Newly Identified Brain Pathways Vital to Understanding Language

ScienceDaily (Nov. 22, 2010) — A complex network of brain connections necessary for language comprehension has been mapped in new detail, according to recent research. These newly charted pathways will help scientists understand how language is processed in the brain, and how brain injuries disrupt the system.

The research was presented at Neuroscience 2010, the annual meeting of the Society for Neuroscience, held in San Diego.

"The question of how the brain understands language has puzzled scientists for generations," said senior author Nina Dronkers, PhD, of the Veterans Affairs Northern California Health Care System and the University of California, Davis. "We found rich connections throughout the brain that have not traditionally been associated with language, but are now found to tie together key areas important for understanding language."

Language and speech disorders affect millions of Americans and include a variety of problems, in both spoken language and in reading. In this study, Dronkers and co-author And Turken, PhD, used structural and functional brain imaging techniques on healthy and injured brains to compose a more complete picture of language processes.

Sixty-four people with problems understanding language due to brain injury were scanned with magnetic resonance imaging. The structural images were used to build a digital atlas of the brain regions thought to be associated with their disorders. The researchers then merged this information with new brain scans of 25 healthy volunteers to illustrate the pathways between brain areas. Finally, functional images of another 25 healthy individuals showed the connections between brain regions actually used for language.

"The results revealed a far more extensive network for language functions than current models would predict," Dronkers said. The network included a core region within the left mid-temporal lobe of the brain, and extended to the frontal and parietal cortex in both halves of the brain -- all connected by long distance communication pathways. The next step for scientists is to explore whether other language abilities, such as talking, reading, and writing, also have such dynamic networks.

Research was supported by the Department of Veteran Affairs' Office of Clinical Sciences Research and Development and the National Institutes of Health.

http://www.sciencedaily.com/releases/2010/11/101116205012.htm

How Do We Understand Written Language?

ScienceDaily (Dec. 16, 2009) — How do we know that certain combinations of letters have certain meanings? Reading and spelling are complex processes, involving several different areas of the brain, but researchers from Johns Hopkins University in the USA have now identified a specific part of the brain -- named the left fusiform gyrus -- which is necessary for normal, rapid understanding of the meaning of written text as well as correct word spelling. Their findings are published in the February 2010 issue of Cortex.

Dr Kyrana Tsapkini, from the Department of Neurology at Johns Hopkins University School of Medicine, and Dr Brenda Rapp, from the Department of Cognitive Science at Johns Hopkins University, studied the reading comprehension and spelling abilities of a patient who had undergone surgical removal of part of his brain due to a tumor. The patient's reading and spelling abilities had been above average prior to the surgery. They tested the patient and a group of control participants using 17 experimental tasks, which evaluated their comprehension and production of written language, spoken language, as well as their processing of other visual categories such as faces and objects.

The results of the study revealed that the patient was able to understand the meaning of spoken language as rapidly as the other participants and was similarly able to process objects and faces in a normal way. However, he showed significant delays in understanding the meaning of written text and also had difficulty in producing accurate spellings when writing dictated text, suggesting that these abilities required the use of the brain area, which had been removed.

According to the authors, the findings provide clear evidence that there are particular structures within this part of the brain -- the left mid-fusiform gyrus -- that are "specialized and necessary for normal orthographic processing."

http://www.sciencedaily.com/releases/2009/12/091216103600.htm

Language Feature Unique To Human Brain Identified

ScienceDaily (Mar. 24, 2008) — Researchers at the Yerkes National Primate Research Center, Emory University, have identified a language feature unique to the human brain that is shedding light on how human language evolved. The study marks the first use of diffusion tensor imaging (DTI), a non-invasive imaging technique, to compare human brain structures to those of chimpanzees, our closest living relative.

To explore the evolution of human language, Yerkes researcher James Rilling, PhD, and his colleagues studied the arcuate fasciculus, a pathway that connects brain regions known to be involved in human language, such as Broca's area in the frontal lobe and Wernicke's area in the temporal lobe. Using DTI, researchers compared the size and trajectory of the arcuate fasciculus in humans, rhesus macaques and chimpanzees.

According to Rilling, "The human arcuate fasiculus differed from that of the rhesus macaques and chimpanzees in having a much larger and more widespread projection to areas in the middle temporal lobe, outside of the classical Wernicke's area. We know from previous functional imaging studies that the middle temporal lobe is involved with analyzing the meanings of words. In humans, it seems the brain not only evolved larger language regions but also a network of fibers to connect those regions, which supports humans' superior language capabilities."

"This is a landmark," said Yerkes researcher Todd Preuss, PhD, one of the study's coauthors. "Until DTI was developed, scientists lacked non-invasive methods to study brain connectivity directly. We couldn't study the connections of the human brain, nor determine how humans resemble or differ from other animals. DTI now makes it possible to understand how evolution changed the wiring of the human brain to enable us to think, act and speak like humans."

The study will be published in the online version of Nature Neuroscience.

http://www.sciencedaily.com/releases/2008/03/080323210220.htm