Journal of Comparative Neurology

The olfactory ventricle (OV), an anterior extension of the lateral ventricular system into the olfactory bulbs, is generally considered a transient developmental structure that closes during early postnatal life. However, this view largely derives from a limited number of laboratory models, and the evolutionary distribution and cellular organization of the adult OV remain poorly understood. Here, we combined a comparative survey of mammalian neuroanatomy with phylogenetic analyses and cellular characterization of the OV across species. We compiled anatomical data for 154 mammalian species spanning 26 orders and 80 families, revealing widespread persistence of a patent OV into adulthood. Phylogenetic analyses supported OV presence as the ancestral mammalian state and indicated that its absence is phylogenetically structured and consistent with repeated secondary losses. Chiroptera displayed multiple lineage-specific losses, whereas variation within Muridae extended to the intraspecific level, with contrasting OV persistence among Mus musculus and Rattus norvegicus populations. Comparative histological analyses in sheep, Peromyscus maniculatus, and CD1 mice revealed that, despite marked interspecific differences in OV morphology, the persistent ventricular region retains a conserved cellular organization characterized by progenitor- and glial-associated markers, proliferative cells, immature neuronal populations, and a differentiated apical/ciliary interface. Although these observations do not establish local neuronal production or demonstrate that the OV constitutes an autonomous neurogenic niche, their convergence across species indicates that the persistent adult OV is not simply an anatomically residual lumen but a specialized component of mammalian olfactory bulb organization. Together, our findings identify the OV as an ancestral and widely conserved feature of the mammalian brain and provide an evolutionary and cellular framework for investigating the developmental mechanisms controlling its persistence and its potential contribution to adult olfactory neurogenesis and plasticity.

The transition of pinnipeds from terrestrial ancestors into marine environments provides a unique opportunity to examine how cortical organisation has changed with adaptation to life in water. Here, we examined neocortical sulcal anatomy in nine species representing all three extant pinniped families using cortical surfaces reconstructed from post-mortem MRI. Building on a standardised framework previously established for land-dwelling (fissiped) carnivorans, we developed identification criteria for major pinniped sulci and compared their configurations with those observed across fissipeds. Major sulci were broadly conserved, but pinnipeds exhibited characteristic modifications, including a complex, highly branched pseudosylvian configuration and distinct frontoparietal sulcal patterns, with further family-level variation in both territories. This observed variation in sulcal patterns may reflect pronounced differences in locomotor, tactile, and vocal specialisations, generating hypotheses about how cortical organisation may vary with adaptation to marine environments. Together, these findings establish a common anatomical framework across Carnivora for investigating how cortical organisation diversified in relation to behaviour and ecology.

Siphonophores are colonial hydrozoans with unprecedented differentiation and specialization, in which individual zooids are transformed into functional organs rather than autonomous polyps capable of feeding. As a result, the entire colony acts as a single, modular-individual with the highest level of coordination and integration, from development through behavior. Deciphering these integrative mechanisms requires understanding the microanatomical organization of the nervous system in all elements of the colony. Here, using two immunohistochemical markers (anti-tubulin and anti-RFamide antibodies), we systematically characterize the neural systems across the entire Nanomia colony, encompassing pneumatophore, stem and all zooid classes (nectophores, gastrozooids, palpons, male and female gonophores, and protective zooids). The use of two neuronal markers enables visualization of distinct neural subpopulations, some of which are not revealed by a single marker. We provide evidence of neuroanatomical interactions within all elements of the colony, including contributions of giant axons, stem polygonal networks, and RFamide-ir neural rings at the base of each zooid, as well as describe different subpopulations of neural networks in the body of various zooids. The presented mapping facilitates identification of novel conductive and signaling pathways for future analysis of the cellular basis of behavioral integration within decentralized, broadly distributed networks and non-neuronal elements of these unique superorganisms.

The subarachnoid space (SAS) plays an important role in central nervous system (CNS) physiology, housing cerebrospinal fluid (CSF), providing nutrients, clearing waste, and protecting CNS tissues from injury. The SAS also contains an intricate arrangement of collagenous fibers, known as subarachnoid trabeculae, which serve as biomechanical support for the subarachnoid space and modulate the flow of CSF. Despite their myriad of roles in health and disease, the ultrastructure of trabeculae is incompletely described, with a specific gap in understanding how fiber structure varies across different regions of the CNS. In this work, we used optimized fixation techniques and scanning electron microscopy (SEM) imaging to study ultrastructural differences in trabeculae that were obtained from different regions of the nonhuman primate (NHP) brain and spinal cord. Qualitative assessments included evaluation of the relative prevalence of different kinds of fiber networks by region, leading us to a redefinition of terminology for fiber morphology. Quantitative measurements yielded dramatic differences in fiber diameter, density, and network porosity between different regions of the CNS. Broadly, trabeculae supporting cauda equina, cervical spinal cord, and exiting nerve roots were observed to have a very high density of small diameter fibers, whereas larger fibers and more complex arrangements were observed in other regions of the CNS. These data contribute to a growing field understanding of CNS-region specific differences in tissue ultrastructure.

The mouse superior colliculus (SC) regulates critical behaviors such as prey capture and visual threat avoidance, each of which depend on binocular visual processing. In contrast to our previous understanding, recent work has demonstrated widespread and diverse binocular interactions in the mouse SC. The SC receives direct input from contralaterally and ipsilaterally projecting retinal ganglion cells (contra- and ipsi-RGCs), but the ways in which eye-specific information is filtered in the SC remain unclear. Here, we utilized a trans-synaptic, intersectional viral tracing strategy to label SC neurons receiving input monocularly from contra-RGCs (SC-C), monocularly from ipsi-RGCs (SC-I), or binocularly from both (SC-B). We show that a surprising number of SC neurons receive ipsi-RGC input and that the proportions of SC-C, SC-I, and SC-B neurons are consistent throughout the SC. Morphometric analysis revealed few differences between neurons receiving different eye-specific patterns of input. Consistent with this, we show that SC-C, SC-I, and SC-B neurons are comprised of similar proportions of five morphologically distinct subtypes. And, the expression of candidate molecular markers appears similar across innervation patterns. Together, these data suggest that eye-specific information is widespread throughout the SC targeting overlapping populations of neurons.

Amacrine cells (ACs) are the most diverse neuron in the retina, with more than sixty different subtypes, each contributing to the detection of specific visual features. Despite their importance in visual feature detection, the genetic basis for this diversity is still not well understood. Recent single-cell transcriptomic datasets have identified several potential genes that may regulate cellular diversity, but the underlying mechanisms have not been investigated. For example, the transcription factor Meis2 is selectively expressed in the GABAergic subclass of ACs. In this study, we focused on how Meis2 regulates the development of GABAergic ACs. We hypothesized that Meis2 is required for specification and survival of GABAergic ACs. To test this, we used the Meis2 conditional knockout mouse (Meis2-CKO) where Meis2 was deleted from either the entire retina or specifically from AC precursor cells. The deletion of Meis2 led to a ~60% reduction in total GABAergic ACs in the retina. This loss of GABAergic ACs occurred only after postnatal day 5 (P5), suggesting Meis2 is not required for early specification but may be required for survival. To further investigate cell death and survival, we quantified cleaved caspase-3 positive cells in the retina at several developmental timepoints. In Meis2-CKO mice, we found an increase in cleaved caspase-3 immunolabeling at P5 and P6 timepoints coinciding with the reduction of GABAergic ACs. Further analysis of GABAergic AC subtypes demonstrated a subtype-specific cell death in Meis2-CKO retinas. For example, the total number of dopaminergic (TH) ACs were significantly reduced, whereas starburst (ChAT) ACs remained unchanged. These findings suggest that Meis2 is important for the survival of a subset of GABAergic AC subtypes in the mammalian retina. In addition, Meis2 may control the expression of specific survival factors that prevent apoptosis during developmental cell death in the retina.

Oxytocin (OT) and vasopressin (AVP) are neuropeptide hormones involved in regulating animal social behavior and a broad spectrum of physiological processes. Although their distributions are well documented in neuroendocrine regions of the forebrain and midbrain, their expression in the hindbrain remains poorly understood. Here, we used immunohistochemistry to quantify OT and AVP immunoreactive puncta within three auditory brainstem nuclei, the lateral superior olive (LSO), the medial superior olive (MSO), and the medial nucleus of the trapezoid body (MNTB) in six wild-caught rodent species differing in sociality. We also quantified the volume of these nuclei and examined variation in total brain volume across species and sociality. OT and AVP puncta count differed among species and social groups. Group-living species exhibited higher OT and AVP puncta counts than monogamous and solitary species in the LSO and MNTB. In the MSO, OT puncta counts did not differ among social groups, whereas AVP puncta counts were higher in group-living than in monogamous and solitary species. Total brain volume and the volumes of the MNTB and MSO differed among species, but not across social groups, whereas LSO volume did not differ among species or sociality. These findings revealed sociality-related variation in OT and AVP immunoreactive puncta within auditory brainstem circuits and suggest that neuropeptide signaling within early auditory brainstem pathways may contribute to the neural integration of social and auditory information.

The preoptic area (POA) is a key regulator of body temperature, orchestrating behavioral and physiological thermoregulatory functions, including fever, torpor, and homeostatic responses to ambient temperature. Histamine regulates body temperature across animal taxa, including mammals, lower vertebrates, and invertebrates. Hrh1, which encodes the histamine H1 receptor, is expressed in several neuronal populations in the POA with limited overlap with other POA thermoregulatory neurons. Acute activation of POAHrh1 neurons increased body temperature and physical activity. Acute inhibition attenuated the dark phase increase in body temperature without affecting physical activity. There was no effect of inhibition on body temperature during the light phase, fever, cold exposure, or warm exposure. Assessing behavioral thermoregulation, we found that POAHrh1 neurons stimulated nest building in both sexes, possibly contributing to cold-induced nesting behavior. Through projections to the arcuate, dorsomedial hypothalamic and tuberomammillary nuclei, POAHrh1 neurons can increase body temperature and physical activity. Overall, POAHrh1 neurons participate in several thermoregulatory functions, including daily body temperature rhythm regulation, physical activity, and nest building behavior.

Understanding how neural circuits transform sensory and bodily signals into motivational states and adaptive behavior is a central problem in neuroscience. In teleost fish, the dorsomedial telencephalon (Dm) is a key pallial region implicated in both sensory processing and aversive behavior, yet whether these functions arise from a functionally uniform region or from interactions among specialized pallial domains has remained unknown. Here we show that the teleost dorsomedial telencephalon exhibits a previously unrecognized functional organization in which distinct but interconnected pallial domains perform complementary computations that progressively transform multimodal sensory and bodily representations into aversive motivational value and adaptive behavioral control. Wide-field voltage-sensitive dye imaging revealed that tactile, auditory, and gustatory stimuli evoke spatially organized, modality-specific activity exclusively within the caudal subdivision of Dm (Dmc), whereas the rostral subdivision (Dmr) showed little or no sensory responsiveness. In contrast, focal intracerebral microstimulation demonstrated that activation of Dmr, but not Dmc, is sufficient to generate robust, flexible, and reversible conditioned place avoidance, identifying Dmr as a pallial node causally involved in the assignment of negative motivational value. Anatomical tracing revealed a circuit in which sensory and bodily-related inputs converge onto Dmc, are relayed intrapallially to Dmr, where they are transformed into an aversive motivational signal before being conveyed to hypothalamic and brainstem centers involved in autonomic and behavioral regulation. Immunohistochemical analyses confirmed the pallial identity of both subdivisions and their distinct rostrocaudal organization, while providing no evidence that Dm corresponds to a classical pallial amygdaloid territory. This functional architecture more closely resembles the distributed organization of mammalian corticolimbic networks than either a unitary pallial amygdala or a neocortical sensory hierarchy, suggesting that the transformation of sensory and bodily representations into motivational control may represent a conserved organizational feature of the pallium that emerged early during vertebrate evolution. Short abstract / Significance statementThis study shows that the teleost dorsomedial pallium is organized into complementary functional domains that dissociate multimodal sensory representation from negative motivational processing while forming an interconnected pallial circuit associated with adaptive behavioral control. Our findings reveal a distributed pallial organization resembling mammalian corticolimbic architectures and provide a new framework for understanding the evolution of vertebrate pallial function.

Hibernation is an extreme physiological state in certain mammals that is characterized by a reversible reduction in metabolic and thermogenic demands. Although the preoptic area has been implicated in the regulation of hibernation, comprehensive molecular and spatial resources for this brain region in hibernating mammals remain limited. Here, we present an integrated transcriptomic resource of the preoptic area generated using single-nucleus RNA sequencing (snRNA-seq) and Xenium-based spatial transcriptomics in a mammalian hibernator, Syrian hamster. The resource includes cross-species transcriptomic annotations relative to mouse preoptic area datasets, seasonal snRNA-seq datasets obtained under non-hibernating and hibernating conditions, and spatially resolved cell-type annotations generated from Xenium profiling. Together, these datasets provide a reference framework for identifying neuronal populations, examining molecular conservation across species and conditions, and integrating transcriptomic identity with spatial organization.

Postnatal brain growth is non-linear, making precise stereotaxic targeting in the developing rat neocortex difficult without age-specific knowledge of cortical area locations. Traditional atlases visualize brain slices in the coronal plane, which can obscure top-down areal boundaries and sub-domains. To address these shortcomings, we created a developmental stereotaxic atlas that maps the neocortex of postnatal day (P) 8, P12, P16, and P20 in Sprague-Dawley and Long-Evans rats onto a coordinate grid. After using a stereotaxic device to create a grid of fluorescent probes, we extracted the brain, flattened neocortical tissue, and stained it for cytochrome oxidase, which is predominantly found in layer IV of primary cortical areas. Reconstructions of the primary somatosensory, auditory, and visual cortices demonstrate high structural reproducibility within each age and strain group. Our atlas captures the location of primary cortical areas at these 4 ages, showing that neocortical expansion is non-isometric, expanding preferentially along the rostral-caudal axis. Finally, we complement these top-down maps by extracting local neocortical surface angles from an existing coronal atlas, enabling proper electrode orientation to be tangential to the developing neocortex. Ultimately, this anatomically verified resource provides a standardized blueprint that eliminates resource-intensive trial-and-error mapping and maximizes experimental reproducibility in developmental systems neuroscience. Significance StatementTargeting specific neocortical areas in developing rats is uniquely challenging because non-linear brain expansion renders scaled adult coordinates inaccurate, while traditional coronal sections obscure top-down areal boundaries. To resolve this, we established a top-down stereotaxic atlas that maps primary sensory cortices onto flattened, cytochrome oxidase-stained tissue across early postnatal development (P8-P20) in both Sprague-Dawley and Long-Evans rats. By combining equidistant coordinate grids with empirical cortical surface angles, this resource provides an accurate, reproducible surgical blueprint. This reference tool eliminates trial-and-error coordinate mapping, reduces animal waste, and maximizes experimental precision for the developmental neuroscience community.

The adult size of the vertebrate telencephalon typically impedes our interpreting its functions within the context of brain-wide circuit dynamics. Danionella, a genus of miniature and transparent teleost fishes closely related to zebrafish (Danio rerio), holds promise for whole-brain imaging and connectomics in an adult vertebrate. These advantages result from progenesis, a form of heterochrony characterized by early developmental onset of sexual maturation and cessation of growth leading to the retention of larval or juvenile characters in adults. Using molecular markers, tract tracing, and quantitative comparisons of cellular distribution patterns, we report a detailed neuroanatomical atlas of the adult Danionella dracula (Dracula fish) telencephalon. The results demonstrate that adults of Dracula fish and other Danionella species show extreme reduction in cellular migration from periventricular zones and topographic reorganization of major pallial divisions, including a compartment-like caudal pallium reminiscent of insect glomeruli (a dense neuropil surrounded by a thin layer of somata). We further document these characters in larval zebrafish, providing essential evidence corroborating a larval-like telencephalon in Danionella adults. Despite this phenotype, most canonical regions of the adult teleost telencephalon are identified. We also generate a transgenic GCaMP Dracula fish line, an annotated 3-dimensional atlas, and align functional imaging data to demonstrate the usefulness of this atlas as a resource for deciphering how the novel progenetic cytoarchitecture of the adult Danionella telencephalon can support its rich behavioral repertoire.

Sensory systems share common circuit organization motifs across mammalian species, however, anatomical subdivisions show varying degrees of complexity depending on ecological niche and species-specific sensory requirements. While coarse neuroanatomical connections seem preserved within the visual system, it remains unknown if molecularly defined cell-types share a similar degree of conservation, regarding not only their functional properties but also connectivity. Here we analyze the organization, molecular marker expression, and connections between two prominent visual centers, the superior colliculus (SC) and the dorsal lateral geniculate nucleus of the thalamus (dLGN), in the mouse and the tree shrew, a highly visual, diurnal species closely related to primates. Previous attempts to link molecular markers to subdivisions and connectivity of the dLGN have shown lack of conservation across species, thus preventing the systematic investigation of brain-wide interactions involved in vision. Leveraging recent single-cell and single-nucleus RNA sequencing studies, our results unravel a conserved molecular marker that shows spatial restriction in the dLGN and correlates with the location of connections from the SC in both the mouse and the tree shrew. We extend our findings by confirming the presence of this molecular marker in the human dLGN. These results provide a molecular definition and genetic access point for SC to dLGN connections in the mouse and tree shrew, enabling cell-type specific studies of the parallel processing of visual information.

The feline auditory cortex is understood to consist of 13 distinct subregions with unique anatomical and functional properties. Differential patterns of SMI-32 immunoreactivity are commonly used to identify the borders between these subregions; however, the detailed description of areal differences that is commonly cited did not include descriptions of the patterns observed along the posterior ectosylvian gyrus. Thus, the current manuscript aims to provide a more complete data set that can used to delineate the dorsal, intermediate, and ventral divisions of the posterior ectosylvian gyrus (auditory cortical regions dPE, iPE, and vPE, respectively) based on SMI-32 reactivity using the same methods and measures. Taken together, the current data and those published previously allow for a standardized approach to identifying all 13 auditory cortical subregions in this essential model of auditory cortical structure and function.

Following nervous system injury, surviving bystander neurons may rewire and form synapses with new postsynaptic targets to restore circuit function. This protocol quantifies compensatory motor neuron sprouting at the Drosophila larval neuromuscular junction. We describe larval dissection, immunostaining, Airyscan imaging, image masking, muscle-specific region-of-interest selection, and Fiji-based quantification of Dlg-positive area, bouton number, mean Dlg-positive area per bouton, NMJ arbor length, axonal versus NMJ branch points, ectopic muscle acquisition, and sprouting penetrance. For complete details on the use and execution of this protocol, please refer to Olsen et al.1

Serotonin is an evolutionarily ancient neurotransmitter that modulates an array of behaviors such as mood, sleep, and appetite across species. Serotonin acts primarily by binding to serotonin receptors, which are expressed in post-synaptic neurons (heteroreceptors) and serotonergic neurons themselves (autoreceptors). Serotonin autoreceptors modulate serotonergic tone, the foundational principles of which have been excellently demonstrated in vertebrate and invertebrate models. However, many aspects of the mechanisms and contexts in which this modulation occurs are still unclear. Drosophila melanogaster is a powerful model organism that can provide unique insights into autoreceptor function by the ability to perform precise spatial and temporal genetic manipulation with structural and functional readouts / behaviors of serotonin systems. However, a systematic characterization of serotonin autoreceptor expression in Drosophila has not been conducted. Here we use single-cell sequencing and genetic labeling to show that all five serotonin receptors are expressed in serotonergic neurons and map their expression at both the larval and adult stages of development. This is the first evidence of 5-HT2A and 5-HT7 expression in serotonergic neurons in any organism. Moreover, the unique combinations of autoreceptor expression in specific neuronal clusters will aid in the development of novel hypotheses for autoreceptor function, and demonstrates the utility of Drosophila as a model organism to study the function of serotonin autoreceptors.

Cervical spinal cord injury (SCI) disrupts descending respiratory circuitry, resulting in debilitating and often persistent ventilatory deficits. Respiratory drive emerges within medulla from the rostral ventral respiratory group (rVRG), whose neurons project to C3-C6 phrenic motor neurons (PhMNs), which then innervate diaphragm, the primary muscle of inspiration. Though rVRG neurons make extensive monosynaptic connection with PhMNs, rVRG input to PhMNs can also be relayed through pre-phrenic interneurons (PP-INs) via polysynaptic pathways. However, the neuroanatomical connectivity between PP-INs and PhMNs remains incompletely understood. In both uninjured rats and the C2 hemisection (C2HS) model of cervical SCI, we performed tracing of PP-INs that were synaptically connected to PhMNs located in rostral (C3-C4) or caudal (C5-C6) portions of the phrenic nucleus by unilaterally injecting retrograde trans-synaptic tracer, pseudorabies (PRV), selectively into ventral or dorsal regions of hemi-diaphragm. We quantified numbers of PRV-labeled PP-INs individually at segments across cervical spinal cord, including separately in dorsal horn, intermediate gray, and ventral horn. We found that PP-INs are widespread throughout C1-C7 spinal cord in the uninjured condition. These PP-INs have a predominant intrasegmental connectivity pattern with PhMNs, though significant numbers of longer distance projecting propriospinal PP-INs also exist both rostral and caudal to the PhMN pool. Furthermore, while PP-INs connect both ipsilaterally and contralaterally with PhMNs, there is a strong bias to ipsilateral projection. C2HS induced major disconnection between PhMNs and ipsilesional propriospinal PP-INs located rostral to the SCI, but conversely induced limited plasticity in connectivity of intrasegmental PP-INs located within C3-C6 spinal cord. These findings greatly improve our knowledge about PP-IN circuitry and also provide important information to aid in developing approaches to target PP-IN plasticity for promoting spinal cord repair.

The serotonergic system originates from a small population of brainstem neurons whose axons form one of the most extensive projection networks in the vertebrate nervous system. Although a number of molecular regulators of serotonergic development have been identified, the core principles that organize this widespread axonal architecture remain poorly understood. Classical neuroanatomical studies have proposed that serotonergic axons may navigate by growing along pre-existing fiber tracts, a process termed epiphytic guidance, but this hypothesis has remained largely untested. Here, we used organotypic transplantation assays to investigate how embryonic serotonergic axons navigate within developing and adult neural tissue. Rostral raphe explants from Tph2-GFP embryos were grafted onto embryonic hindbrain flat-mounts or adult brain slices, allowing donor-derived axons to be visualized in relation to genetically labelled endogenous serotonergic pathways and host tissue architecture. Across different grafting configurations, developmental stages, and both homotopic and heterotopic host territories, donor-derived axons consistently aligned with pre-existing serotonergic pathways adopting local trajectories rather than growing independently of them. This substrate-dependent behavior extended to adult tissue, where transplanted embryonic axons preferentially followed pre-existing serotonergic axon directions. These observations reveal substantial navigational plasticity and indicate that axonal and tissue architectures can provide permissive and potentially instructive substrates for the dispersal of serotonergic fibers. Together, our findings provide experimental support for epiphytic guidance and suggest that serotonergic pathway assembly relies, at least in part, on a pioneer-follower mechanism of progressive self-scaffolding. Such a strategy may help explain how a small population of raphe neurons generates an extensive and spatially coherent neuromodulatory system.

The ventral lateral geniculate nucleus (GLv) is a conserved retinorecipient structure positioned between visual and premotor systems, yet its role in visuomotor transformations remains poorly understood. Here, we examined whether the pigeon GLv contains a spatially organized motor representation linking visual-field locations to orienting movements. Anatomical tracing identified descending projections from neurons in the GLv inner lamina (GLv-li) through pretectal and tegmental regions toward pontine targets. GLv-li projection neurons are GABAergic, yet electrical microstimulation of GLv-li in awake pigeons evoked rapid head movements followed by smaller eye movements. Each stimulation locus produced a reproducible characteristic motor vector whose direction and duration were largely insensitive to stimulation parameters, whereas movement amplitude and velocity approached site-specific plateaus. Movements initiated from different head positions were better explained by repetition of a fixed displacement than by convergence toward a common spatial goal. Critically, motor-vector direction was systematically related to the direction of the visual receptive field represented at the same GLv locus, while motor-vector amplitude covaried with receptive-field eccentricity. These defining features persisted after optic tectum ablation. Together, these findings reveal a retinotopically-organized map of fixed-vector head movements in the avian GLv and identify a tectum-independent route through which visual spatial representations can access descending orienting circuitry.

Visceral sensory neurons sense and modulate the brain, behavior, and the internal organs. However, these neurons have been difficult to study comprehensively due to their projections deep within the body. Here, we establish the transparent miniature fish Danionella cerebrum as a model for studying the sensory vagus nerve in an adult vertebrate. By generating a transgenic line to label D. cerebrum cranial sensory ganglia, we were able to both anatomically characterize and transcriptionally profile the sensory vagus at single-cell resolution. Anatomically, we find that the vagal ganglia have a somatotopic layout. Transcriptionally, the sensory vagus is comprised of diverse sensory subtypes conserved with other vertebrates, including nutrient-sensing, mechanoreceptive, nociceptive, and thermosensitive subtypes, as well as polymodal combinations. Visualizing subtype marker genes identified somatotopic-specific sensory subtypes. Notably, the D. cerebrum sensory vagus is not static across development: it becomes anatomically sexually dimorphic during sexual maturation and undergoes continuous adult neurogenesis. The molecular and anatomical atlas of the sensory vagus lays the foundation for functional studies of body-brain communication in D. cerebrum.