Extinction, spontaneous recovery, and ABA renewal in the cricket Gryllus bimaculatus.

Abstract

Once a Pavlovian conditioned response (CR) has been acquired, it can be extinguished by presenting the conditioned stimulus (CS) alone. However, the extinction of the CR is, in many cases, temporary and context-sensitive, having important implications for psychological therapy and for the understanding of learning and memory. In this study, we tested extinction and two of its recovery phenomena, namely, spontaneous recovery and renewal, in crickets. After being exposed to paired presentations of a CS and water reward (unconditioned stimulus), crickets received extinction training in which only the CS was presented. The unreinforced presentations of the CS led to a decrease in their CR (i.e., extinction) that was still observed 1h after extinction training. However, 24h later, responding to the CS was fully recovered (i.e., spontaneous recovery occurred). For the study of renewal, acquisition training took place in context A, extinction was conducted in context B, and responding to the CS was measured in the original context (context A). Such change of the context resulted in the recovery of the CR 1h after extinction training (i.e., ABA renewal occurred). On the contrary, when the context was not changed (i.e., acquisition, extinction and the test took place in the same context), the CR became extinguished. The results obtained provide the first evidence of ABA renewal in insects and show that extinction in crickets is context-specific, in agreement with theoretical accounts that explain extinction as the acquisition of new inhibitory learning that is more context-dependent than its original excitatory learning.