Intracranial self-stimulation (ICSS) is the operant conditioning method used to produce BSR in an experimental setting. ICSS typically involves subjects with permanent electrode implants in one of several regions of the brain known to produce BSR when stimulated. Subjects are trained to continuously respond to electrical stimulation of that brain region. ICSS studies have been particularly useful for examining the effects of various pharmacological manipulations on reward sensitivity. ICSS has been utilized as a means to gauge addiction liability for drugs of many classes, including those that act on monoaminergic, opioid, and cholinergic neurotransmission. These data correlate well with findings from self-administration studies on the addictive properties of drugs.