Louis DEVERS – PhD defense

Defense in french

  Zoom link

Team : Collective Animal Behaviour (CAB), CRCA-CBI

Supervisor : Vincent Fourcassié (CRCA-CBI)

Committee members :

  • Audrey Dussutour, Directrice de recherche au CRCA-CBI (Toulouse)
  • François-Xavier Dechaume-Moncharmont, Professeur, Laboratoire d’Ecologie des Hydrosystèmes Naturels et Anthropisés, Université Claude Bernanrd Lyon 1
  • Thibaud Monnin, Directeur de Recherche, Institut d’Écologie et des Sciences de l’Environnement de Paris (iEES Paris), Sorbonne Université
  • Andrea Perna, Senior Lecturer, Assistant professor, IMT School for Advanced Studies in Lucca, Italy
  • Claire Detrain, Directrice de recherche au FRS – FNRS (Bruxelles)
  • Vincent Fourcassié, Directeur de recherche, CRCA-CBI (Toulouse)

Abstract :

Ants are well known for their capacity to self-organize and for their feats in foraging and transport activities, that they are able to achieve with relatively limited cognitive capacities. They are able to solve with disconcerting ease complex problems, such as finding the shortest paths among several options, ensuring the thermoregulation of a nest or regulating the colony’s energy and nutrients intake. The solution to a collective problem in ants emerges from the sum of simple, local interactions between them and their environment (by depositing pheromones, for instance). Ants are therefore a relevant model for studying decision-making processes at the interface between simple, cognitively limited individuals and a complex, relevant or even optimal collective.

One of the tasks in which ants excel is transport. In fact, they are one of the few group of species that can move objects of significant mass over long distances. In particular, they are able to organise themselves around a load and to carry it collectively in a way that allow them to overcome their individual limitations. Load-carrying tasks are omnipresent during foraging, nest building and brood care, and are therefore essential for the colony. Each decision to carry an object from point A to point B entails a potentially significant energy cost for the ants. Therefore, a form of effort regulation can be expected. The aim of this thesis is to study decision-making processes in ants in the context of load transport in relation with the energy costs produced. The main question motivating our research is therefore: what role does energy regulation play in the decision-making processes underlying load transport in ants?

This thesis consists of two chapters dealing with the same question studied on two different species in two different contexts. Firstly, we studied load transport in a binary choice task taking place during the clearing of an underground gallery in the species Messor barbarus. Secondly, we examined the impact of load mobility in a context of collective transport in the species Aphaenogaster senilis.

We quantified the quality of the transports performed by ants using objective measures, such as efficiency and mechanical work with mechanical models designed for this thesis. We focused on mandibular grasps on the load as the basis of load transport behaviour. Mandibular grasps mark indeed both the initiative of the transport (at the start of the grasp) and the persistence on the task (through their duration).

We observed that ants, when faced with a choice between two options to remove an object blocking a gallery with different inclinations, pulled the load towards the side requiring the least mechanical work in 75% of cases. However, while individual ants seem to solve this task efficiently, the efficiency remains relatively low at the collective level. We also observed that while the duration of mandibular grasps was shorter on tough tasks, the amount of energy expended remained unchanged. The amount of energy expended seems to depend on the muscular capacities of the ants, which suggests that they make a similar relative effort at each transport attempt.

During collective transports, we observed that ants did not arrange themselves randomly around the transported load. The arrangements preferred by ants are those that reduce the total forces required to keep the object above ground. This preference disappears when the load is held still by a pin. We also noted that disadvantageous arrangements are abandoned more quickly than others, showing a form of energetic regulation of behaviour on the task.

 Keywords : Quantitative ethology, Decision making, Load transportation, Optimisation, Collective behavior, Ants

Manon TERNOIS – PhD defense

PhD defense in french

Zoom link


Supervisors : Audrey Dussutour (CRCA-CBI) & Emmanuel Flahaut (CIRIMAT)

Committee members :

  • Mme Anna Bencsik, ANSES site de lyon, Rapporteure
  • Mme Catherine Santaella, CNRS Institut de Biosciences et Biotechnologies d’Aix-Marseille Université, Rapporteure
  • Mme Mélanie Auffan, CNRS CEREGE, Examinatrice
  • Mme Noélie Davezac, CNRS CRCA-CBI, Examinatrice
  • Mme Audrey Dussutour, CNRS CRCA-CBI, Directrice de thèse
  • Emmanuel Flahaut, CNRS CIRIMAT, Co-directeur de thèse

Abstract :

Carbon nanotubes (CNTs) are carbon nanomaterials with industrial development having reached a stage of maturity enabling them to be used in many everyday applications (composite materials, coatings, energy storage, biomedical, etc.). They are a source of concern for human and environmental health because they can be released into the environment at each stage of their life cycle (production, use and end-of-life of finished products). Even though studies relating to their potential impact on health and the environment started some fifteen years ago, many questions remain unanswered.

The aim of this thesis is to assess the effects of CNTs (we used double-walled CNTs (DWCNTs) as representatives of all the different types of CNTs) on an emerging cellular model at the interface between environmental toxicology and cellular toxicology: the myxomycete Physarum polycephalum. On the one hand, P. polycephalum lives mainly in soil litter, a medium that receives and concentrates pollution, where it plays an essential role in the ecosystem by actively participating in the recycling of organic matter. In addition, the simple organization of P. polycephalum (a unicellular eukaryote) enabled us to assess the internalization and bioaccumulation of CNTs within the cell. Finally, the behavioral complexity of P. polycephalum (problem solving and adaptation of their behavior to environmental diversity) enabled us to measure the effects of CNTs on different behavioral variables such as migration speed and decision making. We first demonstrated that CNTs are internalized in the cell, do not bioaccumulate and are rapidly excreted. We then demonstrated that CNTs induce variable effects on the behavior of P. polycephalum (slowed or accelerated speed, optimal or non-optimal decision-making), which differ depending on the strain used, the duration of exposure, the exposure concentration and the substrate used. By combining exposure to CNT with other stress factors (aversive compound, ageing, temperature), we observed a behavioral response that remains extremely variable.

This work shows that CNTs have moderate and difficult-to-quantify effects on the behavioral response of P. polycephalum. In the future, it will be interesting to examine the effects of CNTs on the physiological and molecular response of this organism.

© Photo : Romain Hacquet – @aker.romain


Léo CLEMENT – PhD Defense

PhD defense in english

 Zoom link : https://us06web.zoom.us/j/86474991977

Team : BeeAntCE

Supervisors : Antoine WYSTRACH & Jacques GAUTRAIS

Committee members :

  • M. Andrew PHILIPPIDES, University of Sussex, Rapporteur
  • Mme Emily BAIRD, Stockholm University, Examinatrice
  • M. Antoine WYSTRACH, CNRS, Co-directeur de thèse
  • M. Franck RUFFIER, CNRS – Institut des Sciences du Mouvement Marseille, Examinateur
  • Mme AUDREY DUSSUTOUR, CNRS, Examinatrice
  • M. Simon BENHAMOU, CNRS / CEFE, Rapporteur

Abstract :

Navigation in natural environments is an essential ability for animals, but it can be highly challenging to achieve due to the complex, ever-changing, nature of the environment they navigate through. Solitary foraging hymenopterans, such as ants, have evolved remarkable abilities to navigate in these complex environments despite a nervous system much simpler than those of vertebrates. What’s more, ants’ displacements can be easily tracked, thus providing a powerful system to investigate the mechanisms underlying navigation in the wild.

Thanks to the development and application of neurobiological tools in insects, we now have an increasingly detailed description of the circuits in these “mini-brains”. These networks, composed of a large number of interacting units (neurons), are the site of very dynamic internal activity that allows for an effective coupling of the organism with its environment. The field of insect navigation has integrated this neurobiological knowledge with a long-standing tradition of behavioural experiments, as well as in-silico modelling approaches, to gain a deeper understanding of the mechanisms and emergent properties in these systems. This multi-level approach has provided valuable insights into how complex behaviour emerges.

This thesis presents an integrative approach combining behavioural experiments and computational modelling with the aim to gain further understanding of the mechanisms of ant navigation.

First, I investigate the dynamics of visual learning when ants navigate in natural conditions. There are already good insights into how the insect brain can memorize and recognize views, and how these views might be used for navigation. However, practically nothing is known about how learning is orchestrated in the first place. Learning a route cannot be governed only by rewards and punishments but may happen ‘continuously’; a vague concept so-called ‘latent learning’ in the vertebrate literature. By combining field experiments and modelling, I show that ants learn the route they travel in a continuous fashion. I also explain how such a continuous mechanism of learning and recalling can be implemented in the light of the known insect brain circuitry. Our work shows that such a continuous spatial learning is supported by egocentric route memories rather than a map-like reconstruction of space.

Secondly, I shed light on how higher-level visual recognition and lower-level motor control interact. Most -if not all-studies in animal navigation have focused on higher level strategies such as the use of path integration, the recognition of learnt visual cues and the reconstruction of so-called cognitive maps. However, how these higher-level strategies are supported by lower level (often more ancestral) motor behaviours remains largely unexplored. We used a multidirectional treadmill set up -a trackball- to record with high precision the motor behaviour of ants directly in their natural environment. Results explain how higher-level navigation strategies are supported by lower-level motor control and demonstrate the existence – and importance – of an intrinsic oscillator at the core of navigational behaviours.

Finally, I investigate the specific cues encoded by ants in visual scenes. Insects’ visual system performs various feature extractions. I used virtual reality (VR) to explore which visual cues are encoded by ants to consider the presence of a natural panorama and trigger exploratory behaviours. Through this approach, I shed light on the perceptual encoding of naturalistic environments and provide a promising avenue for further investigation using virtual reality setups.

Taken together, this thesis allowed me to understand that behaviour, rather than being a set of discrete actions, is a continuous process where intelligence can be seen as an emergent property. I employed various approaches, some successful, some failing, but all improved my vision of how I should ask and answer a scientific question.

Nour SGHAIER – PhD defense

PhD defense in french

 Zoom link coming soon

Team : CAB

Supervisors : Pierre Moretto (CRCA-CBI) and Nicolas Turpin (IRISSE)

Committee members :

  • BARBIER Frank (Rapporteur), Université Polytechnique Hauts-de-France, Laboratoire d’Automatique, de Mécanique et d’Informatique industrielles et Humaines (LAMIH UMR-CNRS 8201)
  • CHEZE Laurence (Rapporteure), Université Gustave Eiffel, Laboratoire de biomécanique et mécanique des chocs (LBMC UMR_T9406)
  • MARIN Frédéric (Examinateur), Université Technologie de Compiègne, Biomécanique et Bioingénierie (BMBI – UMR CNRS 7338)
  • CHAVET Pascale (Examinatrice), Université Aix-Marseille, Institut des Sciences du Mouvement (ISM – UMR 7287)
  • MORETTO Pierre (Directeur de thèse), Université Paul Sabatier, Centre de Recherches sur la Cognition Animale (CRCA – UMR 5169)
  • TURPIN Nicolas (Codirecteur de thèse), Université de la Réunion, Ingénierie de la Santé, du Sport et de l’Environnement (IRISSE – UR 4075)

Abstract :

Collective load transport is a common task that we perform in our daily and professional lives. It involves the collaboration of two or more people to lift and move an object. Until now, the mechanisms underlying this movement and the collaboration have not been widely discussed in the literature. This thesis is part of the ANR CoBot project (Projet-ANR-18-CE10-0003) which aims to make a humanoid robot collaborative during load carrying. The objective of this work is to study the human-human interaction during a load transport, more particularly during a table or stretcher transport, and to extract biomechanical parameters that account for the control of this task. Three main questions motivate this project: (1) Does the participants’ individual and collective efficiency is altered with the task complexity? (2) Are locomotor involvement and strategies affected by backward and forward walking? and (3) Is the energy transfer occurring in the upper limbs efficient during load transport?

To answer these questions, the analysis carried out was based on techniques and methods already described in the literature and focused more specifically on: (i) an analysis of the locomotor pattern, (ii) an analysis of joint efforts and (iii) an analysis of energy transfer in the upper limbs. Our results show an alteration in the pendulum-like-behaviour of the participants’ centre of mass when adding a precision task to load transport. We also identified backward walking as the major factor impacting the locomotor patterns and efficiency in stretcher transport. The results show a distinct involvement and role for each participant. Depending on their placement and perceived environmental feedback, one participant will guide the movement, while the other will lift the load and follow the movement. These results are supported by the third study which shows that the participant who guides the movement generates and dissipates the energy required for handling the load, while the ‘follower’ is neutral. These results provide further insight into the interactions required during load transport and offer a wide range of potential applications. Indeed, the results can be used to improve control in cobotics, securing human-machine interactions, both during interactions with cobots and during tasks assisted by exoskeletons. Finally, our results should help to specify new ergonomic recommendations.


Ricardo SANTIAGO ARAUJO – PhD defense

PhD defense in english


Team : PRADA (EDB)

Supervisors : Guillaume Isabel (CRCA-CBI) et Jean-Louis Hemptinne (EDB)

Committee members :

  • Examinateur: Director of Research Etienne Danchin, Université Toulouse III
  • Co-directeur: Prof. Guillaume Isabel, Université Toulouse III
  • Examinateur: Prof. Paul Seabright, Université Toulouse I
  • Examinateur: Dr. Sabine Noebel, Martin-Luther-University
  • Rapporteur: Prof. Andrew Whiten, University of Saint Andrews
  • Rapporteur:  Prof. Boris van Leeuwen, University of Tilburg
  • Rapporteur: Prof. Jean-Christophe Billeter, University of Groningen

Abstract :

Social learning encompasses all the distinct ways an individual learns from others and has already been identified in many non-human vertebrate and invertebrate species. Conformity, the disproportionate copying of the most common trait in a group, has come to the fore as a major driver in the emergence of culture.

In this interdisciplinary thesis, I study social learning, conformity and related processes in both humans (Homo sapiens, Chapter I) and the fruit fly (Drosophila melanogaster, Chapter II), to (1) build a better understanding of these phenomena across species; (2) find commonalities and differences between these two species; (3) help elucidate the nature of human conformity and (4) contribute to reconciling the distinct approaches from different disciplines.

In the first chapter, we used a novel experimental tool-set in two online experiments in humans to test the role of social information in people’s perception of their environment This provides evidence for conformity in two different contexts. Finally, we tested whether conformity is stronger in mate choice (as suggested by our colleagues in Toulouse), but find no evidence for it when compared to the alternative decision domain of ratio estimation.

In the second chapter, we focused on mate-copying in D. melanogaster to investigate how individuals adjust their behavior in response to social information that changes over time, specifically how they deal with sequentially presented items of conflicting social information. To tackle this question, we used a new video recording protocol in an experiment with two demonstrations one after the other, each consisting of an image of a model female copulating with a different male phenotype. Unexpectedly, in our experimental design, females tended to prefer the male phenotype of the first demonstration, which is suggestive of a primacy bias, defying the intuition that social learning would prioritize recent social information that should, in theory, reflect more accurately the current environment.


Ana MORAN – PhD defense

PhD defense in english

Zoom link coming soon

Team : IVEP

Supervisor : Jacques Gautrais (CRCA-CBI)

Committee members :

  • Dr. Simon Benhamou – CEFE, Montpellier – Reviewer
  • Dr. Carmen Bessa-Gomes – AgroParisTech, Paris – Reviewer
  • Pr. Richard Fournier – LaPlace, Toulouse – Examiner
  • Pr. Frederic Bartumeus – ICREA, Spain – Examiner
  • Dr. Jacques Gautrais – Research Center on Animal Cognition, Toulouse – Thesis supervisor
  • Dr. Alfonso Pérez-Escudero – Research Center on Animal Cognition, Toulouse – Guest
  • Dr. Mathieu Lihoreau – Research Center on Animal Cognition, Toulouse – Guest

Abstract :

Understanding how pollinators move across space is key to understanding plant mating patterns. Bees are usually assumed to search for flowers randomly or using simple movement rules so that the probability of discovering a flower depends primarily on its distance to the nest. However, experimental work shows this is not always the case.

Until now, no one has successfully enunciated a realistic model of bee movement that considers the fact that they are Central Place Foragers and thus they start and end all their movements in the same place: the nest.

To further our knowledge of the exploratory movement of central place foraging bees, I propose a model of central place foraging that produces realistic bee trajectories by accounting for the autocorrelation of the bee’s angular speed, the attraction to the nest (homing), and Gaussian noise.

The four parameters of this model have been tuned based on experimental trajectories collected on bumblebees (Bombus terrestris) in the field. The model not only has the potential to describe the movement patterns of bees but also those of other central place forager animals.

The proposed model paves the way to compute theoretical predictions about pollination in the field. Here, I explored the statistics of flower discovery, depending on flower patch sizes and densities.

Simulations of bumblebee trajectories highlight two effects that were previously overlooked: a masking effect that reduces the detection of flowers close to another and a scale effect that modulates this first effect as a function of the distance between flowers.

At the plant level, flowers distant from the nest were more often discovered by bees in low-density environments. At the colony level, foragers found the most flowers when they were small and at medium densities. These results suggest that pollination would be optimized in a range of intermediate flower densities: when the density is too low, few flowers are discovered; when the density is too high, flowers distant from the nest become masked by closer ones (due to the masking effect).

These results indicate that the processes of search and discovery of resources are potentially more complex than usually assumed, and question the importance of resource distribution and abundance on bee foraging success and plant pollination.

© Crédit photo: Romain Hacquet – @aker.romain


Guillaume BOUISSET – PhD defense

PhD defense in french

Zoom link : https://univ-tlse3-fr.zoom.us/j/99182743985


Supervisor : Lauve VERRET (CRCA-CBI)

Committee members :

  • Bertrand Lamboblez – rapporteur
  • Hélène Marie – rapporteure
  • Francesca Sargolini – rapporteure
  • Vincent Fourcassié – examinateur
  • Laure Verret – directrice de thèse

Abstract :

Alzheimer’s disease (AD) is associated with abnormal brain activity that underlies cognitive deficits. It is now well-established that dysfunction of GABAergic neurons expressing parvalbumin (PV) protein contributes to these alterations in brain activity—and thus to cognitive impairment—in mouse models and AD patients. In the adult brain, PV neurons are frequently associated with a specialized form of extracellular matrix, the perineural net (PNN), the presence of which would contribute to the long-term maintenance of a PV-dependent brain network. We recently demonstrated that the presence of PNN around PV cells is reduced in the hippocampus of the Tg2576 mouse model of AD, and that it could contribute to the memory deficits observed in this model. Furthermore, young adult Tg2576 mice exposed to an enriched environment (EE) show an increase in the number of quantifiable PV/PNN interneurons in the hippocampus, as well as long-lasting cognitive improvement.

In this thesis, we tested the hypothesis that environmental stimulus-induced remodeling of hippocampal PV/PNN interneurons is required for cognitive improvement of Tg2576 mice. To address this question, in a first study we sought to prevent EE-dependent remodeling of PV interneurons and their PNN in hippocampal area CA1 specifically—via a targeted injection of chondroitinase-ABC (ChABC)—and observed that this is sufficient to suppress the beneficial effects of EE on spatial memory performance (CA1-dependent), without affecting social memory improvements (CA2-dependent). This strongly suggests that the beneficial effects of EE on memory performance in AD mouse model is underpinned, at least partially, by an increase in the activity of hippocampal PV neurons and/or the presence of PNN. Furthermore, based on recent studies, we investigated whether exposing Tg2576 mice to visual and/or auditory stimuli at gamma frequency (40Hz) mimics the effects of a stay in EE on PV/PNN remodeling and memory performance. This experiment did not provide conclusive results on the potential effects of multimodal gamma stimulations on PV interneurons. Finally, we used the innovative high-resolution microscopy technique Random Illumination Microscopy (RIM) to determine whether the differences in PNN numbers observed under different experimental conditions (Tg2576 and non-transgenic mice, exposed or not to EE, injected or not by ChABC) are accompanied by remodeling of the presence of perisomatic synapses on hippocampal PV neurons.

Thus, our work identifies PV neurons and their extracellular matrix PNN as key players in the long-term behavioral improvement of AD mice following early environmental stimuli, making them therapeutic targets of interest for fighting cognitive disorders associated with the pathology.



Flora D’OLIVEIRA DA SILVA – PhD defense

PhD defense in french

Zoom link : https://univ-tlse3-fr.zoom.us/j/99150206269


Supervisor : Lionel MOULEDOUS (CRCA-CBI)

Committee members :

  • Dr. Lionel Moulédous – CRCA
  • Pr. Bruno Guiard – CRCA
  • Dr. Catherine Mollereau-Manaute – CRCA
  • Dr. Domonique Massotte – Institut des neurosciences cellulaires et intégratives INCI – Université de Strasbourg
  • Dr. Sophie Tronel – Bordeaux Neurocampus
  • Dr. Jean-Phillipe Guilloux – Université Paris-Sud, Université Paris Saclay

Abstract :

The physiological response to stress allows organisms to adapt. Nevertheless, when stress is sustained in time, the response becomes maladaptive and causes memory deficits and structural impairments in the hippocampus, a key region for memory. However, the mechanisms underlying these deleterious effects are not fully understood. Stress induces the release of a neuropeptide named Nociceptin/OrphaninFQ which acts on its receptors called NOP and possesses amnesic properties. We thus hypothesized that it could be a mediator of these negative effects of chronic stress.

We demonstrated that NOP receptor blockade restores long-term memory performance in mice models of chronic stress. Furthermore, we revealed a protective effect of NOP blockade on the alterations of hippocampus structure due to chronic stress.

This work paves the way for the development of new strategies using the NOP receptor as a pharmacological target for the treatment of memory deficits in stress-related disorders.

Anna B. SZABO – PhD defense

PhD defense in english

Zoom link : https://univ-tlse3-fr.zoom.us/j/92029196377?pwd=aGY4aTRDV2lSYUw3MFp6cmM4amZWZz09


Supervisors : Lionel DAHAN (CRCA-CBI) / Luc VALTON (CerCo)

Committee members :

  • Pr. Marc Dhenain, Rapporteur, Université Paris-Saclay, Fontenay-aux-Roses
  • Dr. Pierre-Pascal Lenck-Santini, Rapporteur, Aix-Marseille Université, Marseille
  • Dr. Laure Peter-Derex, Rapporteure, Université Claude Bernard Lyon 1, Lyon
  • Pr. Marie Sarazin, Examinatrice, Sorbonne Université, Paris
  • Pr. Maria-Eugénia Soto-Martin, Examinatrice, Université Paul Sabatier, Toulouse
  • Pr. Agnès Trebuchon-Da Fonseca, Examinatrice, Aix-Marseille Université, Marseille
  • Dr. Lionel Dahan, Supervisor, Université Paul Sabatier, CRCA-CBI, Team REMEMBER, Toulouse
  • Dr. Luc Valton, Supervisor, CHU de Toulouse, Université Paul Sabatier, CerCo, Team DYNAMO, Toulouse

Abstract :

Previous research on murine models of Alzheimer’s disease (AD) highlighted the potential role of cerebral excitatory-inhibitory imbalance in the pathophysiology of AD. Clinical research has since reported that this imbalance may give rise to epileptic activities in as much as 50% of AD patients as well. However, these epileptic events may remain undetected due to their silent, mostly sleep-occurring nature. Using a translational approach, the aim of this thesis was to better understand the link between AD, epilepsy, sleep and memory.

First, in the framework of a preclinical study, I aimed at (I) characterizing epileptic activities over the sleep-wake cycle in the Tg2576 mouse model and (II) gaining better insight into the mechanistic underpinnings of these peculiar epileptic events. Epileptic activities were frequent, showed a predominance during REM sleep, and were locked to the phase of the theta cycle corresponding to the maximal firing probability of pyramidal cells. Furthermore, these events seemed to be counterbalanced by noradrenergic signalling via α1 adrenoreceptors during wakefulness and partially during SWS, but this effect would be lost during REM sleep when noradrenergic cells cease firing. Given the early degeneration of the locus coeruleus – the primary source of noradrenaline in the brain – in AD patients, this could have important clinical implications in the future.

In the second part of this thesis, the objective was to explore the prevalence and the distribution of epileptic activities during sleep in a cohort of 30 AD patients (selected as early AD, & without epilepsy) compared to a group of age-matched, healthy controls, and to understand the impact of these activities on cognitive decline and sleep-related memory consolidation. To this end, a full-night video-EEG combined with polysomnography was undertaken, together with a two-part neuropsychological test battery with pre-and post-sleep memory tests. These measures were combined with brain imaging (MRI), genetic analyses and the evaluation of lifestyle-related risk factors. The preliminary results with 25 participants per group that are presented hint at a risk ratio for EA occurrence five times higher in patients than controls. In contrast to the preclinical results, epileptic events are predominant during non-REM sleep. Importantly, other sleep-related deficits were also observed, including an increased percentages of superficial sleep in patients at the detriment of deeper ones and unexpectedly high prevalence of newly diagnosed Sleep Apnea Syndrome: 63% in AD patients and 50% in controls. While our sample size is currently insufficient to draw steady conclusions from our results, our preliminary models suggest a combined impact of sleep quantity, sleep apnoea, epileptic events and AD itself on memory consolidation, especially on episodic memory. We suggest that treating EAs, sleep apnoea and improving sleep quality could potentially slow down or lessen memory complaints in AD patients.

Haiyang GENG – PhD defense

Presentation in english

Supervisors : Isabelle Massou and Martin Giurfa

Comitee members :

  • M. Claudio LAZZARI (Université de Tours) – Reviewer
  • Mme Emmanuelle JACQUIN-JOLY (INRAE iEES – Paris) – Reviewer
  • M. Cédric ALAUX (INRAE Avignon) – Examiner
  • Mme Isabelle MASSOU (Research Centre of Animal Cognition) – Thesis co-supervisor
  • M. Martin GIURFA (Research Centre of Animal Cognition) – Thesis co-supervisor

Abstract :

Honey bees are endowed with the capacity of color vision as they possess three types of photoreceptors in their retina that are maximally sensitive in the ultraviolet, blue and green domains owing to the presence of corresponding opsin types. While the behavioral aspects of color vision have been intensively explored based on the easiness by which free-flying bee foragers are trained to color stimuli paired with sucrose solution, the molecular underpinnings of this capacity have been barely explored. Here, to fill this void, we explore opsin properties and gene expression changes in the bee brain, during color learning and retention in controlled laboratory protocols.

We characterized opsin distribution in the honey bee visual system, focusing on the presence of two types of green opsins (Amlop1 and Amlop2), one of which (Amlop2) was discovered upon sequencing of the bee genome. We confirmed that Amlop1 is present in ommatidia of the compound eye but not in the ocelli, while Amlop2 is confined to the ocelli. We developed a CRISPR/Cas9 approach to determine possible functional differences between these opsins. We successfully created Amlop1 and Amlop2 adult mutant bees by means of the CRISPR/Cas9 technology and we also produced white-gene mutants as a control for the efficiency of our method. We tested our mutants using a conditioning protocol in which bees learn to inhibit attraction to chromatic light based on electric-shock punishment (Icarus protocol). White and Amlop2 mutants learned to inhibit spontaneous attraction to blue light while Amlop1 mutants failed to do so. These results indicate that responses to blue light, which is also partially sensed by green receptors, are mediated mainly by compound-eye photoreceptors containing Amlop1 but not by the ocellar system in which photoreceptors contain Amlop2. Accordingly, 24 hours later, white and Amlop2 mutants exhibited an aversive memory for the punished color that was comparable to control bees but Amlop1 mutants exhibited no such memory. We discuss these findings based on controls with eyes or ocelli covered by black paint and interpret our results in the context of chromatic vs. achromatic vision via the compound eyes and the ocelli, respectively.

Finally, we analyzed immediate early gene (IEG) expression in specific areas of the bee brain following color vision learning in a virtual reality (VR) environment. We changed the degrees of freedom of this environment and subjected bees to a 2D VR, in which only lateral movements of the stimuli were possible and to a 3D VR which provided a more immersive perception. We analyzed levels of relative expression of three IEGs (kakuseiHr38, and Egr1) in the calyces of the mushroom bodies, the optic lobes and the rest of the brain after color discrimination learning. In the 3D VR, successful learners exhibited Egr1 upregulation only in the calyces of the mushroom bodies, thus uncovering a privileged involvement of these brain regions in associative color learning. Yet, in the 2D VR, Egr1 was downregulated in the OLs while Hr38 and kakusei were coincidently downregulated in the calyces of the MBs in the group that learned. Although both VR scenarios point towards specific activations of the calyces of the mushroom bodies (and of the visual circuits in the 2D VR), the difference in the type of expression detected suggests that the different constraints of the two VRs may lead to different kinds of neural phenomena. While 3D VR scenarios allowing for navigation and exploratory learning may lead to IEG upregulation, 2D VR scenarios in which movements are constrained may induce higher levels of inhibitory activity in the bee brain. Overall, we provide a series of new explorations of the visual system, including new functional analyses and the development of novel methods to study opsin function, which advances our understanding of honey bee vision and visual learning.

Keywords: Vision, Visual Learning, Honey Bee (Apis mellifera), Opsin Genes, Photoreceptors, CRISPR/Cas9, Inhibition of Color Attraction, Virtual Reality, Brain, IEG expression, Mushroom Bodies, Optic Lobes.