What your brain is really doing across your cycle

Have you noticed how some weeks you're feeling focused, energetic, and social - while other weeks you feel foggy, tired, and just not yourself? There’s a reason for that, and science finally proves it.

In 2024, scientists conducted a first-of-its-kind study looking into this, scanning women's brains at multiple points during their natural cycles. Let's break down what this means for you.

Study overview

In a groundbreaking study published in NPJ Women’s Health, researchers examined the brains of 60 healthy women aged 18–35 who were naturally cycling - meaning they weren't using hormonal contraception and had regular menstrual cycles.

Each participant underwent resting-state functional MRI (fMRI) scans at three key phases:

• Early Follicular Phase: Right after menstruation begins.
• Pre-Ovulatory Phase: Just before ovulation, when estrogen peaks.
• Mid-Luteal Phase: After ovulation, when progesterone peaks.

The focus was on "dynamical complexity," a measure of how flexible and interconnected brain activity is. Higher complexity indicates a more adaptive and responsive brain.

Source: Avila-Varela (2024)

The results

The good news? This study validates what you’ve been feeling but never had concrete proof of: your brain isn’t static during your cycle. It’s dynamic, shifting, and responding to your hormonal fluctuations.

Let’s break it down by phase:

Early follicular phase: mental recalibration

Right after your period begins, both estrogen and progesterone are at their lowest. During this time, the brain showed the lowest level of dynamical complexity.

That means your brain is less networked, less flexible, and more inwardly focused. Activity in areas responsible for attention, sensory processing, and physical coordination drops significantly. You may feel slower, foggier, or more fatigued - not because something is wrong, but because your brain is in recalibration mode.

Basically, this is the time where you might hit the snooze button more often, and projects can take longer to complete than you’d like. This is a time of retreat, recovery, and gentle reset.

Pre ovulatory phase: peak performance

Just before ovulation, estrogen reaches its peak - and your brain shifts into its most dynamic state.

This phase showed the highest level of dynamical complexity across all major brain networks. Key areas such as the Default Mode Network (responsible for memory and reflection), the limbic system (emotion and motivation), and the dorsal attention (supports focused attention and goal-directed thinking) and sensorimotor networks (coordinates movement and physical responsiveness) all became significantly more active and flexible.

Mentally, this is your sharpest time. You may feel energized, confident, social, and generally more ‘on the ball’. This isn’t just a good week by chance - it’s your brain operating in its most responsive and outwardly oriented state.

Mid luteal phase: emotional depth and shifting gears

After ovulation, progesterone becomes the dominant hormone, and your brain transitions once again - this time into a more emotionally heightened, and introspective state.

Although dynamical complexity remains high, the pattern of brain activity changes. Activity in the Default Mode Network and limbic system remains strong - supporting deeper thinking, emotional reflection, and social sensitivity. Meanwhile, networks tied to movement and sensory engagement become less active. You might notice it’s harder to concentrate, you feel more emotionally sensitive, or your energy feels lower than it did earlier in the cycle.

This is the time where you might feel more tearful, worried your bestie is secretly mad at you, and unable to focus as well on your to-do list.

Why is this a big deal?

This is the first study to show, conclusively, that the brain undergoes full-brain changes in response to hormonal fluctuations - not just in one or two spots, but across nearly every major functional network.

It also makes clear that estrogen and progesterone have very different effects: while estrogen boosts network complexity, flexibility, and outward-facing cognition, progesterone supports inward focus, emotion processing, and social reflection.

Want to better understand what your brain needs? Download our Cycle-Brain Guide and start supporting your cycle with clarity, not guesswork.

Samphire Neuroscience & this study

Knowing this, the next question becomes: how can we support your brain through those changes, rather than pushing against them?

Our Samphire app helps you understand what phase you’re in and how your brain is functioning in real time. By logging your patterns and mood, Samphire generates personalized insights that help you plan your week, interpret how you’re feeling, and adjust expectations with neurobiological context. It helps you make sense of why things feel easy one week and heavier the next, and shows you how to work with that rather than against it.

Where the app gives you insight, Nettle™ gives you active support. We don’t treat brain changes as symptoms - we help to ease the mental and emotional strain that can show up during the luteal phase. Less brain fog, fatigue and emotional dysregulation. More focus, motivation and emotional balance. We also offer a 90 day trial policy so you can see if Nettle™ is the right fit for you with peace of mind.