Scientists have measured the blood flow in the brain while subjects listened to a storytelling radio show in order to find out where the meanings of words are encoded in the cortex.
As a result the researchers from UC Berkeley were able to make the first semantic atlas of the brain. The full findings of the study were published in the journal Nature, and reveal fascinating new information on language and meaning in our brains.
Semantic map of the brain
The findings could be used to help patients suffering from some kinds of aphasia or other neurological issues. Researchers had previously that that language function primarily took place in the left-hemisphere in specific spots of the brain, however these areas are used in speech, not for understanding language.
“You could even think of them as pre-motor areas specialized for language,” said senior author Jack Gallant, a computational cognitive neuroscientist at UC Berkeley. “But for semantics, we’re not really even talking about language, we’re talking about the meaning of language. It’s not even words, so it happens at a whole different level.”
Seven test subjects were made to listen to over two hours of stories from a public radio show while lying in an MRI machine. The Moth Radio Show lets callers tell funny, poignant and other kinds of autobiographical stories.
“Our subjects love to be in this experiment because they can just lie there and listen to these really interesting stories,” Gallant said. “It’s a million times better than any other experiment we’ve ever done.”
Meanings of words are grouped according to concepts
Scientists made use of computer programs to take the meanings from common words in the stories, before comparing the time-coded transcripts to the MRI data. The machine had mapped out the blood flow in 50,000 different locations in the brain, and different brain regions responded to different groups of concepts.
For example your brain might associate the word dog with “wolf,” or other areas related to how the animals smell. Those that had dogs as children might relate the animals to words like “home.”
“Each semantic concept is represented in multiple locations in the brain,” Gallant said. “And each brain location represents sort of a family of selected concepts. So … there’s a bunch of regions in the brain that respond to dogs.”
Further research needed in other languages
The resulting brain map helps us to understand the way we process meaning through language. Different parts of the brain are colored differently according to what information they encode.
Red relates to social concepts, while green is for visual and tactile concepts. The team behind the experiment have released the model online in the hope that it can become a resource for other scientists.
“We’re trying to build an atlas just like a world atlas,” he explained. “If I give you a globe, you can do anything with it – you could look at how big the ocean is or what the highest mountain is or what the distance from New York to California is.”
Each of our brains is unique, but the team found that the general layout of the map was largely the same for each of the 7 subjects. The question now is whether this shared semantic structure is innate or influenced by our environment.
These test subjects shared both language and culture, but the patterns might not be the same in those that speak different languages. Results could also be different in bilingual subjects responding to their second language.