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. Author manuscript; available in PMC: 2012 Oct 1.
Published in final edited form as: Neurosci Biobehav Rev. 2011 Jun 6;35(9):1864–1875. doi: 10.1016/j.neubiorev.2011.05.013

Figure 2.

Figure 2

Freezing behavior of mice. (a) Without conditioning or observations of fearful demonstrators, mice from both the BALB and B6 genetic backgrounds expressed minimal freezing responses to the tone. Freezing was measured for 30 sec during each CS presentation. (b) B6 mice expressed more freezing behavior than BALB mice to the CS if they had prior experience with fearful demonstrators. Freezing was measured for 30 sec during each CS presentation on trials 1–5 and for 28 sec on trial 6. (c) B6 mice that had previous experience with distressed demonstrators also expressed increased acquisition of freezing behavior relative to BALB mice when they were exposed to the CS-UCS contingency. Freezing was measured for 28 sec during each CS presentation on trials 7–10. (d) BALB mice that did not have previous experience with distressed demonstrators expressed more freezing behavior than B6 mice to the CS when it was paired with a UCS. Freezing was measured for 28 sec during each CSP presentation on all trials. Asterisks represent a significant difference (P<0.05) between the two genetic backgrounds. All data are presented as the mean ± standard error and were originally reported in Chen et al. (2009).