Frontal brain asymmetries as effective parameters to assess the quality of audiovisual stimuli perception in adult and young cochlear implant users

How is music perceived by cochlear implant (CI) users? This question arises as "the next step" given the impressive performance obtained by these patients in language perception. Furthermore, how can music perception be evaluated beyond self-report rating, in order to obtain measurable data? To address this question, estimation of the frontal electroencephalographic (EEG) alpha activity imbalance, acquired through a 19-channel EEG cap, appears to be a suitable instrument to measure the approach/withdrawal (AW index) reaction to external stimuli. Specifically, a greater value of AW indicates an increased propensity to stimulus approach, and vice versa a lower one a tendency to withdraw from the stimulus. Additionally, due to prelingually and postlingually deafened pathology acquisition, children and adults, respectively, would probably differ in music perception. The aim of the present study was to investigate children and adult CI users, in unilateral (UCI) and bilateral (BCI) implantation conditions, during three experimental situations of music exposure (normal, distorted and mute). Additionally, a study of functional connectivity patterns within cerebral networks was performed to investigate functioning patterns in different experimental populations. As a general result, congruency among patterns between BCI patients and control (CTRL) subjects was seen, characterised by lowest values for the distorted condition (vs. normal and mute conditions) in the AW index and in the connectivity analysis. Additionally, the normal and distorted conditions were significantly different in CI and CTRL adults, and in CTRL children, but not in CI children. These results suggest a higher capacity of discrimination and approach motivation towards normal music in CTRL and BCI subjects, but not for UCI patients. Therefore, for perception of music CTRL and BCI participants appear more similar than UCI subjects, as estimated by measurable and not self-reported parameters

Novel methods to evaluate blindsight and develop rehabilitation strategies for patients with cortical blindness

20 à 57 % des victimes d'un accident vasculaire cérébral (AVC) sont diagnostiqués aves des déficits visuels qui réduisent considérablement leur qualité de vie. Parmi les cas extrêmes de déficits visuels, nous retrouvons les cécités corticales (CC) qui se manifestent lorsque la région visuelle primaire (V1) est atteinte. Jusqu'à présent, il n'existe aucune approche permettant d'induire la restauration visuelle des fonctions et, dans la plupart des cas, la plasticité est insuffisante pour permettre une récupération spontanée. Par conséquent, alors que la perte de la vue est considérée comme permanente, des fonctions inconscientes mais importantes, connues sous le nom de vision aveugle (blindsight), pourraient être utiles pour les stratégies de réhabilitation visuelle, ce qui suscite un vif intérêt dans le domaine des neurosciences cognitives. La vision aveugle est un phénomène rare qui dépeint une dissociation entre la performance et la conscience, principalement étudiée dans des études de cas. Dans le premier chapitre de cette thèse, nous avons abordé plusieurs questions concernant notre compréhension de la vision aveugle. Comme nous le soutenons, une telle compréhension pourrait avoir une influence significative sur la réhabilitation clinique des patients souffrant de CC. Par conséquent, nous proposons une stratégie unique pour la réhabilitation visuelle qui utilise les principes du jeu vidéo pour cibler et potentialiser les mécanismes neuronaux dans le cadre de l'espace de travail neuronal global, qui est expliqué théoriquement dans l'étude 1 et décrit méthodologiquement dans l'étude 5. En d'autres termes, nous proposons que les études de cas, en conjonction avec des critères méthodologiques améliorés, puissent identifier les substrats neuronaux qui soutiennent la vision aveugle et inconsciente. Ainsi, le travail de cette thèse a fourni trois expériences empiriques (études 2, 3 et 4) en utilisant de nouveaux standards dans l'analyse électrophysiologique qui décrivent les cas de patients SJ présentant une cécité pour les scènes complexes naturelles affectives et ML présentant une cécité pour les stimuli de mouvement. Dans les études 2 et 3, nous avons donc sondé les substrats neuronaux sous-corticaux et corticaux soutenant la cécité affective de SJ en utilisant la MEG et nous avons comparé ces corrélats à sa perception consciente. L’étude 4 nous a permis de caractériser les substrats de la détection automatique des changements en l'absence de conscience visuelle, mesurée par la négativité de discordance (en anglais visual mismatch negativity : vMMN) chez ML et dans un groupe neurotypique. Nous concluons en proposant la vMMN comme biomarqueur neuronal du traitement inconscient dans la vision normale et altérée indépendante des évaluations comportementales. Grâce à ces procédures, nous avons pu aborder certains débats ouverts dans la littérature sur la vision aveugle et sonder l'existence de voies neurales secondaires soutenant le comportement inconscient. En conclusion, cette thèse propose de combiner les perspectives empiriques et cliniques en utilisant des avancées méthodologiques et de nouvelles méthodes pour comprendre et cibler les substrats neurophysiologiques sous-jacents à la vision aveugle. Il est important de noter que le cadre offert par cette thèse de doctorat pourrait aider les études futures à construire des outils thérapeutiques ciblés efficaces et des stratégies de réhabilitation multimodale.20 to 57% of victims of a cerebrovascular accident (CVA) develop visual deficits that considerably reduce their quality of life. Among the extreme cases of visual deficits, we find cortical blindness (CC) which manifests when the primary visual region (V1) is affected. Until now, there is no approach that induces restoration of visual function and in most cases, plasticity is insufficient to allow spontaneous recovery. Therefore, while sight loss is considered permanent, unconscious yet important functions, known as blindsight, could be of use for visual rehabilitation strategies raising strong interest in cognitive neurosciences. Blindsight is a rare phenomenon that portrays a dissociation between performance and consciousness mainly investigated in case reports. In the first chapter of this thesis, we’ve addressed multiple issues about our comprehension of blindsight and conscious perception. As we argue, such understanding might have a significant influence on clinical rehabilitation patients suffering from CB. Therefore, we propose a unique strategy for visual rehabilitation that uses video game principles to target and potentiate neural mechanisms within the global neuronal workspace framework, which is theoretically explained in study 1 and methodologically described in study 5. In other words, we propose that case reports, in conjunction with improved methodological criteria, might identify the neural substrates that support blindsight and unconscious processing. Thus, the work in this Ph.D. work provided three empirical experiments (studies 2, 3, and 4) that used new standards in electrophysiological analyses as they describe the cases of patients SJ presenting blindsight for affective natural complex scenes and ML presenting blindsight for motion stimuli. In studies 2 and 3, we probed the subcortical and cortical neural substrates supporting SJ’s affective blindsight using MEG as we compared these unconscious correlates to his conscious perception. Study 4 characterizes the substrates of automatic detection of changes in the absence of visual awareness as measured by the visual mismatch negativity (vMMN) in ML and a neurotypical group. We conclude by proposing the vMMN as a neural biomarker of unconscious processing in normal and altered vision independent of behavioral assessments. As a result of these procedures, we were able to address certain open debates in the blindsight literature and probe the existence of secondary neural pathways supporting unconscious behavior. In conclusion, this thesis proposes to combine empirical and clinical perspectives by using methodological advances and novel methods to understand and target the neurophysiological substrates underlying blindsight. Importantly, the framework offered by this doctoral dissertation might help future studies build efficient targeted therapeutic tools and multimodal rehabilitation training

Sensorimotor Modulations by Cognitive Processes During Accurate Speech Discrimination: An EEG Investigation of Dorsal Stream Processing

Internal models mediate the transmission of information between anterior and posterior regions of the dorsal stream in support of speech perception, though it remains unclear how this mechanism responds to cognitive processes in service of task demands. The purpose of the current study was to identify the influences of attention and working memory on sensorimotor activity across the dorsal stream during speech discrimination, with set size and signal clarity employed to modulate stimulus predictability and the time course of increased task demands, respectively. Independent Component Analysis of 64–channel EEG data identified bilateral sensorimotor mu and auditory alpha components from a cohort of 42 participants, indexing activity from anterior (mu) and posterior (auditory) aspects of the dorsal stream. Time frequency (ERSP) analysis evaluated task-related changes in focal activation patterns with phase coherence measures employed to track patterns of information flow across the dorsal stream. ERSP decomposition of mu clusters revealed event-related desynchronization (ERD) in beta and alpha bands, which were interpreted as evidence of forward (beta) and inverse (alpha) internal modeling across the time course of perception events. Stronger pre-stimulus mu alpha ERD in small set discrimination tasks was interpreted as more efficient attentional allocation due to the reduced sensory search space enabled by predictable stimuli. Mu-alpha and mu-beta ERD in peri- and post-stimulus periods were interpreted within the framework of Analysis by Synthesis as evidence of working memory activity for stimulus processing and maintenance, with weaker activity in degraded conditions suggesting that covert rehearsal mechanisms are sensitive to the quality of the stimulus being retained in working memory. Similar ERSP patterns across conditions despite the differences in stimulus predictability and clarity, suggest that subjects may have adapted to tasks. In light of this, future studies of sensorimotor processing should consider the ecological validity of the tasks employed, as well as the larger cognitive environment in which tasks are performed. The absence of interpretable patterns of mu-auditory coherence modulation across the time course of speech discrimination highlights the need for more sensitive analyses to probe dorsal stream connectivity

Social and Affective Neuroscience of Everyday Human Interaction

This Open Access book presents the current state of the art knowledge on social and affective neuroscience based on empirical findings. This volume is divided into several sections first guiding the reader through important theoretical topics within affective neuroscience, social neuroscience and moral emotions, and clinical neuroscience. Each chapter addresses everyday social interactions and various aspects of social interactions from a different angle taking the reader on a diverse journey. The last section of the book is of methodological nature. Basic information is presented for the reader to learn about common methodologies used in neuroscience alongside advanced input to deepen the understanding and usability of these methods in social and affective neuroscience for more experienced readers

Change blindness: eradication of gestalt strategies

Arrays of eight, texture-defined rectangles were used as stimuli in a one-shot change blindness (CB) task where there was a 50% chance that one rectangle would change orientation between two successive presentations separated by an interval. CB was eliminated by cueing the target rectangle in the first stimulus, reduced by cueing in the interval and unaffected by cueing in the second presentation. This supports the idea that a representation was formed that persisted through the interval before being 'overwritten' by the second presentation (Landman et al, 2003 Vision Research 43149–164]. Another possibility is that participants used some kind of grouping or Gestalt strategy. To test this we changed the spatial position of the rectangles in the second presentation by shifting them along imaginary spokes (by ±1 degree) emanating from the central fixation point. There was no significant difference seen in performance between this and the standard task [F(1,4)=2.565, p=0.185]. This may suggest two things: (i) Gestalt grouping is not used as a strategy in these tasks, and (ii) it gives further weight to the argument that objects may be stored and retrieved from a pre-attentional store during this task