From Attention Control to Stimulus Selection: Neural Mechanisms Revealed by Multivariate Pattern and Functional Connectivity Analyses
Visual spatial attention deployed in advance of sensory stimulation enhances the processing of the stimuli at an attended location. While it is understood that the attention control signals are established even before the stimulus occurs, how these signals help achieve stimulus selection is still not clear. Here, we investigated the neural mechanisms of spatial attention control and subsequent stimulus selection by recording fMRI data from participants performing a cued visual spatial attention task. At the beginning of each trial, participants were cued to covertly attend either the left or the right visual field. Following a random cue-target period, a target stimulus appeared either at the attended location or at the unattended location. Participants discriminated the stimulus appearing at the attended location and ignored the stimulus appearing at the unattended location. Using MVPA decoding and multivariate functional connectivity techniques, we investigated the nature of the information in visual cortex during both the cue and target periods, and further probed how cue-related information was related to target-related sensory processing. The following results were found: (1) attend-left vs. attend-right conditions could be decoded from the cue-period neural activity in visual cortex, (2) target position (target-left vs. target-right) could also be decoded from the target-evoked activity in visual cortex, (3) classifiers built on cue-period neural activity could cross-decode attended target-evoked neural activity in visual cortex and vice versa, (4) higher pattern similarity across cue and target periods, as indexed by cross-decoding accuracy, was correlated with better behavioral performance, (5) the strength of cue-evoked multivariate functional connectivity patterns in visual cortex was positively correlated with behavioral performance, and (6) cue-evoked multivariate functional connectivity patterns were similar to those evoked by the attended targets, and higher connectivity pattern similarity across cue and target periods was correlated with better behavioral performance. These results suggest that top-down attention control enables the formation of (1) a spatial attention template at the level of individual visual cortical areas and (2) an attention network template across visual areas, and these neural patterns support stimulus selection likely via a template matching mechanism at both area and pathway levels.