In a discussion paper (Slotnick, this issue), I conducted a selective review of spatial attention studies to compare experimental parameters and determine whether particular stimulus, task, or analysis conditions were more likely to produce significant attentional modulation of the event-related potential (ERP) C1 component. It was concluded that to maximize C1 attention effects, stimuli should be in the upper visual field, there should be distractors, conditions should be high perceptual or attentional load, there should be exogenous cuing, and effects should be measured at midline parietal-occipital electrodes POz, Pz, and CPz. Commentaries were received by Fu (this issue), Qu and Ding (this issue), Zani and Proverbio (this issue), Pitts and Hillyard (this issue), Di Russo (this issue), and Mohr and Kelly (this issue). Comments included additional ideas to amplify C1 attention effects, support for some conclusions, and challenges to some conclusions. The challenges led to a more in depth analysis of many issues pertaining to C1 attention effects including optimal electrode and stimulus locations, null V1 source localization attention effects, whether all significant C1 attention effects can be discounted, and the number of studies with null versus significant C1 attention effects. Analysis of the studies that survived critical analysis, which included several that observed significant C1 attention effects, led to the same conclusions as Slotnick (this issue). Lines of future research include replicating studies that have observed C1 attention effects using identical experimental parameters and systematically manipulating parameters to determine the impact of each parameter on C1 spatial attention effects.
Keywords: Attention; C1; ERP; P1; V1; spatial attention.