Schematic representation of sequences of stimulus presentation during each condition in one block of the NPU-threat test.

<p>The upper part of the figure represents a complete block, including two P (predictable), two U (unpredictable) and three N (no shock) conditions (order UNPNPNU as shown or PNUNUNP). The lower part shows each condition, including cues (8-s duration), startle probes presented during cues (grey arrow pointing up) or during cue-free periods (dark arrow pointing up), and shocks. Adapted from reference 31.