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Horseshoe bats possess a sophisticated biosonar system that helps them to negotiate complex unstructured environments by relying primarily on the sound as the far sense. For this, the bats emit brief ultrasonic pulses and listen to incoming echoes to learn about the environment. The sites of emission and reception in these bats are surrounded by baffle structures called "noseleaves" and "pinnae (outer ears)". These are the the only places in the biosonar system where direction-dependent information gets encoded. These baffle structures in bats unlike the engineering systems like megaphones have complex static geometry and can undergo fast deformations at the time of pulse emission/reception. However, the functional significance of the baffle motions in biosonar system is not known. The current work primarily focuses on: i) the study of the impact of noseleaf dynamics on the outgoing sound waves, ii) the study of the impact of baffle dynamics on encoding of sensory information and localization performance of bats. For this, we take a numerical approach where we use computer-animated digital models of bat noseleaves that mimic noseleaf dynamics as observed in bats. The shapes are acoustically characterized (beampatterns) numerically using a finite element implementation. These beampatterns are then analyzed using an information-theoretic approach. The followings findings were obtained: i) noseleaf dynamics altered the spatial distribution of energy, ii) baffle dynamics results in encoding of new sensory information, and iii) the new sensory information encoded due to baffle dynamics significantly improves the performance of biosonar system on the two target localization tasks evaluated here -- direction resolution and direction estimation accuracy. These results affirm the importance of dynamics in biosonar system of horseshoe bats and point at the possibility of biosonar dynamics as a key factor behind the astounding sensory capabilities of these animals that are not yet matched by engineering systems. Thus, these biosonar dynamic principles can help improve the man-made sensing systems and help close the performance gap between active sensing in biology and in engineering. / Ph. D.

Bats are known for their highly capable biosonar systems which make them be able to navigate and forage in dense vegetation. Their biosonar system consists of one emitter (nose or mouth) and two receivers (ears). Some bat species, e.g. in the rhinolophid and hipposiderid families, have complicated pinna motion patterns. It has been shown that these pinna motion patterns fall into two distinct categories: rigid motions and non-rigid motions. In the current work, the pinna of Pratt's leaf-nosed bat (Hipposideros pratti) was used as a biological model system to understand how a sensor could benefit from variability. Hence, the variability in the rigid pinna motions and in the non-rigid pinna motions has been investigated by tracking a dense set of landmarks on the pinna surface with stereo vision. Axis-angle representations have shown that the rigid pinna motions exhibited a large continuous variation with rotation axes covering 180 degrees in azimuth and elevation. Distributions of clusters of the landmarks on the pinna surface have shown that the non-rigid pinna motions fall into at least two subgroups. Besides, the acoustic impact of the rigid pinna motions have been investigated using a biomimetic pinna. Normalized mutual information between the acoustic inputs with different rotation axes has shown that different rotation axes can provide at least 50% new sensory information. These results demonstrate that the variability in the pinna motions is an interesting concept for sensor, and how the bats approach that needs to be further investigated. / Master of Science / Sensors have been developed for a long time, and they can be used to detect the environments and then deliver the required sensing information. There are many different types of sensors, such as vision-based sensors (infrared camera and laser scanner) and sound-based sensors (sonar and radar). Ultrasonic transducers are one of the sound-based sensors, and they are more stable and reliable in environments where smoke or steam is present. Similar to human-made ultrasonic transducers, bats have developed highly capable biosonar systems that consist of one ultrasonic emitter (nose or mouth) and two ultrasonic receivers (ears), and these biosonar systems enable them to fly and hunt in cluttered environments. Some bats, e.g. rhinolophid and hipposiderid bats, have dynamic noseleaves (elaborate baffle shapes surrounding the nostrils) and pinna (outer ear), and these could enhance the sensing abilities of bats. Hence, the purpose of this thesis has been to investigate this variability to improve the human-made sensors by focusing on the dynamic pinna of the bats. It has been shown that bats have two distinct categories of pinna motions: rigid motions which change only the orientation of the pinna, and non-rigid motions which change also the shape of the pinna. However, the variability within the rigid and non-rigid pinna motions has received little attention. Therefore, the present work has investigated the variability in the rigid pinna motions and in the non-rigid pinna motions. Landmark points were placed on the pinna of certain bats and the pinna motions were tracked by high-speed video cameras. The rigid pinna motions exhibit a large continuous variation in where the pinna is orientated during rotation. Distributions of clusters of the landmarks on the pinna have shown that the non-rigid pinna motions fall into at least two subgroups. The acoustic impacts of the rigid pinna motions have been studied by a biomimetic pinna which reproduced the observed range of the rigid pinna motions. Ultrasonic signals mimicking the bats were emitted to be received by the biomimetic pinna. Based on these signals, it has been shown that different rotation axes and even small changes can provide over 50% new sensory information. These findings give engineers a potential way to improve the human-made sensors.

This dissertation presents three experiments to investigate the general distribution of hand preference across a reachable working space, as well as the effect of sensory information about the reaching hand, and if this distribution is affected by long term practice. In addition, the underlying mechanisms of hand preference behavior were investigated with the obtained kinematic data. Experiment 1 explored the distribution of hand preferences across the workspace among non-athlete right-handed participants, as well as the role that visual feedback might play in this distribution. Experiment 2 tested the hypothesis, if occlusion of visual feedback influences hand preference, accordingly interlimb differences. The third final experiment examined the effect of long term practice on hand preference among right-handed elite fencers. The first study showed that the choice of arms is related to the energetic cost and dynamic efficiency of the movements. The results of the second experiment displayed that the choice of hands changes under no visual feedback condition, demonstrating that the choice is active and not habitual, depending on sensorimotor performance asymmetries. The final experiment demonstrated that elite athletes have different patterns of limb selection than non- athletes. Athletes, specifically fencers, show improved coordination in their non-dominant arms, which apparently increases the selection of this arm for reaching. Overall, it was concluded that hand preference depends on sensorimotor performance asymmetries and influenced by the long term practice.

Les fuseaux de sommeil sont générés par le noyau réticulaire thalamique puis transmis dans la boucle thalamo-corticale durant le sommeil lent. Ils sont considérés comme ayant un rôle protecteur du sommeil en inhibant les entrées sensorielles. L'objectif de notre travail était de tester ce rôle inhibiteur sur les réactions d'éveil et les réponses évoquées par des stimulations nociceptives chez l'homme en menant trois études électrophysiologiques au cours de nuits entières. Les deux premières études ont utilisé des stimuli laser thermo-nociceptifs délivrés pendant ou en dehors de fuseaux. Les réponses cérébrales étaient obtenues par enregistrements de surface chez des sujets sains, ou intracérébraux chez des patients épileptiques. Les résultats n'ont pas montré de différence significative des réactions d'éveil ou des réponses évoquées, que les stimuli aient été délivrés pendant ou en dehors de fuseaux. Ceci était le cas dans l'étude de surface, mais également dans celle en intracérébral dans laquelle les fuseaux étaient détectés dans le thalamus et les réponses analysées dans l'insula, connue pour répondre systématiquement aux stimuli nociceptifs. Dans la troisième étude, afin d'augmenter la quantité de stimuli, des stimulations électriques ont été utilisées à intensité nociceptive. La relation temporelle entre fuseau et traitement sensoriel a ainsi été étudiée avec des enregistrements de surface à haute densité chez des sujets sains. Les réponses évoquées, présentes dans tous les cas, étaient de plus grande amplitude lors des stimuli délivrés autour du début du fuseau. Ainsi, l'effet inhibiteur du fuseau de sommeil ne semble pas s'appliquer au traitement des informations nociceptives et la modulation des réponses corticales selon le moment du fuseau pourrait refléter l'influence de l'onde lente corticale / Sleep spindles are generated by thalamic reticular nuclei and transmitted into the thalamo-cortical network during nonREM sleep. They are commonly thought to have a sleep-protecting role by inhibiting sensory inputs. The aim of our work was to test their inhibitory effect on behavioural and evoked responses to nociceptive inputs in humans by conducing three electrophysiological experiments during a whole night of sleep. The first two experiments used thermo-nociceptive laser stimuli delivered during or apart from sleep spindles. Cerebral responses were obtained with surface recordings in healthy subjects, or intracerebral ones in epileptic patients. Results showed no significant difference in arousal reactions and cortical evoked responses to stimuli delivered during or apart from sleep spindles. This was the case on surface recordings as well as on intracerebral ones in which spindles were detected within the thalamus while responses were analysed in the insula, known to systematically respond to nociceptive stimuli. In the third experiment, in order to increase the rate of stimuli, electrical ones were used at nociceptive intensities. The relationship between spindle activity and sensory processing was then investigated with surface high-density recordings in healthy subjects. Evoked responses were present in any case, but of higher amplitude around the initiation of spindle activity. Thus, the spindles inhibitory effect of sensory processing does not seem to apply to nociceptive inputs and the modulation of cortical responses according to the timing of spindle might reflect the influence of the slow oscillation

The few microcontroller based active/semi-active prosthetic knee joints available commercially are extremely expensive and do not consider the uncertainties of inputs sensory information. Progressing in the controller of the current prosthetic devices and creating artificial lower limbs compatible with different users may lead to more effective and low-cost prostheses. This can affect the life style of lots of amputees specially the land-mine victims in developing war-torn countries who are unable to partake in the advancement of the current intelligent prosthetic knees. The purpose of the proposed Active Prosthetic Knee (APK) design is to investigate a new schema that allows the device to provide the full necessary torque at the knee joint based on echoing the state of the intact leg. This study involves the design features of the mechanical aspects, sensing system, communication, and knowledge-based controller to implement a cost-effective APK. The proposed microcontroller based prosthesis utilizes a ball screw system accompanied by a high-speed brushed servomotor to provide one degree of freedom for the fabricated prototype. Moreover, a modular test-bed is manufactured to mimic the lower limb motion which contributes investigating different controllers for the prototype. Thus, the test bed allows assessing the primary performance of the APK before testing on a human subject. Different types of sensing systems (electromyography and lower limb inclination angles) are investigated to extract signals from the user’s healthy leg and send the captured data to the APK controller. The methodology to measure each type of signal is described, and comparison analyses are provided. Wireless communication between the sensory part and actuator is established. A knowledge-based control mechanism is developed that takes advantage of an Adaptive-Network-based Fuzzy Inference System (ANFIS) to determine knee torque as a function of the echoing angular state of the able leg considering the uncertainty of inputs. Therefore, the developed controller can make the APK serviceable for different users. The fuzzy membership function’s parameters and rules define the knowledge-base of the system. This knowledge is based on existing experience and known facts about the walking cycle.

The few microcontroller based active/semi-active prosthetic knee joints available commercially are extremely expensive and do not consider the uncertainties of inputs sensory information. Progressing in the controller of the current prosthetic devices and creating artificial lower limbs compatible with different users may lead to more effective and low-cost prostheses. This can affect the life style of lots of amputees specially the land-mine victims in developing war-torn countries who are unable to partake in the advancement of the current intelligent prosthetic knees. The purpose of the proposed Active Prosthetic Knee (APK) design is to investigate a new schema that allows the device to provide the full necessary torque at the knee joint based on echoing the state of the intact leg. This study involves the design features of the mechanical aspects, sensing system, communication, and knowledge-based controller to implement a cost-effective APK. The proposed microcontroller based prosthesis utilizes a ball screw system accompanied by a high-speed brushed servomotor to provide one degree of freedom for the fabricated prototype. Moreover, a modular test-bed is manufactured to mimic the lower limb motion which contributes investigating different controllers for the prototype. Thus, the test bed allows assessing the primary performance of the APK before testing on a human subject. Different types of sensing systems (electromyography and lower limb inclination angles) are investigated to extract signals from the user’s healthy leg and send the captured data to the APK controller. The methodology to measure each type of signal is described, and comparison analyses are provided. Wireless communication between the sensory part and actuator is established. A knowledge-based control mechanism is developed that takes advantage of an Adaptive-Network-based Fuzzy Inference System (ANFIS) to determine knee torque as a function of the echoing angular state of the able leg considering the uncertainty of inputs. Therefore, the developed controller can make the APK serviceable for different users. The fuzzy membership function’s parameters and rules define the knowledge-base of the system. This knowledge is based on existing experience and known facts about the walking cycle.

On pense souvent que notre mémoire nous joue des tours et nous fait défaut. Ces oublis concernent généralement des souvenirs qui ne sont pourtant pas si vieux. Alors quand il s’agit de se rappeler d’informations sensorielles auxquelles nous n’avons pas repensé depuis plusieurs dizaines d’années, pas de doute, il ne reste plus rien… Mais en est-on vraiment sûr? Et si l’information était toujours là, prête à se manifester de manière explicite -comme sous forme de rappel ou de sentiment de familiarité- pour peu que les conditions le lui permettent? A ce jour, très peu d’expériences ont été menées sur ce sujet. L’objectif de ma thèse a donc été d’apporter des premiers éléments de réponse concernant la récupération de mémoires laissées inactives. Ma recherche s’est orientée selon deux axes principaux : une première partie théorique où je montre a) qu’il n’est pas nécessaire de réactiver une trace mnésique pour la maintenir à très long-terme si elle a été suffisamment répétée et b) que la récupération explicite de cette mémoire serait possible grâce à la présentation d’informations qui cibleraient au mieux le souvenir ; une seconde partie expérimentale où je montre a) que des participants sont capables de récupérer de manière explicite des informations laissées en dormance pendant au moins une dizaine d’années et b) que cette trace mnésique pourrait être détectée sur des tracés d’Electroencéphalographie (EEG). Ainsi, et aussi étonnant que cela puisse paraître, dans des conditions favorables à leur réactivation, d’anciennes traces mnésiques que l’on croyait disparues, peuvent de nouveau surgir sous la manifestation de rappel ou de sentiment de familiarité par exemple. Ces résultats soulèvent des questions majeures concernant le stockage neuronal de cette information. / Memory plays tricks on us and fails us even for recent events. So for the retrieval of sensory information that we have not experienced for decades, surely the memories are gone without a trace, but can we be sure of this? What if the information had been there all along ready to be explicitly retrieved through recall or familiarity for example? So far, experimental evidence is lacking. The purpose of my thesis was to shed some light on the retrieval of these inactive memories. To tackle this problem I developed my research around two main axes: For the first part which is theoretical, I suggest that a) reactivations are not necessary to maintain very long-term memories if the memories were sufficiently repeated at first; b) it might be possible to retrieve explicitly remote inactive memories using specific cues; in the second part which is experimental, I show that a) within specific conditions participants are able to retrieve explicitly very long-term memories that were left inactive for decades and b) such memory traces could be found on the Electroencephalography (EEG) signals. Surprisingly, when conditions are met, remote memories that were thought to be lost can again elicit recall or familiarity. With these results, a question remains: How do neurons store such information?

Le syndrome du X fragile (SXF) est la première cause héréditaire de déficience intellectuelle et également la première cause monogénique d’autisme. Le SXF est causé par l'expansion de la répétition du nucléotide CGG sur le gène FMR1, ce qui empêche l’expression de la protéine FMRP. L’absence du FMRP mène à une altération du développement structurel et fonctionnel de la synapse, ce qui empêche la maturation des synapses induite par l’activité et l’élagage synaptique, qui sont essentiels pour le développement cérébral et cognitif. Nous avons investigué les potentiels reliés aux événements (PRE) évoqués par des stimulations fondamentales auditives et visuelles dans douze adolescents et jeunes adultes (10-22) atteints du SXF, ainsi que des participants contrôles appariés en âge chronologique et développemental. Les résultats indiquent un profil des PRE altéré, notamment l’augmentation de l’amplitude de N1 auditive, par rapport aux deux groupes contrôle, ainsi que l’augmentation des amplitudes de P2 et N2 auditifs et de la latence de N2 auditif. Chez les patients SXF, le traitement sensoriel semble être davantage perturbé qu’immature. En outre, la modalité auditive semble être plus perturbée que la modalité visuelle. En combinaison avec des résultats anatomique du cerveau, des mécanismes biochimiques et du comportement, nos résultats suggèrent une hyperexcitabilité du système nerveux dans le SXF. / We investigated early auditory and visual information processing in Fragile X Syndrome (FXS), the most common form of X-linked Intellectual Disability (ID) and the only known monogenetic cause of autism. FXS is caused by a trinucleotide repeat expansion in the FMR1 (‘Fragile X mental retardation 1’) gene, which prevents expression of the ‘fragile X mental retardation protein’ (FMRP). FMRP absence leads to altered structural and functional development of the synapse, while also preventing activity-based synapse maturation and synaptic pruning, which are essential for cerebral and cognitive development. We review the contribution of electrophysiological signal studies for the understanding of information processing in FXS and compare event-related potential (ERP) findings to those concerning other clinical populations that share symptoms with FXS. In our research project, we investigated ERPs evoked by basic auditory and visual stimulation in twelve adolescents and young adults (10-22) with FXS, as well as healthy chronological- and developmental- age matched controls. We found an altered ERP profile in FXS, including increased auditory N1 amplitude, relative to both control groups, as well as increased auditory P2 and N2 amplitudes and increased auditory N2 latencies. Rather than being immature, sensory processing appears to be specifically disrupted in FXS. Furthermore, the auditory modality seems to be more affected than the visual modality. In combination with brain anatomical, biochemical and behavioural findings, our results suggest a hyperexcitable nervous system in FXS.