Researchers hope two emerging technologies-fMRI and cortical stimulation-can one day improve our understanding of and subsequent treatment efficacy for patients with aphasia.

Leora Cherney, PhD, CCC-SLP, BC-NCD, director of the Center for Aphasia Research and Treatment at the Rehabilitation Institute of Chicago, and Steven Small, PhD, MD, a professor of neurology and psychology at the University of Chicago, are using functional magnetic resonance imaging (fMRI) to record changes in brain activity in patients with aphasia following speech and language therapy. The technology allows researchers to observe changes in blood flow and blood oxygenation levels that occur during activities such as communication. Dr. Cherney said the imaging technique "is an indirect way of measuring neuronal activity in the brain during a mental operation, including the production, formulation and understanding of language."

Researchers are cautiously optimistic about fMRI, though existing studies generally have small subject numbers and use various imaging techniques, testing tasks and analyses. "We're in our infancy in terms of being able to interpret what the changes in brain activity that we're recording actually mean," she told ADVANCE. "Many variables impact our interpretation of the fMRI," including differences in lesion location and size, the tasks used in the scanner, and the language skills of the person with aphasia.

Still, she believes the technology holds the potential to determine which treatment approaches could best benefit individual patients based on the severity and type of their aphasia. "It can tell us which areas [of the brain] are active during a particular task and whether there is a change in activity as a result of therapy. At this point in time, it is a research tool and not a clinical tool in the area of aphasia," she noted.

Observing brain activity during a language task is thought to be valuable since language is supported by a neuronal network that involves several areas of the brain. Researchers hope to use fMRI to observe the parts that are most essential to language production. "We want to be able to compare behavioral changes in language to those that occur neurophysiologically and determine if these are the result of the specific treatment," she explained.

She and Dr. Small are collecting cognitive and language data on patients with stroke-induced aphasia before and after an intense course of speech and language therapy. They are using fMRI to scan patients during recovery to determine if there are relationships between behavioral and neurophysiological language-based changes that occur before and after the speech and language therapy.

Dr. Cherney also is conducting research involving the use of cortical stimulation to facilitate brain plasticity in patients with aphasia. "When a patient is going through rehabilitation, the brain is changing because it is plastic," she said. "Applying stimulation to the cerebral cortex may help facilitate brain plasticity."

The rationale of stimulating the brain is based, in part, on a theoretical model of interhemispheric rivalry. The model purports that a healthy brain relies on the balance between the right and left hemispheres and a lesion in either one causes an imbalance. "Aphasia usually occurs because of a lesion in the left hemisphere, where the language areas are strongly supported," Dr. Cherney said. "It has been proposed that there may be less activity in the hemisphere with the lesion or too much activity of the intact hemisphere. The left hemisphere normally imposes some kind of balance on the right hemisphere to keep its activity in check. When the left hemisphere is damaged, too much activity from the right hemisphere may be maladaptive and interfere with language recovery."

She will use a non-invasive technique, transcranial direct current stimulation, to stimulate the left hemisphere during intensive speech and language therapy.

"You can increase or inhibit neural activity depending on the kind of stimulation you use and where you apply it," she said. "Doing one or the other puts the hemispheres a little more back into balance. "

Dr. Cherney developed the therapy course used in the stimulation study. Oral Reading for Language in Aphasia (ORLA) is a procedure of reading aloud systematically and simultaneously with a clinician or with a "virtual therapist" on a computer program. (For more information, visit www.advance?web.com/speech and enter "ORLA" in the search box at the top of the homepage.)

She and Dr. Small previously used another type of cortical stimulation in a small pilot study involving patients with Broca's aphasia. Epidural cortical stimulation is a more invasive procedure that requires surgical electrode implantation.

All eight patients in the study received three hours of daily (Monday through Friday) speech and language therapy for six weeks. Four also received cortical stimulation during speech and language therapy, while the others served as a control.

"Overall, those who received cortical stimulation plus the speech and language therapy made a greater change than those who received the speech therapy alone," Dr. Cherney cautiously reported.

The researchers used the standardized Western Aphasia Battery to measure patient progress. Patients also were assessed six and 12 weeks after the completion of therapy. Some who received cortical stimulation showed continued improvement even after therapy had stopped. "Electrical stimulation may have done something to enhance plasticity so there would be continued improvement, even when the therapy had been completed," she said.

The severity of the aphasia was a key factor, the researchers noted. Patients who had severe aphasia showed greater changes with epidural cortical stimulation than those with mild aphasia.

Like fMRI, cortical stimulation research is in its infancy. Researchers are studying many different aspects of the stimulation techniques and their potential to enhance the effects of speech and language therapy. Chief among their questions is the safety and efficacy of each stimulation method. Scientists are unsure of the optimal location within each brain hemisphere to apply stimulation or when a patient is most likely to benefit from the technique.

The use of fMRI to document neurophysiological mechanism changes during cortical stimulation treatment may prove beneficial. "There's a whole lifetime of research questions to be answered," Dr. Cherney said.

Resources

• Cherney, L.R. (2008). Cortical stimulation and aphasia: The state of the science. Perspectives on Neurophysiology and Neurogenic Speech and Language Disorders, 18: 33-39.

• Cherney, L.R., Small, S.L. (2006). Task-dependent changes in brain activation following therapy for nonfluent aphasia: Discussion of two individual cases. Journal of the International Neuropsychological Society, 12: 828-42.

• Crinion, J.T.. Leff, A.P. (2007). Recovery and treatment of aphasia after stroke: Functional imaging studies. Current Opinion in Neurology, 10: 667-73.

• Thompson, C.K., den Ouden, D-B. (2008). Neuroimaging and recovery of language in aphasia. Current Neurology and Neuroscience Reports, 8: 475-83.

For More Information

• Leora Cherney, lcherney@ric.org

Alyssa Banotai is a Senior Associate Editor at ADVANCE. She can be contacted at abanotai@advanceweb.com.