The exchange of words in a conversation may seem unremarkable for most people. But, for people with aphasia, communication problems can make it difficult to work and maintain social relationships. Aphasia is an impairment of language that often happens after stroke or other brain injury.

Brain Waves

Aphasia affects about 1 in 250 people, making it more common than Parkinson’s or cerebral palsy.

A new Drexel study published in the journal Nature Communications provides a detailed brain map of language impairments in aphasia following stroke.

Assistant Professor of Psychology Daniel Mirman, the lead author of the study with colleagues at the Moss Rehabilitation Research Institute, says his team’s findings could help “improve our clinical understanding of aphasia and get new insights into how language is organized in the mind and brain.”

The researchers found that spoken language impairments vary along four dimensions or factors: semantic recognition (matching related pictures and/or words); speech recognition (telling “ba” and “da” apart, for example); speech production (making speech errors like saying “girappe” for “giraffe”); and semantic errors (such as saying “zebra” instead of “giraffe”).

Next, the researchers determined how each of these impairments was associated with the locations in the brain damaged by stroke. They created a four-factor lesion-symptom map of hotspots in the language-specialized left hemisphere where damage from a stroke tended to cause deficits for each specific type of language impairment.

Studying the association between patterns of brain injury and cognitive deficits is a classic approach, with roots that go back to the dawn of cognitive neuroscience in the 19th century. Mirman and his colleagues have scaled up this approach, both in terms of the number of participants and the number of performance measures, and combined it with 21st-century brain imaging and statistical techniques.