Stroke impacts speech sound integration, not speed, study reveals

Following stroke, some people experience a language disorder that hinders their ability to process speech sounds. How do their brains change from stroke? Researchers led by Laura Gwilliams, faculty scholar at the Wu Tsai Neuroscience Institute and Stanford Data Science and assistant professor at the Stanford School of Humanities and Sciences, and Maaike Vandermosten, associate professor at the Department of Neurosciences at KU Leuven, compared the brains of 39 patients following stroke and 24 healthy age-matched controls to unveil language processing brain mechanisms. 

As reported in their JNeurosci paper, the researchers recorded brain activity while volunteers listened to a story. People with verbal speech processing issues from stroke were not slower to process speech sounds but had much weaker processing than healthy participants. According to the researchers, this suggests that people with this language disorder can hear sounds of all kinds as well as healthy people but have issues integrating speech sounds to understand language. 

Additionally, when there was uncertainty about what words were being said, healthy people processed speech sound features longer compared to those who had experienced a stroke. This could mean that, following stroke, people do not process speech sounds long enough to successfully comprehend words that are difficult to detect. 

This work points to brain activity patterns that may be crucial for understanding verbal language, according to the authors. First author Jill Kries expresses excitement about continuing to explore how this simple approach-listening to a story-can be used to improve diagnostics for conditions characterized by language processing issues, which currently involve hours of behavioral tasks.