Motivation dependence of brain self-stimulation in the pigeon.

Several brain sites in the pigeon were identified as maintaining electrical brain self-stimulation. Depending on the site, stimulus currents yielding maximal responding varied from 20 to 160 μA. A high proportion of the sites only yielded self-stimulation behaviour if the subjects were deprived of food; when the birds were at full weight there was only one site at which the stimulation continued to be rewarding. Some, but weak, evidence of stimulus satiation was found. Overt behaviour elicited by non-contingent stimulation did not correlate with the reinforcing or neutral nature of the sites tested. While some positive sites were associated with structures known to be involved in the control of feeding, others were not. The hypothesis that stimulation at the hunger-dependent sites might have elicited temporary satiation signals is considered.