Meet the neuroscientist investigating the “ultimate clock problem”

When Dr. Sydney Aten runs, she doesn’t think about science. Actually, it’s probably the only time she doesn’t think about science. As her heartbeat quickens and her breath falls in line with her feet pounding the pavement, Aten falls into rhythm and her mind quiets.

In the span of three years, Aten has run a marathon in all 50 states (“plus a couple extra,” she said). This herculean feat was the result of a question about her body’s physical limits and the hypothesis that she could push past them to achieve something extraordinary. It’s a hypothesis she’s also applying to her neuroscience research at Harvard Medical School, Beth Israel Deaconess Medical Center where she studies circadian biology and fertility.

One of Aten’s favorite facts about circadian rhythms is that nearly every individual cell has the ability to keep time — it has its own internal clock. Additionally, if a cell is taken out of the body’s master clock, the suprachiasmatic nucleus (SCN) located in the brain, and kept alive in a petri dish, the cell would maintain its own intrinsic circadian rhythm, she explained. Almost every system in our body — from metabolism and digestion, to immunity and reproduction — is regulated by the circadian clock, and can be affected when circadian rhythms are disrupted.

“There are so many things that we don’t know about our circadian system. What happens when your circadian system is misaligned?,” Aten said. “We know that it’s bad, but we don’t exactly know why. That’s what I’m trying to figure out.”

Aten said that when it comes to fertility — whether in clinical treatments or natural conception — “when” might be a critical question. Asking the question about the “time of day” impact on fertility (and its treatments) felt like “low-hanging fruit” to Aten; she wondered why others aren’t asking the same questions — and if having more women in science asking research questions about women’s health will contribute to more of these questions being answered. “It’s my hope that we can start to solve some of these longstanding questions that may be so obvious, but it’s something that actually hasn’t been really teased apart in depth,” she said.

Aten is one of five 2025 awardees of the L’Oréal USA For Women in Science in Program. Not only will the award support her continued research into this critical area of scientific inquiry, it will enable Aten to combine her love of running, science, and mentorship to host a “EmpowHER” 5K race for women and girls in STEM.

Aten teaches an anatomy class at Simmons University, a women’s college down the road from Harvard Medical School. As she holds up a collection of (plastic) bones to her class, Aten sees her own face staring back at her. “The most important part of teaching for me is knowing that my enthusiasm for the subject can actually change the view for those girls of what science is,” she said.

The first time Aten thought about being a scientist was in Mrs. Deak’s high school anatomy class. Mrs. Deak opened Aten’s eyes to what careers in science and medicine could look like and even brought her and her classmates along to scientific events where they could witness these careers in action.

Now, in her post-doctorate and on the brink of opening a lab of her own, Aten dreams of a lab full of curious and passionate women scientists investigating the pressing questions about fertility and circadian rhythms.

Looking back to all the women who encouraged and supported her scientific career, Aten is working to inspire the next generation of women in science along the next leg of her scientific marathon.

“Science is great, but I’d like to say that science actually comes second to mentorship. And I know that’s a big statement,” Aten said. “We are bringing up the next generation of scientists, and it’s our job to teach so that they can come up with these new incredible discoveries.”