Biology subjects

Dennis, E. J.

Publications and source records attributed to Dennis, E. J..

7 recordsLinked to original sources

bioRxiv2026

Mice navigate complex landscapes by learning a sparse vocabulary of paths

Effective navigation is critical for survival, but how animals contend with the scale, complexity, and self-similarity of natural landscapes is unknown. Here, we investigate spontaneous exploratory mouse behavior, both outdoors and in dark self-similar landscapes made from tens to hundreds of tiles of varying heights. Within 2 hours of exploration, mice detected small covert changes to the landscape and jumped across ledges to invisible landing spots, revealing detailed spatial knowledge. In this process, mice converged on a sparse set of memorized paths. These routes depended on prior experience and increased the compressibility of sensory information over time. Our results demonstrate that mice rapidly learn sparse internal representations of their surroundings and suggest that animals use structured behavioral sequences to reduce the complexity of natural navigation.

animal behavior and cognition↗

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↗

bioRxiv2025

Reconstructing a physiological state space via chronic jugular microdialysis in freely moving mice

Maintaining physiological homeostasis requires a complex interplay among endocrine organs, peripheral tissues, and distributed neuroendocrine control circuits, all of which are coupled through feedback loops that operate over minutes to hours. Although many physiological needs are broadcast through hormones, metabolites, and other chemical compounds circulating in the bloodstream, we rarely observe more than a few of these messengers together and at high cadence during behavior. To address this, we developed a minimally disruptive workflow to measure the free fraction of hundreds of amines and small peptides at a 7.5-minute cadence for [~]8 hrs in freely moving mice using chronic jugular microdialysis implants and chemical isotope labeling Liquid Chromatography-Mass Spectrometry. Single-compound profiles behave according to known physiology, such as purine turnover correlating with movement, delayed histamine/5-HIAA changes, and coordinated amino-acid dynamics. Our multiplexed measures enable high-dimensional analyses that uncover properties of the underlying dynamics. For example, systems-level analyses show that 10 dimensions explain over 70% of the variance in hormone/metabolite covariation, consistent with a low rank description of the physiological state space, with projections aligned to locomotion state transitions. Our work opens avenues for the discovery of hormonal dynamics, compound interactions, and their effects on behavior.

physiology↗

bioRxiv2023

Social association predicts immunological similarity in rewilded mice

Environmental influences on immune phenotypes are well-documented, but our understanding of which elements of the environment affect immune systems, and how, remains vague. Behaviors, including socializing with others, are central to an individuals interaction with its environment. We tracked behavior of rewilded laboratory mice of three inbred strains in outdoor enclosures and examined contributions of behavior, including social associations, to immune phenotypes. We found that the more associated two individuals were, the more similar their immune phenotypes were. Social association was particularly predictive of similar memory T and B cell profiles and was more influential than sibling relationships or worm infection status. These results highlight the importance of social networks for immune phenotype and reveal important immunological correlates of social life.

immunology↗

bioRxiv2021

Stable choice coding during changes of mind

How do we choose the best action in a constantly-changing environment? Many natural decisions unfold in dynamic environments where newer observations carry better information about the present state of the world. Recent work has shown that rats can learn to optimally discount old evidence, updating their provisional decision when the environmental state changes. Provisional decisions are thought to be represented in the Frontal Orienting Fields (FOF), but this has only been tested in static environments where the provisional and final decisions are not easily dissociated. Here, we characterize the representation of accumulated evidence in rat FOF during decision-making in a dynamic environment. We find that FOF encodes evidence throughout decision formation with a temporal gain modulation that rises until the period when the animal may need to act. Using a behavioral model to predict the timing of changes of mind revealed that FOF neurons respond rapidly to these events, representing the new provisional decisions in their firing rates. Our results suggest that the FOF represents provisional decisions even in dynamic, uncertain environments, allowing for rapid motor execution when it is time to act.

neuroscience↗

bioRxiv2018

DEET feet: Aedes aegypti mosquitoes use their tarsi to sense DEET on contact

DEET (N, N-diethyl-meta-toluamide) is the most effective and broadly used insect repellent, but its mechanism of action is both complex and controversial [1]. Previous work demonstrated that DEET acts both on insect smell [2-6] and taste [7-11] systems. Its olfactory mode of action requires the odorant co-receptor orco [2, 3, 6], while its gustatory repellency is mediated by activation of bitter taste receptors and neurons in the proboscis upon ingestion [8]. Together, these data have led to the assumption that DEET acts only on olfactory and gustatory pathways. We previously observed that orco mutant female Aedes aegypti mosquitoes are strongly attracted to humans even in the presence of DEET, but are rapidly repelled after contacting DEET-treated skin [6]. To understand the basis of this contact chemorepellency, we carried out a series of behavioral experiments and discovered that DEET acts in three distinct ways: through smell, taste, and contact. DEET and bitter tastants are feeding deterrents when ingested, but only DEET is capable of mediating contact repellency on human skin. We show that the repellent touch of DEET is mediated by the tarsal segments of the legs, and not gustatory neurons in the proboscis as previously believed. This work establishes mosquito leg appendages as the actual sensors of DEET, and highlights the existence of an unknown sensory pathway that is independent of bitter taste. These results will inform the search for novel contact-based insect repellents.\n\nHighlightsO_LIDEET and bitters are both repellent when ingested by Aedes aegypti female mosquitoes\nC_LIO_LIOnly DEET is additionally repellent upon contact\nC_LIO_LIRepellency of DEET on skin is mediated solely by the legs\nC_LIO_LIAny of the three pairs of legs can sense DEET and prevent mosquitoes from biting\nC_LI

neuroscience↗

bioRxiv2017

A natural variant and an engineered mutation in a GPCR promote DEET resistance in C. elegans

DEET (N,N-diethyl-meta-toluamide) is a synthetic chemical, identified by the United States Department of Agriculture in 1946 in a screen for repellents to protect soldiers from mosquito-borne diseases1,2. Since its discovery, DEET has become the worlds most widely used arthropod repellent3, and is effective against invertebrates separated by millions of years of evolution, including biting flies4, honeybees5, ticks6, and land leeches4,7. In insects, DEET acts on the olfactory system5,8-14 and requires the olfactory receptor co-receptor orco9,11-13, but its specific mechanism of action remains controversial. Here we show that the nematode Caenorhabditis elegans is sensitive to DEET, and use this genetically-tractable animal to study its mechanism of action. We found that DEET is not a volatile repellent, but interferes selectively with chemotaxis to a variety of attractant and repellent molecules. DEET increases pause lengths to disrupt chemotaxis to some odours but not others. In a forward genetic screen for DEET-resistant animals, we identified a single G protein-coupled receptor, str-217, which is expressed in a single pair of DEET-responsive chemosensory neurons, ADL. Misexpression of str-217 in another chemosensory neuron conferred strong responses to DEET. Both engineered str-217 mutants and a wild isolate of C. elegans carrying a deletion in str-217 are DEET-resistant. We found that DEET can interfere with behaviour by inducing an increase in average pause length during locomotion, and show that this increase in pausing requires both str-217 and ADL neurons. Finally, we demonstrated that ADL neurons are activated by DEET and that optogenetic activation of ADL increased average pause length. This is consistent with the \"confusant\" hypothesis, in which DEET is not a simple repellent but modulates multiple olfactory pathways to scramble behavioural responses12,13. Our results suggest a consistent motif for the effectiveness of DEET across widely divergent taxa: an effect on multiple chemosensory neurons to disrupt the pairing between odorant stimulus and behavioural response.

neuroscience↗