Neuroscientists have for the first time have come up with a way to observe brain activity during natural reading, the reading of actual text and not just individual words. The findings are already helping settle some ideas about how we read.
Says John Henderson, a psychology professor at the University of California, Davis:
“It’s a key advance in understanding reading in the brain, because people are just reading normally.”
Until now, neuroscientists have only measured brain activity as a volunteer fixes his or her attention on individual words. The signals of brain activity from functional magnetic resonance imaging, or fMRI, last for several seconds—too slow to keep up with natural reading, which processes several words a second.
Eye Tracking Natural Reading
Instead, researchers combined functional MRI with eye tracking. Lying in an MRI scanner, subjects read text on a screen while the eye-tracking device registers which word they are paying attention to at any given time.
“By tracking their eye movements as they read natural paragraphs, we can know which word they are attending to, and see the neural signal for fixation on each word,” Henderson says.
For the study, researchers applied the technology to test two theories about how words are represented in the brain. The first holds that words are represented by connections to the real world—what does it look like, how do I handle it, how does it make me feel— reflected in brain areas for vision, touch, emotion, and so on.
The second theory holds that words are represented as abstract symbols that interact with each other.
To test these ideas, the researchers scored the nouns in their test paragraphs for manipulability— do they refer to real objects that can be manipulated to some degree?
As volunteers read the manipulable nouns, the left anterior inferior parietal lobule and posterior inferior temporal gyrus and sulcus, areas of the brain that deal with manipulation and carrying out physical actions lit up, lending support to the view that words are represented in the brain by connections with real actions.
By providing a window into brain activity during natural reading, the fixation-related or “FIRE” fMRI technique allows researchers to look at all kinds of unanswered questions, Henderson says, such as whether language and grammar are handled by a specific part of the brain, and whether the brain anticipates upcoming words as we read.
The discoveries may have implications not just for human psychology but also for artificial intelligence, and could help clarify dyslexia and other reading deficits.
Rutvik H. Desai, et al.
Toward Semantics in the Wild: Activation to Manipulable Nouns in Naturalistic Reading
The Journal of Neuroscience, 6 April 2016, 36(14): 4050-4055; doi: 10.1523/JNEUROSCI.1480-15.2016