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. 2003 Feb 15;23(4):1535–1547. doi: 10.1523/JNEUROSCI.23-04-01535.2003

Fig. 1.

Fig. 1.

Conditioned HR fear responses. Top panels shows the HR change from baseline on CS-alone trials comparing 10 sec trace conditioned rabbits (n = 5) and the matched pseudoconditioning rabbits (n = 5).Bottom panels shows the HR change from baseline on CS-alone trials comparing the 20 sec trace group (n= 4) and the matched pseudoconditioning group (n = 4). Changes in HR were averaged across the last five CS-alone trials of habituation (left) and the five CS-alone test trials during fear conditioning and pseudoconditioning (middle). Right panels show changes in HR measured across the first five CS-alone trials of retention for the 10 sec trace group and the first 10 CS-alone trials of retention for the 20 sec trace group. The 10 and 20 sec trace groups showed larger bradycardiac-HR fear responses during trace fear conditioning and during the initial trials of retention compared with the matched pseudoconditioning control groups. Although no USs were presented on any of these CS-alone trials, the arrow marks the time of US delivery on CS–trace–US trials during the fear conditioning sessions.