Shettigar, N. | bioRxiv Science

bioRxiv2026

Learned attraction replaces innate aversion in the evolution of an olfactory response in Mus musculus

The evolution of behavior is typically attributed to changes in innate circuitry, but learning can also drive behavioral evolution. Mus musculus evolved to produce trimethylamine (TMA) and behaviorally approach it, unlike the ancestral response retained by other mammals including Mus caroli. Here we demonstrate that this attraction is not innate but learned, depending on developmental TMA exposure. Whole brain immediate-early gene mapping reveals experience-dependent patterns of activation in response to TMA olfaction. Using activity-dependent TRAP2 labelling, we find that TMA-responsive neurons in the anterior olfactory nucleus are necessary and sufficient for attraction, consistent with a memory engram. Meanwhile, Mus caroli innate aversion is dependent on excitatory neurons in the posterior cortical amygdala. These results demonstrate how innate and learned circuitry both contribute to behavioral evolution in mammals.

neuroscience↗

bioRxiv2026

Mus musculus mice self-organize existing behaviors into structured bouts as they become expert hunters.

In the wild, a mouse must flexibly perform multiple computations at once, rapidly navigating, sampling its environment, forming and using memories, and balancing internal needs. Capturing the self-paced, low-repetition, complex nature of decision making in the wild while preserving the experimental control needed to interpret its process remains a challenge. Here we show that lab mice, without food restriction, learn to forage for hidden resources cued by ambiguous sounds in a dynamic environment by spatiotemporally reorganizing their existing behavioral repertoire. Using a novel closed-loop assay, we required mice to sit still to receive informative but hard-to-localize sound cues emanating from one correct location they must find, out of 157 possible locations in a large arena. With experience, mice become efficient hunters. Efficient hunting cannot be explained by an increase in a particular behavioral module, but instead, mice reorganize existing behaviors into clustered bouts of high-quality sampling and site-checking. Looking forward, this work establishes an approach for studying the neural, molecular, and evolutionary basis of naturalistic decision-making in mice.

animal behavior and cognition↗