Johns Hopkins researchers are studying transcranial direct-current stimulation (TDCS) to augment language therapy after stroke. Pictured: areas of brain activation during an overt picture-naming task (compared to rest) in a patient with a left hemisphere stroke (primarily in the parietal cortex), used to localize the area of stimulation for TDCS during language therapy. Areas significantly activated include bilateral visual processing areas in the occipital lobes as well as in the left temporal cortex—important for language comprehension—and in in the left posterior frontal cortex—critical for articulation of speech.
Before Argye Hillis was a Johns Hopkins neurologist, she was a speech-language pathologist. Many of her patients were trying to recover from aphasia, the communication disorder caused mainly by stroke and characterized by difficulty producing or comprehending speech or written language.
“It’s a problem that I’ve been interested in a long time,” she says.
The most common treatment for aphasia is language therapy delivered by a speech-language pathologist that’s augmented largely by computer-based programs at home. However, Hillis says, this therapy has limited effectiveness—patients who receive it often continue to have debilitating language problems that persist for years or become permanent.
That’s why Hillis and colleagues at Johns Hopkins, the University of South Carolina (USC) and the University of California, Irvine (UCI), recently launched a multisite effort known as the Center for the Study of Aphasia Recovery (C-STAR) to better understand aphasia and develop new ways to treat this condition. C-STAR is funded by an $11.1 million grant from the National Institutes of Health over five years.
Hillis, who serves as the principal investigator of C-STAR’s clinical core, is leading a study at Johns Hopkins to investigate the use of transcranial direct-current stimulation (TDCS) to augment language therapy. In this approach, electrodes placed on the scalp deliver a constant, low current to the brain.
“Our ultimate hope is that we find something that can really improve aphasia recovery and give patients the ability to communicate effectively again.” - Argye Hillis
The theory behind TDCS suggests that, when delivered while subjects perform a task, the current changes threshold of activation that neurons involved in the task need to fire. Over time, this lower threshold leads to neuroplasticity, with new neurons taking over the functions of those damaged during stroke.
The researchers will compare those who receive this additional intervention during language therapy to those who receive conventional language therapy alone, enrolling only patients who’ve had strokes within three months. They’ll compare results to a similar study currently taking place at USC for patients whose strokes occurred longer ago.
Hillis’ team Will also study the interaction of these treatments with selective serotonin reuptake inhibitors (SSRIs), a class of drugs typically used to treat depression and often prescribed to patients following stroke. Because some evidence suggests that SSRIs can aid post-stroke motor recovery, Hillis and her colleagues are looking to see if these drugs can give language therapy a similar boost, particularly when combined with TDCS.
These efforts will be combined with imaging and theoretical studies taking place at USC and UCI. Together, Hillis says, the study will attack the problem of aphasia from multiple angles.
“Our ultimate hope,” she says, “is that we find something that can really improve aphasia recovery and give patients the ability to communicate effectively again.”
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