Figure 1.

Reversible fear learning dynamically regulates defensive behavior. A, The behavioral procedure used in the experiment. Conditioned fear was tested 8 h after conditioning or reconditioning. Single-unit recordings of LA neurons were performed throughout all of the sessions on days 2–4. The white and gray shades represent different contexts. B, Averaged freezing responses during the first four CS presentations of the retention test sessions (bold characters in A) in each group (paired group, n = 32 rats; unpaired controls, n = 13 rats). C, The learning curves of the entire behavioral session (paired group, filled circle; unpaired controls, open circle). Error bars indicate SEM. ***p < 0.0001.