Hopkins Scientists Clock The Speed Of Comprehension

May 26, 1998

New Data To Aid Efforts To Understand How The Brain Processes Language

Capitalizing on an opportunity presented by a patient scheduled for tests using electrodes surgically placed on his brain, Johns Hopkins scientists have clocked the speed of thought, measuring the time the patient took to understand what everyday objects are in pictures.

The Hopkins team, led by neurologist John Hart, M.D., discovered that it took their volunteer patient about 250 to 300 milliseconds, or a fourth of a second, to begin to understand a pictured object, and another 250 to 450 milliseconds to fully comprehend what the object was. He appeared to complete the process more quickly when the object shown was familiar to him, Hart notes.

"The data, obtained within a single stage at a single site in the brain, are further evidence that information accumulates gradually in the brain, rather than in a strictly all-or-none fashion," Hart says.

Understanding the individual steps that cause this accumulation, and how they relate to each other functionally and temporally, could help scientists better understand comprehension and word loss from disorders like stroke or Alzheimer's disease, he notes.

In an article describing the unusual experiment in the May 25 Proceedings of the National Academy of the Sciences, Hart and Hopkins specialists in epilepsy, biomedical engineering, neurosurgery, neuropsychology and cognitive science said knowing the time sequence and speed of language processing and other "cognitive operations" is "critical for building theories of higher mental activity."

"This information has been difficult to acquire," Hart notes, "even with different combinations of behavioral tests, electrical recordings and imaging studies such as PET scans."

Their task was somewhat simplified by an adult epilepsy patient preparing for surgery to control intractable seizures experienced since age 8. The patient was scheduled to have a grid of 174 electrodes temporarily implanted on the surface of his brain to pinpoint the source of his seizures for removal in surgery.

The patient, a 22-year-old, agreed to participate in a series of language experiments while the electrodes were still implanted.

Scientists asked him to name and categorize a variety of pictures and words. During some of these tests, scientists used the grid to monitor brain activity; in others, they applied a mild electrical current through two electrodes.

"The current temporarily and safely depolarizes the nerve cells in the vicinity of the electrodes," says Hart. "We've shown previously that this will temporarily disable the area of the brain where it's applied, but the effect doesn't spread to other nearby areas and is safely reversible."

That makes the current a good test of whether a brain area is critical for a task, Hart notes.

"We were able to show that an area known as the left occipitotemporal gyrus, located on the base of the brain, is linked in our patient to many of the word recognition activities we tested," says Hart. "Applying current here as we presented the patient with a new test could cause problems in understanding what objects are; misinterpretations of verbs, colors, or shapes; and word-finding difficulties in spontaneous speech."

Hart says the finding suggests that there may a stage in language processing where different kinds of language activities, all performed in various parts of the brain, come to the same brain area to complete a common step.

To time brain activity, researchers applied the current at various times while the subject was recognizing a picture, noting when the current disabled his ability to name a picture and when it didn't, a technique Hart calls "timeslicing."

"Applying the current anytime before 400 milliseconds after the picture was shown disrupted his ability to name it," says Hart. "This disruption started to fade away for familiar objects at 450 milliseconds, and for less familiar objects at 750 milliseconds."

Other authors on the study were Nathan Crone, Jeffrey Sieracki, Diana Miglioretti, Charles Hall, David Sherman and Barry Gordon.
Johns Hopkins Medical Institutions' news releases are available on a PRE-EMBARGOED basis on EurekAlert at http://www.eurekalert.org, Newswise at http://www.newswise.com and from the Office of Communications and Public Affairs' direct e-mail news release service. To enroll, call 410-955-4288 or send e-mail to bsimpkin@welchlink.welch.jhu.edu or 76520.560@compuserve.com.

On a POST-EMBARGOED basis find them at http://hopkins.med.jhu.edu, Quadnet at http://www.quad-net.com, ScienceDaily at http://www.sciencedaily.com or on CompuServe in the SciNews-MedNews library of the Journalism Forum under file extension ".jhm".

Johns Hopkins Medicine

Related Language Articles from Brightsurf:

Learning the language of sugars
We're told not to eat too much sugar, but in reality, all of our cells are covered in sugar molecules called glycans.

How effective are language learning apps?
Researchers from Michigan State University recently conducted a study focusing on Babbel, a popular subscription-based language learning app and e-learning platform, to see if it really worked at teaching a new language.

Chinese to rise as a global language
With the continuing rise of China as a global economic and trading power, there is no barrier to prevent Chinese from becoming a global language like English, according to Flinders University academic Dr Jeffrey Gil.

'She' goes missing from presidential language
MIT researchers have found that although a significant percentage of the American public believed the winner of the November 2016 presidential election would be a woman, people rarely used the pronoun 'she' when referring to the next president before the election.

How does language emerge?
How did the almost 6000 languages of the world come into being?

New research quantifies how much speakers' first language affects learning a new language
Linguistic research suggests that accents are strongly shaped by the speaker's first language they learned growing up.

Why the language-ready brain is so complex
In a review article published in Science, Peter Hagoort, professor of Cognitive Neuroscience at Radboud University and director of the Max Planck Institute for Psycholinguistics, argues for a new model of language, involving the interaction of multiple brain networks.

Do as i say: Translating language into movement
Researchers at Carnegie Mellon University have developed a computer model that can translate text describing physical movements directly into simple computer-generated animations, a first step toward someday generating movies directly from scripts.

Learning language
When it comes to learning a language, the left side of the brain has traditionally been considered the hub of language processing.

Learning a second alphabet for a first language
A part of the brain that maps letters to sounds can acquire a second, visually distinct alphabet for the same language, according to a study of English speakers published in eNeuro.

Read More: Language News and Language Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.