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

Reinforcement learning theories postulate that prediction error, i.e., a discrepancy between the actual and expected outcomes, drives reconsolidation and new learning, inducing an updating of the initial memory.

Updating temporal expectancy of an aversive event engages striatal plasticity under amygdala control.

Pavlovian aversive conditioning requires learning of the association between a conditioned stimulus (CS) and an unconditioned, aversive stimulus (US) but also involves encoding the time interval between the two stimuli. The neurobiological bases of this time interval learning are unknown. Here, we show that in rats, the dorsal striatum and basal amygdala belong to a common functional network underlying temporal expectancy and learning of a CS-US interval.

Large neurotoxic amygdala lesion impairs reinforcement omission effects.

The amygdala has been implicated in a variety of motivational and attentional functions related to appetitive learning. Some studies showed that electrolytic lesions of the amygdaloid complex disrupted reinforcement omission effects (ROEs). However, recent studies that investigated ROEs employing neurotoxic lesions in specific amygdala areas - the central nucleus (CeA) or basolateral complex (BLA) of the amygdala - showed that CeA lesions or BLA lesions can interfere with, but do not eliminate ROEs.

Involvement of the basolateral complex and central nucleus of amygdala in the omission effects of different magnitudes of reinforcement.

Evidence from appetitive Pavlovian and instrumental conditioning studies suggest that the amygdala is involved in modulation of responses correlated with motivational states, and therefore, to the modulation of processes probably underlying reinforcement omission effects. The present study aimed to clarify whether or not the mechanisms related to reinforcement omission effects of different magnitudes depend on basolateral complex and central nucleus of amygdala. Rats were trained on a fixed-interval 12s with limited hold 6s signaled schedule in which correct responses were always followed by one of two reinforcement magnitudes.

Influence of the reinforcement magnitude on omission effects.

Reinforcement Omission Effects (ROEs), indicated by higher rate of responses after nonreinforced trials in a partial reinforcement schedule, have been interpreted as behavioral transient facilitation after nonreinforcement induced by primary frustration, and/or behavioral transient inhibition after reinforcement induced by demotivation or temporal control. The size of the ROEs should depend directly on the reinforcement magnitude. The present experiment aimed to clarify the relationship between reinforcement magnitude and the omission effects manipulating the magnitude linked to discriminative stimuli in a partial reinforcement FI schedule.