Biology subjects

Jeanne, J. M.

Publications and source records attributed to Jeanne, J. M..

4 recordsLinked to original sources

bioRxiv2025

Sensory processing reformats odor coding around valence and dynamics

Extracting relevant features of a complex sensory signal typically involves sequential processing through multiple brain regions. However, identifying the logic and mechanisms of these transformations has been difficult, due to the challenges of measuring both activity within and long-range connectivity between multiple neural populations. Here, we investigate the reformatting of odor information across two stages of the Drosophila olfactory system. We measure the odor tuning of 20 types of anatomically-defined third order lateral horn neuron (LHN) and compare to predictions based on the odor tuning of second-order projection neurons (PNs) and PN-LHN connectivity. We find that LHNs reformat PN activity in two distinct ways. First, LHNs selectively discard information about odor identities with similar valence (i.e., attractiveness or aversiveness). This emerges from a precise alignment of PN odor tuning and PN-LHN connectivity, as well as odor-specific inhibition and boosting of LHN activity. This creates a population code for valence that is more explicit than in PNs. Second, a subset of LHNs selectively discard information about continuing odor presence, by responding only transiently to odor onset. This creates a population code for odor dynamics that is more explicit than in PNs. Across LHNs, valence and dynamics are independent of each other. Thus, feedforward connectivity and local inhibition combine to extract two orthogonal dimensions of olfactory information.

neuroscience↗

bioRxiv2024

Divergent short-term plasticity creates parallel pathways for computation and behavior in an olfactory circuit

To enable diverse sensory processing and behavior, central circuits use divergent connectivity to create parallel pathways. However, linking subcellular mechanisms to the circuit-level segregation of computation has been challenging. Here, we investigate the generation of parallel processing within a divergent network in the Drosophila olfactory system, where single projection neurons target multiple types of lateral horn neuron (LHN). One LHN type generates sustained responses and adapts divisively to encode temporal odor contrast. The other generates transient responses and adapts subtractively to encode a form of positive temporal prediction error. These coding differences originate from subcellular differences in short-term plasticity in projection neuron axons. Prediction error arises from strongly facilitating synapses, which depend on the presynaptic priming factor Unc13B. The temporal contrast code arises from mildly depressing synapses that engage additional gain control implemented by the Na+/K+ ATPase in the postsynaptic neuron. Each LHN type makes corresponding dynamic contributions to behavioral odor attraction. Subcellular synaptic specialization is a compact and efficient way to generate diverse parallel information streams.

neuroscience↗

bioRxiv2021

Connectomic features underlying diverse synaptic connection strengths and subcellular computation

Connectomes generated from electron microscopy images of neural tissue unveil the complex morphology of every neuron and the locations of every synapse interconnecting them. These wiring diagrams may also enable inference of synaptic and neuronal biophysics, such as the functional weights of synaptic connections, but this requires integration with physiological data to properly parameterize. Working with a stereotyped olfactory network in the Drosophila brain, we make direct comparisons of the anatomy and physiology of diverse neurons and synapses with subcellular and subthreshold resolution. We find that synapse density and location jointly predict the amplitude of the somatic postsynaptic potential evoked by a single presynaptic spike. Biophysical models fit to data predict that electrical compartmentalization allows axon and dendrite arbors to balance independent and interacting computations. These findings begin to fill the gap between connectivity maps and activity maps, which should enable new hypotheses about how network structure constrains network function.

neuroscience↗

bioRxiv2021

An ammonium transporter is a non-canonical olfactory receptor for ammonia

Two families of ligand-gated ion channels function as olfactory receptors in insects. Here, we show that these canonical olfactory receptors are not necessary for responses to ammonia, a key ecological odor that is attractive to many insects including disease vectors and agricultural pests. Instead, we show that a member of the ancient electrogenic ammonium transporter family, Amt, is a new type of olfactory receptor. We report two hitherto unidentified olfactory neuron populations that mediate neuronal and behavioral responses to ammonia. Their endogenous ammonia responses are Amt-dependent, and ectopic expression of either Drosophila or Anopheles Amt confers ammonia sensitivity. Amt is the first transporter known to function as an olfactory receptor in animals, and its role may be conserved across insect species.

neuroscience↗