To successfully interact with objects in the environment, sensory evidence must be continuously acquired, interpreted, and used to guide appropriate motor responses. For example, when driving, a red light should motivate a motor command to depress the brake pedal. Single-unit recording studies have established that simple sensorimotor transformations are mediated by the same neurons that ultimately guide the behavioral response. However, it is also possible that these sensorimotor regions are the recipients of a modality independent decision signal that is computed elsewhere. Here, we used fMRI and human observers to show that the timecourse of activation in a subregion of the right insula is consistent with a role in accumulating sensory evidence independently from the required motor response modality (saccade vs. manual). Furthermore, a combination of computational modeling and simulations of the BOLD response suggests that this region is not simply recruited by general arousal or by the tonic maintenance of attention during the decision process. Our data thus raise the possibility that a modality-independent representation of sensory evidence may guide activity in effector-specific cortical areas prior to the initiation of a behavioral response.