PP_007

Objective: To evaluate the effects of early versus delayed environmental enrichment on motor and cognitive function after experimental traumatic brain injury (TBI). Design: Randomized controlled study. Setting: Experimental research laboratory. Animals: 30 adult male Sprague-Dawley rats. Interventions: Anesthetized rats received a cortical impact or sham injury and then were randomly assigned to either early or delayed environmental enrichment. Early environmental enrichment consisted of housing rats (n=10 per cage) in a large 3-level cage with multiple sensory stimuli immediately after surgery for 1 week and then transferring them to standard conditions (n=2 per cage) for the remainder of the study (ie, 12d). Delayed environmental enrichment consisted of placing rats in a standard environment after surgery for 1 week and then transferring them to an environmental enrichment. Function was assessed by established motor (beam balance, walk) and cognitive (spatial learning, memory) tests on postoperative days 1 through 5 and 14 through 18, respectively. Main Outcome Measures: Latency (in seconds) to maintain beam balance, traverse a narrow elevated beam, and to locate a submerged platform in a Morris water maze. Results: No significant differences in any task or condition were observed between sham controls. In TBI, early environmental enrichment facilitated beam walking versus delayed (P=.000), but did not affect beam balance (P=.953). This finding may be explained by increased locomotor opportunity afforded to rats in larger cages versus the minimal experience in standard cages. In marked contrast, early environmental enrichment yielded worse water maze performance than delayed environmental enrichment (P<.001). Explanations for this finding are more complex and may include an attenuation of early environmental enrichment benefits, necessity of environmental enrichment during the task, or more days of enrichment in the delayed paradigm. Conclusions: These data suggest that environmental enrichment as a therapeutic strategy after TBI provides significant benefit, but is more complicated than previously thought and requires further investigation.