Can the content of our thoughts be predicted?
By Chloe Thomas
A large amount of neuroscience has been dedicated to examining the origins of thoughts. Despite some thoughts feeling spontaneous, neuroscientists and psychologists have questioned how much of these thoughts are biased by pre-existent neural activity. A study at the University of New South Wales was conducted to find out whether it is possible to predict the freely chosen content of voluntary imagery from prior neural signals.
Researchers at UNSW created an experiment to investigate the origins of the content and the strength of voluntary imagery. In every trial, participants had to choose to imagine one of two possible different coloured and oriented gratings while their brain blood-oxygen-level dependant was recorded using an fMRI. Once the trial had started, participants had a maximum of 20 seconds to freely decide which pattern to think of. As soon as they made their decision, they pressed a button, starting 10 seconds where participants imagined the chosen grating as detailed as they could. To investigate which brain areas contained information about the contents of imagery, the researchers used a searchlight decoding analysis on fMRI data from the whole brain. They were able to predict participants choices as far as -11 seconds before they made the choice of what to imagine, which implies that the contents of future visual imagery could be biased by current or prior neural representations. These findings may have implications for mental disorders involving thought intrusions that use mental imagery, such a post-traumatic stress disorder.
To summarise, the study found that when a decision is made, if any pre-existing brain activity matches one of the choices, then the brain is more likely to pick that option as it is boosted by the pre-existing brain activity. Lab director Joel Pearson believes that what could be happening in the brain is that we may have thoughts on ‘standby’ based on previous brain activity, which then influences the final decision without us being aware. He believes that when people are faced with the choice between two or more options of what to think about, non-conscious traces of the thoughts are there already, and if one of the choices matches up with the traces in the brain then the executive parts of the brain will be more likely to choose that option. These results raise questions about our sense of volition for our own private and personal mental and visual images.
Paper reference
Koenig-Robert, R., and Pearson, J. Decoding the contents and strength of imagery before volitional engagement. Scientific Reports (2019). doi: https://www.nature.com/article...
About the author
Chloe Thomas is studying for her A levels in Chemistry, Physics and Sociology. She wrote this article as part of her week's work experience with Scientifica.
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