Biology subjects

Dowell, C. K.

Publications and source records attributed to Dowell, C. K..

3 recordsLinked to original sources

bioRxiv2025

A vector-based strategy for olfactory navigation in Drosophila

Odors serve as essential cues for navigation. Although tracking an odor plume has been modeled as a reflexive process, it remains unclear whether animals can use memories of their past odor encounters to infer the spatial structure of their chemical environment or their location within it. Here we developed a virtual-reality olfactory paradigm that allows head-fixed Drosophila to navigate structured chemical landscapes, offering insight into how memory mechanisms shape their navigational strategies. We found that flies track an appetitive odor corridor by following its boundary, alternating between rapid counterturns to exit the plume and directed returns to its edge. Using a combination of behavioral modeling, functional calcium imaging, and neural perturbations, we demonstrate that this edge-tracking strategy relies on vector-based computations within the Drosophila central complex in which flies store and dynamically update memories of the direction to return them to the plumes boundary. Consistent with this, we find that FC2 neurons within the fan-shaped body, which encode a flys navigational goal, signal the direction back to the odor boundary when flies are outside the plume. Together, our studies suggest that flies leverage the plumes boundary as a dynamic landmark to guide their navigation, analogous to the memory-based strategies other insects use for long-distance migration or homing to their nests. Plume tracking thus uses components of a conserved navigational toolkit, enabling flies to use memory mechanisms to navigate through a complex shifting chemical landscape.

neuroscience↗

bioRxiv2024

Subsets of extraocular motoneurons produce kinematically distinct saccades during hunting and exploration.

Animals construct diverse behavioural repertoires by moving a limited number of body parts with varied kinematics and patterns of coordination. There is evidence that distinct movements can be generated by changes in activity dynamics within a common pool of motoneurons, or by selectively engaging specific subsets of motoneurons in a task-dependent manner. However, in most cases we have an incomplete understanding of the patterns of motoneuron activity that generate distinct actions and how upstream premotor circuits select and assemble such motor programmes. In this study, we used two closely related but kinematically distinct types of saccadic eye movement in larval zebrafish as a model to examine circuit control of movement diversity. In contrast to the prevailing view of a final common pathway, we found that in oculomotor nucleus, distinct subsets of motoneurons were engaged for each saccade type. This type-specific recruitment was topographically organised and aligned with ultrastructural differ-ences in motoneuron morphology and afferent synaptic innervation. Medially located motoneu-rons were active for both saccade types and circuit tracing revealed a type-agnostic premotor pathway that appears to control their recruitment. By contrast, a laterally located subset of motoneurons was specifically active for hunting-associated saccades and received premotor in-put from pretectal hunting command neurons. Our data support a model in which generalist and action-specific premotor pathways engage distinct subsets of motoneurons to elicit varied movements of the same body part that subserve distinct behavioural functions.

neuroscience↗

bioRxiv2023

The saccadic repertoire of larval zebrafish reveals kinematically distinct saccades that are used in specific behavioural contexts.

Saccades are rapid eye movements that are used by all species with good vision. They have been extensively studied, especially in vertebrates, and are understood to be controlled by a conserved brainstem circuit. However, despite the fact that saccades play important roles during diverse visually guided behaviours, little is known about whether their properties, including the manner in which they are coordinated with head/body movements, vary in the context of different visuomotor tasks. Here, we characterise the saccadic repertoire of larval zebrafish and identify five saccade types, defined by systematic differences in kinematics and binocular coordination. Each type was differentially expressed during visually guided behaviours. Conjugate saccades form a large group that are used in at least four contexts: Fast phases of the optokinetic nystagmus, visual scanning in stationary animals, and to shift or maintain gaze during locomotion. Convergent saccades play a specialised role during hunting and are coordinated with body movements to foveate prey. Furthermore, conjugate and convergent saccades follow distinct velocity main sequence relationships and show differences in the millisecond coordination of the eyes and body, pointing to differences in underlying neurophysiology. In summary, this study reveals unexpected diversity in horizontal saccades and predicts saccade type-specific neural activity patterns. HighlightsO_LIKinematic analysis of thousands of rapid eye movements reveals five saccade types. C_LIO_LIConjugate saccades have at least four identifiable visual functions. C_LIO_LIConvergent saccades are coordinated with body movements to foveate prey. C_LIO_LITiming, kinematics and main sequence relationships indicate saccade type-specific neural control. C_LI

neuroscience↗