Noradrenaline and partial reinforcement in rats.

Lesions of the dorsal nonadrenergic bundle produced by 6-hydroxydopamine, which depleted telencephalic noradrenaline by over 95%, were found to produce resistance to extinction in animals trained on a continuously reinforced schedule for food reward but not to alter the extinction rate after partial reinforcement training. These results confirm the dorsal bundle extinction effect reported previously but suggest that it is confined to continuously reinforced situations. The pattern of results is consistent with a role for the dorsal bundle in attentional processes but appears to contradict the predictions required if the dorsal bundle were to have a role in frustrative nonreward.