The fifth stage was an intra-dimensional shift discrimination in which a new pair of shape stimuli and a new pair of line stimuli was p-Coumaric-acid presented, with one of the shape stimuli associated with reinforcement. This stage was labeled the intra-dimensional shift stage because, despite new examples of shape and line stimuli, the same dimension of ��stimulus shape�� remained relevant for reinforcement. The sixth stage was an IDS reversal discrimination in which responding to the other shape stimulus was reinforced; line stimuli remained irrelevant to reinforcement in this stage as well. During the habituation phase of the task, after 24 h of familiarization to the presence of four beads in an animal��s home environment, the four now-familiar beads were removed for 1 h, after which a novel-odor wood bead, taken from an odordonor cage, and three familiar beads that had been previously taken from an animal��s home cage 1 h previously, were introduced into the cage. Rats were exposed to these four beads for three 1min trials with 1-min intertrial intervals during which the beads were removed from the testing enclosure. For each 1-min trial, the three familiar-odor beads and the N1 bead were placed in the middle of the testing cage, and the rats were allowed 1 min to actively explore the beads. The first approach to a bead made during this period initiated the timing of the 1-min trial. Exploration time for each of the four beads was recorded and scored by experimenters blinded to which beads were familiar or novel. The spatial arrangement of the beads in the middle of the cage was randomly altered between trials. In the present instance, this was accomplished by excluding any irradiated animal at a particular stage if it did not complete a particular stage in at least the maximum number of trials needed by control rats at that particular stage. This allowed for the calculation of a ��percent of irradiated rats remaining�� Obacunone measure, and thus provides a different picture of the irradiated group��s performance as to whether or not they were completing a specific stage in the maximum number of trials needed for control rats to complete that same stage.