Biology subjects

Carbo-Tano, M.

Publications and source records attributed to Carbo-Tano, M..

5 recordsLinked to original sources

bioRxiv2026

Whole brain mapping of spinal-projecting neurons in larval zebrafish

To elicit voluntary movements and integrative reflexes underlying behavior, the brain sends command signals to the spinal cord via specialized long-range descending neurons, known as spinal-projecting neurons (SPNs). The vast and widespread distribution of SPNs, combined with their complex long-distance connectivity, poses a significant challenge for mapping their anatomical organization and associating specific populations with distinct functions. Here we took advantage of the transparency and genetic accessibility of larval zebrafish to uncover the fundamental principles of SPN anatomical organization in a Teleost. Using an optical backfilling method relying on photoactivable GFP, we generate a whole-brain map of all neurons sending axons towards the spinal cord. This approach reveals far more SPNs than previously described through conventional strategies, offering an unparalleled opportunity to revisit distinct spinal-projecting nuclei distributed across hindbrain, midbrain, and diencephalic structures. Combining information on cell location, morphology, and projection patterns, we propose tentative homological designations for zebrafish of SPN nuclei based on established descriptions in mammals and other vertebrates.

neuroscience↗

bioRxiv2026

Noradrenaline prolongs the state of motor arrest via cerebrospinal fluid signaling

Neuromodulators can mediate whole-body physiological changes, however how signaling from relatively small populations of neurons produces widespread and sustained effects remains incompletely understood. Here, we demonstrate that sustained noradrenergic activation induces prolonged motor arrest accompanied by postural collapse, bradycardia, and emetic responses. Motor suppression arises from inhibition of brainstem commands to the spinal cord rather than motoneuron silencing. Noradrenaline induces a glial calcium wave that propagates throughout the central nervous system. This wave most prominently persists at the brainstem-spinal cord boundary and ventricular midline. At this location, ependymal radial glia express Adra1a receptors on cilia contacting cerebrospinal fluid (CSF). Ventricular noradrenaline injections recapitulated the glial wave and motor arrest, while CSF administration of an Adra1 antagonist shortened motor arrest. Altogether, noradrenaline sustains motor arrest by signaling through the CSF via ciliary Adra1a receptors on ependymal radial glia showing that cerebrospinal fluid as a critical transmission route for persistence of behavioral states. HighlightsO_LINoradrenergic surges coordinate a whole-body response with motor arrest, postural disruptions, bradycardia, and emesis-like reflexes C_LIO_LIMotor arrest results from silencing of brainstem motor commands to the spinal cord C_LIO_LINoradrenaline-induced glial calcium waves last longest at the obex/ventricular midline where cilia of CSF-contacting glial cells bear Adra1 receptors C_LIO_LINoradrenergic signaling in the CSF is necessary and sufficient for motor arrest to persist C_LI

neuroscience↗

bioRxiv2025

Whole-body central processing of lateral line inputs encodes flow direction relative to the center-of-mass

From shifting visual scenes to tactile deformations and fluid motion, animals must interpret patterns of sensory flow around their body to construct stable internal models and produce adaptive behavior. Understanding of how such transformations are encoded within the brain remains incomplete. To tackle this question, we leverage the lateral line of larval zebrafish as a tractable sensory system sensitive to fluid motion that is used to steer navigation, feed, and avoid predators. By presenting stimuli of either direction to neuromasts along the body, we used high-resolution calcium imaging to map hindbrain responses. Unexpectedly, our findings challenge the notion that central lateral line processing lacks topographic structure by revealing a simple yet powerful principle centered on a egocentric spatial framework: the direction and location of local flow motions are encoded in reference to the animals center-of-mass. This simple representation enables the brain to register complex flow patterns and provides a robust basis for subsequent behavioral action selection. MON neurons that encode flow toward the center-of-mass broadly project to form bilateral connections onto reticulospinal neurons that coordinate forward locomotion while MON neurons that encode flow away from the center-of-mass displayed a more selective and unilateral projection profile to command neurons for turns. Our discovery represents a shift from purely somatotopic encoding toward an integrative representation of axial position and directionality combined, revealing a novel principle of encoding spatio-directional cues in the hindbrain. This study advances our understanding of how complex mechanosensory inputs select appropriate motor outputs via simple egocentric neural maps in the hindbrain. Significance StatementSpatial and directional cues are essential to select appropriate actions in response to changes in the environment. How information from broadly distributed mechanosensors across the entire body occurs in the brain enables motor selection remains elusive. By directionally stimulating each and virtually all neuromasts distributed along the lateral line of larval zebrafish, our study uncovers that spatial and directional inputs from each flow sensors is encoded in the medial octavolateralis nuclei relative to the animals center-of-mass in order to subsequently recruit reticulospinal neurons driving forward and turn bouts. These results establish a new framework for understanding how broadly distributed inputs get integrated to recruit motor command neurons responsible for producing diverse behaviors.

neuroscience↗

bioRxiv2022

Functional coupling of the mesencephalic locomotor region and V2a reticulospinal neurons driving forward locomotion

Locomotion in vertebrates relies on high brain centers converging onto the mesencephalic locomotor region (MLR). How the MLR recruits brainstem reticulospinal neurons (RSNs) to initiate locomotion is incompletely understood due to the challenge of recording these cells in vivo. To tackle this question, we leveraged the transparency and genetic accessibility of larval zebrafish. In this model organism, we uncovered the locus of the MLR as a small region dorsal to the locus coeruleus containing glutamatergic and cholinergic neurons. MLR stimulations reliably elicited forward bouts of controlled duration and speed. We find that the MLR elicits forward locomotion by recruiting V2a RSNs in the pontine and retropontine regions, and gradually in the medulla. Remarkably, recruited V2a RSNs in the medulla act as maintain cells encoding speed of forward locomotion. Altogether, our study reveals that the MLR recruits genetically-identified reticulospinal neurons in the medulla to control the kinematics of exploration.

neuroscience↗

bioRxiv2021

Evolutionary divergence of locomotion in two related vertebrate species

Locomotion exists in diverse forms in nature and is adapted to the environmental constraints of each species1. However, little is known about how closely related species with similar neuronal circuitry can evolve different navigational strategies to explore their environments. We established a powerful approach in comparative neuroethology to investigate evolution of neuronal circuits in vertebrates by comparing divergent swimming pattern of two closely related larval fish species, Danionella translucida (DT) and Danio rerio or zebrafish (ZF)2,3. During swimming, we demonstrate that DT utilizes lower half tail-beat frequency and amplitude to generate a slower and continuous swimming pattern when compared to the burst-and-glide swimming pattern in ZF. We found a high degree of conservation in the brain anatomy between the two species. However, we revealed that the activity of a higher motor region, referred here as the Mesencephalic Locomotion Maintenance Neurons (MLMN) correlates with the duration of swim events and differs strikingly between DT and ZF. Using holographic stimulation, we show that the activation of the MLMN is sufficient to increase the frequency and duration of swim events in ZF. Moreover, we propose two characteristics, availability of dissolved oxygen and timing of swim bladder inflation, which drive the observed differences in the swim pattern. Our findings uncover the neuronal circuit substrate underlying the evolutionary divergence of navigational strategies and how they are adapted to their respective environmental constraints.

neuroscience↗