Figure 4.

Magnitude of startle in each virtual context in the presence and absence of the CS (during inter-trial interval or ITI). As expected, startle was significantly larger during the CS compared with ITI (fear-potentiated startle) only in the predictable condition, when the cue signaled the shock (two middle bars). Startle during ITI (green bars) is a measure of context conditioning, reflecting the degree of contextual anxiety associated with each context. Startle increased linearly from the control, to the predictable, to the unpredictable contexts confirming that (1) context conditioning develops to environments associated with an aversive event and (2) context conditioning is affected by the predictability of the aversive event, with unpredictable environments resulting in greater context conditioning compared with predictable environments. ^*Significant increased in startle magnitude during the cue compared with ITI.