THE BRAIN AND STROKE
Cognitive scientist Greg Hickok studies what happens when words fail
It can be heart-wrenching to watch a loved one struggle to verbally express him- or herself after suffering stroke-induced brain damage.
Known as conduction aphasia, the disorder produces lesions that interfere with the neurological process of translating thought into speech, according to UCI cognitive neuroscientist Greg Hickok. The interference is believed to occur in the Sylvian fissure dividing the brain’s parietal and temporal lobes. The same region, he says, could help explain why some people stutter and how schizophrenics can misinterpret their internal thoughts as external voices.
To date, Hickok has received more than $12 million in funding from the National Institutes of Health to support 15 years of continued research on how neural abnormalities affect speech and language in an area of the brain tied to autism, schizophrenia and stroke-induced aphasia.
The act of speech involves coordination between auditory and motor functions in the brain ... a word’s sound guides our speech.
“The act of speech involves coordination between auditory and motor functions in the brain,” Hickok says. “This is obvious in visuomotor tasks like reaching for a cup, where we use visual information about its shape and location to guide our reach. It’s less obvious in language, but studies have shown that in the same way, a word’s sound guides our speech.
”The director of UCI’s Center for Language Science, Hickok first began seeing this in action at a neural level when utilizing fMRI to study brain processes related to speech production. He noticed that, in addition to the expected motor regions, auditory areas of the brain “lit up,” or activated, when participants named pictures – even if they only thought about, and didn’t actually vocalize, the words.
“Stroke-based research found that these activations reflected the critical involvement of auditory areas in speaking. When these regions are damaged, patients tend to struggle to come up with words, and when they do speak, they make a lot of errors,” says Hickok.
He has since been using fMRI and stroke-based methods to zero in on the Sylvian parietal-temporal (SPT) region of the brain, in which he believes the regulation of auditory and motor processes occurs.
“In people with schizophrenia or aphasia and those who stutter, the coordination between perception and production is dysfunctional, and it appears to be happening in the SPT region,” Hickok says. “Depending on exactly how the process misfires, the result can be speech errors, stuttering or auditory hallucinations.”
While Hickok explains that it’s generally accepted in the cognitive neuroscience community that auditory and motor functions work together, the details are not well understood. He is currently working to close this knowledge gap.
His findings have been published in journals such as Neuron, Cognition, the Journal of Cognitive Neuroscience, the Journal of Neuroscience, and others. He has also created a multi-university consortium for this type of research. Hickok’s hope is that by conducting studies and sharing findings, he and others will contribute to the development of better therapies for people with brain damage, lesions or neural abnormalities.