Biology subjects

Semmelhack, J. L.

Publications and source records attributed to Semmelhack, J. L..

3 recordsLinked to original sources

bioRxiv2024

Integration of binocular vision and motor state to promote prey pursuit

Most animals with two eyes combine the inputs to achieve binocular vision, which can serve numerous functions, and is particularly useful in hunting prey. However, the mechanisms by which visual information from the two eyes are combined remain largely unknown. Here, we designed a device to reversibly occlude the eyes of a head-fixed zebrafish larva, and used large-scale volumetric two-photon imaging to identify binocular neurons that respond to prey stimuli. We found these binocular prey-responsive neurons (bino-PRNs) were primarily located in three areas, the pretectum, thalamus, and nucleus isthmi. We then characterized the bino-PRNs functional properties, and found that their left and right eye receptive fields are offset to varying degrees, which would correspond to objects at naturalistic hunting distances for a larva with converged eyes. We also found that bino-PRNs have a significantly greater response in hunting trials, which could be the result of an eye convergence-related corollary discharge. We then optogenetically induced prey capture eye and tail movements, and found that this hunting command activates prey responsive neurons in the pretectum, thalamus, and nucleus isthmi. These findings indicate that bino-PRNs receive visual and motor input that would allow them to encode prey position in three dimensions.

neuroscience↗

bioRxiv2024

The visuomotor transformations underlying defensive behaviors and hunting

The visual system can process diverse stimuli and make the decision to execute appropriate behaviors, but it remains unclear where and how this transformation takes place. We imaged the zebrafish visual system while larvae responded with hunting, freezing, and escape behaviors, and systematically identified visually driven neurons and behaviorally correlated sensorimotor neurons. Our analyses indicate within the optic tectum, broadly tuned sensory neurons are functionally connected to sensorimotor neurons that respond specifically during one behavior, transforming visual information into motor output. We also identified sensorimotor neurons in four other areas downstream of the tectum, and these neurons are also specific for one behavior, indicating that once the decision to behave has been made, the segregation of the pathways continues in later areas. Our findings suggest that the tectum receives visual sensory information and is responsible for selecting a single behavioral outcome, which is then relayed to downstream areas. Significance statementHere, we developed a novel visually-evoked freezing paradigm in zebrafish, and combined this with escape and hunting behaviors to ask how visual stimuli are identified and converted into different behavioral outcomes. We found that the optic tectum contains neurons that detect all three stimuli, as well as sensorimotor neurons for the three behaviors, suggesting that it is a site of sensorimotor transformation, which was supported by our analysis of correlations between the populations. The sensorimotor neurons in the tectum are highly specific for one behavior, and this segregation is maintained in the three downstream areas where we also identified sensorimotor neurons, indicating that the tectum flexibly transforms visual information into a single behavioral output.

neuroscience↗

bioRxiv2019

Deconstructing hunting behavior reveals a tightly coupled stimulus-response loop

Animals build behavioral sequences out of simple stereotyped actions. A comprehensive characterization of these actions and the rules underlying their temporal organization is necessary to understand sensorimotor transformations performed by the brain. Here, we use unsupervised methods to study behavioral sequences in zebrafish larvae. Generating a map of swim bouts, we reveal that fish modulate their tail movements along a continuum. We cluster bouts that share common kinematic features and contribute to similar behavioral sequences into seven modules. Behavioral sequences comprising a subset of modules bring prey into the anterior dorsal visual field of the larvae. Fish then release a capture maneuver comprising a stereotyped jaw movement and fine-tuned stereotyped tail movements to capture prey at various distances. We demonstrate that changes to chaining dynamics, but not module production, underlie prey capture deficits in two visually impaired mutants. Our analysis thus reveals the temporal organization of a vertebrate hunting behavior, with the implication that different neural architectures underlie prey pursuit and capture.

neuroscience↗