The advent of neuroimaging techniques such as magnetic resonance imaging (MRI) has revolutionized autism research. We can now look into the brain and see the "neural correlates" of autism. But, as with any form of correlation, identifying a neural correlate doesn't necessarily mean that we have identified a neural cause.
A case in point. Earlier this week I stumbled across a press release doing the rounds of the internet, proclaiming that "Brain imaging research reveals why autistic individuals confuse pronouns". Pronouns are the words like "he", "she", "you" and "I" that can stand in for real names. Kids with autism often struggle with them (there goes another one). In particular, they'll say "you" to refer to themselves and "I" to refer to other people.
Various theories have been put forward over the years to try and explain pronoun "reversal". Leo Kanner thought it happened just because the autistic kids were echoing things other people had said. Bruno Bettelheim (he of 'refrigerator mother' fame) reckoned kids with autism didn't have a sense of self, and so "you" and "I" were indistinguishable to them. An intriguing theory, proposed more recently by Yuriko Oshima-Takane is that kids with autism don't learn how pronouns work because they don't attend to other people's conversations.
So what does brain imaging add to this debate?
The study
The study was conducted by Akiko Mizuno, a graduate student working with Marcel Just at Carnegie Mellon Uni. She tested a group of 15 high-functioning adults with autism on what is known in the trade as a first-order visual-perspective-taking task. On each trial, they saw a series of photographs in which a woman (called Sarah) first showed them a card with different pictures on each side and then asked "What can you see now?" or "What can I see now?" Participants had to press a button on the left or right to give the correct answer.
Interpreting Sarah's questions required the participants to comprehend the pronouns "you" and "I". The adults with autism were slower and less accurate at this task than non-autistic adults. They were also a little slower on control questions that didn't involve pronouns, such as "What can Sarah see?" and "Who can see the carrot?" but the group differences weren't quite as marked. This is crucial because it suggests that the adults with autism had specific problems with the pronoun condition.
These results in themselves are really interesting. They suggest that subtle difficulties with pronouns are apparent, even amongst high functioning adults with autism. It's not clear whether these individuals ever reversed pronouns themselves in their speech, and it's important to remember that the study looked at comprehension of pronouns rather than production. But it's nevertheless striking that there are group differences, even on such a simple task.
The focus, however, was on the brainy stuff.
While the participants were completing the task, their brains were being scanned using fMRI. The headline finding was that, in the autism group, there was reduced "connectivity" between two brain regions, the right anterior insula and the precuneus. Furthermore, within the autism group, there was a significant correlation between brain connectivity and reaction time. People who were slower had weaker connectivity.
Mizuno et al. imply that this is what ultimately causes pronoun reversal:
"The observed lower functional connectivity between those two neural nodes in the autism group, therefore, may result in disturbed perspective-taking processes in shifting a centre of reference between self and other."Finer grained analyses showed that group differences in "connectivity" were observed only when Sarah asked "what can you see?" and not when she asked "what can I see?". The author's explanation is as follows:
"These findings indicate that the critical disturbance... may be dysfunctional processing when recognizing the self as a referent of ‘you’, and shifting to map self onto the pronoun ‘I’."
In other words, when Sarah says "What can you see?", the participant has to translate that into "What can I see?" and this translation process is reliant on the "connectivity" between the precuneus and anterior insula [1].
Reasons to be cautious:
It's possible that Mizuno and colleagues are correct in their interpretation. In fact, I'd really like them to be right, because I've been waffling on about brain connectivity in autism for ages. But there are a number of reasons to query their conclusions.
1. Everyone uses the term "functional connectivity" in the context of fMRI scans, but it's pretty misleading. fMRI measures brain activity indirectly via changes in blood oxygen levels. Here's an example of the time course of oxygen level changes for a control participant in Just et al.'s original fMRI "connectivity" in autism study.
The two brain regions in this figure are considered to be "functionally connected" because their activation goes up and down at roughly the same time. What isn't obvious from the figure (and is rarely acknowledged) is the fact that the changes are happening really slowly - roughly one cycle of activation and deactivation every trial.
If the two brain regions are 'talking' to each other in order to complete the pronoun task, they're doing it a much faster rate than anything fMRI can hope to measure.
2. Since that first paper, Just and colleagues (as well as several other research groups) have published a large number of studies demonstrating changes (usually reductions) in "functional connectivity" throughout the autistic brain. Their new study adds to this impressive body of evidence. But this in turn raises a second concern.
As mentioned before, Mizuno et al. looked at connectivity between two brain regions - the right anterior insula and the precuneus. Importantly, this was the only pair of regions they considered looked at [2]. Based on their previous findings, there's a fair chance that they could have chosen any number of brain regions and would have found "underconnectivity" between them too. They may be right and this is the only connection that relates to pronoun comprehension difficulties. But we don't know this.
3. The claim is that differences in "connectivity" are responsible for difficulties in comprehending pronouns. But it could just as easily be the other way around. People with autism struggle to comprehend pronouns, so they have to work harder or (as the reaction time data suggests) for longer, so it's no surprise that their brain activity while they're doing the task is different.
Brains vs Minds
Neuroimaging studies have provided many important insights into the workings of autistic brains. But sometimes, it's easy to be seduced by the fancy gadgets, the pretty pictures, and the funny words and think that brain imaging is somehow more scientific than good old-fashioned cognitive psychology (as exemplified by Mizuno et al.'s reaction time data), or that it offers privileged insights into the autistic mind.
Neural correlates are just that - correlations. All the usual caveats apply.
Notes:
[1]. Unfortunately, Mizuno et al. don't report whether the same effect is apparent in the reaction time data. If the people with autism had specific difficulty comprehending the word "you", they should be slower on this condition than control participants.
[2]. As far as I can tell, there is no direct evidence from previous studies that the precuneus and right anterior insula are involved in pronoun comprehension, so effectively Mizuno et al. are relying on a hunch. And in their own analyses, they show that, while the right anterior insula is one of 7 brain regions activated by the task, the precuneus isn't.
Reference:
Mizuno A, Liu Y, Williams DL, Keller TA, Minshew NJ, & Just MA (2011). The neural basis of deictic shifting in linguistic perspective-taking in high-functioning autism. Brain : a journal of neurology PMID: 21733887
Further reading:
- BishopBlog: Brain scans show that...
- Neuroskeptic: Brain scans prove that the brain does stuff
- SFARI: You and I