Auditory-Motor Adaptation to Frequency-Altered Auditory Feedback Occurs When Participants Ignore Feedback

Background Auditory feedback is important for accurate control of voice fundamental frequency (F0). The purpose of this study was to address whether task instructions could influence the compensatory responding and sensorimotor adaptation that has been previously found when participants are presented with a series of frequency-altered feedback (FAF) trials. Trained singers and musically untrained participants (nonsingers) were informed that their auditory feedback would be manipulated in pitch while they sang the target vowel [/ɑ /]. Participants were instructed to either ‘compensate’ for, or ‘ignore’ the changes in auditory feedback. Whole utterance auditory feedback manipulations were either gradually presented (‘ramp’) in -2 cent increments down to -100 cents (1 semitone) or were suddenly (’constant‘) shifted down by 1 semitone. Results Results indicated that singers and nonsingers could not suppress their compensatory responses to FAF, nor could they reduce the sensorimotor adaptation observed during both the ramp and constant FAF trials. Conclusions Compared to previous research, these data suggest that musical training is effective in suppressing compensatory responses only when FAF occurs after vocal onset (500-2500 ms). Moreover, our data suggest that compensation and adaptation are automatic and are influenced little by conscious control

Relationship of neurite architecture to brain activity during task-based fMRI

Functional MRI (fMRI) has been widely used to examine changes in neuronal activity during cognitive tasks. Commonly used measures of gray matter macrostructure (e.g., cortical thickness, surface area, volume) do not consistently appear to serve as structural correlates of brain function. In contrast, gray matter microstructure, measured using neurite orientation dispersion and density imaging (NODDI), enables the estimation of indices of neurite density (neurite density index; NDI) and organization (orientation dispersion index; ODI) in gray matter. Our study explored the relationship among neurite architecture, BOLD (blood-oxygen-level-dependent) fMRI, and cognition, using a large sample (n = 750) of young adults of the human connectome project (HCP) and two tasks that index more cortical (working memory) and more subcortical (emotion processing) targeting of brain functions. Using NODDI, fMRI, structural MRI and task performance data, hierarchical regression analyses revealed that higher working memory- and emotion processing-evoked BOLD activity was related to lower ODI in the right DLPFC, and lower ODI and NDI values in the right and left amygdala, respectively. Common measures of brain macrostructure (i.e., DLPFC thickness/surface area and amygdala volume) did not explain any additional variance (beyond neurite architecture) in BOLD activity. A moderating effect of neurite architecture on the relationship between emotion processing task-evoked BOLD response and performance was observed. Our findings provide evidence that neuro-/social-affective cognition-related BOLD activity is partially driven by the local neurite organization and density with direct impact on emotion processing. In vivo gray matter microstructure represents a new target of investigation providing strong potential for clinical translation

Cortico-amygdalar connectivity and externalizing/internalizing behavior in children with neurodevelopmental disorders

Background: Externalizing and internalizing behaviors contribute to clinical impairment in children with neurodevelopmental disorders (NDDs). Although associations between externalizing or internalizing behaviors and cortico-amygdalar connectivity have been found in clinical and non-clinical pediatric samples, no previous study has examined whether similar shared associations are present across children with different NDDs. Methods: Multi-modal neuroimaging and behavioral data from the Province of Ontario Neurodevelopmental Disorders (POND) Network were used. POND participants aged 6–18 years with a primary diagnosis of autism spectrum disorder (ASD), attention-deficit/hyperactivity disorder (ADHD) or obsessive–compulsive disorder (OCD), as well as typically developing children (TDC) with T1-weighted, resting-state fMRI or diffusion weighted imaging (DWI) and parent-report Child Behavioral Checklist (CBCL) data available, were analyzed (total n = 346). Associations between externalizing or internalizing behavior and cortico-amygdalar structural and functional connectivity indices were examined using linear regressions, controlling for age, gender, and image-modality specific covariates. Behavior-by-diagnosis interaction effects were also examined. Results: No significant linear associations (or diagnosis-by-behavior interaction effects) were found between CBCL-measured externalizing or internalizing behaviors and any of the connectivity indices examined. Post-hoc bootstrapping analyses indicated stability and reliability of these null results. Conclusions: The current study provides evidence towards an absence of a shared linear relationship between internalizing or externalizing behaviors and cortico-amygdalar connectivity properties across a transdiagnostic sample of children with different primary NDD diagnoses and TDC. Different methodological approaches, including incorporation of multi-dimensional behavioral data (e.g., task-based fMRI) or clustering approaches may be needed to clarify complex brain-behavior relationships relevant to externalizing/internalizing behaviors in heterogeneous clinical NDD populations

Resting-State Connectivity Biomarkers of Cognitive Performance and Social Function in Individuals With Schizophrenia Spectrum Disorder and Healthy Control Subjects

BACKGROUND: Deficits in neurocognition and social cognition are drivers of reduced functioning in schizophrenia spectrum disorders, with potentially shared neurobiological underpinnings. Many studies have sought to identify brain-based biomarkers of these clinical variables using a priori dichotomies (e.g., good vs. poor cognition, deficit vs. nondeficit syndrome). METHODS: We evaluated a fully data-driven approach to do the same by building and validating a brain connectivity-based biomarker of social cognitive and neurocognitive performance in a sample using resting-state and task-based functional magnetic resonance imaging (n = 74 healthy control participants, n = 114 persons with schizophrenia spectrum disorder, 188 total). We used canonical correlation analysis followed by clustering to identify a functional connectivity signature of normal and poor social cognitive and neurocognitive performance. RESULTS: Persons with poor social cognitive and neurocognitive performance were differentiated from those with normal performance by greater resting-state connectivity in the mirror neuron and mentalizing systems. We validated our findings by showing that poor performers also scored lower on functional outcome measures not included in the original analysis and by demonstrating neuroanatomical differences between the normal and poorly performing groups. We used a support vector machine classifier to demonstrate that functional connectivity alone is enough to distinguish normal and poorly performing participants, and we replicated our findings in an independent sample (n = 75). CONCLUSIONS: A brief functional magnetic resonance imaging scan may ultimately be useful in future studies aimed at characterizing long-term illness trajectories and treatments that target specific brain circuitry in those with impaired cognition and function

The role of the dorsolateral prefrontal cortex in self-initiating elaborative episodic encoding: evidence from fMRI and TMS

Several clinical populations (e.g. Schizophrenia, Alzheimer's disease, frontal lobe damage, and healthy aging with memory decline) display memory deficits which may be related to a failure to engage efficient memory encoding strategies. However, these groups often show improved memory performance when cued towards the use of efficient encoding strategies, suggesting the deficits are related to self-initiating elaborative encoding processes. At present, little is know about the neural correlates of self-initiating elaborative encoding strategies in episodic memory. The purpose of this thesis was to better understand the process of initiating elaborative encoding strategies. We hypothesized that the left dorsolateral prefrontal cortex (DLPFC) was involved in self-initiating elaborative encoding strategies. Experiment 1 was an fMRI study in which we presented conditions in which participants were either cued to use an efficient encoding strategy (semantic analysis) or were not cued to do so (a self-initiated condition), while presenting stimuli with variable semantic relatedness. We observed activity in the left DLPFC and bilateral supramarginal gyrus in response to semantic relatedness in the non-semantic (self-initiated) encoding condition. In experiment 2, we attempted to confirm the role of the left DLPFC in self-initiating elaborative encoding using transcranial magnetic stimulation (TMS), a method in which we can transiently disrupt neural activity in a limited cortical area. We performed stimulation of the left DLPFC and a control site (the vertex) during a memory encoding task. We observed a significant correlation in a subsequent cued recall task (a measure of encoding success) between the effects of TMS during encoding and participant's use of memory strategies during encoding only in the condition in which self-initiated elaborative encoding was beneficial to memory performance. This suggests a causative role for the DLPFC in self-initiating elaborative encoding. Experiment 3 was a concurrent TMS-fMRI study. Participants performed an encoding task (similar to the self-initiated condition in experiment 1) while we measured brain activity using fMRI. TMS stimulation was presented for 300ms on ¾ of trials. The onset of stimulation was varied, starting at 200ms, 600ms, or 1000ms after stimulus onset. We observed time-specific changes in neural activity in response to TMS stimulation, suggesting that concurrent TMS-fMRI can be used to measure time-varying interactions between the DLPFC and distal brain regions These three experiment provide evidence o f the role of the left DLPFC in self-initiating elaborative encoding strategies, and the utility of TMS and fMRI (separately or combined) as research techniques to address these techniques. These studies also demonstrate the utility of our selected paradigms to directly address the issue of self-initiating elaborative encoding (rather than correlating activity to specific encoding strategies).Plusieurs populations cliniques (ex. schizophrénie, maladie d'Alzheimer, lésions du lobe frontal, vieillissement normal avec déclin de mémoire) démontrent des déficits de mémoire qui peuvent être reliés à une incapacité d'initier des stratégies efficaces d'encodage de mémoire. Cependant, ces groupes démontrent souvent une amélioration de leur performance lorsqu'on les aide à choisir une stratégie d'encodage efficace, suggérant que les déficits seraient reliés à l'utilisation spontanée de stratégies d'encodage élaborées. A ce jour, nous savons très peu de choses à propos des corrélats neuronaux de l'utilisation spontanée de stratégies d'encodage élaborées. Le but de cette thèse est de mieux comprendre les processus de l'initiation de stratégies d'encodage élaborées. Nous émettons l'hypothèse que le cortex préfrontal dorsolatéral (DLPFC) est impliqué dans l'utilisation spontanée de stratégies d'encodage élaborées. L'expérience 1 consiste en une étude d'IRMf dans laquelle nous avons présenté des conditions dans lesquelles les participants étaient guidés à utiliser une stratégie d'encodage efficace (analyse sémantique) ou non guidés d'utiliser cette stratégie (condition auto-initiée), en présentant des stimuli de relations sémantiques variées. Nous avons observé une activité dans le DLPFC gauche et le gyrus supramarginal bilatéral en réponse à la relation sémantique dans la condition d'encodage non-sémantique (auto-initiée). Dans l'expérience 2, nous avons tenté de confirmer le rôle du DLPFC gauche dans l'utilisation spontanée de stratégies d'encodage élaborées en utilisant la stimulation magnétique transcrânienne (SMT), une méthode avec laquelle nous pouvons perturber l'activité neuronale de façon transitoire dans une aire corticale limitée. Nous avons performé une stimulation du DLPFC gauche et d'un site contrôle (le vertex) durant une tâche d'encodage de mémoire. Nous avons observé une corrélation significative dans la tâche de reconnaissance subséquente (une mesure de la réussite de l'encodage) entre les effets de la SMT durant l'encodage et l'utilisation de stratégies de mémoire du participant pendant l'encodage seulement dans la condition où l'utilisation spontanée de stratégies d'encodage élaborées était bénéfique pour la performance de mémoire. Ceci suggère un rôle causal du DLPFC dans l'utilisation spontanée de stratégies d'encodage élaborées. L'expérience 3 était une étude simultanée de SMT-IRMf. Les participants devaient faire une tâche d'encodage (similaire à la condition auto-initiée de l'expérience 1) pendant que l'on mesurait l'activité du cerveau avec l'IRMf. Une SMT était faite pendant 300ms sur les trois-quarts des essais. Le début de la stimulation était varié, commençant à 200ms, 600ms ou 1000ms après le début du stimulus. Nous avons observé des changements spécifiques au temps dans l'activité neuronale en réponse à la stimulation SMT, indiquant que l'utilisation simultanée de SMT-IRMf peut être utilisée pour mesurer l'interaction en fonction du temps entre le DLPFC et les régions distales du cerveau. Ces trois expériences apportent des évidences du rôle du DLPFC gauche dans l'utilisation spontanée de stratégies d'encodage élaborées et l'utilité de la SMT et de l'IRMf (séparément ou combinées) comme techniques de recherche pour étudier ces processus. Ces études démontrent aussi l'utilité de nos paradigmes pour étudier directement l'utilisation spontanée de stratégies d'encodage élaborées (au lieu de corréler l'activité à des stratégies d'encodage spécifique)

Auditory-motor adaptation to frequency-altered auditory feedback occurs when participants ignore feedback

Background Auditory feedback is important for accurate control of voice fundamental frequency (F0). The purpose of this study was to address whether task instructions could influence the compensatory responding and sensorimotor adaptation that has been previously found when participants are presented with a series of frequency-altered feedback (FAF) trials. Trained singers and musically untrained participants (nonsingers) were informed that their auditory feedback would be manipulated in pitch while they sang the target vowel [/ɑ /]. Participants were instructed to either ‘compensate’ for, or ‘ignore’ the changes in auditory feedback. Whole utterance auditory feedback manipulations were either gradually presented (‘ramp’) in -2 cent increments down to -100 cents (1 semitone) or were suddenly (’constant‘) shifted down by 1 semitone. Results Results indicated that singers and nonsingers could not suppress their compensatory responses to FAF, nor could they reduce the sensorimotor adaptation observed during both the ramp and constant FAF trials. Conclusions Compared to previous research, these data suggest that musical training is effective in suppressing compensatory responses only when FAF occurs after vocal onset (500-2500 ms). Moreover, our data suggest that compensation and adaptation are automatic and are influenced little by conscious control

Heightened Responses of the Parahippocampal and Retrosplenial Cortices during Contextualized Recognition of Congruent Objects

Context sometimes helps make objects more recognizable. Previous studies using functional magnetic resonance imaging (fMRI) have examined regional neural activity when objects have strong or weak associations with their contexts. Such studies have demonstrated that activity in the parahippocampal cortex (PHC) generally corresponds with strong associations between objects and their spatial contexts while retrosplenial cortex (RSC) activity is linked with episodic memory. However these studies investigated objects viewed in associated contexts, but the direct influence of scene on the perception of visual objects has not been widely investigated. We hypothesized that the PHC and RSC may only be engaged for congruent contexts in which the object could typically be found but not for neutral contexts. While in an fMRI scanner, 15 participants rated the recognizability of 152 photographic images of objects, presented within congruent and incongruent contexts. Regions of interest were created to examine PHC and RSC activity using a hypothesis-driven approach. Exploratory analyses were also performed to identify other regional activity. In line with previous studies, PHC and RSC activity emerged when objects were viewed in congruent contexts. Activity in the RSC, inferior parietal lobe (IPL) and fusiform gyrus also emerged. These findings indicate that different brain regions are employed when objects are meaningfully contextualized