Similar to functional magnetic resonance imaging (fMRI), a more recent neuroimaging technology called functional near-infrared spectroscopy (fNIRS) leverages the fact that neuronal activation correlates with increases in blood flow to study the brain. However, instead of relying on the magnetic properties of hemoglobin in the blood like fMRI, fNIRS relies on the optical properties of hemoglobin. This difference yields several advantages that make fNIRS a promising modality for investigating recovery from post-stroke aphasia: it has fewer contraindications for participants (e.g., compatibility with cardiac pacemakers), it is more affordable, it can be conducted portably in an upright and seated position similar to a typical speech therapy session, and it has more effective motion-correction methods that are useful when examining expressive language. Although the use of fNIRS in the post-stroke aphasia literature is growing, no studies have yet explored the reliability of fNIRS in the post-stroke aphasia population. To prevent research waste as more aphasia research begins to incorporate the use of fNIRS, this study will address the need for evidence of fNIRS reliability.

 Aphasia is an acquired language impairment that occurs in approximately one-third of stroke survivors. Currently, evidence-based practice for treating aphasia consists of behavioral speech-language therapy, administered by a trained speech-language pathologist (SLP). Such behavioral interventions have been shown to alter brain activity in a way that leads to reorganization, overcoming the deficits left by lesioned tissue. However, little is known about the real-time effects of speech-language therapy on the brain, or the mechanism by which brain activity is ultimately altered. Functional near-infrared spectroscopy (fNIRS) is a neuroimaging method that presents the opportunity to investigate these questions due to its ability to be conducted portably, wherever speech-language therapy is conducted, in a natural, upright, and seated position, unlike other neuroimaging methods. Few studies have implemented fNIRS in the study of post-stroke aphasia recovery and none have used it during treatment sessions. We will record fNIRS activity during administration of Oral Reading for Language in Aphasia® (ORLA), an evidence-based treatment that targets sentence-level comprehension and production. The broad objective of this project is to advance our understanding of brain activity during language tasks for patients with aphasia, by using fNIRS recording during a naturalistic clinical intervention for patients with aphasia and a matched healthy adult comparison group.

This NIH-funded project is investigating patient-specific factors that may influence response to therapy for language impairment after stroke, or aphasia. Results from this work will assist with better estimation of prognosis for stroke survivors with aphasia, which could empower patients and families to make more informed health care decisions about how to pursue the most appropriate rehabilitation services based on their unique characteristics, such as genetics, cognitive skills, and brain structure after stroke. Dr. Stacy Harnish (Associate Professor in Speech and Hearing Science) with co-investigators Christopher Bartlett (Nationwide Children’s Hospital), Jeff Pan (Biomedical Informatics), Stephen Petrill (Psychology), David Osher (Psychology), and Vivien Lee (Neurology) were awarded a five-year, $2.3 million grant from the National Institute on Deafness and other Communication Disorders to complete this work. My role in this project has been to manage staff and student training, recruitment, and data collection.

Aphasia impacts approximately one-third of stroke survivors as a result of damage to the language network in the brain. After only a few months, recovery begins to plateau, leading to less than a quarter of individuals with aphasia making a full recovery by 18 months post-stroke. Rehabilitation can continue to facilitate improvements in these individuals with chronic aphasia; however, progress is slow, despite continued use of evidence-based therapeutic interventions by trained speech-language pathologists. Crucially, little is known about the compensatory mechanisms that take place at the neurological level among individuals recovering from aphasia, which could be promoted using technology such as non-invasive brain stimulation to improve recovery. Motivated by a lack of clarity surrounding cortical compensation within the language network, this study aims to use resting state functional connectivity neuroimaging and a series of semantic and phonological working memory tasks to explore compensatory activity further. Sites such as the anterior superior temporal gyrus and posterior middle temporal gyrus have been implicated by previous findings to compensate for language processing in individuals with lesions to the inferior frontal gyrus. Our findings will have broad implications for our understanding of neuroplasticity within the language network of individuals with aphasia and more specifically inform montage placement for future clinical trials of non-invasive brain stimulation techniques.