Biology subjects

Stih, V.

Publications and source records attributed to Stih, V..

5 recordsLinked to original sources

bioRxiv2024

The representation of visual motion and landmark position aligns with heading direction in the zebrafish interpeduncular nucleus

Sensory information is fundamental for navigation. Visual motion is used by animals to estimate their traveling distance and direction, and visual landmarks allow animals to tether their location and orientation to their environment. How such signals are integrated in the vertebrate brain is poorly understood. Here we investigate the representation of directional whole field visual motion and landmark position in a circuit in the larval zebrafish consisting of the habenula, interpeduncular nucleus (IPN) and anterior hindbrain (aHB). This circuit has been recently implicated in the representation of heading direction. Using calcium imaging we show that these stimuli are represented in the habenula, IPN and aHB. We further show that their representation in the IPN of both these stimuli is topographically arranged in a way that aligns itself with the representation of the heading signal in this region. We use neuronal ablations to show that the landmark responses, but not the whole field motion responses, require intact habenula input to the IPN. Overall our findings suggest the IPN as a site for integration of the heading signal from the aHB with visual information, shedding light on how different types of navigational signals are processed in the vertebrate brain.

neuroscience↗

bioRxiv2022

Comparing the representation of a simple visual stimulus across the cerebellar network

The cerebellum is a highly conserved structure of the vertebrate central nervous system that plays a role in the timing and calibration of motor sequences. Its function is supported by the convergence of fibers from granule cells (GCs) and inferior olive neurons (IONs) onto Purkinje cells (PCs). Theories of cerebellar function postulate that IONs convey error signals to PCs that, paired with the contextual information provided by GCs, can be used as a teaching signal to guide motor learning. Here, we use the larval zebrafish to investigate (i) how sensory representations of the same stimulus vary across GCs and IONs and (ii) how PC activity reflects these two different input streams. We use population calcium imaging to measure the cell responses to flashes of diverse luminance and duration to show that IONs and GCs encode different stimulus properties. First, most GCs show tonic and graded responses, as opposed to IONs, whose activity peaks only at on and off luminance transitions, in agreement with the notion that GCs and IONs encode context and error information, respectively. Secondly, we show that GC activity is patterned over time: some neurons had sustained responses for the entire duration of the stimulus, while in others activity was ramping up with slow time constants. This suggests that, by performing temporal integration, GCs could provide a basis that PCs may use to decode time. Finally, we show how PC activity can be largely reconstructed by a linear combination of granule cells and inferior olive neurons. Together, our observations give support to the notion of an error signal coming from IONs, and provide the first experimental evidence for a temporal patterning of GC activity over many seconds.

neuroscience↗

bioRxiv2022

Neural dynamics and architecture of the heading direction circuit in a vertebrate brain

Animals can use different strategies to navigate. They may guide their movements by relying on external cues in their environment or, alternatively, by using an internal cognitive map of the space around them and their position within it. An essential part of this representation are heading cells, neurons whose activity depends on the heading direction of the animal. Although those cells have been found in vertebrates, the full network has never been observed and there is very little mechanistic understanding of how these cells acquire their response properties. In this study, we use volumetric functional imaging in larval zebrafish to observe, for the first time in a vertebrate, a full network that encodes allocentric heading direction. This network of approximately one hundred inhibitory neurons is arranged in an anatomical circle in the anterior hindbrain. Its activity is driven purely by the integration of internally generated signals, indicating that a simple vertebrate brain can encode maps of how an animal moves within its surroundings. Single cell reconstructions of electron micrographs allow us to uncover how the connectivity pattern of neurons within the network supports the implementation of a ring attractor network. The neurons we identify share features with neurons in the dorsal tegmentum nucleus of rodents and the fly central complex, showing that similar connectivity and mechanistic principles underlie the generation of cognitive maps of heading direction across the animal kingdom.

neuroscience↗

bioRxiv2019

Valence and state-dependent population coding in dopaminergic neurons in the fly mushroom body

Neuromodulation permits flexibility of synapses, neural circuits and ultimately behavior. One neuromodulator, dopamine, has been studied extensively in its role as reward signal during learning and memory across animal species. Newer evidence suggests that dopaminergic neurons (DANs) can modulate sensory perception acutely, thereby allowing an animal to adapt its behavior and decision-making to its internal and behavioral state. In addition, some data indicate that DANs are heterogeneous and convey different types of information as a population. We have investigated DAN population activity and how it could encode relevant information about sensory stimuli and state by taking advantage of the confined anatomy of DANs innervating the mushroom body (MB) of the fly Drosophila melanogaster. Using in vivo calcium imaging and a custom 3D image registration method, we find that the activity of the population of MB DANs is predictive of the innate valence of an odor as well as the metabolic and mating state of the animal. Furthermore, DAN population activity is strongly correlated with walking or running, consistent with a role of dopamine in conveying behavioral state to the MB. Together our data and analysis suggest that distinct DAN population activities encode innate odor valence, movement and physiological state in a MB-compartment specific manner. We propose that dopamine shapes innate odor perception through combinatorial population coding of sensory valence, physiological and behavioral context.

neuroscience↗

bioRxiv2018

Stytra: an open-source, integrated system for stimulation, tracking and closed-loop behavioral experiments

We present Stytra, a flexible, open-source software package, written in Python, that we designed to cover all the general requirements involved in larval zebrafish behavioral experiments. It allows timed stimulus presentation, interfacing with external devices and simultaneous real-time tracking of position, tail and eye motion in both freely-swimming and head-restrained preparations. It logs in standardized formats all recorded quantities, metadata, and code version to allow full provenance tracking, from data acquisition through analysis to publication. The package is modular and expandable for different experimental protocols and setups. Current releases can be found at https://github.com/portugueslab/stytra. We also provide complete documentation with examples for extending the package to new stimuli and hardware, as well as a schema and parts list for behavioral setups. We showcase Stytra by reproducing two previously behavioral protocols, one with head-restrained and the other with freely-swimming larvae, as well as an experiment in which the software is used in the context of a calcium imaging experiment, where it can trigger and communicate with other acquisition devices. Our aims are to help laboratories with little or no experience in the field to start implementing behavioral experiments and to provide a platform for sharing stimulus protocols to enable easy reproduction of experiments and straightforward validation. In addition, Stytra can easily serve as a base platform to design behavioral experiments in other model organisms.

neuroscience↗