The proposed experiments will investigate how prior knowledge and expectations affect the control of visual attention and processing of visual inputs. Specifically, activity in the cholinergic nuclei of the basal forebrain is hypothesized to signal the level of uncertainty subjects have about upcoming events. Under conditions of low uncertainty, top-down attention-related signals representing subjects' expectations should be emphasized in the analysis of visual information in early cortical areas. On the other hand, when uncertainty is high, there is little useful information in these top-down inputs, and bottom-up stimulus-related signals should be facilitated. The technique of functional magnetic resonance imaging (fMRI) will be employed to measure brain activity in different brain areas while subjects are making visual judgments under conditions of low or high uncertainty. These studies will also identify candidate areas in the parietal and frontal lobes that mediate attention to a location in space versus attention to specific features of visual objects. Finally, the interactions between bottom-up sensory inputs and their modulation by top-down attentional signals will be measured in early visual cortex and correlated with performance on psychophysical tasks. In addition to providing information about how attention is represented in the brain and how it affects processing of visual stimuli, the present experiments should also shed light on the function of the cholinergic projection from the basal forebrain to the cerebral cortex. As this projection is thought to be selectively impaired in Alzheimer's disease, knowledge concerning its function in the healthy brain may be useful for understanding the etiology of this disease and for development of appropriate therapies.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Postdoctoral Individual National Research Service Award (F32)
Project #
3F32EY014520-01S1
Application #
6690261
Study Section
Special Emphasis Panel (ZRG1)
Program Officer
Oberdorfer, Michael
Project Start
2002-09-27
Project End
2003-09-26
Budget Start
2002-09-27
Budget End
2003-09-26
Support Year
1
Fiscal Year
2003
Total Cost
$600
Indirect Cost
Name
Stanford University
Department
Psychology
Type
Schools of Arts and Sciences
DUNS #
009214214
City
Stanford
State
CA
Country
United States
Zip Code
94305