Fig. 4.

Lack of Dlx1 impairs fear conditioning responses in the adult mutant mice. (a) Mean (± SEM) of percent of freezing as a response to the context after fear conditioning (without the light or tone stimulus). In this experiment, one shock after 3-min exposure to the context was administered to elicit the fear response. Baseline freezing before training was zero for all three groups. Dlx1 ^+/+, n = 6; Dlx1 ^+/−, n = 10; Dlx1 ^−/−, n = 10. (b) Mean (± SEM) of percent of freezing as a response to the light cue after trace fear conditioning. In this experiment, the light-pulse-shock procedure was performed three times during the training. Baseline freezing before the light cue (in the novel context) was (or close to) zero for all three groups. Dlx1 ^+/+, n = 6; Dlx1 ^+/−, n = 6; Dlx1 ^−/−, n = 6. (c) Mean (± SEM) of percent of freezing as a response to the tone after trace fear conditioning. One tone-pulse-shock procedure was performed to elicit the fear response. Baseline freezing before the tone (in the novel context) was (or close to) zero for all three groups. Dlx1 ^+/+, n = 6; Dlx1 ^+/, n = 5; Dlx1 ^−/−, n = 10. For all panels, * = p < 0.05; ** = p < 0.01