ABSTRACTReward-associated stimuli can acquire both predictive and incentive motivational properties. These conditioned stimuli (CS) can then guide reward-seeking behaviour in adaptive (e.g., locating food) and maladaptive (e.g., binge eating) ways. The basolateral amygdala (BLA) contributes to learning of the predictive value of CS, but less is known about BLA contributions to the incentive motivational properties of appetitive CS. Here we studied the influence of BLA neuron activity on both the predictive and incentive motivational effects of CS. Water-restricted male rats learned to associate a light-tone cue (CS) with water delivery into a port. We assessed the predictive value to the CS by measuring CS-evoked port entries during Pavlovian conditioning. We assessed CS-evoked incentive motivation by measuring lever-pressing for the CS during instrumental responding sessions. During Pavlovian conditioning, we paired CS presentations with photo-stimulation of channelrhodopsin-2 (ChR2)-expressing BLA neurons. This potentiated CS-evoked port entries during conditioning, but suppressed subsequent lever-pressing for the CS. This indicates increased conditioned responding to the CS, but an apparent decrease in incentive motivation for that CS. However, in rats previously naïve to photo-stimulation, pairing BLA-ChR2 stimulations during lever-pressing for the CS intensified responding, indicating enhanced motivation for the CS. Rats did not self-administer BLA-ChR2 stimulations, suggesting that BLA activation does not carry a primary reward signal. Lastly, intra-BLA infusions of d-amphetamine also intensified lever-pressing for the CS. These converging findings suggest that BLA mediated-activity enhances both the predictive and incentive motivational properties of CS, allowing BLA-dependent circuits to guide behaviour in the presence of reward-associated cues.SIGNIFICANCE STATEMENTCues paired with rewards can guide animals to valuable resources such as food. Cues can also promote dysfunctional reward-seeking behaviour, as in over-eating. Reward-paired cues influence reward seeking through two major mechanisms. First, reward-paired cues are predictive and thus evoke anticipation of future rewards. Second, reward-paired cues are powerful motivators and they can evoke pursuit in their own right. Here we show that increasing neural activity in the basolateral amygdala enhances both the predictive and motivational effects of reward-paired cues. The basolateral amygdala therefore facilitates cue-induced control over behaviour by both increasing anticipation for impending rewards and making reward cues more attractive.
On the role of responses in Pavlovian acquisition
