This experiment will test the efficacy of acute anti-histamine doses on the acoustic startle response and prepulse inhibition (or PPI, a well-known neurobehavioral phenomenon used to characterize sensorimotor modulation described in detail below) in a male population with high baseline sensory startle levels. In addition, sex differences in baseline PPI (i.e. without anti-histamine administration) in subjects of this population will be investigated.