RESUMEN
Genomic studies have identified hundreds of candidate genes near loci associated with risk for schizophrenia. To define candidates and their functions, we mutated zebrafish orthologs of 132 human schizophrenia-associated genes. We created a phenotype atlas consisting of whole-brain activity maps, brain structural differences, and profiles of behavioral abnormalities. Phenotypes were diverse but specific, including altered forebrain development and decreased prepulse inhibition. Exploration of these datasets identified promising candidates in more than 10 gene-rich regions, including the magnesium transporter cnnm2 and the translational repressor gigyf2, and revealed shared anatomical sites of activity differences, including the pallium, hypothalamus, and tectum. Single-cell RNA sequencing uncovered an essential role for the understudied transcription factor znf536 in the development of forebrain neurons implicated in social behavior and stress. This phenotypic landscape of schizophrenia-associated genes prioritizes more than 30 candidates for further study and provides hypotheses to bridge the divide between genetic association and biological mechanism.
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Esquizofrenia/genética , Esquizofrenia/fisiopatología , Animales , Encéfalo , Corteza Cerebral , Modelos Animales de Enfermedad , Regulación de la Expresión Génica/genética , Predisposición Genética a la Enfermedad , Estudio de Asociación del Genoma Completo , Fenotipo , Polimorfismo de Nucleótido Simple/genética , Pez Cebra/genéticaRESUMEN
Quantifying animal behaviour during microscopy is crucial to associate optically recorded neural activity with behavioural outputs and states. Here, I describe an imaging and tracking system for head-restrained larval zebrafish compatible with functional microscopy. This system is based on the Raspberry Pi computer, Pi NoIR camera and open-source software for the real-time tail segmentation and skeletonization of the zebrafish tail at over 100â Hz. This allows for precise and long-term analyses of swimming behaviour, which can be related to functional signals recorded in individual neurons. This system offers a simple but performant solution for quantifying the behaviour of head-restrained larval zebrafish, which can be built for 340.
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Programas Informáticos , Pez Cebra , Animales , Pez Cebra/fisiología , Conducta Animal , NataciónRESUMEN
High-resolution serial-section electron microscopy (ssEM) makes it possible to investigate the dense meshwork of axons, dendrites, and synapses that form neuronal circuits. However, the imaging scale required to comprehensively reconstruct these structures is more than ten orders of magnitude smaller than the spatial extents occupied by networks of interconnected neurons, some of which span nearly the entire brain. Difficulties in generating and handling data for large volumes at nanoscale resolution have thus restricted vertebrate studies to fragments of circuits. These efforts were recently transformed by advances in computing, sample handling, and imaging techniques, but high-resolution examination of entire brains remains a challenge. Here, we present ssEM data for the complete brain of a larval zebrafish (Danio rerio) at 5.5 days post-fertilization. Our approach utilizes multiple rounds of targeted imaging at different scales to reduce acquisition time and data management requirements. The resulting dataset can be analysed to reconstruct neuronal processes, permitting us to survey all myelinated axons (the projectome). These reconstructions enable precise investigations of neuronal morphology, which reveal remarkable bilateral symmetry in myelinated reticulospinal and lateral line afferent axons. We further set the stage for whole-brain structure-function comparisons by co-registering functional reference atlases and in vivo two-photon fluorescence microscopy data from the same specimen. All obtained images and reconstructions are provided as an open-access resource.
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Encéfalo/ultraestructura , Microscopía Electrónica , Pez Cebra , Anatomía Artística , Animales , Atlas como Asunto , Axones/metabolismo , Axones/ultraestructura , Encéfalo/anatomía & histología , Encéfalo/citología , Conjuntos de Datos como Asunto , Larva/anatomía & histología , Larva/citología , Larva/ultraestructura , Microscopía de Fluorescencia por Excitación Multifotónica , Publicación de Acceso Abierto , Pez Cebra/anatomía & histología , Pez Cebra/crecimiento & desarrolloRESUMEN
Expansion microscopy (ExM) allows scalable imaging of preserved 3D biological specimens with nanoscale resolution on fast diffraction-limited microscopes. Here, we explore the utility of ExM in the larval and embryonic zebrafish, an important model organism for the study of neuroscience and development. Regarding neuroscience, we found that ExM enabled the tracing of fine processes of radial glia, which are not resolvable with diffraction-limited microscopy. ExM further resolved putative synaptic connections, as well as molecular differences between densely packed synapses. Finally, ExM could resolve subsynaptic protein organization, such as ring-like structures composed of glycine receptors. Regarding development, we used ExM to characterize the shapes of nuclear invaginations and channels, and to visualize cytoskeletal proteins nearby. We detected nuclear invagination channels at late prophase and telophase, potentially suggesting roles for such channels in cell division. Thus, ExM of the larval and embryonic zebrafish may enable systematic studies of how molecular components are configured in multiple contexts of interest to neuroscience and developmental biology.
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Microscopía/métodos , Pez Cebra/anatomía & histología , Animales , Encéfalo/ultraestructura , Núcleo Celular/ultraestructura , Biología Evolutiva/métodos , Larva/anatomía & histología , Neurociencias/métodos , Sinapsis/ultraestructura , Pez Cebra/embriologíaRESUMEN
The mature vertebrate retina is a highly ordered neuronal network of cell bodies and synaptic neuropils arranged in distinct layers. Little, however, is known about the emergence of this spatial arrangement. Here, we investigate how the three main types of retinal inhibitory neuron (RIN)--horizontal cells (HCs), inner nuclear layer amacrine cells (iACs) and displaced amacrine cells (dACs)--reach their specific laminar positions during development. Using in vivo time-lapse imaging of zebrafish retinas, we show that RINs undergo distinct phases of migration. The first phase, common to all RINs, is bipolar migration directed towards the apicobasal centre of the retina. All RINs then transition to a less directionally persistent multipolar phase of migration. Finally, HCs, iACs and dACs each undergo cell type-specific migration. In contrast to current hypotheses, we find that most dACs send processes into the forming inner plexiform layer (IPL) before migrating through it and inverting their polarity. By imaging and quantifying the dynamics of HCs, iACs and dACs from birth to final position, this study thus provides evidence for distinct and new migration patterns during retinal lamination and insights into the initiation of IPL formation.
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Movimiento Celular/fisiología , Neuronas/fisiología , Retina/embriología , Pez Cebra/embriología , Animales , Animales Modificados Genéticamente , Procesamiento de Imagen Asistido por Computador , Cinética , Microscopía Fluorescente , Neuronas/citología , Imagen de Lapso de TiempoRESUMEN
In order to localize the neural circuits involved in generating behaviors, it is necessary to assign activity onto anatomical maps of the nervous system. Using brain registration across hundreds of larval zebrafish, we have built an expandable open-source atlas containing molecular labels and definitions of anatomical regions, the Z-Brain. Using this platform and immunohistochemical detection of phosphorylated extracellular signalregulated kinase (ERK) as a readout of neural activity, we have developed a system to create and contextualize whole-brain maps of stimulus- and behavior-dependent neural activity. This mitogen-activated protein kinase (MAP)-mapping assay is technically simple, and data analysis is completely automated. Because MAP-mapping is performed on freely swimming fish, it is applicable to studies of nearly any stimulus or behavior. Here we demonstrate our high-throughput approach using pharmacological, visual and noxious stimuli, as well as hunting and feeding. The resultant maps outline hundreds of areas associated with behaviors.
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Encéfalo/metabolismo , Quinasas MAP Reguladas por Señal Extracelular/metabolismo , Procesamiento de Imagen Asistido por Computador/métodos , Neuritas/metabolismo , Algoritmos , Animales , Automatización , Conducta Animal , Encéfalo/fisiología , Mapeo Encefálico/métodos , Calcio/química , Inmunohistoquímica , Microscopía Confocal , Neuronas/metabolismo , Neuronas/fisiología , Fosforilación , Análisis de Componente Principal , Reproducibilidad de los Resultados , Programas Informáticos , Natación , Pez CebraRESUMEN
As animals grow, their nervous systems also increase in size. How growth in the central nervous system is regulated and its functional consequences are incompletely understood. We explored these questions, using the larval Drosophila locomotor system as a model. In the periphery, at neuromuscular junctions, motoneurons are known to enlarge their presynaptic axon terminals in size and strength, thereby compensating for reductions in muscle excitability that are associated with increases in muscle size. Here, we studied how motoneurons change in the central nervous system during periods of animal growth. We find that within the central nervous system motoneurons also enlarge their postsynaptic dendritic arbors, by the net addition of branches, and that these scale with overall animal size. This dendritic growth is gated on a cell-by-cell basis by a specific isoform of the steroid hormone receptor ecdysone receptor-B2, for which functions have thus far remained elusive. The dendritic growth is accompanied by synaptic strengthening and results in increased neuronal activity. Electrical properties of these neurons, however, are independent of ecdysone receptor-B2 regulation. We propose that these structural dendritic changes in the central nervous system, which regulate neuronal activity, constitute an additional part of the adaptive response of the locomotor system to increases in body and muscle size as the animal grows.
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Adaptación Biológica/fisiología , Tamaño Corporal/fisiología , Sistema Nervioso Central/crecimiento & desarrollo , Dendritas/fisiología , Drosophila/fisiología , Locomoción/fisiología , Neuronas Motoras/citología , Análisis de Varianza , Animales , Inmunohistoquímica , Larva/crecimiento & desarrollo , Receptores de Esteroides/metabolismo , Estadísticas no ParamétricasRESUMEN
Habituation allows animals to learn to ignore persistent but inconsequential stimuli. Despite being the most basic form of learning, a consensus model on the underlying mechanisms has yet to emerge. To probe relevant mechanisms, we took advantage of a visual habituation paradigm in larval zebrafish, where larvae reduce their reactions to abrupt global dimming (a dark flash). We used Ca2+ imaging during repeated dark flashes and identified 12 functional classes of neurons that differ based on their rate of adaptation, stimulus response shape, and anatomical location. While most classes of neurons depressed their responses to repeated stimuli, we identified populations that did not adapt or that potentiated their response. These neurons were distributed across brain areas, consistent with a distributed learning process. Using a small-molecule screening approach, we confirmed that habituation manifests from multiple distinct molecular mechanisms, and we have implicated molecular pathways in habituation, including melatonin, oestrogen, and GABA signalling. However, by combining anatomical analyses and pharmacological manipulations with Ca2+ imaging, we failed to identify a simple relationship between pharmacology, altered activity patterns, and habituation behaviour. Collectively, our work indicates that habituation occurs via a complex and distributed plasticity processes that cannot be captured by a simple model. Therefore, untangling the mechanisms of habituation will likely require dedicated approaches aimed at sub-component mechanisms underlying this multidimensional learning process.
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Perciformes , Pez Cebra , Animales , Larva , Aprendizaje Espacial , Encéfalo , ConsensoRESUMEN
Studying chemosensory processing desires precise chemical cue presentation, behavioral response monitoring, and large-scale neuronal activity recording. Here we present Fish-on-Chips, a set of optofluidic tools for highly-controlled chemical delivery while simultaneously imaging behavioral outputs and whole-brain neuronal activities at cellular resolution in larval zebrafish. These include a fluidics-based swimming arena and an integrated microfluidics-light sheet fluorescence microscopy (µfluidics-LSFM) system, both of which utilize laminar fluid flows to achieve spatiotemporally precise chemical cue presentation. To demonstrate the strengths of the platform, we used the navigation arena to reveal binasal input-dependent behavioral strategies that larval zebrafish adopt to evade cadaverine, a death-associated odor. The µfluidics-LSFM system enables sequential presentation of odor stimuli to individual or both nasal cavities separated by only ~100 µm. This allowed us to uncover brainwide neural representations of cadaverine sensing and binasal input summation in the vertebrate model. Fish-on-Chips is readily generalizable and will empower the investigation of neural coding in the chemical senses.
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Encéfalo , Pez Cebra , Animales , Pez Cebra/fisiología , Larva , Cadaverina , Encéfalo/fisiología , Microscopía Fluorescente/métodosRESUMEN
Multipotent progenitors in the vertebrate retina often generate clonally related mixtures of excitatory and inhibitory neurons. The postmitotically expressed transcription factor, Ptf1a, is essential for all inhibitory fates in the zebrafish retina, including three types of horizontal and 28 types of amacrine cell. Here, we show that specific types of inhibitory neurons arise from the cell-autonomous influence of Ptf1a in the daughters of fate-restricted progenitors, such as Ath5 or Vsx1/2-expressing progenitors, and that in the absence of Ptf1a, cells that would have become these specific inhibitory subtypes revert to the histogenetically appropriate excitatory subtypes of the same lineage. Altered proportions of amacrine subtypes respecified by the misexpression of Ptf1a in the Ath5 lineage suggest that Ath5-expressing progenitors are biased, favoring the generation of some subtypes more than others. Yet the full array of inhibitory cell subtypes in Ath5 mutants implies the existence of Ath5-independent factors involved in inhibitory cell specification. We also show that an extrinsic negative feedback on the expression of Ptf1a provides a control mechanism by which the number of any and all types of inhibitory cells in the retina can be regulated in this lineage-dependent way.
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Diferenciación Celular/genética , Linaje de la Célula/genética , Regulación del Desarrollo de la Expresión Génica/fisiología , Inhibición Neural/fisiología , Retina/citología , Células Amacrinas/clasificación , Células Amacrinas/fisiología , Animales , Animales Modificados Genéticamente , Blastómeros/trasplante , Bromodesoxiuridina/metabolismo , Diferenciación Celular/efectos de los fármacos , Proteínas de Unión al ADN/genética , Proteínas de Unión al ADN/metabolismo , Embrión no Mamífero , Células Madre Embrionarias/efectos de los fármacos , Células Madre Embrionarias/fisiología , Regulación del Desarrollo de la Expresión Génica/genética , Glicina/metabolismo , Proteínas Fluorescentes Verdes/genética , Proteínas Luminiscentes/genética , Proteínas del Tejido Nervioso/genética , Proteínas del Tejido Nervioso/metabolismo , Inhibición Neural/genética , Oligonucleótidos Antisentido/farmacología , Retina/metabolismo , Trasplante de Células Madre/métodos , Factores de Transcripción/genética , Factores de Transcripción/metabolismo , Pez Cebra , Proteínas de Pez Cebra/genética , Proteínas de Pez Cebra/metabolismo , Ácido gamma-Aminobutírico/metabolismo , Proteína Fluorescente RojaRESUMEN
Animals have a remarkable ability to use local cues to orient in space in the absence of a panoramic fixed reference frame. Here we use the mechanosensory lateral line in larval zebrafish to understand rheotaxis, an innate oriented swimming evoked by water currents. We generated a comprehensive light-microscopy cell-resolution projectome of lateralis afferent neurons (LANs) and used clustering techniques for morphological classification. We find surprising structural constancy among LANs. Laser-mediated microlesions indicate that precise topographic mapping of lateral-line receptors is not essential for rheotaxis. Recording neuronal-activity during controlled mechanical stimulation of neuromasts reveals unequal representation of water-flow direction in the hindbrain. We explored potential circuit architectures constrained by anatomical and functional data to suggest a parsimonious model under which the integration of lateralized signals transmitted by direction-selective LANs underlies the encoding of water-flow direction in the brain. These data provide a new framework to understand how animals use local mechanical cues to orient in space.
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Sistema de la Línea Lateral , Orientación Espacial , Pez Cebra , Animales , Larva , MecanorreceptoresRESUMEN
Delayed emergence from anesthesia was previously reported in a case study of a child with Glycine Encephalopathy. To investigate the neural basis of this delayed emergence, we developed a zebrafish glial glycine transporter (glyt1 - / -) mutant model. We compared locomotor behaviors; dose-response curves for tricaine, ketamine, and 2,6-diisopropylphenol (propofol); time to emergence from these anesthetics; and time to emergence from propofol after craniotomy in glyt1-/- mutants and their siblings. To identify differentially active brain regions in glyt1-/- mutants, we used pERK immunohistochemistry as a proxy for brain-wide neuronal activity. We show that glyt1-/- mutants initiated normal bouts of movement less frequently indicating lethargy-like behaviors. Despite similar anesthesia dose-response curves, glyt1-/- mutants took over twice as long as their siblings to emerge from ketamine or propofol, mimicking findings from the human case study. Reducing glycine levels rescued timely emergence in glyt1-/- mutants, pointing to a causal role for elevated glycine. Brain-wide pERK staining showed elevated activity in hypnotic brain regions in glyt1-/- mutants under baseline conditions and a delay in sensorimotor integration during emergence from anesthesia. Our study links elevated activity in preoptic brain regions and reduced sensorimotor integration to lethargy-like behaviors and delayed emergence from propofol in glyt1-/- mutants.
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Retraso en el Despertar Posanestésico/genética , Proteínas de Transporte de Glicina en la Membrana Plasmática/genética , Glicina/metabolismo , Hiperglicinemia no Cetósica/genética , Neuronas/metabolismo , Área Preóptica/metabolismo , Proteínas de Pez Cebra/genética , Aminobenzoatos , Anestesia General , Anestésicos , Animales , Animales Modificados Genéticamente , Craneotomía , Retraso en el Despertar Posanestésico/metabolismo , Retraso en el Despertar Posanestésico/fisiopatología , Retraso en el Despertar Posanestésico/prevención & control , Modelos Animales de Enfermedad , Expresión Génica , Glicina/farmacología , Proteínas de Transporte de Glicina en la Membrana Plasmática/deficiencia , Hiperglicinemia no Cetósica/tratamiento farmacológico , Hiperglicinemia no Cetósica/metabolismo , Hiperglicinemia no Cetósica/fisiopatología , Ketamina , Locomoción/fisiología , Neuronas/efectos de los fármacos , Neuronas/patología , Área Preóptica/efectos de los fármacos , Área Preóptica/patología , Propofol , Pez Cebra , Proteínas de Pez Cebra/deficiencia , eIF-2 Quinasa/genética , eIF-2 Quinasa/metabolismoRESUMEN
Habituation is an adaptive learning process that enables animals to adjust innate behaviors to changes in their environment. Despite its well-documented implications for a wide diversity of behaviors, the molecular and cellular basis of habituation learning is not well understood. Using whole-genome sequencing of zebrafish mutants isolated in an unbiased genetic screen, we identified the palmitoyltransferase Huntingtin interacting protein 14 (Hip14) as a critical regulator of habituation learning. We demonstrate that Hip14 regulates depression of sensory inputs onto an identified hindbrain neuron and provide evidence that Hip14 palmitoylates the Shaker-like K+ voltage-gated channel subunit (Kv1.1), thereby regulating Kv1.1 subcellular localization. Furthermore, we show that, like for Hip14, loss of Kv1.1 leads to habituation deficits and that Hip14 is dispensable in development and instead acts acutely to promote habituation. Combined, these results uncover a previously unappreciated role for acute posttranslational palmitoylation at defined circuit components to regulate learning.
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Aciltransferasas/fisiología , Proteínas Adaptadoras Transductoras de Señales/fisiología , Habituación Psicofisiológica/genética , Aprendizaje/fisiología , Lipoilación/genética , Lipoilación/fisiología , Proteínas del Tejido Nervioso/fisiología , Procesamiento Proteico-Postraduccional/genética , Procesamiento Proteico-Postraduccional/fisiología , Canales de Potasio de la Superfamilia Shaker/fisiología , Pez Cebra/genética , Pez Cebra/fisiología , Animales , Terminales Presinápticos/metabolismo , Canales de Potasio de la Superfamilia Shaker/metabolismoRESUMEN
Habituation is a simple form of learning where animals learn to reduce their responses to repeated innocuous stimuli [1]. Habituation is thought to occur via at least two temporally and molecularly distinct mechanisms, which lead to short-term memories that last for seconds to minutes and long-term memories that last for hours or longer [1, 2]. Here, we focus on long-term habituation, which, due to the extended time course, necessitates stable alterations to circuit properties [2-4]. In its simplest form, long-term habituation could result from a plasticity event at a single point in a circuit, and many studies have focused on identifying the site and underlying mechanism of plasticity [5-10]. However, it is possible that these individual sites are only one of many points in the circuit where plasticity is occurring. Indeed, studies of short-term habituation in C. elegans indicate that in this paradigm, multiple genetically separable mechanisms operate to adapt specific aspects of behavior [11-13]. Here, we use a visual assay in which larval zebrafish habituate their response to sudden reductions in illumination (dark flashes) [14, 15]. Through behavioral analyses, we find that multiple components of the dark-flash response habituate independently of one another using different molecular mechanisms. This is consistent with a modular model in which habituation originates from multiple independent processes, each adapting specific components of behavior. This may allow animals to more specifically or flexibly habituate based on stimulus context or internal states.
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Habituación Psicofisiológica , Memoria a Largo Plazo , Aprendizaje Espacial , Pez Cebra/fisiología , Animales , Estimulación LuminosaRESUMEN
Animals have evolved specialized neural circuits to defend themselves from pain- and injury-causing stimuli. Using a combination of optical, behavioral and genetic approaches in the larval zebrafish, we describe a novel role for hypothalamic oxytocin (OXT) neurons in the processing of noxious stimuli. In vivo imaging revealed that a large and distributed fraction of zebrafish OXT neurons respond strongly to noxious inputs, including the activation of damage-sensing TRPA1 receptors. OXT population activity reflects the sensorimotor transformation of the noxious stimulus, with some neurons encoding sensory information and others correlating more strongly with large-angle swims. Notably, OXT neuron activation is sufficient to generate this defensive behavior via the recruitment of brainstem premotor targets, whereas ablation of OXT neurons or loss of the peptide attenuates behavioral responses to TRPA1 activation. These data highlight a crucial role for OXT neurons in the generation of appropriate defensive responses to noxious input.
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Tronco Encefálico/fisiología , Vías Nerviosas/fisiología , Nocicepción/fisiología , Nociceptores/fisiología , Animales , Tronco Encefálico/citología , Hipotálamo/citología , Hipotálamo/fisiología , Vías Nerviosas/citología , Nociceptores/citología , Oxitocina , Pez CebraRESUMEN
Medial and lateral hypothalamic loci are known to suppress and enhance appetite, respectively, but the dynamics and functional significance of their interaction have yet to be explored. Here we report that, in larval zebrafish, primarily serotonergic neurons of the ventromedial caudal hypothalamus (cH) become increasingly active during food deprivation, whereas activity in the lateral hypothalamus (LH) is reduced. Exposure to food sensory and consummatory cues reverses the activity patterns of these two nuclei, consistent with their representation of opposing internal hunger states. Baseline activity is restored as food-deprived animals return to satiety via voracious feeding. The antagonistic relationship and functional importance of cH and LH activity patterns were confirmed by targeted stimulation and ablation of cH neurons. Collectively, the data allow us to propose a model in which these hypothalamic nuclei regulate different phases of hunger and satiety and coordinate energy balance via antagonistic control of distinct behavioral outputs.
How soon after a meal do you start feeling hungry again? The answer depends on a complex set of processes within the brain that regulate appetite. A key player in these processes is the hypothalamus, a small structure at the base of the brain. The hypothalamus consists of many different subregions, some of which are responsible for increasing or decreasing hunger. Wee, Song et al. now show how two of these subregions interact to regulate appetite and feeding, by studying them in hungry zebrafish larvae. The brains of zebrafish have many features in common with the brains of mammals, but they are smaller and transparent, which makes them easier to study. Wee, Song et al. show that as larvae become hungry, an area called the caudal hypothalamus increases its activity. But when the larvae find food and start feeding, activity in this area falls sharply. It then remains low while the hungry larvae eat as much as possible. Eventually the larvae become full and start eating more slowly. As they do so, the activity of the caudal hypothalamus goes back to normal levels. While this is happening, activity in a different area called the lateral hypothalamus shows the opposite pattern. It has low activity in hungry larvae, which increases when food becomes available and feeding begins. When the larvae finally reduce their rate of feeding, the activity in the lateral hypothalamus drops back down. The authors posit that by inhibiting each other's activity, the caudal and lateral hypothalamus work together to ensure that animals search for food when necessary, but switch to feeding behavior when food becomes available. Serotonin which is produced by the caudal hypothalamus and drugs that act like it have been proposed to suppress appetite, but they have varied and complex effects on food intake and weight gain. By showing that activity in the caudal hypothalamus changes depending on whether food is present, the current findings may provide insights into this complexity. More generally, they show that mapping the circuits that regulate appetite and feeding in simple organisms could help us understand the same processes in humans.
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Apetito , Hipotálamo/fisiología , Red Nerviosa/fisiología , Neuronas Serotoninérgicas/fisiología , Pez Cebra/fisiología , Animales , Larva/fisiologíaRESUMEN
Simultaneous recordings of large populations of neurons in behaving animals allow detailed observation of high-dimensional, complex brain activity. However, experimental approaches often focus on singular behavioral paradigms or brain areas. Here, we recorded whole-brain neuronal activity of larval zebrafish presented with a battery of visual stimuli while recording fictive motor output. We identified neurons tuned to each stimulus type and motor output and discovered groups of neurons in the anterior hindbrain that respond to different stimuli eliciting similar behavioral responses. These convergent sensorimotor representations were only weakly correlated to instantaneous motor activity, suggesting that they critically inform, but do not directly generate, behavioral choices. To catalog brain-wide activity beyond explicit sensorimotor processing, we developed an unsupervised clustering technique that organizes neurons into functional groups. These analyses enabled a broad overview of the functional organization of the brain and revealed numerous brain nuclei whose neurons exhibit concerted activity patterns.
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Química Encefálica/fisiología , Encéfalo/fisiología , Larva/fisiología , Neuronas/fisiología , Desempeño Psicomotor/fisiología , Animales , Animales Modificados Genéticamente , Encéfalo/citología , Larva/química , Larva/citología , Actividad Motora/fisiología , Neuronas/química , Optogenética/métodos , Estimulación Luminosa/métodos , Pez CebraRESUMEN
In the absence of salient sensory cues to guide behavior, animals must still execute sequences of motor actions in order to forage and explore. How such successive motor actions are coordinated to form global locomotion trajectories is unknown. We mapped the structure of larval zebrafish swim trajectories in homogeneous environments and found that trajectories were characterized by alternating sequences of repeated turns to the left and to the right. Using whole-brain light-sheet imaging, we identified activity relating to the behavior in specific neural populations that we termed the anterior rhombencephalic turning region (ARTR). ARTR perturbations biased swim direction and reduced the dependence of turn direction on turn history, indicating that the ARTR is part of a network generating the temporal correlations in turn direction. We also find suggestive evidence for ARTR mutual inhibition and ARTR projections to premotor neurons. Finally, simulations suggest the observed turn sequences may underlie efficient exploration of local environments.
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Conducta Animal , Mapeo Encefálico , Locomoción , Rombencéfalo/fisiología , Pez Cebra/fisiología , AnimalesRESUMEN
To investigate the cellular basis of tissue integrity in a vertebrate central nervous system (CNS) tissue, we eliminated Müller glial cells (MG) from the zebrafish retina. For well over a century, glial cells have been ascribed a mechanical role in the support of neural tissues, yet this idea has not been specifically tested in vivo. We report here that retinas devoid of MG rip apart, a defect known as retinoschisis. Using atomic force microscopy, we show that retinas without MG have decreased resistance to tensile stress and are softer than controls. Laser ablation of MG processes showed that these cells are under tension in the tissue. Thus, we propose that MG act like springs that hold the neural retina together, finally confirming an active mechanical role of glial cells in the CNS.