1. An apparatus for targeting delivery of a treatment chemical to a target region of the brain of a subject, the apparatus comprising: a storage medium on which is stored digital representations of one or more subject-specific selective visual stimuli that selectively stimulate blood flow to the target area of the brain when viewed by the subject; and an electronic display device coupled to the storage medium and configured for converting the stored digital representations to images viewable by the eye of the subject; wherein the one or more selective visual stimuli were determined by exposing the subject to a plurality of potential stimuli, and then were selected from among the plurality of potential stimuli; means for measuring, for each potential stimulus, the blood flow response to multiple regions of the brain of the subject, including the target area and one or more non-target areas; comparing the blood flow responses to the potential stimuli, means for selecting based upon and derived from a result generated by said means for measuring as selective stimuli one or more of the potential stimuli that result in relatively more blood flow to the target area and relatively less blood flow to at least one of the one or more non-target areas when the subject is exposed thereto, and means for injecting a drug to at least one selected target area during the period of stimulation as determined by the means for selecting; wherein the apparatus is further configured, via the electronic display, to present to an eye of the subject one or more attenuation stimuli that selectively stimulate at least one of the one or more non-target areas without substantially stimulating the target area when the subject is exposed thereto, wherein the one or more attenuation stimuli are determined by: (a) exposing the subject to a potential stimulus; (b) determining the response of the subject to the potential stimulus by the means for measuring of the apparatus, wherein determining the response comprises determining the blood flow to the at least one target area and the one or more non-target areas in response to the potential stimulus; (c) repeating (a) and (b) for a plurality of potential stimuli; and (d) comparing the responses of the subject by the means for measuring of the apparatus to the potential stimuli and selecting as at least one attenuation stimulus, via the means for selecting of the apparatus, one or more of the potential stimuli to which the response determined in (b) was substantial blood flow to at least one of the one or more non-target areas and minimal blood flow to the at least one target area, injected during the period of stimulation.