In this dissertation, I will discuss my research on the effect of spatial and feature attention effects on human electrophysiological responses to visual stimuli. This work involved minimizing previous sensory confounds in the physical structure in attention tasks, as well as separately analyzing how the brain responds to an orienting cue and a target that requires an overt behavioral response. By controlling for previous confounds, I was able to examine the effect of attention on sensory-evoked components in the absence of a sensory account for brain modulation.