05 Dec 2013

Exploring the Source of Language Comprehension

Scientists are mapping the brain in order to pinpoint areas crucial to language comprehension

The mental processes involved in understanding language are far more complex that simply matching words to objects or actions. When listening to someone talk, or read a piece of text, a person’s mind paints a complex picture that helps them visualise what is being described, even to the point of attributing feelings and emotions to the subject, and creating a context full of prior history and elaborate background.

Human beings rely on this ability, known as discourse comprehension, to function with one another on a day-to-day level. In fact, the social life of mankind would be unrecognisable without the means to understand written or spoken language as we do.

Now, a study is attempting to pinpoint the exact region of the brain that relates to discourse comprehension.

Principal author Aron Barbey, a professor of neuroscience, of psychology, and of speech and hearing science at the University of Illinois, has been working with injured American war veterans in his research into discourse comprehension.

All of the 145 men in the study, published in Brain: A Journal of Neurology, suffered injuries to the brain caused by shrapnel. Shrapnel injuries tend to be specific to small areas, unlike other brain conditions such as stroke or neurological disorders, which affect multiple regions. By looking at these types of injuries, researchers can pinpoint the structures that are critically important to discourse comprehension.

Prof Barbey is also the director of the Decision Neuroscience Laboratory at the Beckman Institute for Advanced Science and Technology in Illinois. His previous work includes mapping general intelligence, emotional intelligence and a host of other high-level cognitive functions.

He said: “Neuropsychological patients with focal brain lesions provide a valuable opportunity to study how different brain structures contribute to discourse comprehension.”

Prof Barbey and his team used the latest mapping techniques to create a three-dimensional map of the cerebral cortex based on the data from the veterans’ computerised tomography (CT) scans.

The technique, called voxel-based lesion-symptom mapping, divides the brain into small three-dimensional sections known as voxels, much like two-dimensional pixels but with an extra axis. By creating this map, the scientists were able to compare the discourse comprehension abilities of patients with damage to a particular voxel or cluster of voxels, with those of patients without injuries to those brain regions.

The results of the study suggest that the frontal and parietal cortex areas of the brain are heavily linked to discourse comprehension.

Prof Barbey explained: “Rather than engaging brain regions that are classically involved in language processing, our results indicate that discourse comprehension depends on an executive control network that helps integrate incoming language with prior knowledge and experience.”

Executive function (also known as executive control) is a set of processes in the brain that allows people to connect past experience with present action. It is necessary to perform activities such as planning, organising, strategising and remembering details, as well as functioning effectively in time and space.

Working memory is also linked to executive function. It is important for guiding actions as it allows a person to recall things in their ‘mind’s eye, and sum up situations.

“The findings help us understand the neural foundations of discourse comprehension, and suggest that core elements of discourse processing emerge from a network of brain regions that support language processing and executive functions. The findings offer new insights into basic questions about the nature of discourse comprehension,” Barbey said.

“This could offer new targets for clinical interventions to help patients with cognitive-communication disorders. Discourse comprehension is a hallmark of human social behaviour. By studying the mechanisms that underlie these abilities, we’re able to advance our understanding of the remarkable cognitive and neural architecture from which language comprehension emerges.”



 
 

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