong structural changes” across pregnancy. The DMN is the brain’s resting-state system. It’s the network that activates when you are not focused on an external task—when you are daydreaming, reflecting, making narrative sense of your experience, imagining the future, praying. It’s the realm of inward turning, associated with sense of self, imagination, and meaning making. Decades of neuroscience research establish its role in self-referential thought, autobiographical memory, and what researchers call “internal mentation”—the spontaneous, uninvited inner life.
During pregnancy and early motherhood, the architecture of the DMN reorganizes specifically around the mother-infant bond; increased coherence across the DMN was associated with slowing of the mother’s heart rate in response to her baby’s laughter, with nesting behavior and maternal-fetal attachment, and with what researchers described as the quality of pleasure a mother experiences while interacting with her infant. Pregnancy drafted, in Hoekzema’s word, a neurological blueprint for the mother-infant relationship—made part of the brain’s permanent structure by every subsequent interaction with the child. Far from metaphor, this is measurable neural architecture.
A mother’s pull is necessarily inward, so that she may attune totally to the tiny, pre-verbal being in her care. Her child’s survival depends on her inward turning. In the contemplative traditions of yoga therapy, the layer of the self concerned with discernment and deep knowing — the vijnanamaya kosha — is understood to be implicated whenever the structures of cognition shift. Writing about these changes in my clinical work with postpartum women, I observed that what we call maternal brain fog is less damage than adaptation: the brain reorganizing its priorities around what matters most to infant survival, redirecting cognitive resources toward the relational and sensory demands of early motherhood at the temporary expense of other functions.²ᵃ The brain doesn’t malfunction—it reassigns. The sense of malfunction is only relative to the demands of modern life, hyper-novel in the context of human evolution.
Hoekzema’s findings have important implications for the Tender—the archetype I’ve named in the previous two posts. The Tender is a woman whose brain was neurologically structured for a chapter that is now closing. The blueprint drafted in pregnancy — organized around the infant, the mother-infant bond, and the intensive relational demands of early motherhood — is losing its organizing context. The children are no longer infants; the primary attachment chapter is ending; and simultaneously, as we will see, the metabolic shift of perimenopause is beginning.
The groundwater years — the terrain the Tender inhabits — are the second time she has been remade. But where the first remaking had a clear organizing principle — the child, the bond, the blueprint — the second one is still searching for something that gives it form. That a woman is disorientated in this strange stage, without anchor, isn’t weakness. It’s the brain in the process of becoming.
You’re not crazy, it’s your hormones.
Women are largely told that perimenopause begins when their periods become irregular. In fact, for many women, hormonal fluctuation begins in their late thirties—and the brain responds accordingly.
Lisa Mosconi’s research team at Weill Cornell has been imaging the brains of women at multiple points across the menopausal transition, watching in real time as the brain reorganizes itself.² The average woman’s brain, despite being only 2% of body weight, consumes about 20% of her body’s total energy, mostly in the form of glucose, which is the brains preferred fuel. Mosconi and her team found that when estrogen begins its perimenopausal drawdown, it disrupts the brain’s ability to regulate glucose uptake and metabolism efficiently. The brain’s energy supply becomes less reliable.
The brain compensates through alternative mechanisms, and research by Roberta Diaz Brinton, Professor of Pharmacology at the University of Arizona and a leading researcher on the bioenergetics of the aging female brain, has traced one of these: as estrogen’s regulation of glucose metabolism is disrupted during perimenopause, the brain shifts toward ketone bodies as an alternative fuel source.³
These hormonal changes manifest in the mental and emotional realm. The brain is running on a less efficient, less familiar fuel source during the transition. A woman may feel her brain is broken, but it’s not—it’s actually effectively compensating. But compensation has a cost. Tasks that require sustained glucose-intensive processing — focused analytical work, verbal recall, holding multiple complex things in working memory simultaneously — become harder. Her working life doesn’t accommodate these changes, though it must absorb its costs.
The brain fog associated with perimenopause is not a personal failure. It’s the brain reorganizing its energy supply. The fog is real, and it is metabolic. In the modern context, it may manifest as anxiety and depression. The psycho-emotional symptoms are real. But a woman in this phase isn’t necessarily having a mental health crisis—she’s out of sync with what her body needs. Modern medicine rarely has the language, or the diagnostic will, to say: you’re not crazy — it’s your hormones. Some things help: physical movement, dietary fat, sleep, reduced cognitive load where possible. These are the same things that support ketone metabolism generally. The body is wise, if we can pause long enough to listen.
Meanwhile, the brain may become better at certain other things — pattern recognition, intuitive synthesis, tolerance for ambiguity — which are less metabolically demanding and may actually benefit from the shift in how the brain is allocating its resources. Perhaps this is why we wandering mystics in our groundwater years feel called to make sense from this strange terrain as we move between fertile and post-fertile countries.
Estrogen is a neuromodulator, and its lack is felt everywhere.
Estrogen’s role as the orchestrator of the entire reproductive cycle is well understood. What is less discussed is its function as a neuromodulator—a chemical that shapes how the nervous system processes experience. Estrogen modulates the serotonin system (mood, emotional regulation, sense of meaning), the dopamine system (motivation, desire, pleasure, reward), and the acetylcholine system (memory encoding, the capacity to learn). It influences sleep architecture, and it calibrates threat detection.
Given how pervasive a role it plays, its gradual diminishment over the perimenopausal years impacts a host of systems. Estrogen’s drawdown is not linear, or abrupt, but a long, fluctuating tide that, over years, recedes and then partially surges. With each change, the nervous system has to recalibrate each system, and all at once. This, all while the Tender is also parenting, working, sustaining relationships, feeling joy and carrying grief.
The tenderness of the period is as literal as it is metaphorical. A recalibrating nervous system is more permeable and sensitive. The heightened emotional intensity of the groundwater years is born from a body and a brain that is becoming differently tuned.
The inner life gets louder.
In the groundwater years, as children grow, the Default Mode Network architecture loses its primary subject. The DMN is released from its previous organizing purpose at the same moment the perimenopausal metabolic shift is beginning. What women in the groundwater years consistently report — an inner life that feels louder, more persistent, less suppressible by distraction — coheres with what is known about DMN function: that it is the brain’s meaning-making engine, and that when its previous organizing purpose recedes, it searches for a new one. The specific mechanism linking the perimenopausal transition to this experience has not yet been mapped in the literature. Regardless, the experience itself is real.
In my experience, new as I am in this Tender skin, in the groundwater years the brain begins reaching for a new organizing principle: a new form for the creative and relational energy that once poured into children. The Tender, like groundwater, is seeking the place to inhabit, and the new form she will take.
Read Post Four: The Evolutionary Logic of the Long Middle
References
¹ The maternal brain study (2017) Hoekzema, E., Barba-Müller, E., Pozzobon, C. et al. “Pregnancy leads to long-lasting changes in human brain structure.” Nature Neuroscience 20, 287–296 (2017). https://doi.org/10.1038/nn.4458
¹ᵇ The maternal brain study (2022) Hoekzema, E., van Steenbergen, H., Straathof, M., Beekmans, A., Freund, I.M., Pouwels, P.J.W. & Crone, E.A. “Mapping the effects of pregnancy on resting state brain activity, white matter microstructure, neural metabolite concentrations and grey matter architecture.” Nature Communications 13, 6931 (2022). https://doi.org/10.1038/s41467-022-33884-8
²ᵃ Clinical observations on maternal brain fog Romano, J. Yoga Therapy for the Whole Mother: Developing Awareness in Service of Postpartum Healing. London: Singing Dragon, 2024.
² The menopause brain imaging study Mosconi, L., Berti, V., Dyke, J. et al. “Menopause impacts human brain structure, connectivity, energy metabolism, and amyloid-beta deposition.” Scientific Reports 11, 10867 (2021). https://doi.org/10.1038/s41598-021-90084-y
³ Perimenopause as a neurological transition: the bioenergetic shift Brinton, R.D., Yao, J., Yin, F., Mack, W.J. & Cadenas, E. “Perimenopause as a neurological transition state.” Nature Reviews Endocrinology 11, 393–405 (2015). https://doi.org/10.1038/nrendo.2015.82