The brain activity recordings also indicated that the attentional orienting activity in the frontal-parietal network regions was followed by increased activity in the visual cortex, prior to the occurrence of any visual target stimulus.
Woldorff said activity in the visual cortex before the target is even presented seems to reflect a preparatory biasing of those sensory brain regions to facilitate processing for a possible upcoming target. Moreover, this biasing activity was exclusive to the part of visual cortex corresponding to the region of space where the upcoming target would appear.
These results indicate that specific regions of the frontal cortex activate first, followed by the parietal cortex, in a sequence that initiates the shifting of the focus of visual attention in space, according to Woldorff. "Those frontal and parietal areas then seem to work together to exercise control over the sensory inputs at the early stages of the visual pathways," he said.
This control appears to prime the appropriate brain areas to more fully process certain aspects of the visual scene, he said. In this particular study, the priming was for a certain region of the visual field. In other circumstances, the brain might be primed for a certain color or shape.
In the case of the researchers' hypothetical motorist and bicyclist, "such enhanced processing might then enable the motorist to make a faster accident-avoiding response if the bicyclist suddenly made an unexpected movement toward the car," Woldorff said.
"Or, once upon a time, it may have helped our prehistoric ancestors forage for berries while carefully maintaining attention on a distant, hopefully not too hungry, lion."
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Contact: Monte Basgall
monte.basgall@duke.edu
919-681-8057
Duke University
3-Jan-2007