Drexel University Psychologist John Medaglia, PhD, and colleagues at the University of Pennsylvania are trailblazing a new field of research called “cognitive neuroengineering.”
As head of the Cognitive Neuroengineering & Wellbeing Laboratory, Medaglia is the principal investigator on a recent study uncovering new insight into the correlation between brain networks and language — and how noninvasive brain stimulation could be used to repair cognitive function.
Effective verbal communication depends on one’s ability to retrieve and select the appropriate words to convey an intended meaning. For many, this process is instinctive, but for someone who has suffered a stroke or other brain damage, communicating even the most basic message can be arduous.
Scientists know that a brain region called the left inferior frontal gyrus (LIFG) is critical for language production and word processing. However, it remains unclear exactly how the LIFG interacts with the brain’s complex net- works to facilitate controlled language performance, or how these interactions might go awry in a damaged brain.
Medaglia and his colleagues have taken a novel approach to understanding how networks in the brain interact to make word-choice decisions using two techniques: transcranial magnetic stimulation, which uses an external magnetic field to induce currents in parts of the brain, and network control theory, which applies engineering and network science to brain systems. Their results, published in the Journal of Neuroscience, pave the way for the treatment of aphasia, or language loss, and other language disorders.
“Our ability to understand neural systems is fundamentally related to our ability to control them,” says Medaglia. “This research provides direct evidence that how we choose the words we want to say in natural language is related to the capability of the brain to integrate and segregate activity across major networks.”
Twenty-eight study subjects were asked to complete two different language tasks while the team administered the noninvasive brain stimulation. In the first task, study participants were asked to complete open- ended sentences such as, “They left the dirty dishes in the…” In the second task, study participants were asked to name specific images or numerals presented to them.
The researchers found that boundary controllability — the theoretical ability of a brain region to guide distinct brain networks to communicate with each other — was important for responding to the open-ended language tasks, when participants needed to retrieve and select a single word in the face of competing, alternative responses.
By contrast, modal controllability — the ability of a brain region to drive a network into “difficult to reach” states — was closely related to closed- ended language tasks.
Medaglia says his group was surprised to find this very clear distinction between how the brain responds to two similar language tasks.
The findings suggest that the LIFG’s ability to integrate and segregate communication between brain networks may not play an important role when people are selecting a single word from several alternative responses.
“There are debates about how unique these processes truly are, and now we have evidence that you can make a clear distinction between them,” Medaglia says. “It was also surprising to me that you could find this effect when studying the whole brain, whereas a lot of traditional views on language would have you focus on a much more specific area.”
Next, the research team is using the same type of techniques with stroke patients to see if stimulating certain areas of the brain can help them improve speech.
Study co-author Roy Hamilton, MD, of the University of Pennsylvania, suggests that these findings may someday benefit patients with aphasia due to stroke. For patients with aphasia, partial language recovery is often associated with the reorganization of the language system in the brain — essentially, when language functions performed by damaged areas of the brain shift to new areas that had not previously been involved in language processing.
“This study gives us new insight into the underlying properties of areas like the LIFG that enable the brain to process language,” Hamilton says. “But there are still questions we’re looking to answer. With further research, we can begin to uncover which areas of the brain are likely to be utilized if there’s an injury to the language system. This approach may provide exciting new targets for treatment with focal therapies, including neuromodulation.”
Earlier this year, the team also published the first research to link brain network anatomy and function to find correlates of mental flexibility — another type of cognitive control — in Nature Human Behaviour.
“In language and other functions like divided attention and focused perception, we’re combining brain anatomy and function to find the best targets for brain stimulation treatments in patients,” Medaglia says. “The idea behind cognitive neuroengineering is to take the best that cognitive neuroscience has to offer and approach treatments like an engineer.”