Cochlear implants are a recognised treatment for severe and profound hearing losses, and can greatly improve speech discrimination in a quiet listening environment. However, poor specificity of neural excitation resulting from wide current spread within the cochlea leads to inadequate complex pitch perception, affecting speech discrimination in noisy environments and music perception. Tripolar is a stimulation mode with a greater degree of current focusing than the monopolar mode currently used in the clinic. The overall aim of the experiments in this thesis was to evaluate the potential of tripolar stimulation mode to improve complex pitch perception compared to monopolar stimulation mode in a group of Advanced Bionics cochlear implant listeners. First, the place specificity of tripolar and monopolar stimulation was compared using a psychophysical forward masking task with a dual-electrode masking stimulus to limit off-site listening. An overall improvement in the place specificity of tripolar compared to monopolar stimulation indicated that current focusing may provide more independent transmission of temporal information from different electrode places. This conclusion was unaffected by the degree of residual masking which, although measurable, was similar in both modes. Second, the effect of current focusing on delivery of independent temporal patterns was evaluated, specifically whether transmission of fine temporal information about interpulse intervals was improved using tripolar over monopolar stimulation. No advantage was found for current focusing in the delivery of temporal patterns on either a single electrode site, or across-electrodes. Third, the effect of mode on complex pitch perception was investigated by comparing a tripolar with a monopolar listening program. Results showed no improvement in pitch ranking ability from current focusing using sung vowel stimuli, and further suggested that a cue related to the centroid of excitation was providing a stronger cue to pitch than the temporal modulations available in both modes in this group. In conclusion, tripolar stimulation, on average, improved place specificity using forward masking, but not temporal cues to pitch using the methods chosen to evaluate this. Furthermore, current focusing did not improve the ability to rank sung vowels based on pitch over monopolar mode. Current focusing, therefore, was not found to enhance perception of complex harmonic pitch in this group. However, a degree of inter-participant variability in amount of benefit from current focusing observed in this series of experiments suggests that it may be useful for some cochlear implant listeners if a predictive measure of benefit were developed.

The principle of time-lapse system is based on the continuous sensing of the development of the pre-implantation embryo and the assessment of its morphology. This is advantageous in assessing the quality and implantation potential of embryos, which are subsequently evaluated according to certain established criteria. This gives the opportunity to select the highest quality embryo to be implanted into the mother's womb during embryo transfer. This system also allows us to detect any abnormalities in embryo development. This is very important, because the occurrence of abnormalities in early embryonic cell division is quite common. Morphological evaluation of embryos indicates a high incidence of tripolar mitosis during this early embryo development. The result of this division is three blastomers instead of two, which is associated with an irregular chromosome separation, each of them may contain a different number of chromosomes. In the case where conventional embryo observation is used to observe embryo morphology at longer intervals, it may be that the changes associated with tripolar mitosis are not detected at all, and such embryos appear to be falsely prosperous and are often selected for transfer. This can have serious consequences in the case of implantation, because these embryos are not...

Cette thèse se situe dans la perspective de la philosophie de l’éducation et de l’art. Elle propose d’aborder, au travers de grands textes issus de la philosophie et de l’esthétique, la question des valeurs éducatives des arts. Cette question est ici considérée dans une perspective comparative et historique entre la culture chinoise et la culture occidentale. Le critère de comparaison, notamment inféré depuis des données de la mythologie chinoise et/ou de la Grèce ancienne, est celui d’approches soit « binaires », fondées sur deux pôles, ce que nous qualifions aussi de « bipolaire », soit « ternaires » ou « tripolaires », avec le rôle d’un Tiers, d’un « milieu ». La problématique ainsi retenue est la suivante :Quelles sont les valeurs éducatives des arts attribuées par de grandes approches de la culture occidentale et chinoise, par rapport à une configuration « bipolaire » ou « tripolaire » ?Au niveau historique, pour chaque culture, deux périodes jugées « significatives » dans le cadre de la philosophie de l’éducation esthétique/artistique ont été retenues. La première période correspond à l’Antiquité. Pour la chine, il s’agit de l’époque des Printemps et Automnes (771 à 476 av. J.-C.), pendant laquelle sont nés les courants philosophiques du confucianismeet du taoïsme. Pour l’Occident, il s’agit de la pensée grecque telle qu’elle est soulignée par Platon et Aristote. La seconde période, ne correspond pas à une synchronie entre la Chine et l’Occident. En revanche, elle se traduit dans un cas comme dans l’autre, par une profonde réforme des valeurs éducatives des arts. Cette réforme correspond pour l’Occident aux Lumières, notamment allemandes, par exemple avec la naissance, au XVIIIe siècle, de l’esthétique sous la plume de Baumgarten. Si la Chine était restée en phase avec la tradition de l’époque des Printemps et Automnes, il fallut attendre l’époque républicaine, à partir de 1919, pour que cette réforme se produise, précisément sous l’influence d’intellectuels chinois qui introduisirent de nouvelles conceptions très influencées par les Lumières européennes.Tel est le parcours historique que propose cette thèse, pour revenir finalement à la question de sa démarche comparative sur la base du « binaire » ou du « ternaire », base sur laquelle oscille l’ensemble du corpus présenté, tant en Chine qu’en Occident. Cette double configuration, repérée au centre des axiologies ici présentées, se prête ainsi, au-delà des valeurs éducatives des arts, à articuler un opérateur comparatif « transculturel » dont la proposition et l’essai constituent l’originalité de cette thèse au regard des approches sino-occidentales. / This thesis is situated in the perspective of the philosophies of education and of art. It proposes to broach, through the principal texts stemming from philosophy and aesthetics, the question of the educational value of the arts. This question is considered in a comparative and historical perspective between Chinese and Western cultures. The object of the comparison, especially inferred from the figures of Chinese and/or ancient Greek mythology, is that of the “binary” approach, based on two poles that we also describe as “bipolar”, or of the “ternary”/“tripolar” approach, with the role of a Third, or a “middle”. The issue retained is as follows: What are the educational values of the arts attributed by the approaches of Western and Chinese cultures, in relation to a “bipolar” or “tripolar” configuration?At a historical level, for each culture, two periods judged “significant” within the context of the philosophy of education/aesthetic/art were retained. The first period corresponds to antiquity. For China, it is the Spring and Autumn period (771 to 476 BC), during which the Confucianism, and Taoist movements were born. For the West, it is Greek thought asemphasized by Plato and Aristotle. The second period does not correspond to synchrony between China and the West. However, it manifests in both cases a profound reformation of the educational value of the arts. For the West, this reform corresponds to the Luminaries, especially German, for example with the 18th century birth of aesthetics in the writings ofBaumgarten. If China stayed within the tradition of Spring and Autumn, it wasn’t until the republic period, from 1919 onward, that this reform happened, precisely under the influence of the Chinese intellectuals, who introduced new conceptions which were highly influenced by the European Luminaries.This is the historical course that this thesis proposes, in order to return to the question of its comparative approach on the basis of the “bipolar” or the “tripolar” configuration. The entire corpus that we present oscillates on this basis, in China as well as in the West. This double configuration, found at the center of the axes presented here, is well suited, beyond the educational value of the arts, to articulate a “transcultural” comparative operator. This proposition constitutes the originality of this thesis with respect to Chinese-Western approaches.

This thesis describes a novel method to reversibly and safely block nerve conduction using a low frequency alternating current (LFAC) waveform at 1 Hz applied through a bipolar extrafascicular electrode. This work follows up on observations made on excised mammalian peripheral nerves and earthworm nerve cords. An<i> in-situ</i> electrophysiology setup was used to assess the LFAC<br>waveform on propagating action potentials (APs) within the cervical vagus nerve in anaesthetized Sprague-Dawley rats (n = 12). Two sets of bipolar cuff or hook electrodes were applied unilaterally to the cervical vagus nerve, which was crushed rostral to the electrodes to exclude reflex effects<br>on the animal. Pulse stimulation was applied to the rostral electrode, while the LFAC conditioning waveform was applied to the caudal electrode. The efferent volley, if unblocked, elicits acute bradycardia and hypotension. The degree of block of the vagal stimulation induced bradycardia<br>was used as a biomarker. Block was assessed by the ability to reduce the bradycardic drive by monitoring the heart rate (HR) and blood pressure (BP) during LFAC alone, LFAC with vagal stimulation, and vagal stimulation alone. LFAC applied via a hook electrode (n = 7) achieved 86.6 +/- 11% block at current levels 95 +/- 38 uAp (current to peak). When applied via a cuff electrode (n = 5) 85.3 +/- 4.60% block was achieved using current levels of 110 +/- 65 uAp. Furthermore, LFAC was explored on larger vagal afferent fibers in larger human sized nerve bundles projecting to effects mediated by a reflex. The effectiveness of LFAC was assessed in an <i>in-situ</i> electrophysiological setup on the left cervical vagus in anaesthetized domestic swine (n = 5). Two bipolar cuff electrodes were applied unilaterally to the cervical vagus nerve, which was crushed caudal to the electrodes to eliminate cardiac effects. A tripolar extrafascicular cuff electrode was placed most rostral on the nerve for recording of propagating APs induced by<br>electrical stimulation and blocked via the LFAC waveform.<br>Standard pulse stimulation was applied to the left cervical vagus to induce the Hering-Breuer reflex. If unblocked, the activation of the Hering-Breuer reflex would cause breathing to slow down and potentially cease. Block was quantified by the ability to reduce the effect of the Hering-Breuer<br>reflex by monitoring the breathing rate during LFAC alone, LFAC and vagal stimulation, and vagal stimulation alone. LFAC achieved 87.2 +/- 8.8% (n = 5) block at current levels of 0.8 +/- 0.3 mAp. Compound nerve action potentials (CNAP) were monitored directly. They show changes<br>in nerve activity during LFAC, which manifests itself as the slowing and amplitude reduction of components of the CNAPs. Since the waveform is balanced, all forward reactions are reversed, leading to a blocking method that is similar in nature to DC block without the potential issues of<br>toxic byproduct production. These results suggest that LFAC can achieve a high degree of nerve block in both small and large nerve bundles, resulting in the change in behavior of a biomarker, <i>in-vivo </i>in the mammalian nervous system at low amplitudes of electrical stimulation that are within the water window of the electrode.<br>