Wednesday, November 24, 2010

Thinking About Our Own Thoughts Increases Gray Matter

decision making or undecided concept - iStockphoto

This is a brief research summary from Alpha Galileo on a study looking at the impact of introspection on the brain's gray matter and connections. Introspection makes our brains bigger and more connected. The full article that is summarized here is available as a PDF - link below.

The Biology of Thinking

18 November 2010 The British Council

Tracking accuracy
A new study reveals that ‘introspection’ (thinking about our own thoughts or behaviour) is anchored in a specific part of our brain. The research by scientists from the Institute of Cognitive Neuroscience and the Wellcome Trust Centre for Neuroimaging at UCL (University College London) examined people’s accuracy when reflecting on decisions they had made. ‘We were not studying the tendency to think too much, or the tendency to introspect,’ says Steve Fleming, joint first author of the study, ‘we were studying the accuracy of that process when it does occur.’ Then the team linked this to brain structure.

‘We don’t have any data on the people who come into our study,’ explains Fleming, such as how much they engage in introspection. ‘We just know that when we actually ask them to do our task, some people are more accurate at reflecting on their own decisions than others.’ They arranged the experiment so that while all the participants had a similar accuracy in judging the comparative brightness of patches on a computer screen, what differed was the ability to reflect accurately on the correctness of their response. ‘After every decision,’ explains Fleming, ‘and they made hundreds of these simple visual decisions, we asked them to rate their confidence that they had got that decision correct. That was the key measure of introspective ability, we could then say that people who were good at introspection will try to use high confidence ratings when they actually were correct, and low confidence ratings when they weren’t correct, even without getting any feedback on their decisions.’

Grey matter
When the test was completed, the participants underwent magnetic resonance imaging (MRI) scans, giving the researchers an image of the grey matter in the brain which contains cells and the white matter which is the connection between the cells, and it showed that those better at introspection had more grey matter in the prefrontal cortex near the front of the brain. ‘There is still more evidence to be gained here,’ says Fleming, ‘we are just looking at a snapshot of the structure of the brain, but what we really want to know is why does the structure there play a role in introspection?’ In order to get closer to an answer, a next step is to measure introspection in real time.


Full Reference:
Stephen M. Fleming, et al. (2010). Relating Introspective Accuracy to Individual Differences in Brain Structure. Science, 329, 1541. DOI: 10.1126/science.1191883

Relating Introspective Accuracy to Individual Differences in Brain Structure
Stephen M. Fleming, Rimona S. Weil, Zoltan Nagy, Raymond J. Dolan, Geraint Rees

The ability to introspect about self-performance is key to human subjective experience, but the neuroanatomical basis of this ability is unknown. Such accurate introspection requires discriminating correct decisions from incorrect ones, a capacity that varies substantially across individuals. We dissociated variation in introspective ability from objective performance in a simple perceptual decision task, allowing us to determine whether this interindividual variability was associated with a distinct neural basis. We show that introspective ability is correlated with gray matter volume in the anterior prefrontal cortex, a region that shows marked evolutionary development in humans. Moreover, interindividual variation in introspective ability is also correlated with white-matter microstructure connected with this area of the prefrontal cortex. Our findings point to a focal neuroanatomical substrate for introspective ability, a substrate distinct from that supporting primary perception.

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