Blood oxygenation level-dependent contrast response functions identify mechanisms of covert attention in early visual areas.

ABSTRACT: Covert attention can lead to improved performance in perceptual tasks. The neural and functional mechanisms of covert attention are still under investigation. Using both rapid event-related and mixed designs, we measured the blood oxygenation level-dependent functional MRI contrast response functions over the full range of contrast (0-100%) in the retinotopically defined early visual areas (V1, V2, V3, V3A, and V4) in humans. Covert attention increased both the baseline activities and contrast gains in the five cortical areas. The effect on baseline can be decomposed into a transient trial-by-trial component and a component across an entire attention block. On average, increase in contrast gain accounted for approximately 88.0%, 28.5%, 12.7%, 35.9%, and 25.2% of the trial-by-trial effects

SUBMITTER: Li X 

PROVIDER: S-EPMC2329700 | biostudies-literature | 2008 Apr

REPOSITORIES: biostudies-literature