Biology subjects

Risse, B.

Publications and source records attributed to Risse, B..

3 recordsLinked to original sources

bioRxiv2023

Compensation to visual impairments and behavioral plasticity in navigating ants

Desert ants are known to rely heavily on vision while venturing for food and returning to the nest. During these foraging trips, ants memorize and recognize their visual surroundings, which enables them to recapitulate individually learnt routes in a fast and effective manner. The compound eyes are crucial for such visual navigation; however, it remains unclear how information from both eyes are integrated and how ants cope with visual impairment. Here we manipulated the ants visual system by covering one of the two compound eyes and analyzed their ability to recognize familiar views in various situations. Monocular ants showed an immediate disruption of their ability to recapitulate their familiar route. However, they were able to compensate for the visual impairment in a few hours by restarting a route-learning ontogeny, as naive ants do. This re-learning process with one eye forms novel memories, without erasing the previous memories acquired with two eyes. Additionally, ants having learnt a route with one eye only are unable to recognize it with two eyes, even though more information is available. Together, this shows that visual memories are encoded and recalled in an egocentric and fundamentally binocular way, where the visual input as a whole must be matched to enable recognition. We show how this kind of visual processing fits with their neural circuitry. Significance StatementIf humans look at the world with both eyes, they have no problem to then recognize it with one eye only, and vice-versa. Thus, our way of encoding the world is robust to changes of the visual field. Yet ants do so very differently. Views learnt with two eyes can only be recognized with two eyes, and views learnt with one eye can only be recognized with one eyes (the same eye). However, this rigidity is compensated by a remarkable behavioral flexibility. Upon covering one eye, ants - which can no longer recognize their familiar surroundings - will restart a learning process to store these novel visual inputs in a parallel memory and resume their normal foraging activity.

animal behavior and cognition↗

bioRxiv2018

From skylight input to behavioural output: a computational model of the insect polarised light compass

Many insects navigate by integrating the distances and directions travelled on an outward path, allowing direct return to the starting point. Fundamental to the reliability of this process is the use of a neural compass based on external celestial cues. Here we examine how such compass information could be reliably computed by the insect brain, given realistic constraints on the sky polarisation pattern and the insect eye sensor array. By processing the degree of polarisation in different directions for different parts of the sky, our model can directly estimate the solar azimuth and also infer the confidence of the estimate. We introduce a method to correct for tilting of the sensor array, as might be caused by travel over uneven terrain. We also show that the confidence can be used to approximate the change in sun position over time, allowing the compass to remain fixed with respect to true north during long excursions. We demonstrate that the compass is robust to disturbances and can be effectively used as input to an existing neural model of insect path integration. We discuss the plausibility of our model to be mapped to known neural circuits, and to be implemented for robot navigation.\n\nAuthor summaryWe propose a new hypothesis for how insects process polarised skylight to extract global orientation information that can be used for accurate path integration. Our model solves the problem of solar/anti-solar meridian ambiguity by using a biologically constrained sensor array, and includes methods to deal with tilt and time, providing a complete insect celestial compass output. We analyse the performance of the model using a realistic sky simulation and various forms of disturbances, and compare the results to both engineering approaches and biological data.

animal behavior and cognition↗

bioRxiv2018

A MULTI-PURPOSE WORM TRACKER BASED ON FIM

The analysis of behavioural traits of Caenorhabditis elegans is an important method for understanding neuromuscular functions and diseases. Since C. elegans is a small and translucent animal which conducts a variety of complex movement patterns many different imaging and tracking protocols are used for different behavioural traits. Thus a unified multi-purpose imaging and tracking system for multiple behavioural assays would be favourable to improve statistical strength and comparability. Here we present a novel worm tracking toolbox based on the FIM (Frustrated total internal reflection (FTIR) based Imaging Method) system incorporating a variety of different behavioural assays into a single imaging and tracking setup.\n\nFirst, we apply the FTIR-based imaging method to C. elegans, thus we are able to improve the overall image quality compared to state of the art recording techniques. This method is easy to use and can be utilised to image animals during crawling on agar and trashing in water. Second, we extended the existing FIMTrack software to extract skeleton-based posture and motion features of multiple worms with very high accuracy in a comparatively large field-of-view. Third, we integrated a variety of different assays into this system. We carried out chemotaxis assays both with attractant and repellent chemicals. A novel electrotaxis dome compatible with FIM allows locomotion analyses that are not corrupted by random aberrations in unrestricted movement. Additionally, the FIM based worm tracker is able to analyse thrashing behaviour of multiple worms automatically with a high accuracy. Finally we demonstrate the capacity of the FIM based worm tracker to observe GFP signals in C. elegans worms. We tested our new C. elegans tracking suite with mutant strains of the ubiquitin-fold modifier 1 (Ufm1) cascade. We identified intermediate chemosensory phenotypes in Ufm1 cascade mutants which were previously undetected.

animal behavior and cognition↗