It is commonly accepted that the MFB is a part of the reward system, involved in the integration of reward and pleasure.
Electrical stimulation of the medial forebrain bundle is believed to cause sensations of pleasure. This hypothesis is based upon intracranial self-stimulation (ICSS) studies. Animals will work for MFB ICSS, and humans report that MFB ICSS is intensely pleasurable. It is possible that the medial forebrain bundle carries some of the input from the ventral tegmental area (VTA) to the nucleus accumbens (NAcc or Acb). The NAcc is a recognized reward center, and activation of the pathway from the VTA to the NAcc is believed to be rewarding, which is why it is sometimes referred to as the hedonic highway. The MFB also contains serotonergic and noradrenergic fibers.