Recovery of Pavlovian sign-tracking (autoshaping) following the discontinuation of inter-trial interval food in rats

In pigeons, Pavlovian autoshaped keypecking produced by keylight-food pairings has been eliminated by introducing food during periods between CS presentations (i.e., during the inter-trial intervals). Keypecking eliminated in this manner reappears when the inter-trial USs are discontinued even though the CS is no longer paired with US. The present experiment investigated whether this recovery of responding produced by discontinuing unpaired inter-trial US presentations could be extended to another species, rats, within a Pavlovian sign-tracking paradigm. Rats were initially trained on a procedure where insertion of one retractable lever (CS+) was followed, response independently, with food, while insertion of another lever (CS−) was not paired with food. Rats quickly came to contact the CS+ lever at high rates, but contacted the CS− lever infrequently. In the next phase, CS+ was no longer followed by food. Explicitly unpaired food was presented only during the inter-trial intervals when both levers were absent. This treatment essentially eliminated the sign-tracking response. In the final phase, the unpaired inter-trial food presentations were discontinued while both CSs continued to be presented without food. This produced a significant recovery of the sign-tracking elicited by the CS+ lever, extending the species generality of the Pavlovian resurgence phenomenon that has previously only been reported in pigeons, to rats.