Functional MRI (fMRI) has helped researchers at Carnegie Mellon University (CMU) find "diminished synchronization" between two areas of the brain to explain why high-functioning autistic adults use the wrong pronouns in their speech, according to a study in the August issue of Brain.
The ability to distinguish between "I" and "you" -- called deictic shifting -- appears linked to functional communication between the right anterior insula and precuneus regions of the brain, which helps a person understand the difference between one's self and another person, as well as time, location, or various actions.
The study, led by medical student Akiko Mizuno from CMU's Center for Cognitive Brain Imaging, found that subjects with autism were slower and less accurate in their behavioral processing of the pronouns, with slower synchronization between the right anterior insula and precuneus when answering a question that contained the pronoun "you," compared with answering a question about the person's view.
Deictic shifting
Mizuno and colleagues from CMU, Duquesne University, and the University of Pittsburgh noted that shifting from one pronoun to another, depending on who the speaker is, constitutes a challenge not just for children with autism, but also for adults with high-functioning autism, particularly when referring to one's self.
"The underlying neural basis of deictic shifting, however, is not understood, nor has the process of pronouns been studied in adults with autism," the authors wrote.
CMU researchers enrolled 15 adults (14 males and one female) with high-functioning autism and 15 male control subjects. Both groups were matched relative to age, performance IQ, and verbal IQ.
In one task, both groups were asked to reply to a question on a card from either a first- or second-person perspective. The subject was first shown an opened book, with one object visible on the front cover and another on the back cover. The book was then closed; the subject could only see one side of the book, while a researcher could see the other side. The question asked was "What can you see now?"
The participant had to comprehend that the personal pronoun "you" referred to himself or herself, and select the object that he or she could see. The next question asked was "What can I see now?" and referred to the researcher. The participant had to comprehend that the pronoun "I" referred to the other person.
The same questions were also phrased using proper names, such as "What can John see now?" and "What can Sarah see now?" -- again referring to the subject and the researcher.
Both autistic and control subjects also answered 48 questions that used a "Who" question to confirm their ability to perform deictic shifting. The questions asked who could see a particular object, the participant or the other person. The participant would reply either "I can" or "You can," or "John can" or "Sarah can."
MR imaging
Functional MRI was conducted on a 3-tesla scanner (Allegra, Siemens Healthcare) at the Brain Imaging Research Center, which is jointly owned by Carnegie Mellon and the University of Pittsburgh. Brain activation was measured using blood oxygen level-dependent contrast.
The central analyses focused on the precuneus and the right anterior insula. Both functional regions of interest were defined to encompass the main clusters of activation in the group activation map for each group in the overall task versus fixation contrast.
The functional connectivity was computed (separately for each participant) as a correlation between the average time course of signal intensity of all the activated voxels of regions of interest.
Response analysis
The analysis of fMR images showed that adults with high-functioning autism gave slower and less accurate responses compared with the control group for the items requiring deictic shifting. In addition, fMR images showed lower functional connectivity between the right anterior insula and precuneus for deictic shifting in this group.
Functional connectivity was reliably greater among controls for the tasks requiring a deictic shift compared with the other items, "suggesting that the autism group failed to show a typical adaptive change of insula-precuneus communication," Mizuno and colleagues concluded.
In addition, activation in the right anterior insula was significantly greater for deictic shifting in the autism group only, and there was reduced connectivity between the right anterior insula and precuneus when the autism group had to go from "you" to "I," but not when transforming "I" to "you."
Activation in the precuneus did not change between the two tasks in the autism group, but activation was significantly lower when shifting from "you" to "I" than "I" to "you" in the control group.
"These findings indicate that deictic shifting constitutes a challenge for adults with high-functioning autism, particularly when reference to one's self is involved, and that the functional collaboration of two critical nodes, right anterior insula and precuneus, may play a critical role for deictic shifting by supporting an attention shift between oneself and others," the authors wrote.
| The U.S. National Institute of Child Health and Human Development and the Autism Speaks Foundation funded the research. |
