Comparisons of connectivity and conduction velocities for medial forebrain bundle fibers subserving stimulation-induced feeding and brain stimulation reward.

A behavioral adaptation of the paired-pulse collision technique was used to determine whether the same medial forebrain bundle (MFB) fibers of passage mediate brain stimulation reward (BSR) and stimulation-induced feeding (SIF) induced by lateral hypothalamic and ventral tegmental electrical stimulation. Step-functions relating second-pulse effectiveness to interpulse interval suggested connectivity between the directly activated SIF fibers at these two stimulation sites were seen in 4 animals; these data indicate that SIF, like BSR, is mediated, at least in part, by long-axon MFB fibers. In the two animals that could be tested in both paradigms, similar effects were seen in BSR tests; this suggests that either the same fibers or fibers with remarkably similar conduction velocities and medial-lateral and dorsal-ventral alignment contribute to the two behaviors.