Conditioned fear expression after 3 days or 33 days of incubation. Plots are shown for (A) the total sample at 3 days (GT, n = 14; IR, n = 18; ST, n = 15) and 33 days (GT, n = 15; IR, n = 19; ST, n = 13); (B) HI-conditioning animals at 3 days (GT, n = 5; IR, n = 10; ST, n = 6) and 33 days (GT, n = 8; IR, n = 10; ST, n = 8); and (C) LO-conditioning animals at 3 days (GT, n = 9; IR, n = 8; ST, n = 9) and 33 days (GT, n = 7; IR, n = 9; ST, n = 5). Six tones were presented without shock in a new context while the rats were continuously nose-poking for food at a rate of ~1 nose-poke per second. Fear to the tone is indicated by a reduction in the conditioned suppression ratio (tone responses/[tone responses + pre-tone responses]). Data are presented as mean ratios ± SEM. On this scale, a ratio of 0.5 = no suppression, and 0.0 = complete suppression. *Significant difference 3-day vs 33-day incubation p < 0.05.