Roozbeh Behroozmand, Ph.D. - US grants

PROJECT SUMMARY/ABSTRACT Stroke is a leading cause of disability in the United States, which in many cases can lead to speech impairment that creates barriers to participation in professional, social, and family settings. Aphasia is the most common type of post-stroke speech impairment that has profound consequences for the patients and results in diminished ability to comprehend, produce and control speech. While recovery can be promoted with speech treatment, improvement remains modest and typically requires a large amount of therapy which contributes to rising health care costs. A major shortcoming of currently existing treatment approaches is that they have focused on enhancing the outcome measures associated speech production, without taking into account that targeting deficits in sensory feedback processing of speech may significantly increase treatment efficiency and effectiveness. Therefore, a key step toward refining treatment strategies is to develop objective biomarkers that can probe the integrity of sensorimotor mechanisms of speech and identify their impaired function in patients with post-stroke aphasia. This proposed project is significant because it takes the first step toward exploring the behavioral and neuroanatomical biomarkers of impaired sensorimotor processing, with focus on understanding the critical role of auditory feedback mechanisms for speech production in aphasia. The career development plan combines the candidate's former research training with expertise of the mentoring team to meet the goals of the proposed project. The research and training plans provide an empirical foundation for the proposed project and will allow the candidate to establish a translational line of research as an independent investigator to study the behavioral and neural bases of speech sensorimotor impairment in stroke patients with aphasia. This project aims to use the behavioral biomarkers of altered auditory feedback (AAF) combined with neuroimaging data to identify the patterns of brain damage and diminished structural connectivity within the auditory-motor areas of the left hemisphere that predict impaired sensorimotor processing of speech in aphasia. The long-term goal of this research is to develop a model that relates patterns of brain damage to sensorimotor deficits causing speech impairment. The main objective of this proposal is to identify behavioral and neuroanatomical biomarkers that characterize deficits in sensorimotor mechanisms of speech. The central hypothesis is that damages to auditory-motor network will impair speakers' ability to detect and/or correct for AAF-induced speech errors. We also hypothesize that the patterns of damage will predict the degree of diminished speech error processing, as indexed by the AAF biomarkers. The rationale for the proposed research is that identifying the source of sensorimotor deficit will improve diagnosis and targeted treatment of speech disorders in aphasia. The proposed research is relevant to that part of NIH's mission that pertains to developing fundamental knowledge that will potentially help to reduce the burdens of human disability.

Project Summary/Abstract Aphasia is a common and devastating effect of left hemisphere stroke and is one of the most debilitating communication disorders characterized by speech/language production and comprehension deficits. According to the National Institute of Neurological Disorders and Stroke (NINDS), approximately one million individuals in the U.S. suffer from aphasia. This number is anticipated to rise as life expectancy increases and life-saving procedures in acute stroke decrease mortality rates. Although speech therapy can improve communication in aphasia, most patients with chronic stroke never fully recover and are left with life-long disability and some only experience very minimal return of communicative function. Therefore, a major public health need is to identify biomarkers to inform targeted treatment and improve its long-term outcomes in aphasia. A major shortcoming of currently existing treatment approaches is that they primarily focus on enhancing the outcome measures associated vocal motor production, without taking into account that targeting deficits in sensory feedback and/or sensorimotor integration mechanisms may significantly increase treatment efficiency and effectiveness. Therefore, a key step toward refining treatment strategies is to develop objective biomarkers that can probe the integrity of vocal sensorimotor mechanisms and identify their impaired function in stroke patients with aphasia. This proposed project is significant in that it takes a key step toward examining the biomarkers of impaired vocal sensorimotor function in patients with post-stroke aphasia, with particular focus on understanding the role of auditory feedback mechanisms in vocal communication. The central hypothesis is that distinct patterns of brain damage and diminished connectivity within the audio-vocal networks leads to patient-specific impairment of feedforward motor, sensory feedback, and/or sensorimotor integration mechanisms. The main objective is to incorporate multi-modality measures including the behavioral biomarkers of altered auditory feedback (AAF), lesion anatomy, white matter tractography, functional neuroimaging (MRI), and neurophysiological (EEG/ERP) data to build integrative computational models for examining impaired vocal sensorimotor function in stroke patients with aphasia. We also aim to use an innovative visual feedback training paradigm to provide a secondary source of sensory information via the visual modality to improve audio-vocal integration function in patients with aphasia. The validation of the visual feedback training paradigm will pave the way toward developing individually tailored targeted therapies that focus on patient-specific functional deficits for vocal communication. The long-term goal of this research is to identify the source and modality (motor, sensory, and/or sensorimotor) of vocal communication deficits to provide information for clinicians on how to fine-tune their strategies to maximize the long-term treatment outcomes and improve the communicative function and quality of life in patients suffering from aphasia. This proposed research is relevant to the NIH?s mission pertaining to developing fundamental knowledge that will help to reduce the burdens of human disability.