Consciousness Blog 20 March 2010

Attentional mechanisms have long been the poor relation of consciousness studies. Intuitively, it is easy to believe that consciousness, the stream of awareness that all humans inhabit while they are awake, is applied according to a series of moment-to-moment 'top down' cognitive decisions as to what now warrants attention (the A-word, again) plus responses to sensory stimuli, internal or external. This is not wrong, but is over-simplified, and researchers have been aware for a long time that there are unconscious attentional mechanisms which guide and enable consciousness itself.

Research at Vanderbilt University published recently in Nature Neuroscience has identified an area of the brain which is involved in this process.

"The simple example of having your reading interrupted by a fire alarm illustrates a fundamental aspect of attention: what ultimately reaches our awareness and guides our behavior depends on the interaction between goal-directed and stimulus-driven attention. For coherent behavior to emerge, you need these two forms of attention to be coordinated," René Marois, associate professor of psychology and co-author of the new study, said. "We found a brain area, the inferior frontal junction, that may play a primary role in coordinating these two forms of attention."

"We wanted to understand what caused limitations in our conscious perception when we are surprised," Christopher Asplund, a graduate student in the Department of Psychology and primary author of the new study, said. "We found that when shown a surprise stimulus, we are temporarily blinded to subsequent events." This response, often called 'the attentional blink', is of course a well-established phenomenon.

Subjects in the study were asked to detect the letter "X" in a stream of letters appearing on a screen during fMRI monitoring. The unexpected insertion of a face in the letter stream caused subjects to miss "X"s.

The researchers found that the inferior frontal junction, a region of the lateral prefrontal cortex, was involved in both the original task and in the reaction to the surprise. "What we think might be happening is that this brain area is coordinating different attention systems – it has a response both when you are controlling your attention and when you feel as though your attention is jerked away," Asplund said.

Marois' laboratory has previously suggested that the interior frontal junction constitutes an attentional bottleneck – limiting our ability to multitask and attend to many things at once.

"These new findings and our previous findings suggest that this area is centrally involved in the control of attention and may limit our attentional capacities," Marois said. "It is a very exciting convergence of findings across our studies. We're conducting studies now to demonstrate whether in fact disruption of activity in this brain region leads to loss of control of attention."

John G Taylor's account of the neural basis of consciousness, employing the CODAM (COrollary Discharge of Attention Movement) theory has close relevance to the mechanisms being explored at Vanderbilt and elsewhere.

Read more in Chapter Two of Agent Human by Michael Bell, The Evolution of Social Consciousness in Animals.


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