Allocation of spatial attention in human visual cortex as a function of endogenous cue validity

Certain areas of the brain are known to contain retinotopic maps of the visual field, and covert attentional guidance has been shown to result in spatially-specific increases of neural activity within certain cortical regions representing the attended locations. However, little research has been done to directly compare how attentional cues that carry differing levels of task-relevant spatial information will impact cue-modulated neural activity, particularly in terms of preparatory (i.e., pre-stimulus) attention. Here, we used fMRI to investigate how activity in area V4 would respond depending on if participants were cued with deterministic or probabilistic spatial information. Every trial began with a central arrow cue and subsequent pre-array delay, followed by a four-item memory array and subsequent post-array delay prior to the presentation of the memory probe for one of the array items. Critically, at the start of each run of trials, participants were informed that the arrow cues would indicate the to-be-probed location with either 100% validity (deterministic spatial cue) or 70% validity (probabilistic spatial cue). Our results revealed significantly higher cued versus noncued V4 quadrant activity for both probabilistic and deterministic cues prior to the onset of the memory array, but following the onset of the memory array, only significantly higher cued versus noncued V4 quadrant activity for deterministic cue trials. These findings reveal how cue validity alone can drive a differential allocation of neural resources across cued and noncued locations, and how this allocation can vary over time within a trial. Information providing certainty regarding the target’s upcoming location appeared to bias attention both in anticipation of, and following, the presentation of task-relevant stimuli. In contrast, while information regarding where a target is most probable (but not guaranteed) to appear initially biased attention, this bias was more likely to spread or wane after the onset of task-relevant stimuli.