title: Two modulatory effects of attention that mediate object categorization in human cortex.
abstract: Attentional modulation of cortical activity was examined by varying the rate of visual stimuli in object categorization tasks according to single and conjoined features. Activation of dorsolateral frontal cortex was independent of the stimulus presentation rate and elicited by the participant's attention to conjoined compared with single features. Several cortical regions showed attentionally modulated activity. In inferior temporal cortex, modulation was due to an additional bias signal underlying normal rate-correlated activity. In two other regions (premotor cortex and cerebellum), attention modified the correlation of activity and the stimulus presentation rate. Attentional effects in the human cortex are expressed by at least two physiologically distinct mechanisms acting on spatially distributed areas.
authors.affiliation: The Wellcome Department of Cognitive Neurology, Institute of Neurology, Queen Square, London WC1N 3BG, UK.
authors.forename: G
authors.initials: G
authors.lastname: Rees
authors.forename: R
authors.initials: R
authors.lastname: Frackowiak
authors.forename: C
authors.initials: C
authors.lastname: Frith
mesh_terms: D000328:Adult; D000368:Aged; D001288:Attention; D001931:Brain Mapping; D002531:Cerebellum / Q000098:blood supply / Q000502:physiology; D002540:Cerebral Cortex / Q000098:blood supply / Q000502:physiology*; D005625:Frontal Lobe / Q000098:blood supply / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000098:blood supply / Q000502:physiology; D009474:Neurons / Q000502:physiology; D012039:Regional Blood Flow; D013702:Temporal Lobe / Q000098:blood supply / Q000502:physiology; D014055:Tomography, Emission-Computed; D014796:Visual Perception / Q000502:physiology*