For delivery of a chemical to a target region of a subjects brain, an apparatus comprising a storage medium on which is stored digital representations of subject-specific selective visual stimuli that, when viewed, selectively stimulate blood flow to the target area of the brain and an electronic display device coupled thereto and configured for converting the stored digital representations to images viewable by the subject wherein the one or more selective visual stimuli were determined by exposing the subject to a plurality of potential stimuli measuring the blood flow response to multiple regions of the brain, including the target area and one or more non-target areas comparing the blood flow responses to the potential stimuli, and selecting as selective stimuli potential stimuli that result in relatively more blood flow to the target area and relatively less blood flow one or more non-target areas.
