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. Author manuscript; available in PMC: 2014 Mar 3.
Published in final edited form as: Behav Neurosci. 2012 Dec 17;127(1):114–120. doi: 10.1037/a0031298

Figure 1.

Figure 1

Development of eyeblink trace conditioning to shock-shock pairings. Sample integrated EMG activity in the upper eyelid muscle to a shock-alone unconditioned stimulus (US1) probe trial for individual rat pups given paired (Paired, left) or explicitly unpaired (Unpaired, right) US1 and US2 presentations beginning at postnatal day 12, 15, and 18 (P12, P15, and P18). The black arrow indicates the onset of the first shock unconditioned stimulus (US1) which is followed by an unconditioned response (UR). The gray arrow indicates where the second shock unconditioned stimulus (US2) would have occurred on US1-US2 paired trials for rat pups in the Paired groups. The left samples of integrated EMG activity show the occurrence of a conditioned response (CR) that begins in anticipation of and overlaps with the point at which US2 would have occurred on a paired US1-US2 trial particularly at P18 and the magnitude of the CR increases with age. The right samples show there was no evidence of CRs in the sample integrated EMG activity from rat pups in any age group that received explicitly unpaired presentations of US1 and US2.