Abstract
Action reading is thought to engage motor simulations, such as those involved during the generation of mental motor images. These simulations would yield modulations in activity of motor-related cortical regions and contribute to action language comprehension. To test these ideas, we measured corticospinal excitability during action reading, and reading comprehension ability, in individuals with normal and impaired imagery (i.e., phantasia and aphantasia, respectively). Thirty-four participants (17 phantasic and 17 aphantasic) were asked to read manual action sentences. By means of TMS, we triggered motor-evoked potentials in the target right index finger. Motor-evoked potential amplitude, a marker of corticospinal excitability, increased during action reading relative to rest for phantasic individuals, but not for aphantasic individuals. This result provides neurophysiological evidence that individuals living with aphantasia present a real neurophysiological deficit in motor system engagement during action reading. Furthermore, deep-level reading comprehension ability was impaired in individuals with aphantasia, who had difficulty selecting words that best fit the context of sentences. Altogether, these findings support the idea that motor simulations, along with the activation within the motor system, contribute to action language comprehension.
What This Study Is About
Researchers wanted to know if having aphantasia—the inability to create "mental imagery" (pictures in your mind)—changes how you understand stories. Specifically, they wondered if your brain "practices" an action, like grabbing a cup, just by reading about it.
How They Studied It
The team worked with 34 people: 17 with aphantasia and 17 who can visualize normally. Participants read sentences about hand actions (like "I pull it out") while researchers used a special tool called TMS (a painless magnetic pulse) to measure the activity in the part of the brain that controls hand movements. They also gave everyone reading comprehension tests to see how well they understood the "deep" meaning of the sentences versus just remembering the facts.
What They Found
For people who can visualize, reading about an action "woke up" the movement part of their brain, even though they weren't actually moving! However, for people with aphantasia, that part of the brain stayed quiet.
The study also found that while both groups were great at remembering basic facts, people with aphantasia were about 8% less accurate on "deep" comprehension tasks—like picking the best word to fit a specific context. It was as if they could remember the "what" of the story but had a slightly harder time "feeling" the scene.
What This Might Mean
This suggests that for most people, understanding a story is like running a "flight simulator" in the brain; you "see" and "feel" the actions to make sense of them. Because people with aphantasia don't run this automatic simulation, their brains might use a different, more logic-based path to understand language.
Note: This was a small study with only 34 people, so we can’t say this applies to every aphantasic person. Everyone’s brain works a little differently!
One Interesting Detail
The researchers found that the more a person’s motor brain "woke up" during reading, the better they did on the deep comprehension tests. It’s like your brain is "shadowboxing" with the words to help you understand them better!