Figure 4.

Not more than 45 sec after CS termination are required to acquire extinction memory. (Upper diagram) Experimental protocol. Crabs were trained on Day 1 and re-exposed on Day 2 to the training context for 2 h. The CS-offset is denoted by an above-to-below shift of illumination. The test trial was given immediately before CS-offset (0 sec) or after a period ranging from 9 sec to 5 min with illumination from below. Test trials with light from above. (Lower panel) Mean responses and S.E.M. at test, normalized with respect to the UN group. Other symbols and indications as in Figure 1.