Biology subjects

Straka, H.

Publications and source records attributed to Straka, H..

5 recordsLinked to original sources

bioRxiv2023

Bilateral retinofugal pathfinding impairments limit behavioral compensation in near-congenital one-eyed Xenopus laevis

To generate a coherent visual percept, information from both eyes must be appropriately transmitted into the brain, where binocular integration forms the substrate for visuomotor behaviors. To establish the anatomical substrate for binocular integration, the presence of bilateral eyes and interaction of both optic nerves during retinotectal development play a key role. However, the extent to which embryonic monocularly derived visual circuits can convey visuomotor behaviors is unknown. In this study, we assessed the retinotectal anatomy and visuomotor performance of embryonically generated one-eyed tadpoles. In one-eyed animals, the axons of retinal ganglion cells from the singular remaining eye exhibited striking irregularities in their central projections in the brain, generating a non-canonical ipsilateral retinotectal projection. This data is indicative of impaired pathfinding abilities. We further show that these novel projections are correlated with an impairment of behavioral compensation for the loss of one eye.

neuroscience↗

bioRxiv2023

Magnetic actuation of otoliths allows behavioral and brain-wide neuronal exploration of vestibulo-motor processing in larval zebrafish.

The vestibular system in the inner ear plays a central role in sensorimotor control by informing the brain about the orientation and acceleration of the head. However, most experiments in neurophysiology are performed using head-fixed configurations, depriving animals of vestibular inputs. To overcome this limitation, we decorated the utricular otolith of the vestibular system in larval zebrafish with paramagnetic nanoparticles. This procedure effectively endowed the animal with magneto-sensitive capacities: applied magnetic field gradients induced forces on the otoliths resulting in robust behavioral responses comparable to that evoked by rotating the animal by up to 25{degrees}. We recorded the whole-brain neuronal response to this fictive motion stimulation using light-sheet functional imaging. Experiments performed in unilaterally injected fish revealed the activation of a commissural inhibition between the brain hemispheres. This magnetic-based stimulation technique for larval zebrafish opens new perspectives to functionally dissect the neural circuits underlying vestibular processing and to develop multisensory virtual environments, including vestibular feedback. HighlightsO_LIAfter injecting a ferrofluid into the inner ear of a larval zebrafish, the ear-stones can be actuated via magnetic forces. C_LIO_LIThis method allows one to elicit vestibular-like behavioral responses without impairing physiological inner ear functions. C_LIO_LIIt is compatible with brain-scale functional imaging and thus offers a promising avenue to investigate the neural underpinnings of vestibular-driven behaviors. C_LI eTOCFerrofluid injection into zebrafish inner ear allows magnetic manipulation of ear-stones to evoke vestibular responses in static animals. This in vivo method is compatible with brain-scale imaging, offering a promising approach to investigate neural mechanisms underlying vestibular-driven behaviors.

neuroscience↗

bioRxiv2022

Strategies of developmental vestibular plasticity after unilateral embryonic ear removal in Xenopus laevis

Appropriate gaze control mechanisms rely on bilateral mirror-symmetric vestibular endorgans, central circuits, and extraocular motor effectors. Embryonic removal of one inner ear prior to the formation of these structures was used to evaluate the extent to which animals can develop appropriate motor outputs in the presence of only a singular inner ear. Near-congenital one-eared tadpoles subjected to separate or combinatorial visuo-vestibular motion stimulation exhibited vestibular-ocular reflexes, though smaller in gain compared to controls, whereas isolated visuo-motor responses remained largely unaltered. Surprisingly, direction-specific responses in one-eared tadpoles revealed a spectrum of vestibulo-ocular reflex performance, where in many cases rather robust responses were observed during head motion towards the missing ear. Rotation toward the remaining ear elicited eye movements which were often severely attenuated. This suggests that embryonically generated one-eared animals develop bidirectional vestibular signal detection and downstream processing capacities that allow activation of robust compensatory eye movements. However, this capability seems to occur at the expense of performance of vestibular reflexes during motion in the canonical activation direction of the singular ear. Consequently, the development of central vestibulo-motor circuits in one-eared animals likely relies on strategies in which the outcome for gaze stabilization is driven by balanced homeostatic levels and individual temporal tuning of abducens motoneuron activity. Despite the lack of bilateral symmetric vestibular afferent input, the developing central nervous system is capable of creating a framework for symmetric sensorimotor transformations.

neuroscience↗

bioRxiv2021

Locomotion-induced ocular motor behavior in larval Xenopus is developmentally tuned by visuo-vestibular reflexes

Locomotion requires neural computations to maintain stable perception of the world despite disturbing consequences of the motor behavior on sensory stability. The developmental establishment of locomotor proficiency is therefore accompanied by a concurrent maturation of gaze-stabilizing motor behaviors. Using developing larval Xenopus, we demonstrate mutual plasticity of predictive spinal locomotor efference copies and multi-sensory motion signals with the aim to constantly ensure dynamically adequate eye movements during swimming. Following simultaneous ontogenetic onsets of locomotion, spino-ocular, optokinetic and otolith-ocular motor behaviors, locomotor efference copy-driven eye movements improve through gradually augmenting influences of semicircular canal signals. Accordingly, neuronal computations change from a predominating cancelation of angular vestibulo-ocular reflexes by locomotor efference copies in young larvae to a summation of these signals in older larvae. The developmental switch occurs in synchrony with a reduced efficacy of the tail-undulatory locomotor pattern generator causing gradually decaying influences on the ocular motor output.

neuroscience↗

bioRxiv2017

Wall following in Xenopus laevis is passive

The tendency of animals to follow boundaries within their environment can serve as a strategy for spatial learning or defence. We examined whether animals of Xenopus laevis employ such a strategy by characterizing their swimming behaviour. We also investigated potential developmental changes, the influence of tentacles, which some of the developmental stages possess, and whether wall-following is active (animals seek out wall contact) or passive. Animals swimming movements were recorded with a camera from above in a square tank with shallow water and their trajectories were analysed especially for proximity to the nearest wall. With the exception of young larvae, in which wall following was less strong, the vast majority of animals - tadpoles and froglets - spent more time near the wall than what would be expected from the proportion of the area near the wall. The total distance covered was not a confounding factor. Wall following was also not influenced by whether the surrounding of the tank was black or white, illuminated by infrared light, or by the presence or absence of tentacles. Animals were stronger wall followers in smaller tanks. When given a choice in a convex tank to swim straight and leave the wall or turn to follow the wall, the animals consistently left the wall, indicating that wall following in Xenopus laevis is passive. This implies that wall following behaviour in Xenopus derives from constraints imposed by the environment (or the experimenter) and is unlikely a strategy for spatial learning or safety-seeking.\n\nSummary statementXenopus laevis tadpoles and froglets tend to swim along the walls of a square tank; but this wall following is passive - in a convex tank, they leave the wall.

animal behavior and cognition↗