The broad goal of this proposal is to understand how certain aspects of working memory performance depend on neural activity in specific areas of the human brain, measured with functional magnetic resonance imaging (fMRI). There are three specific aims: to relate behavior to neural activity, to make topographic maps of the brain regions, and to determine whether striate cortex (V1) is active at any stage during a working memory task. Working memory activity has been reported throughout the brain. The first specific aim is to identify the parietal, temporal, and prefrontal areas that exhibit activity during a threshold-difficulty working memory task; test the hypothesis that working memory activity is greater when observers perform well; and test the hypothesis that intervening stimuli (task-relevant or otherwise), when presented during a working memory delay, alter working memory in the parietal lobe while leaving prefrontal working memory unchanged. The second specific aim is to test the hypothesis that complex patterns made of random elements have to be remembered in an image-like representation, and thus are topographically organized. We will test separately for retinotopic and head-centered organizations. The third specific aim is to explore the discrepancy between imagery tasks that have been reported to evoke fMRI activity in V1 and similar working memory tasks that have not. We will test the hypotheses that this can be explained by differences in the stimuli, the tasks, or the time during the task when brain activity is measured. The proposed work, by allowing us to understand working memory in normals, is meant ultimately to contribute to better characterization of cognitive deficits due to acquired brain injuries.
| Muller, James R; Philiastides, Marios G; Newsome, William T (2005) Microstimulation of the superior colliculus focuses attention without moving the eyes. Proc Natl Acad Sci U S A 102:524-9 |
