Fig. 4.

Verbal instructions experiment. Subjects were verbally instructed that they would be safe in the no shock (N) condition, and that they would receive aversive stimuli signaled by a threat cue in the predictable (P) condition and unsignaled aversive stimuli in the unpredictable (U) condition. An 8-sec duration cue was presented in each context. The cue signaled the aversive stimulus in the P context, but had no signal value in the N and U contexts. Two types of aversive stimuli were used in a between-group design, a shock, and a blast of air directed to the throat at the level of the larynx. The results of the shock group are very similar to results in the context conditioning shown in Fig. 3. In the predictable condition, startle was larger during the CS compared to ITI (fear-potentiated startle). In addition, startle during ITI (black bars) increased linearly from the control, to the P, to the U condition. However, such a pattern of response was not seen in the airblast group. * indicates a significant increased in startle magnitude during the cue compared to ITI. (Adapted from Grillon et al 2004).