People of the Department of Neuroscience: Celia Kjærby

25/06/2025

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Meet Associate Professor Celia Kjærby and learn more about the lucky accident that led her towards sleep research, investing time and energy in establishing a well-functioning research group and the importance of public science outreach.

Dedication, determination – and a lucky accident. This sums up the career of Associate Professor Celia Kjærby who recently moved from the Center for Translational Medicine to a tenured position at the Department of Neuroscience. Celia has led her own research group since 2022, bringing with her expertise on how the arousal system regulates sleep and its role in memory consolidation and cognitive function.​

From kittelbiolog to sleep researcher

Celia is a biologist by training, and she initially thought she would become a gummistøvlebiolog, which translates to 'rubber boot biologist', meaning a biologist who studies animals or plants in the field. Instead, she ended up as a kittelbiolog – a 'lab coat biologist'. At first, it was because she found it to be the sensible career choice, but she fell in love with health science and never looked back.

One thing on Celia's bucket list was working abroad, and like everything else, she pursued this goal with determination. Halfway through her PhD, Celia and her husband - who is also in neuroscience research – started visiting labs in the US and preparing grant applications. As luck would have it, they both got postdoc funding and found positions in the USA. Celia spent three years as a postdoc at UCSF in San Francisco, where she – among many other things – got the chance to learn fiber photometry, at that time a new and groundbreaking technique for measuring calcium activity in cells.

With two children now part of the picture, Celia and her husband started thinking about going back home. Through a colleague, Celia connected with Professor Maiken Nedergaard who was in the process of establishing the Center for Translational Neuromedicine. Here, Celia got a postdoc position and started focusing more on in vivo lab work, including implementing the fiber photometry technique in the new centre to measure astrocytes.

Maiken's group and Celia were conducting a large behaviour screening of mice when they noticed something interesting:

"We were expecting that the arousal system would be inactive while the mouse was sleeping, as it is usually only activated when we are awake, surprised or scared. As it turned out, the signal was not inactive at all – in fact, there were very large slow fluctuations in activity, so much that we thought we were doing something wrong. But it was real, and we shifted our focus to these large fluctuations in activity and their significance. We found that the noradrenaline fluctuations were important for brain synchronisation during sleep. They completely controlled brain synchronicity, making a novel sleep microstructure, and we found that this was important for memory consolidation. We could see that if we stretched out or slowed down the fluctuations, we could build more neuronal synchronicity and improve the mouse's memory," Celia explains.

These insights could be an important piece of the puzzle of understanding neurodegenerative diseases.  In these diseases, as well as in aging, we experience cell loss in Locus coeruleus, which controls noradrenaline production and is a central part of the arousal system:

“With our knowledge that the arousal system controls sleep microstructure, our hypothesis was that this sleep microstructure would be lost early, affecting memory consolidation and contributing to symptoms of dementia. As such, it both serves as a marker of how well your locus coeruleus and your sleep is functioning, but also that we might be able to improve sleep and thereby delay cognitive decline by modulating the arousal system," Celia describes.

Celia might have become a sleep researcher by accident, but her career is characterised by determination, hard work and clear goals:

“After I went into research, I have never doubted that I wanted a career in science, but I have often doubted if I would succeed. Sometimes, it has felt silly to work with such determination towards getting a tenured position, which has seemed close to impossible," she says.

With that goal now accomplished, Celia is excited to expand and advance her research and establish new collaborations with researchers at the Department of Neuroscience.

Becoming a people person

Every scientist eventually learns that research is not just lab work - it requires collaboration, networking and people skills:

“While I once thought I would just be sitting in a lab all the time, as an independent scientist, things increasingly revolve around your relations to others. I enjoy that much more than I thought I would when I was younger.

Celia's engagement in other people is characteristic of her approach to being a group leader, a role she takes very seriously: 

“I am the boss, but I am also a mentor. Naturally, I have an interest in publishing because productivity is important for securing funding, but I also need to consider how we can get there in a sustainable way. Science is a stressful environment where the working conditions are often challenging. At the same time, people are very ambitious, so there is both external and internal pressure, and I see it as my responsibility to help my group members navigate this," Celia explains.

Celia enjoys the responsibility that comes with being a group leader and all the good things that come with working together: the shared passion and the new ideas, supporting each other through challenging times and failed experiments. She also deeply enjoys seeing her group members grow and develop, and she tries her best to create a work environment where everyone looks forward to coming into work.

Sharing her passion from research and her knowledge also translates to Celia's engagement in public outreach. Celia sees it as part of her responsibility as a scientist to communicate just how important sleep is for our health and wellbeing. She likes sharing and discussing her findings with different audiences:

“I really enjoy public outreach. Everyone can relate to sleep, so people are very engaged, and they have many, many questions. Talking about my research and answering questions often gives me new inspiration as well," Celia says.

Celia's passion for her work permeates every aspect of her life, so much so that she often finds herself thinking about research 24 hours a day (as she has shown, our brains are also surprisingly active during sleep!) This also means that her time is divided between the two main priorities in her life: work and family.

“As a parent of three kids, it has been difficult to balance science and family life because I cannot give 100% of my time in both places. I think you just need to learn to live with that. I want to say to everyone – especially young women – that you can have it all in science, both a career and a family. It just requires determination," she concludes. ​

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