Extinction of one of the components of the compound stimulus induces the concomitant extinction of the other component. (A) Rats trained using a compound stimulus conditioning protocol and subjected 1 d later to 28 repeated presentations of the light component of the compound (extinction procedure) show decreased freezing to the tone during LTM test. Top panel: chart showing the experimental design. Left graph: freezing average (mean ± SEM) across the first (Early) three and the last (Late) three light presentations during extinction. Right graph: mean ± SEM freezing in response to the tone and the light averaged across stimuli presentations during LTM. (B) If light and tone were not presented as a compound during training but were paired individually with the US, the extinction of the light does not induce the extinction of the tone. Top panel: chart presenting the experimental design. Left graph: freezing average (mean ± SEM) across the first three and the last three (out of 28) light presentations during extinction. Right graph: mean ± SEM freezing in response to the tone and the light averaged across stimuli presentations during LTM. (T) Tone, (L) light, (US) unconditioned stimulus, (LTM) long-term memory, (#) P < 0.05 vs. Early extinction, (*) P < 0.05 vs. Tone.
