People often compare the brain to a computer, but who knew it came with MapQuest? Princeton University psychology graduate student Sara Szczepanski is exploring how people's visual perception and attention maps onto the brain--literally pinpointing parts of the brain that correspond to points in space.
Szczepanski recently completed a two-part experiment designed to isolate the neural underpinnings of spatial orientation using fMRI. First, she had participants focus on a target in the middle of a computer screen while a dot flashed briefly in their periphery. She instructed them not to look at the dot but to remember its location. Then, three seconds later, participants looked toward where the dot had flashed. Szczepanski found that eight different locations in the frontal and parietal cortices corresponded with the eight locations of the dots.
"There was a traveling wave of activity across the cortex," Szczepanski says.
A second task captured which parts of the brain correspond to attentional cues rather than sensory ones. Participants fixated on a series of flashing letters in the middle of the screen while colorful images popped up in the periphery. First, Szczepanski told participants to ignore the peripheral images and to click a button each time an "A," "B," or "C" appeared on the screen. Then she told them to ignore the letters (but still fixate on that point) and instead click the button when a certain target image appeared in the periphery.
By comparing the fMRI scans from the periphery-focused and the periphery-ignoring tasks, Szczepanski located which parts of the brain participants used during attention, identifying the "control center" areas in the frontal and parietal cortices. She then overlaid the results with the topographic maps from the earlier test. Places where the brain activations overlap, Szczepanski says, indicate where in the brain visual-spatial attention is controlled. Next, Szczepanski will look at people's brain activations when they attend to a point in space without any visual stimuli. Ultimately, she says, the goal is to figure out exactly what each region of the brain is doing when paying attention to objects in the visual field. Such research holds promise for better understanding and treating people with attentional impairments due to brain damage.
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