Reinforcement omission effects in rats with bilateral lesions in the substantia nigra pars compacta and ventral tegmental area

Abstract

Reinforcement omission effects (ROEs) are characterized by higher response rates after reinforcement omission than after reinforcement delivery. This pattern of behavior is interpreted in terms of motivational and attentional processes. Recent studies from our laboratory have shown that the amygdala, nucleus accumbens, and medial prefrontal cortex are involved in ROE modulation. Also, the literature has demonstrated a role of other areas such as substantia nigra pars compacta (SNc) and the ventral tegmental area (VTA) in processes related to surprising events, such as prediction error and presentation or omission of an event (exteroceptive stimulus and reinforcement). Since these structures send projections to areas related to ROE modulation such as the amygdala, nucleus accumbens, and prefrontal cortex, the objective of the present study was to determine whether the SNc and VTA also integrate the circuit involved in ROE modulation. Rats were trained on a fixed-interval 12 s with limited-hold 6 s signaled schedule of reinforcement (Pre-lesion training). After acquisition of stable performance, the rats received bilateral neurotoxic lesions of the SNc (Experiment 1) and VTA (Experiment 2). Following postoperative recovery, the rats were submitted to two refresher sessions (Post-lesion training). Subsequently, the training was changed from a 100 to a 50% schedule of reinforcement (Post-lesion testing). In both experiments, the results showed that there was no difference in performance between sham rats and rats with bilateral lesions of the SNc or the VTA.

Temporal prediction error triggers amygdala-dependent memory updating in appetitive operant conditioning in rats

“…After Training, in which animals demonstrated temporal expectancy for the reward in a FI 6 s LH 12 s schedule of reinforcement (Black et al, 1972;Judice-Daher et al, 2011, 2012Bueno et al, 2012;Tavares et al, 2014Tavares et al, , 2019, a session with temporal prediction error generated a memory updating of reward expectancy to a new temporal schedule. The prediction error, either due to the temporal change or to the omission of reward, increased in the BLA the activation of a protein (Arc) that is critical for memory formation.…”

“…Twenty-seven rats were trained to respond on a Fixed-Interval (FI) 6 s with Limited Hold (LH) 12 s schedule signaled by a 18-s tone (FI 6 s LH 12 s). In this schedule, a tone is played for 18 s and, from 6 s after the tone onset, a reward is available during the last 12 s, but only the first lever press during this last 12 s period results in delivery of one pellet ( Bueno et al, 2012 ; Judice-Daher et al, 2012 ; Tavares et al, 2014 , 2019 ). Fifteen sessions were performed.…”