Scientists have recently explored whether comprehending common metaphors can activate parts of the brain that provide sensory experiences. For example, do your fingers feel rough if someone is said to have a gritty style?
Prior research on metaphors, such as George Lakoff and Mark Johnson’s Metaphors we live by, suggests that our daily language is so full of metaphors, some of which are so familiar (like “rough day”), that they may not seem especially novel or striking. They argued that metaphor comprehension is grounded in our sensory and motor experiences.
In a new study using brain imaging, investigators discovered a region of the brain important for sensing texture through touch, the parietal operculum, is activated when someone listens to a sentence with a textural metaphor. The same region is not activated when a similar sentence expressing the meaning of the metaphor is heard.
The results were published online this week in the journal Brain & Language.
“We see that metaphors are engaging the areas of the cerebral cortex involved in sensory responses even though the metaphors are quite familiar,” said senior author Krish Sathian, M.D., Ph.D. “This result illustrates how we draw upon sensory experiences to achieve understanding of metaphorical language.”
In the study, seven college students were asked to listen to sentences containing textural metaphors as well as sentences that were matched for meaning and structure, and to press a button as soon as they understood each sentence.
Blood flow in their brains was monitored by functional magnetic resonance imaging (fMRI). On average, response to a sentence containing a metaphor took slightly longer (0.84 vs 0.63 seconds).
In a previous study, the researchers had already mapped out, for each of these individuals, which parts of the students’ brains were involved in processing actual textures by touch and sight.
This allowed the researchers to analyze the link within the brain between metaphors involving texture, and the sensory experience of texture itself.
“Interestingly, visual cortical regions were not activated by textural metaphors, which fits with other evidence for the primacy of touch in texture perception,” said research associate Simon Lacey, Ph.D., the first author of the paper.
The researchers did not find metaphor-specific differences in cortical regions well known to be involved in generating and processing language, such as Broca’s or Wernicke’s areas. However, this result doesn’t rule out a role for these regions in processing metaphors, Sathian said.
Also, other neurologists have seen that injury to various areas of the brain can interfere with patients’ understanding of metaphors.
“I don’t think that there’s only one area responsible for metaphor processing,” Sathian said. “Actually, several recent lines of research indicate that engagement with abstract concepts is distributed around the brain.”
“I think our research highlights the role of neural networks, rather than a single area of the brain, in these processes. What could be happening is that the brain is conducting an internal simulation as a way to understand the metaphor, and that’s why the regions associated with touch get involved.
“This also demonstrates how complex processes involving symbols, such as appreciating a painting or understanding a metaphor, do not depend just on evolutionarily new parts of the brain, but also on adaptations of older parts of the brain.”
Sathian’s future plans include asking whether similar relationships exist for other senses, such as vision. The researchers also plan to probe whether magnetic stimulation of the brain in regions associated with sensory experience can interfere with understanding metaphors.
Source: Emory University