What We Actually Mean by "Brain Fog": A Guide to Your Cognitive Symptoms

"Brain fog" gets used for so many different experiences; losing a word mid-sentence, forgetting why you walked into a room, staring at a work email you cannot make sense of, struggling to hold a thought while someone talks to you, these are interestingly different things happening in different parts of your brain.

Cognition is many things

Cognition comes from the Latin word cognoscere, meaning "to know," and is a term for mental processes including thinking, attention, language, learning, memory and perception.

When researchers study "cognition," they are not measuring one single ability. A 2026 study from King's College London and Imperial College London tested 14,234 women using eight separate tasks, each measuring a distinct mental skill: immediate memory, mental manipulation of information, working memory, planning, verbal reasoning, word knowledge, information sampling, and delayed memory.¹ These are not interchangeable, a woman can struggle with one and be entirely unaffected in another.

This distinction matters in daily life too. If you put your phone down while talking to someone and cannot find it five minutes later, that is usually not a memory failure, it is more likely that your brain never fully paid attention to where you placed it in the first place. Attention and memory are different systems, and knowing which one is involved changes how worried you need to be.

Memory has many elements

Working memory is what lets you hold a piece of information in your mind long enough to use it, remembering a phone number while you walk to write it down, or following a multi-step instruction without losing track partway through. This type of memory relies heavily on the prefrontal cortex, the part of your brain that sits just behind your forehead.²

Verbal memory governs word retrieval and language recall, and depends on regions including the hippocampus, deep in the brain's temporal lobe.³ This is the memory type most often behind the frustrating experience of knowing exactly what you want to say and not being able to find the word. The hippocampus is essential for forming new memories, converting today's experiences into tomorrow's recollections, and it is also involved in spatial navigation, which is part of why misplacing your keys or forgetting where you parked can show up alongside word-finding difficulty.²

Delayed memory is what lets you recall something minutes or hours after you first learned it, distinct again from the moment-to-moment demands of working memory.

Oestrogen receptors are heavily concentrated in both the hippocampus and prefrontal cortex, which is a large part of why hormonal fluctuation in perimenopause can affect memory and word retrieval specifically, rather than everything at once.²

Attention, concentration and processing speed

Attention is your ability to notice and hold focus on something in the moment.

Concentration is sustaining that focus over time, which is why a five-minute task can feel manageable while an hour-long one does not.

Processing speed is different from both, it is how quickly your brain moves through information, not whether you can do the task at all.

Research on the menopause transition has specifically flagged processing speed and working memory as more affected than long-term memory or general attention, though findings vary across the research.⁴ This is why many women describe being able to do the same work they always could, just more slowly, and feeling frustrated that they cannot point to anything actually being wrong.

Executive function, the part almost nobody explains

Executive function is the brain's project manager, governing planning, organising, starting tasks, and juggling more than one thing at once. When women say "I can't multitask anymore" or "I know what I need to do but I can't get started," this is usually executive function, not memory, and it lives largely in the prefrontal cortex alongside working memory.²

Reassuringly, general intelligence is not reduced by this transition. Vocabulary, accumulated knowledge, reasoning and long-term memories are typically preserved, even when the specific symptoms above are genuinely disruptive day to day.

Three takeaways

1. "Brain fog" is a catch-all term for several distinct cognitive experiences, word-finding, working memory, processing speed and executive function are genuinely different things.

2. Oestrogen receptors are concentrated in the exact brain regions that govern memory and executive function, which is why these particular symptoms show up during hormonal fluctuation.

3. Naming your specific symptom precisely gives you a clearer, more useful conversation to have with your GP.

This is not your body failing you. It is your body changing, and asking for a different kind of support.

Start by keeping a simple note for one week. Each time you notice a cognitive symptom, write down exactly what happened, a lost word, a forgotten task, difficulty concentrating, rather than just "brain fog."

This information is educational only and does not constitute personal medical advice. Always consult a qualified health professional about your individual circumstances. © Menopause Hub 2026.

REFERENCES

1. Naysmith LF, Ward H, Elliott P, et al. Cognition and the menopause transition: cross-sectional evidence from a large community cohort. npj Women's Health. 2026;4:14.

2. Russell JK, Jones CK, Newhouse PA. The role of estrogen in brain and cognitive aging. Neurotherapeutics. 2019;16:649 to 665.

3. Maki PM, Jaff NG. Brain fog in menopause: a health-care professional's guide for decision-making and counseling on cognition. Climacteric. 2022;25(6):570 to 578.

4. Healthdirect Australia, citing Australasian Menopause Society and Jean Hailes for Women's Health. How to combat menopausal brain fog. Healthdirect, reviewed Nov 2024.