Figure 5.

Contextual and cued fear conditioning. Mice reared in an enriched environment for 8 wk (dark bars) displayed significantly enhanced memory for contextual fear conditioning (24 h contextual) as compared to control mice kept in standard nonenriched cages (open bars; * P < 0.01). Ordinate shows freezing behavior expressed as a percentage of total time spent in the test chamber. Immediate learning, measured after presentation of the unconditioned stimulus, was slightly, but not significantly, increased by enrichment. Memory for cued fear conditioning, measured before and during the CS (24 h pre-CS and 24 h CS, respectively), was not significantly different between enriched and control mice. CS = conditioned stimulus (tone).