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Abstract:
Abstract: The goal of the study was to establish the
feasibility of using a rapid intermixed event related fMRI design
to study visual search. A simple visual search task was used in
which subjects pressed a button whenever a target letter appeared.
Previous results using a block design showed areas of visual,
parietal, premotor, and prefrontal cortex activated during visual
search. Using an event related design allows for the comparison and
manipulation of the individual components in the task. The search
task was divided into five components: Encode, Rehearse, Search,
Detect, and Wait. The components were presented in a pseudo-random
counterbalanced order. Each component lasted 7.6 seconds, with 24
axial slices being collected every 3.8 seconds. A total of 64 whole
brain images were collected each scan using a 1.5 Tesla clinical
scanner. Reconstruction, motion correction, t-tests, and VOI
processing were done using the Integrated Functional Imaging System
(IFIS) from Psychology Software Tools, Inc., Pittsburgh, PA.
Preliminary results provide activation maps similar to what was
seen using the block design. The encoding component activated a
bilateral network of prefrontal, parietal, and premotor cortex. In
contrast, the search component produced large activations in
parietal and premotor cortex, with less activation in prefrontal
regions. Ongoing studies involve manipulating the memory size and
display size to assess their affects on the network of regions
activated.
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