Figure 1.
Schematic representation of DH and amygdala cannulae placements.
Placements determined to be outside of the target regions are marked with crosses, placements within the target region are marked with solid circles.
Figure 2.
Effects of DH or amygdala inactivation on contextual and cued components of delay and trace fear conditioning.
Infusion of muscimol into the DH disrupts acquisition/consolidation of trace (B) and contextual (A & B) but not delay conditioning (B), while muscimol infusion into the amygdala disrupts delay (C) and contextual (C & D), but not trace conditioning (D). These results suggest that the amygdala may be differently involved in trace conditioning than in contextual and delay conditioning. Additionally, deficits in vehicle compared to sham in contextual (A, B, C & D) and CS freezing (B & C) show that disruption of DH or amygdala can interfere with conditioning. Subjects per group from top to bottom by panel, were: (A) 4, 6, 6; (B) 4, 6, 6; (C) 8, 8, 8; (D) 7, 14, 6, 12. Data represented as Mean ± SEM, * denotes significant difference from vehicle control group.
Figure 3.
Parametric manipulations demonstrate that amygdala inactivation has similar effects on 1-pairing and 4-pairing trace fear conditioning, and that amygdala inactivation prior to or immediately after training of 2-pairing trace conditioning has similar effects.
(A) Inactivation of the amygdala prior to 1-pairing or (B) 4-pairing trace fear conditioning produces deficits in the contextual component but does not affect the cued component or freezing to an altered context. Additionally, comparison of sham and vehicle groups demonstrates that infusion of vehicle into the amygdala produces deficits in contextual but not trace conditioning and does not affect freezing to an altered context. (C) Inactivation of the amygdala 20-minutes pre-training or immediately post-training produced deficits in the contextual but not the cued component of 2-pairing trace fear conditioning, and did not affect freezing to an altered context. Subjects per group from top to bottom by panel, were: A 4, 6, 6; B 4, 4, 5; C 4, 6, 6. Data represented as Mean ± SEM, * denotes significant difference from vehicle control group.
Figure 4.
Double dissociation of effects of muscimol infusion on 2-pairing trace and delay cued freezing.
Inactivation of the DH with muscimol produces deficits in trace but not delay conditioned CS freezing, while inactivation of the amygdala produces deficits in delay but not trace conditioned CS freezing. These findings suggest that amygdala independent circuitry can support trace fear conditioning. Data are Muscimol (0.25 ug/side) freezing to CS from experiments 1–4 as percent vehicle.