Neural Bases of Vocal Sensorimotor Impairment in Aphasia

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.

Grant Number: 5R01DC018523-06
NIH Institute/Center: NIH
Principal Investigator: Roozbeh Behroozmand