Fatal earthquakes such as that which occurred in Christchurch on February 22nd 2011, can result in survivors having difficulties with cognitively processing the event, which may be the precursor to posttraumatic stress symptoms. Trauma related dissociation has been proposed to be a mechanism related to these cognitive processing difficulties. Most research focusing on information processing and dissociation post-trauma has conducted controlled analogue studies or has not focused solely on information processing and dissociation. There is also scant research on these constructs across therapy. In response to this gap in research, two studies were developed. An association was proposed between dissociation and information processing as demonstrated by an increase in conceptual processing and a reduction in dissociation. It was predicted that an improvement in these constructs would be related to a reduction in PTSD symptoms over therapy. Study1 applied a case-study design to 5 individuals who were attending therapy for post-traumatic stress disorder in response to the trauma they had experienced from the Christchurch earthquakes. Study 2 assessed information processing and dissociation (via self and observer report) in 20 individuals who had direct exposure to the effects of the earthquake. Earthquake information processing and dissociation were assessed as they were happening nearly two year’s post-quake using correlation analyses and hierarchical regressions. The hypotheses were partially confirmed, in that an increase in conceptual processing was not shown to be associated with a reduction in dissociation. However, an increase in conceptual processing was shown to be related to trauma symptom improvement particularly for re-experiencing symptoms. In addition, study 2 demonstrated a possible relationship between trait dissociation and arousal symptoms. These findings partially support the proposed role information processing and dissociation play in the recovery from PTSD. The findings suggest that trauma related difficulties should be assessed as early as possible to resolve issues related to a delay in symptom reporting.

abstract: The experience of language can, as any other experience, change the way that the human brain is organized and connected. Fluency in more than one language should, in turn, change the brain in the same way. Recent research has focused on the differences in processing between bilinguals and monolinguals, and has even ventured into using different neuroimaging techniques to study why these differences exist. What previous research has failed to identify is the mechanism that is responsible for the difference in processing. In an attempt to gather information about these effects, this study explores the possibility that bilingual individuals utilize lower signal strength (and by comparison less biological energy) to complete the same tasks that monolingual individuals do. Using an electroencephalograph (EEG), signal strength is retrieved during two perceptual tasks, the Landolt C and the critical flicker fusion threshold, as well as one executive task (the Stroop task). Most likely due to small sample size, bilingual participants did not perform better than monolingual participants on any of the tasks they were given, but they did show a lower EEG signal strength during the Landolt C task than monolingual participants. Monolingual participants showed a lower EEG signal strength during the Stroop task, which stands to support the idea that a linguistic processing task adds complexity to the bilingual brain. Likewise, analysis revealed a significantly lower signal strength during the critical flicker fusion task for monolingual participants than for bilingual participants. Monolingual participants also had a significantly different variability during the critical flicker fusion threshold task, suggesting that becoming bilingual creates an entirely separate population of individuals. Future research should perform analysis with the addition of a prefrontal cortex electrode to determine if less collaboration during processing is present for bilinguals, and if signal complexity in the prefrontal cortex is lower than other electrodes. / Dissertation/Thesis / Masters Thesis Psychology 2019

In this thesis, we are interested in processing noisy speech signals that are meant to be heard by humans, and hence we approach the noise-suppression problem from a perceptual perspective. We develop a noise-suppression paradigm that is based on a model of the human auditory system, where we process signals in a way that is natural to the human ear. Under this paradigm, we transform an audio signal in to a perceptual domain, and processes the signal in this perceptual domain. This approach allows us to reduce the background noise and the audible artifacts that are seen in traditional noise-suppression algorithms, while preserving the quality of the processed speech. We develop a single- and dual-microphone algorithm based on this perceptual paradigm, and conduct subjecting tests to show that this approach outperforms traditional noise-suppression techniques. Moreover, we investigate the cause of audible artifacts that are generated as a result of suppressing the noise in noisy signals, and introduce constraints on the noise-suppression gain such that these artifacts are reduced.

xviii, 216 p. : ill. (some col.) / The focus of this dissertation is on how language experience shapes perception of a non-native prosodic contrast. In Tokyo Japanese, fundamental frequency (F0) peak and fall are acoustic cues to lexically contrastive pitch patterns, in which a word may be accented on a particular syllable or unaccented (e.g., tsúru 'a crane', tsurú 'a vine', tsuru 'to fish'). In English, lexical stress is obligatory, and it may be reinforced by F0 in higher-level prosodic groupings. Here I investigate whether English listeners can attend to F0 peaks as well as falls in contrastive pitch patterns and whether training can facilitate the learning of prosodic categories. In a series of categorization and discrimination experiments, where F0 peak and fall were manipulated in one-word utterances, the judgments of prominence by naïve English listeners and native Japanese listeners were compared. The results indicated that while English listeners had phonetic sensitivity to F0 fall in a same-different discrimination task, they could not consistently use the F0 fall to categorize F0 patterns. The effects of F0 peak location and F0 fall on prominence judgments were always larger for Japanese listeners than for English listeners. Furthermore, the interaction between these acoustic cues affected perception of the contrast by Japanese, but not English, listeners. This result suggests that native, but not non-native, listeners have complex and integrated processing of these cues. The training experiment assessed improvement in categorization of Japanese pitch patterns with exposure and feedback. The results suggested that training improved identification of the accented patterns, which also generalized to new words and new contexts. Identification of the unaccented pattern, on the other hand, showed no improvement. Error analysis indicated that native English listeners did not learn to attend specifically to the lack of the F0 fall. To conclude, language experience influences perception of prosodic categories. Although there is some sensitivity to F0 fall in non-native listeners, they rely mostly on F0 peak location in language-like tasks such as categorization of pitch patterns. Learning of new prosodic categories is possible. However, not all categories are learned equally well, which suggests that first language attentional biases affect second language acquisition in the prosodic domain. / Committee in charge: Susan Guion Anderson, Chairperson; Melissa A. Redford, Member; Vsevolod Kapatsinki, Member; Kaori Idemaru, Outside Member

Due to various shortcomings of the visual system, some visual stimuli can only be identified with 100% accuracy if they are shown for a certain amount of time. This time can be measured using the Inspection Time (IT) paradigm. In an IT task, a “pi” figure with differing leg lengths is typically presented briefly (e.g., 20-200 ms) and is then immediately masked to prevent retinal afterimages. Participants are subsequently required to choose which of the two legs was longer. The objective of this task is to determine the shortest amount of time the pi figure needs to be shown for it to be perceived with 80% accuracy. Given that visual processing has been shown to be altered during and /or prior to a movement, the present experiment sought to test how the requirement to perform a motor task affected IT. Twenty-eight participants took part in the experiment, which was comprised of three conditions: no-movement (NM), peak velocity (PV), and foreperiod (FP). In the NM condition, participants grasped a manipulandum and engaged in the IT paradigm. At the end of every trial, participants verbally stated which leg they believed was longest. In the PV condition participants made a rapid movement to a target, and the IT stimulus was presented when their limb reached peak velocity. Finally in the FP condition the IT stimulus was presented during foreperiod (FP). In all three conditions the IT stimulus was randomly presented from between 15-105 ms (in 15 ms increments) and masked for 400 ms. Results showed no significant differences on the IT task between the NM and FP conditions, suggesting no visual upregulation during foreperiod. However, IT performance was significantly poorer in the PV condition in comparison to both the NM and FP condition, suggesting a visual downregulation at that particular movement kinematic.

La vidéo sur IP a connu un essor rapide ces dernières années allant de la diffusion télévisuelle en haute qualité via des réseaux dédiés à la diffusion sur internet de contenus vidéo grand public. L’optimisation de l’encodage vidéo H.264/AVC permet aux différents acteurs du marché de se différencier en proposant des solutions pour réduire le débit nécessaire à la représentation d’un flux vidéo ainsi que pour améliorer la qualité perçue par les utilisateurs. C’est dans ce contexte de vidéo professionnelle en haute qualité que s’inscrivent ces travaux de thèse CIFRE réalisés au sein de l’entreprise Digigram, proposant des encodeurs vidéo temps réel pour des diffusions professionnelles en direct. Nous proposons deux solutions de prétraitement pour répondre aux problématiques du secteur de la distribution vidéo. Les deux solutions considèrent les caractéristiques du système visuel humain en exploitant un modèle de JND (Just Noticeable Distortion) définissant des seuils de perception en fonction d’une analyse du contenu des séquences vidéo à encoder. La première solution utilise un préfiltre adaptatif indépendant de l’encodeur, contrôlé par un modèle JND afin d'éliminer le contenu perceptuellement non pertinent et ainsi réduire le débit sans altérer la qualité ressentie. Une analyse approfondie de plusieurs filtres de la littérature, dont le filtre AWA (Adaptive Weighted Averaging) et le filtre bilatéral, nous a également amené à définir deux nouveaux filtres à support étendu qui permettent d’exploiter au mieux les corrélations dans les images haute définition. A l’aide de tests subjectifs, nous montrons que les préfiltres perceptuels proposés permettent en moyenne de diminuer le débit en sortie du codeur d'environ 20% pour une qualité constante en encodage VBR (débit variable) Intra et Inter-image. Finalement, une deuxième solution s’attache à améliorer la qualité perçue dans un contexte d’encodage CBR (débit constant) en intégrant un modèle JND dans l’une des implémentations de la norme H.264/AVC la plus reconnue, le codec x264. Une quantification adaptative perceptuelle est ainsi proposée permettant d’améliorer les performances du codec x264 en améliorant le codage de l’information de contour à moyen et bas débits en encodage intra et inter-image. / The use of digital video over IP has increased exponentially over the last years, due to the development of high-speed networks dedicated to high quality TV transmission as well as the wide development of the nonprofessional video webcast. Optimization of the H.264/AVC encoding process allows manufacturers to offer differentiating encoding solutions, by reducing the bandwidth necessary for transmitting a video sequence at a given quality level, or improving the quality perceived by final users at a fixed bit rate. This thesis was carried out at the company Digigram in a context of professional high quality video. We propose two solutions of preprocessing which consider the characteristics of the human visual system by exploiting a JND profile (Just Noticeable Distortion). A JND model defines perceptual thresholds, below which a distortion cannot be seen, according to the video content. The first solution proposes an adaptive pre-filter independent to the encoder, controlled by a JND profile to reduce the perceptually non-relevant content and so reduce the bitrate while maintaining the perceived quality. By analyzing the state-of-the-art literature, the AWA (Adaptive Weighted Averaging) and Bilateral filters have been selected. Then we define two new filters using a large convolution mask, which enable to better exploit correlations in high-definition video contents. Through subjective tests, we show that the proposed perceptual prefilters give an average bitrate reduction of 20% for the same visual quality in VBR (Variable Bitrate) H.264/AVC Intra and Inter encoding. Finally, the second solution enables to improve the perceived quality in CBR (Constant Bitrate) encoding, by integrating the JND profile into the x264 codec, one of the best implementation of the H.264/AVC standard. Thus, we propose a perceptual adaptive quantization which enhances the x264 performance by improving edge information coding in low and middle bitrate applications.

Des anomalies du traitement des informations sensorielles sont observées dans l'autisme, notamment, les signaux dynamiques semblent trop rapides et/ou complexes pour être convenablement traités par les personnes avec TSA. Aussi, ralentir ces signaux (Gepner, 2001, 2005) pourrait les aider à les percevoir et faciliterait leur compréhension aux interactions sociales. Nous avons proposé des enfants avec TSA, âgés de 3 à 8 ans, pendant un an des séances hebdomadaires d'orthophonie impliquant l'utilisation d'un logiciel ralentissant le son et les images des vidéos (Logiral(TM)). Un groupe contrôle d'enfants avec TSA, bénéficiant de séances d'orthophonie mais sans l'utilisation de Logiral(TM), a également été constitué. Nous avons comparé l'évolution des compétences socio-communicatives des deux groupes ainsi que les comportements d'exploration visuelle lors de la présentation du visage d'une narratrice racontant une histoire. Nos résultats montrent une amélioration significative de la capacité à imiter et diminution des comportements inadaptés uniquement pour les enfants du groupe expérimental. Après un an d'utilisation de Logiral(TM), ces enfants regardent davantage le visage et ses caractéristiques internes (yeux et bouche). / Sensory processing abnormalities are observed in autism, in particular dynamic signals involved in interactions seem too fast and/or too complex to be adequately treated by people with ASD. Also, slow down the speed of these signals (Gepner, 2001, 2005; Gepner et al, 2001, 2002, 2005) could help them to perceive informations and could facilitate their understanding in social interactions. We proposed to children with ASD, aged from 3 to 8 years, speech therapy weekly for a year with the use of a software (Logiral(TM)) to slow down sound and pictures. A control group of children with ASD, receiving speech therapy without the use of Logiral (TM) was also set up. We compared the evolution of the social communication skills of the two groups and their visual exploration behavior during the presentation of the face of a narrator telling a story. Our results show a significant improvement in the ability to imitate and a decrease in inappropriate behaviors, and this, only for the children in the experimental group. After a year of using Logiral(TM), these children watch more facial and internal features (eyes and mouth) which is no observed for children in the control group.

En plus de la triade de symptômes caractérisant l’autisme, ce trouble neurodévelopmental est associé à des particularités perceptives et motrices et, au niveau cérébral, par une connectivité atypique entre les différentes régions du cerveau. Au niveau anatomique, un des résultats les plus communs est la réduction du corps calleux. Toutefois, des effets directs de cette altération anatomique sur l’intégrité et l’efficacité du transfert interhémisphérique restent à être démontrés. Pour la présente thèse, trois différentes études investiguent différents aspects du traitement de l’information visuomotrice : le transfert interhémisphérique entre les régions bilatérales motrices et visuelles, la vitesse de traitement perceptif, et les habiletés motrices visuellement guidées. Dans la première étude, le paradigme visuomoteur de Poffenberger a été utilisé pour mesurer le temps de transfert interhémisphérique (TTIH). L’imagerie par résonnance magnétique fonctionnelle (IRMf) et structurale ainsi que l’imagerie de diffusion ont aussi été utilisées pour étudier les réseaux cérébraux impliqués dans la tâche de Poffenberger. Les autistes ont été comparés à un groupe d’individus à développement typique. La deuxième étude avait pour but d’investiguer la vitesse de traitement perceptif en autisme. Dans la troisième étude, deux tâches motrices (Purdue et Annett) ont été utilisées pour examiner la nature et l’importance des déficits moteurs. La tâche de Purdue inclut deux conditions bimanuelles utilisées comme indice additionnel d’intégration interhémisphérique. Dans les études 2 et 3, le groupe d’autistes a aussi été comparé à un groupe d’individus Asperger afin de voir si, et comment, les deux sous-groupes peuvent être distingués en ce qui concerne le traitement visuel et les déficits moteurs. Aucune différence entre les groupes n’a été observée en termes de TTIH. Les résultats de l’étude IRMf révèlent des différences d’activations corticales en lien avec la tâche de Poffenberger. Dans les groupes d’autistes et de typiques, l’efficacité de la communication interhémisphérique était associée à différentes portions du corps calleux (frontales/motrices chez les typiques, postérieures/visuelles chez les autistes). De façon globale, les résultats de cette étude démontrent un patron atypique de transfert interhémisphérique de l’information visuomotrice en autisme, reflétant un rôle plus important des mécanismes visuels dans le comportement sensorimoteur possiblement en lien avec une réorganisation cérébrale. Les résultats des études comportementales 2 et 3 indiquent que les autistes excellent dans la tâche mesurant la vitesse de traitement perceptif alors que les Asperger accomplissent la tâche à des niveaux similaires à ceux des typiques. La nature des déficits moteurs diffère aussi entre les deux sous-groupes; la dextérité et la coordination bimanuelle est affectée chez les individus Asperger mais pas chez les autistes, qui eux sont plus atteints au niveau de la rapidité unimanuelle. Les sous-groupes d’autistes et de syndrome d’Asperger sont caractérisés par des profils cognitifs différents dont les particularités perceptives et motrices font partie intégrante. / In addition to the triad of symptoms characterizing autism, this neurodevelopmental condition is characterized by visual and motor atypicalities and, at the cerebral level, by atypical connectivity between the different brain areas. Anatomically, one of the most replicated finding is a reduction of the corpus callosum. However, evidence of a direct effect of the corpus callosum reductions on integrity and efficiency of interhemispheric transfer is lacking. Three different studies were designed to investigate different aspect of visuo-motor processing: interhemispheric transfer between bilateral motor and visual brain areas, perceptual processing speed, visually guided motor performance. In the first study, the visuo-motor Poffenberger paradigm was used to measure interhemispheric transfer time (IHTT). Structural and functional magnetic resonance imaging (fMRI) and diffusion tensor imaging (DTI) were also used to study the brain networks involved in the Poffenberger task. Autistics were compared to typically developing individuals. The second study investigates whether perceptual processing speed (Inspection Time task) is atypical in autism. In the third study, two visually-guided motor tasks (the Purdue pegboard and Annett peg moving task) were used to verify the nature and magnitude of motor deficits. The Purdue task includes two bimanual conditions used as additional measures of interhemispheric communication integrity. Moreover, in studies 2 and 3, behavioral differences between autistic and Asperger individuals were investigated in order to see if and how the two subgroups can be distinguished in terms of perceptual processing and motor deficits. No group difference was observed in terms of IHTT. The fMRI results reveal a different pattern of cortical activations associated to the Poffenberger task. In the autism and typical groups, the efficiency of interhemispheric communication was associated with different portions of the corpus callosum (frontal/premotor in typicals, posterior/visual in autistics). These results demonstrate an atypical pattern of interhemispheric visuo-motor information transfer, possibly reflecting a more prominent role of visual mechanisms guiding sensorimotor behavior in autism, related to cerebral reorganizations. Results of the behavioral studies indicate that autistics have an excellent visual processing speed while Asperger individuals performed like typicals. Motor impairments also differed between the two subgroups; dexterity and bimanual coordination was impaired in Asperger individuals but not in autistics, who presented more difficulties in unimanual conditions. Autism and Asperger subgroups are characterized by different cognitive profiles in which visual processing and motor deficits are important factors.