title: Activity in the visual cortex is modulated by top-down attention locked to reaction time.
abstract: We studied the correlation between perception and hemodynamic activity in the visual cortex in a change detection task. Whenever the observer perceived the location of a change, rightly or wrongly, the blood oxygenation level-dependent signal increased in the primary visual cortex and the nearby extrastriate areas above the baseline activity caused by the visual stimulation. This non-sensory-evoked activity was localized and corresponded to the perceived location of the change. When a change was missed, or when observers attended to a different task, the change failed to evoke such a response. The latency of the nonsensory component increased linearly with subjects' reaction time, with a slope of one, and its amplitude was independent of contrast. Control experiments are compatible with the hypothesis that the nonsensory hemodynamic signal is mediated by top-down spatial attention, linked to (but separate from) awareness of the change.
authors.affiliation: Computation and Neural Systems Program, California Institute of Technology, Pasadena, CA 91125, USA. farshadm@caltech.edu
authors.forename: Farshad
authors.initials: F
authors.lastname: Moradi
authors.forename: Constanze
authors.initials: C
authors.lastname: Hipp
authors.forename: Christof
authors.initials: C
authors.lastname: Koch
mesh_terms: D000328:Adult; D001288:Attention / Q000502:physiology*; D005074:Evoked Potentials, Visual / Q000502:physiology*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D010100:Oxygen / Q000097:blood; D010364:Pattern Recognition, Visual / Q000502:physiology*; D010775:Photic Stimulation / Q000379:methods; D011930:Reaction Time / Q000502:physiology*; D013028:Space Perception / Q000502:physiology*; D014793:Visual Cortex / Q000098:blood supply / Q000502:physiology*
chemical_list: D010100:Oxygen