Basolateral amygdala parvalbumin neurons report aversive prediction error to constrain fear learning

Abstract

Animals, including humans, use prediction error to guide learning about danger in the environment. The basolateral amygdala (BLA) is obligatory for this learning and BLA excitatory projection neurons are instructed by aversive prediction error to form fear associations. Complex networks of inhibitory interneurons, dominated by parvalbumin (PV) expressing GABAergic neurons, form the intrinsic microcircuitry of the BLA to control projection neuron activity. Whether BLA PV interneurons are also sensitive to prediction error and how they use this error to control fear learning remains unknown. We used PV cell-type specific recording and manipulation approaches in male transgenic PV-Cre rats to address these issues. We show that BLA PV neurons control fear learning about aversive events but not learning about their omission. Furthermore, during fear learning BLA PV neurons express the activity signatures of aversive prediction error: greater activity to unexpected than expected aversive events and greater activity to better rather than poorer predictors of these events. Crucially, we show that BLA PV neurons act to limit fear learning across these variations in prediction error. Together, this demonstrates that prediction error instructs and regulates BLA fear association formation in a cell-type specific manner. Whereas BLA projection neurons use prediction error signals to form and store fear associations, BLA PV interneurons use prediction error signals to constrain fear association formation. Significance StatementThe capacity to predict sources of danger in the environment is essential for survival. This capacity is supported by associative learning mechanisms that are triggered when the danger experienced is greater than the danger expected. Here we show that the activity of parvalbumin positive GABAergic interneurons in the rat basolateral amygdala neurons report this difference between the danger expected and the danger experienced and that they use this difference to limit the amount of fear which is learned.