Finding meaning in the brain's hemispheres

Most researchers receive their inspiration from a mentor, or colleague, or perhaps even a lecture that strikes a chord. Beckman Institute researcher Kara Federmeier got hers from her younger brother when she was still in high school.

Most researchers receive their inspiration from a mentor, or colleague, or perhaps even a lecture that strikes a chord. Beckman Institute researcher Kara Federmeier got hers from her younger brother when she was still in high school.

"I had a brother who died of a brain tumor," Federmeier said. "I saw in him going through the various struggles, the many surgeries, that it's hard to lose motor control, it's hard to lose a lot of things. But the communication part of language is maybe one of the more devastating things to have to struggle with. So I went into graduate school wanting to study language, in particular to study the meaning aspect of language, the communication aspect of language."

Federmeier kept her focus through her undergraduate years at the University of Illinois at Urbana-Champaign and while earning a doctorate at the University of California at San Diego. Now, that search for how we communicate meaning frames Federmeier's work as part of the Cognitive Neuroscience group at Beckman.

Federmeier studies how people comprehend language, centering on the process of turning stimuli like another person's words into meaning based on memory.

"What we mean by meaning is, basically, how you go from sensory input to memory," Federmeier said.

To accomplish her research goals, Federmeier uses traditional psychological measures and newer techniques like eye-tracking devices and an electrophysiological cap developed at her laboratory that measures event-related brain potentials (ERPs) used to gauge how the brain reacts to certain stimuli.

"We use a measure that really allows us to decompose the (brain) signal in time," Federmeier said. "There is a particular ERP response, we call it a component, a feature in the waveform, that is really nicely correlated with meaning. The size of this component (known as the N400) goes up and down as a function of how easy it is to appreciate the meaning of what you're looking at, for words, but also for other specific things such as pictures and sounds."

Federmeier's investigation of meaning has led her to concentrate on the differences between the two hemispheres of our brains.

"A lot of people who study language focus on the grammatical aspect of language and how words are put together, but we really focus on the meaning aspect of language," Federmeier said. "We think it ties it all together. And we do think that what we find out about how the two hemispheres comprehend might translate into other aspects of how they process information in general."

Federmeier, director of the Cognition and Brain Laboratory at Beckman, said her research has shown that the two hemispheres work much more in tandem than what many people realize. She said her work could provide some answers in the ongoing debate among psychologists, neuroscientists, and others about the predictive nature of language processing. She addresses the issue in a paper titled 'Both sides get the point: Bihemispheric sensitivity to sentential constraint' published in the July 2005 issue of Memory and Cognition.

Federmeier said the left hemisphere is known to control speech output and it was expected that would also be the case for language comprehension.

"But what we think is going on is that both hemispheres can comprehend and what we see in the left hemisphere is what a language system looks like when that language system can both understand and produce," she said. "So we think that there is a constant sort of interplay between language comprehension and production in the left hemisphere, and that this affects processing at all levels. So, for the left hemisphere, gaining meaning from a word and putting a word into a sentence is all in the context of 'what if I need to produce this word, what if I need to respond to this word.'

"Whereas the right hemisphere is taking a more passive approach because it doesn't control production. So it's kind of what a language system looks like when that language system isn't involved in any kind of output control and is really just trying to make sense of the world."

Federmeier said the brain's hemispheres work in ways that are more nuanced than what is typically portrayed in the popular media.

"The thing that really fascinates me, and my students, about hemisphere differences is that the answer we keep getting is the brain doesn't do anything in just one way," she said. "When you hear about the hemispheres in magazines or read about them in newspapers it's always one does this and one does something very different. We think that they both do a little bit of everything, but that they shift exactly how they're doing it, which is really quite important from an information processing point of view."

Federmeier's work on a federally funded project that looks at hemispheric differences in older adults ties in with that theory.

"There's some interesting convergence with our other line of research where we've seen that as people age their language comprehension, although at the level of 'do they comprehend?' may look very similar to younger adults, how they seem to be coming to that understanding seems to be quite different in older adults," Federmeier said.

Federmeier said that one theory is that the aging brain is compensating for a loss of ability in one area by reconfiguring its resources, so even though comprehension and behavior may be relatively unchanged there could still be underlying neural processing changes.

"We think that one of the ways that the system may be going wrong or may be compensating - we don't know which it is yet - is that things that would normally be done by the left hemisphere are coming to be done perhaps by both hemispheres," she said. "We think ERPs are going to be a particularly good way to measure that and figure out which stages of processing are changing in that way.

"It may be that the right hemisphere is coming in to help the left hemisphere as it ages, or it may be that the connections that would normally send information to the right place and keep it there are breaking down so that both hemispheres are getting the information even though they don't both need it."

Federmeier has also focused on topics such as the mediation of word processing through long-term memory and how the meaning we assign to words or other stimuli can vary depending on mood and availability of various cognitive resources.

"What we've found is that people who are in a pleasant mood have an easier time dealing with unexpected language events. People have seen that in behavioral measures for awhile, and we're seeing it now with ERPs as well," she said.

Their work has also shown that the context of the stimuli can affect meaning. She cited the word dog as an example that, based on size, or smell, can induce different meanings for people.

"It seems like the context that a word is in really shapes which aspects of that information you're going to call up," Federmeier said. "The system is pretty flexible about it."

While at Illinois as an undergraduate, Federmeier studied under Biological Intelligence Co-chair Bill Greenough and walked the hallways shortly after the Beckman Institute first opened in 1989. She never expected to return one day as a Beckman faculty member.

"I didn't think so seriously, but I always thought it would be great if I could come back," said the Danville native. "I liked the area and it seemed like a great place to raise kids, and this is a great intellectual environment."

And while she has pursued other research interests over the years, Federmeier has maintained her focus on how people communicate meaning to one another.

"There were lots of little jogs along the way but I always wanted to work at that interface," she said.