Figure 1. Potential treatment targets beyond Fear Acquisition and Extinction.

Standard fear conditioning paradigms highlight three phases: 1) Fear acquisition, 2) Extinction and 3) Extinction Retention. During fear acquisition, fear responses are learned when a conditioned stimulus (CS+) is paired with an unconditioned stimulus (e.g., a shock; UCS). Meanwhile a neutral stimulus (CS−) is never paired with the UCS, resulting in little to no fear response. During fear extinction, the CS+ and CS− are repeatedly presented without the UCS; thus, safety is learned, and fear responses diminish. When re-exposed to the CS+ following extinction training (i.e., extinction retention), fear and safety memories compete when re-exposed to the CS+. Depending on the circumstance, fear response may return or be inhibited.

In this review, we expand the focus to processes beyond the standard fear conditioning paradigm:

1. Fear Generalization.
2. Fear Memory Consolidation. Fear memories are later stabilized in a process known as consolidation.
3. Extinction Memory Consolidation. Extinction memories then undergo consolidation, where the safety associations are stabilized.
4. Reconsolidation. When extinction learning is conducted within the reconsolidation window, learned fear responses may be persistently inhibited such that safety associations are more easily recalled. In cases of extinction training outside the reconsolidation window, fear response mimics standard extinction retention, where learned fear memories are often recalled.