11 November 2011
Although the mental processes involved in attention and awareness seem intimately related – and have been thought to be so for many years – a recent study shows that the two may be fundamentally different in actuality. In the study, published in Science, researchers from the Max Planck Institute for Biological Cybernetics in Tübingen and the RIKEN Brain Science Institute, and Masataka Watanabe from the University of Tokyo detailed their findings, which constitute the first experimental evidence that this is the case.
Based on the hypothesis that attention and awareness affect brain cells differentially, the scientists were able to show that the primary visual cortex, which begins cortical visual processing, is affected by attention rather than awareness. Using functional magnetic resonance imaging to measure the blood oxygen level dependent (BOLD) signal, they could gauge the neural activity at the primary visual cortex.
The process of developing the methods used posed some problems. ‘We knew from previous experiments that visual awareness can occur without attention, and attention without awareness,’ said Masataka Watanabe. ‘But it was a real challenge to design experiments that can reliably record BOLD activity while reproducing the rather unnatural two laboratory conditions.’ The team presented participants with two-by-two factorial designs in which the variables were whether the visual target was ‘visible’ or ‘invisible’, and whether attention was directed ‘to’ or ‘away’ from the target. As the action of declaring it visible would in itself draw attention to the target, Watanabe explained, ‘it was important not to depend on the participant to report the visibility of the target.’
‘I, myself, was surprised by the finding, it shifted my mind a little,’ said Watanabe. The results demonstrated that paying attention to the target almost doubled BOLD activity, whereas visibility alone produced next to no effect. Previous studies conducted without controlling attention independently have indicated a strong response to target awareness in the primary visual cortex, but these findings call them into question. Although further research is needed, the discovery may have ramifications for cognitive psychology and even philosophy.