Progressive ratio performance in rats with gustatory thalamus lesions

To determine whether damage of the gustatory thalamus (the parvicellular re gion of the ventroposteromedial nucleus) disrupts the perceived value of re inforcing stimuli, the performance of rats with bilateral, electrophysiolog ically guided, electrolytic lesions of the area was examined in Experiment 1 with a progressive-ratio schedule of reinforcement. Lesioned rats showed normal concentration-dependent changes in break point (an index of the amou nt of effort a subject will expend to obtain reinforcement) and in consumma tory responding (licking) for the sucrose reward. In the reward comparison procedure of Experiment 2, however, the same lesioned rats failed to show m orphine-induced suppression of alanine consumption. The results provide no support for the view that the thalamic taste area is involved in the percep tion of the absolute reinforcing value of gustatory stimuli.