title: Top-down enhancement and suppression of the magnitude and speed of neural activity.
abstract: Top-down modulation underlies our ability to selectively attend to relevant stimuli and to ignore irrelevant stimuli. Theories addressing neural mechanisms of top-down modulation are driven by studies that reveal increased magnitude of neural activity in response to directed attention, but are limited by a lack of data reporting modulation of neural processing speed, as well as comparisons with a perceptual (passive view) baseline necessary to evaluate the presence of enhancement and suppression. Utilizing functional MRI (fMRI) and event-related potential recordings (ERPs), we provide converging evidence that both the magnitude of neural activity and the speed of neural processing are modulated by top-down influences. Furthermore, both enhancement and suppression occur relative to a perceptual baseline depending on task instruction. These findings reveal the fine degree of influence that goal-directed attention exerts upon activity within the visual association cortex. We further document capacity limitations in top-down enhancement corresponding with working memory performance deficits.
authors.affiliation: University of California, Berkeley, CA, USA. adamgazz@comewander.com
authors.forename: Adam
authors.initials: A
authors.lastname: Gazzaley
authors.forename: Jeffrey W
authors.initials: JW
authors.lastname: Cooney
authors.forename: Kevin
authors.initials: K
authors.lastname: McEvoy
authors.forename: Robert T
authors.initials: RT
authors.lastname: Knight
authors.forename: Mark
authors.initials: M
authors.lastname: D'Esposito
mesh_terms: D000328:Adult; D001288:Attention; D001931:Brain Mapping; D000077463:Carbamide Peroxide; D004338:Drug Combinations; D004569:Electroencephalography / Q000379:methods; D005071:Evoked Potentials / Q000502:physiology; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D009433:Neural Inhibition / Q000502:physiology*; D010545:Peroxides / Q000097:blood; D010775:Photic Stimulation / Q000379:methods; D011930:Reaction Time / Q000502:physiology*; D021641:Recognition, Psychology / Q000502:physiology; D014508:Urea / Q000031:analogs & derivatives* / Q000097:blood; D014793:Visual Cortex / Q000098:blood supply / Q000166:cytology / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology*
chemical_list: D004338:Drug Combinations; D010545:Peroxides; D000077463:Carbamide Peroxide; D014508:Urea