This thesis introduces a new theoretical framework from which to view the factors that contribute to stuttering variability. The speech and monitoring interaction (SAMI) framework proposes that there are two systems that account for stuttering variability: the speech production system and the monitoring system. Each system has unique factors that modulate them. Within SAMI, the interaction of these two categories of factors is formalized in a mathematical equation. What is particularly novel about SAMI is the use of a mathematical equation to formalize the interaction between these systems and the specific proposal of the biological substrates of the monitoring system and its interaction with the speech system. The focus of this thesis is on the anticipation of stuttering, which is one of the factors from SAMI that modulates the monitoring system. The goals of the studies were to 1) characterize the degree to which people who stutter (PWS) anticipate stuttering and how accurately they can predict actual stuttering, 2) investigate the correlation between stuttering expectancy on words and the verbal response time to say those word in word naming tasks, and 3) make a qualitative comparison of the behavioral results and the results from a neural network model. Utilizing the SAMI framework it was hypothesized that stuttering expectancy would be positively correlated with the response time and the results from the simulations would qualitatively match the behavioral results. The key finding was that across the group of PWS, there was positive correlation between stuttering expectancy scores and relative reaction times on those words. The degree to which stuttering expectancy was correlated with reaction time within subjects was positively correlated with stuttering severity. A qualitative comparison showed a good fit in between results of the simulations and the behavioral study. This is the first study to show that the expectation of stuttering has an effect on fluent speech production, providing evidence that the anticipation of stuttering is not only correlated with moments of stuttering but may also be a contributing factor to stuttering. The model provides a means of hypothesizing and testing specific neural substrates associated with anticipation of stuttering and its effects on the speech production process.

Previous investigations comparing direct versus indirectly cued movements have consistently shown that indirectly cued movements take longer to prepare (Neely and Heath, 2010) and involve the recruitment of additional brain areas (Connolly et al., 2000). This increase in processing time has been associated with the additional cognitive transformations required of the task (Neely and Heath, 2010). In the present study we investigated whether differences between direct versus indirectly cued movements are also reflected in the time course of motor preparation. Participants performed a targeting task, moving directly to the location of a visual cue (i.e., directly cued movement) or to a location that differed by 60˚, 90˚, or 120˚ with respect to the visual cue provided (i.e., indirectly cued movements). Participants were instructed to initiate their movements concurrently with an anticipated go-signal. To examine the time course of motor preparation, a startling acoustic stimulus (SAS, 124dB) was randomly presented 150 ms, 500 ms, or 1000 ms prior to the go-signal. Results from the startle trials revealed that the time course of motor preparation was similar regardless of the angle of rotation required and hence whether it was a direct or indirectly cued trial. Specifically, motor preparation was delayed until less than 500 ms prior to movement initiation for both direct and indirectly cued movements. These findings indicate that similar motor preparation strategies are engaged for both types of cued movements, suggesting that the time to prepare a motor response may be similar regardless of whether a cognitive transformation is required.

Candida albicans is the most common human commensal fungus, able to colonize host niches such as skin, mouth and gastrointestinal tract. Colonization of diverse microenvironments requires the ability to evade or overcome innate host protection and adapt to rapid transitions between environments with different stresses and nutrient availability. Colonization of the gastrointestinal tract requires passage through the stomach containing toxic levels of nitric oxide, generated from acidification of nitrite in the low pH of the stomach. Although resistance of C. albicans to nitric oxide is mediated by the flavohemoglobin Yhb1, little is known about the physiologically relevant ligands that regulate YHB1 expression. Here I propose the hypothesis that nontoxic saliva chemicals induce YHB1 expression and promote resistance to nitric oxide generated in the stomach. Supporting this hypothesis is the observation that two ions actively concentrated in the saliva – nitrate and thiocyanate – induce YHB1 expression. Indeed, whole-genome transcriptional analysis of C. albicans treated with nitrate or thiocyanate produce gene expression profiles nearly identical to cells treated with nitrite or nitric oxide. Pretreatment of C. albicans with either of these two nontoxic compounds increases resistance of the yeast to nitric oxide. I propose that this is an evolved response in which C. albicans anticipates nitric oxide stress generated in the stomach. C. albicans thus upregulates nitric oxide stress response genes in response to saliva signals that precede nitric oxide formation further on in the gut. Only a few examples of anticipatory signaling have so far been identified and it is not known how common this type of regulation is among microbes. Expression of the YHB1 gene in response to nitric oxide is regulated by the transcription factor Cta4. I show that Cta4 binds to the YHB1 promoter in vivo as a homodimer and is necessary, but not sufficient, for nitric oxide, nitrate and thiocyanate induced expression of YHB1. Based on these data I propose a model in which Cta4 transcriptional activation is inhibited under non-inducing conditions by a negative regulator. Understanding the mechanism by which C. albicans senses and responds to nitric oxide, nitrate and thiocyanate remains a question for future research.

Reproduction de : Thèse de doctorat : Intelligence artificielle : Toulouse, INPT : 2008. / Titre provenant de l'écran-titre. Bibliogr. 142 réf.

Les mouvements volontaires sont accompagnés par des ajustements posturaux anticipateurs (APAs). Leur rôle consiste à prévenir et à compenser de possibles perturbations du corps provoquées par l'exécution du mouvement. Des études antérieures ont montré que la coordination posture / mouvement est modifiée selon que le mouvement est exécuté le plus rapidement possible en réponse à un signal externe (réactif :TRS), ou que le mouvement est auto-initié (prédictif :AI). L'objectif de ce travail est d'examiner le mode de coordination posture / mouvement impliqué dans une situation d'anticipation-coïncidence (AC) lors de l'exécution de mouvements simples et complexes, et ensuite, comparer ce mode aux modes TRS et AI. Trois études expérimentales ont été menées pour vérifier si : (1) les modes de coordination, obtenus sur des gestes simples, s'étendent à des mouvements complexes ; (2) le mode de coordination en AC dépend des caractéristiques temporelles du mobile utilisé dans la tâche ; (3) les commandes impliquant les APAs et le mouvement focal sont associées ou dissociées en fonctions des contraintes temporelles TRS et AC. Ainsi, nous avons démontré que : (1) les stratégies de coordination posture / mouvement s'appliquent sur les mouvements complexes ; (2) la prédictibilité du moment de déclenchement dans la condition AC rapproche celle-ci de la situation AI ; (3) les différences de coordination entre les conditions réactive (TRS) et prédictives (AC, AI) sont liées à des différences dans les mécanismes de préparation consistant à dissocier les commandes posturales et focales en situation prédictive et à associer ces commandes dans la situation réactive. Les implications théoriques qui émergent de ces résultats sont discutées.

Return temporal anticipation on the basis of the ball trajectory estimation Abstract Ball-hitting in tennis involves spatio-temporal information about the ball's flight trajectory. We have focused on the temporal part of the information during returning a tennis serve that was simulated by a ball machine. The tested people had occlusion glasses placed on their head, which occluded their vision at the exact time, when the ball was being sent from the ball machine. The tested person did not know which part of the ball flight trajectory would be occluded, nor the ball speed. We examined the effect of part ball flight trajectory occlusion on the correct return timing of the ball. The analysis revealed that the greatest problems occurred while the second third of the ball flight trajectory had been occluded and reached most temporal errors at that time. Keywords: tennis, anticipation, ball flight trajectory, return stroke, occlusion glasses

The current body of work aims to apply Processing Efficiency Theory (PET) and Attentional Control Theory (ACT) to novel dynamic settings by examining how anxiety influences perceptual-cognitive and perceptual-motor skills. Sporting domains and fall-risk in older adults are studied. Applying ACT to a tennis anticipation paradigm examines whether state anxiety influences processing efficiency and the use of contextual information during anticipation. Processing efficiency was reduced under anxiety, while overall response accuracy was unchanged. Furthermore, skilled performers were seemingly less able to utilise contextual information when anxious. Studies in Chapters 4 and 5 sought to test the predictions of PET and ACT compared with those of Reinvestment Theory (RT) in the field of fall-risk in older adults. In Chapter 4, trait anxiety, alongside increasing dual-task demands, produced processing and motoric inefficiencies through reduced visual planning and mean gait velocity. Furthermore, greater and more variable gait velocity reductions were found in those with higher trait anxiety. By contrast, greater reinvestment levels were associated with poorer visuospatial recall, higher stepping accuracy, plus larger and less variable gait velocity reductions. Chapter 5 further investigates the motoric inefficiencies observed in anxious older adults’ gait. The influences of trait anxiety, movement specific reinvestment, and falls efficacy on body segmental control during adaptive turning are studied. Trait anxiety and falls efficacy were mainly shown to influence differing facets of turning behaviour, though both were associated with greater coupling of body segments (en-bloc rotations), whereas, limited support was offered for RT. Overall, PET and ACT were supported when applied to these new dynamic domains. However, discrepancies are discussed due to testing theoretical hypotheses in more representative environments.

Previous investigations comparing direct versus indirectly cued movements have consistently shown that indirectly cued movements take longer to prepare (Neely and Heath, 2010) and involve the recruitment of additional brain areas (Connolly et al., 2000). This increase in processing time has been associated with the additional cognitive transformations required of the task (Neely and Heath, 2010). In the present study we investigated whether differences between direct versus indirectly cued movements are also reflected in the time course of motor preparation. Participants performed a targeting task, moving directly to the location of a visual cue (i.e., directly cued movement) or to a location that differed by 60˚, 90˚, or 120˚ with respect to the visual cue provided (i.e., indirectly cued movements). Participants were instructed to initiate their movements concurrently with an anticipated go-signal. To examine the time course of motor preparation, a startling acoustic stimulus (SAS, 124dB) was randomly presented 150 ms, 500 ms, or 1000 ms prior to the go-signal. Results from the startle trials revealed that the time course of motor preparation was similar regardless of the angle of rotation required and hence whether it was a direct or indirectly cued trial. Specifically, motor preparation was delayed until less than 500 ms prior to movement initiation for both direct and indirectly cued movements. These findings indicate that similar motor preparation strategies are engaged for both types of cued movements, suggesting that the time to prepare a motor response may be similar regardless of whether a cognitive transformation is required.

INTRODUCTION: Sensory systems within the head provide us with rich perceptual information and may require complex control of the head during locomotion when changing direction. Head position in space is maintained by head on trunk motion as well as lower extremity kinematic modifications, such as increased knee flexion and increased stance time in order to facilitate shock attenuation and reduce vertical CoM displacement. It has been established that the body organizes its degrees of freedom of the trunk, pelvis and lower extremities differently during anticipated and unanticipated sidestepping, which raises the question of how these modifications affect head control during change of direction tasks. METHODS: Fourteen collegiate soccer players performed 7 anticipated and 7 unanticipated sidestepping tasks. Kinematic data were recorded using an 11-camera motion capture system (Qualysis, Inc., Gothenburg, Sweden) sampling at 240 Hz. Head and trunk orientation was quantified at penultimate toe off. A modified vector coding analysis was used to quantify the coordination and coordination variability between the head and trunk during the anticipated and unanticipated side-stepping trials. Differences in head-trunk orientation and coordination pattern frequencies were assessed with a paired t-test with an . One-dimensional statistical parametric mapping (SPM1D) was used to compare coordination variability waveforms. RESULTS: The head (p < 0.01, ES = 0.82) and trunk (p < 0.05, ES = 0.59) were significantly more oriented toward the new travel direction during anticipated compared to unanticipated sidestepping. No significant differences in transverse or sagittal plane coordination were observed throughout the change of direction stride. However, during unanticipated sidestepping we observed significantly reduced in-phase head-trunk coordination during the preparatory phase in the sagittal (p = 0.04, ES = 0.63) and transverse (p = 0.02, ES = 0.73) planes but did not find differences in the stance or post-transition phases. Coordination variability did not differ between anticipated and unanticipated conditions. Irrespective of planning time, greater transverse plane coordination variability was observed during the flight phases compared to the stance phase (p < 0.01) of the change of direction stride. Sagittal plane coordination variability was significantly greater during the preparatory phase than the stance phase (p < 0.01), and stance phase coordination variability was significantly greater than post-transition phase variability (p < 0.01). SIGNIFICANCE: Our results suggest differences in coordination between the head and trunk between anticipated and unanticipated sidestepping emerge during the preparatory phase of the change of direction stride, from penultimate step toe off to transition step heel strike. Anticipated and unanticipated sidestepping are different tasks, but individuals are consistent in the way the head-trunk coupling is controlled. Relating variability to task goals may allow for a better understanding of the beneficial aspects of variability observed at the head.

The purpose of this study was to determine whether practice or different experiential background has an effect on anticipation time. Anticipation time is performing a movement upon the arrival of an outside stimulus and having them meet at a designated point or objective. It was hypothesized that Division I baseball players would have better anticipation timing scores than Division III players because of their experiential background. Twelve Division I baseball players were compared to twelve Division III baseball players using a BASSIN Anticipation Timer. A ten foot runway with a string activated microswitch was used for the anticipation task. Subjects were asked to swing their hands, mimicing their regular batting motion through the string switch to coincide with the illumination of the last light on the runway. Each subject had twenty random trials at each of the two speeds. Nine mph represented a collegiate fastball, while eight mph represented a collegiate off-speed pitch. Independent t-tests indicated that Division I players had significantly better anticipation time for the collegiate fastball (9 mph) than Division III players. There was no significant difference at 8 mph. Thus, the hypothesis, that Division I would have better anticipation time was supported for the higher speed pitches. / Master of Science