Figure 7.

Learning-related changes in lateral amygdala at 24 h after fear conditioning are exclusively observed in a subset of neurons. (A) Spike-frequency adaptation in LA neurons is reduced only in neurons that were defined as “changed” (n = 9). Notice that LA neurons classified as “unchanged” (n = 19) were virtually identical with those from control animals (n = 28). (B) The AHP amplitude (from 0.09–4.0 sec following current offset) was reduced in Cond-24hr changed but not Cond-24hr unchanged neurons relative to Control group. (C) Area of the post-burst AHP is also significantly smaller for Cond-24hr changed but not Cond-24hr unchanged neurons relative to neurons from the Control group. (D) The Cond-24hr changed neurons are LA pyramidal neurons. In addition to electrophysiological criteria, representative neurobiotin cell fills from Cond-24hr changed neurons confirm that these are LA projection neurons because (1) they either have a prominent apical dendrite and a characteristic pyramidal morphology (left panel) or (2) numerous spines on the dendrites (right panel). (Inset) A higher magnification image of a dendrite from the area in the white box in the right panel. Scale, left panel, 25 µm; right panel, 25 µm; inset, 10 µm. (*) P < 0.05.