See your thoughts

Powerful brain imaging technology is allowing researchers to accurately tell what a person is thinking before they reveal what it is.

The study, led by Dr. Kathleen O’Craven at Massachusetts General Hospital, has shown that it is possible for researchers to look at brain imaging data and determine whether a person is imagining a face or a place.

In the study, six women and two men, aged 20 to 39, were put through two cognitive exercises: one involved looking at pictures of faces, and a second involved looking at pictures of places or landscapes.

Later these same adults were asked to mentally ‘imagine’ the faces and the places they had earlier seen. During both tests, functional magnetic resonance imaging (fMRI) scans were taken of their brains.

Previous studies have shown that certain areas of the brain can be selective for processing a particular type of visual information. In the cortical brain regions associated with mental processing, the ‘fusiform’ face area is said to respond strongly to faces while the ‘parahippocampal’ place area responds strongly to indoor and outdoor scenes depicting the layout of local space.

In this study, Dr. O’Craven and colleague Dr. Nancy Kanwisher of the Massachusetts Institute of Technology found evidence that this specialisation is true, even when participants were given no visual stimulus and were simply asked to ‘imagine’ a face or a place.

They also found that the magnitude of activity in these two brain areas is stronger when one is seeing the picture in front of them compared with just imagining it.

An interesting finding, however, is when the researchers who interpret data were asked to look at fMRI scans and guess whether the study participant was thinking of a face or place. They were able to accurately report what the participant was thinking about on 85 percent of the trials.

‘What we’ve shown is that we can actually tell, on a moment-by-moment basis, what an individual is thinking about, by measuring brain activity rather than having the person tell us,’ said Dr. O’Craven. ‘Of course, this can be done only in a limited context – we’ve been able to demonstrate it for differentiating between faces and places – but the implications are far-reaching.’

She said the technique could be used to gain some insight into what is happening in the minds of people who are unable to communicate because they are suffering from an injury or disorder that makes speech impossible.

‘We may someday be able to get a glimpse of what a patient is able to comprehend, even when that person can’t answer questions directly. We could show them pictures of faces and places and, using fMRI technology, see whether their visual system is processing them. In addition, if these brain areas respond differentially to the ‘spoken’ names of people and places, we may be able to infer that they understand.’