Freeman Hrabowski Scholar Bianca Jones Marlin studies how caregiving takes shape in the brain and how some biological adaptations are passed to the next generation.
"Biology has prepared us for survival." It's a conclusion that HHMI Freeman Hrabowski Scholar Bianca Jones Marlin keeps coming back to. After more than a decade studying transgenerational inheritance and the neuroscience of parenthood, she remains struck by the many ways our brains adapt to improve our chances of survival.
Marlin is interested in parenthood and epigenetics — the ways environmental experiences influence gene expression. In her lab at Columbia University, she studies these topics in mice from multiple angles: biological mothers, whose attachment to pups can be tracked through their sensory responses; virgin females that learn to care for pups; and male mice that pass along unexpected biological adaptations.
The great power of a tiny cry
Mouse pups are born blind, deaf and unable to regulate their own body temperature. In other words, they rely completely on adult mice for warmth and food to survive infancy. Oxytocin is a critical maternal hormone and neuromodulator that is vital for labor and supports maternal bonding. It floods the mother mouse's body during the birthing process. When a pup cries, oxytocin is the reason a mother mouse brings it back into the nest and cares for it.
Conversely, when a virgin mouse hears a crying pup, she will either ignore it, run away or attack it. (Marlin explains this instinct by pointing out, "We've all been stuck on an airplane with a crying baby that isn't ours.") But Marlin and her colleagues were able to induce oxytocin in female virgins by housing them with mother mice and pups.
They then used whole-cell in vivo physiology to record a single neuron in the auditory cortex — the one that picks up the pup's cry. That cell lit up for oxytocin-bearing nonmothers, just as it did in biological mothers, and both groups cared for the pups, regardless of their biological relationship.
Having found these effects in the auditory cortex, Marlin was determined to understand what was happening across the brain. She tapped into iDISCO, an imaging technique that makes brain tissue transparent, making it easier to visualize all sorts of protein markers, including neuronal activity markers, across the whole brain at once.
Then, she compared three sets of brains: virgins, the "experienced virgins" that had cohabitated with the mothers and pups, and biological mothers. In response to the pup's cry, the neuronal activity of "experienced virgins" fell between that of the virgins and the mothers — but was significantly closer to that of the mothers.
"The pregnancy and childbirth process generate caretaking hormones — but our findings suggest that biology also uses these mechanisms simply through exposure and caretaking," explains Marlin. "Across the mom and experienced virgin brains, the signature is quite similar."
A nose for newborns
Hearing is only one signal that draws a mother mouse to her pups. Marlin and her lab also wanted to understand how another powerful sense — smell — shapes caregiving behavior. They used pup urine as a sort of "pup perfume," testing whether mother mice preferred its scent over other mouse odors or neutral smells.
They found that first-time mothers did show that selective odor preference — but only if they had also cared for their new pups. When postpartum mothers were separated from their pups immediately after birth, there was no preference; nor did one exist for the "experienced virgins" that cohabitated with, but didn't birth, the pups.
The olfactory epithelium — the part of the nose that detects odors and sends that information to the brain — is made up of stem cells that constantly turn over and respond to new hormonal cues. Marlin believes this region's plasticity helps explain why mice can develop such precise and flexible responses to pup scents.
Lessons from dad
Marlin's lab is also interested in inherited adaptations, but to address those questions, she turns to dads. Within the nose, there are more than a thousand neurons, but each one expresses a specific receptor — meaning it can only detect one particular smell.
As a postdoc, Marlin and her colleagues trained male mice to associate the smell of almond with a mild but unpleasant stressor. Then they looked in the nose. The trained male mice had more M71-expressing neurons, which detect the smell of almond. And when they mated with mice without the fear association, 100% of their offspring also had additional M71 olfactory receptor neurons.
"These receptors might have been destined to detect mint, or rose, but because of this stimulus, their cellular fate changes. That kind of morphological adaptation requires a lot of energy — the vast majority of epigenetic markers like this disappear when sperm meets egg," Marlin explains. "I wanted to find out what's going on in the brain that's cementing these changes in the next generation."
Where stress meets memory
Marlin's lab zeroed in on the locus coeruleus, the brain's primary source of norepinephrine, a stress hormone that dictates the "fight-or-flight" response and has been linked to fear memory formation. By recording the locus coeruleus's projections into the nose using optogenetic fiber photometry, they observed that the almond smell alone produced a major norepinephrine spike in both the fathers and their offspring.
A mouse's sperm turns over every 40 days, yet even when the males bred more than 40 days after the shock, the adaptation persisted.
Marlin and her team are digging into how this happens. In future research, she hopes to uncover the precise mechanisms of this process — the transmission from nose to brain to testes to offspring — and whether these effects might grow stronger when multiple ancestors have the adaptation.
"It's amazing to see these ancestral memories passed along, even when they aren't directly communicated," Marlin says. "It makes you wonder what else might be transmitted without us realizing it and how it influences our biological drive to survive — for ourselves and for the next generation."
Who's behind this story?
PhD nano-engineering from Delft University. Published researcher and journal reviewer. Brings scientific insight to content standards. Full profile →
Citation: Mom or not, caring for babies changes the brain (2026, August 2) retrieved 2 August 2026 from https://phys.org/news/2026-07-mom-babies-brain.html
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