title: Spatial and object-based attention modulates broadband high-frequency responses across the human visual cortical hierarchy.
abstract: One of the puzzling aspects in the visual attention literature is the discrepancy between electrophysiological and fMRI findings: whereas fMRI studies reveal strong attentional modulation in the earliest visual areas, single-unit and local field potential studies yielded mixed results. In addition, it is not clear to what extent spatial attention effects extend from early to high-order visual areas. Here we addressed these issues using electrocorticography recordings in epileptic patients. The patients performed a task that allowed simultaneous manipulation of both spatial and object-based attention. They were presented with composite stimuli, consisting of a small object (face or house) superimposed on a large one, and in separate blocks, were instructed to attend one of the objects. We found a consistent increase in broadband high-frequency (30-90 Hz) power, but not in visual evoked potentials, associated with spatial attention starting with V1/V2 and continuing throughout the visual hierarchy. The magnitude of the attentional modulation was correlated with the spatial selectivity of each electrode and its distance from the occipital pole. Interestingly, the latency of the attentional modulation showed a significant decrease along the visual hierarchy. In addition, electrodes placed over high-order visual areas (e.g., fusiform gyrus) showed both effects of spatial and object-based attention. Overall, our results help to reconcile previous observations of discrepancy between fMRI and electrophysiology. They also imply that spatial attention effects can be found both in early and high-order visual cortical areas, in parallel with their stimulus tuning properties.
authors: Interdisciplinary Center for Neural Computation, Hebrew University, Jerusalem 91904, Israel.
authors: Ido
authors: I
authors: Davidesco
authors: Michal
authors: M
authors: Harel
authors: Michal
authors: M
authors: Ramot
authors: Uri
authors: U
authors: Kramer
authors: Svetlana
authors: S
authors: Kipervasser
authors: Fani
authors: F
authors: Andelman
authors: Miri Y
authors: MY
authors: Neufeld
authors: Gadi
authors: G
authors: Goelman
authors: Itzhak
authors: I
authors: Fried
authors: Rafael
authors: R
authors: Malach
mesh_terms: D000293:Adolescent; D000328:Adult; D001288:Attention / Q000502:physiology*; D004827:Epilepsy / Q000503:physiopathology / Q000601:surgery; D005074:Evoked Potentials, Visual / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010775:Photic Stimulation; D011930:Reaction Time / Q000502:physiology; D013028:Space Perception / Q000502:physiology*; D014793:Visual Cortex / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology*