Neural mechanisms of fear memory precision and generalization: from auditory cortex to amygdala

Identifying neural networks that infer safety versus danger is of great interest across multiple disciplines. Recent research has started to elucidate the brain networks mediating fear discrimination and generalization. Here, we focus on the contribution of the auditory cortices to auditory fear memory and discrimination processes. We first review studies showing that the primary auditory cortex (Te1) is involved in fear memory for tones with complex perceptual features only. Conversely, Te1 is essential for fear discrimination across all types of acoustic stimuli. These studies support the idea that Te1 plays a key role in the precision of auditory fear memory and in discriminating between aversive sounds and other, non-aversive sounds. We also discuss potential neuronal mechanisms within Te1 that may support these functions. Next, we review studies showing that higher-order auditory cortices, particularly those located in the posterior auditory field, constitute a critical hub for the encoding of auditory fear memories, regardless of the physical characteristics of the tones. We present evidence suggesting that these cortices may be involved in encoding the emotional and motivational significance that sounds acquire through experience. We also summarize studies suggesting that these areas might contribute to fear discrimination, although more compelling evidence is needed. We then discuss how descending pathways from auditory cortices may influence neuronal processes within the basolateral amygdala that participate in fear discrimination. We conclude by proposing that a better understanding of these sensory cortical mechanisms may inform novel strategies to address pathological fear generalization in fear- and anxiety-disorders.