THE ROTAROD TEST - AN EVALUATION OF ITS EFFECTIVENESS IN ASSESSING MOTOR DEFICITS FOLLOWING TRAUMATIC BRAIN INJURY

The purpose of the present experiment was to examine the effectiveness of a modified rotarod test in detecting motor deficits following mild and moderate central fluid percussion brain injury. In addition, this investigation compared the performance of the rotarod task with two o ther commonly used measures of motor function after brain injury (beam -balance and beam-walking latencies). Rats were either injured with a mild (n = 14) or moderate (n = 8) level of fluid percussion injury or were surgically prepared but not injured (n = 8). All rats were assess ed on all tasks for 5 days following their respective treatments. Resu lts revealed that both the mild and moderate injury levels produced si gnificant deficits in the ability of the animals to perform the rotaro d task. Performance on the beam-balance and beam-walking tasks were no t significantly impaired at the mild injury level. It was only at the moderate injury level that the beam-balance and beam-walking tasks det ected deficits in motor performance. This result demonstrated that the rotarod task was a sensitive index of injury-induced motor dysfunctio n following even mild fluid percussion injury. A power analysis of the three tasks indicated that statistically significant group difference s could be obtained with the rotarod task with much smaller sample siz es than with the beam-balance and beam-walking tasks. Performance on t he rotarod, beam-walk, and beam-balance tasks were compared and evalua ted by a multivariate stepdown analysis (multiple analysis of variance followed by univariate analyses of covariance). This analysis indicat ed that the rotarod task measures aspects of motor impairment that are not assessed by either the beam-balance or beam-walking latency. Thes e findings suggest that compared to the beam-balance and beam-walking tasks, the rotarod task is a more sensitive and efficient index for as sessing motor impairment produced by brain injury.