The "staircase test": a measure of independent forelimb reaching and grasping abilities in rats.

A novel reaching test for the rat has been developed to assess the independent use of forelimbs in skilled reaching and grasping tasks. The apparatus is a plexiglas box with a removable baited double staircase. Food pellets are placed on the staircase and presented bilaterally at 7 graded stages of reaching difficulty to provide objective measures of side bias, maximum forelimb extension and grasping skill. In the present experiment, the apparatus was used to assess the reaching performance of rats following unilateral lesions of the sensorimotor cortex, unilateral lesions of the posterior cortex or bilateral lesions of the olfactory bulbs. The task has the advantage of objective over rating measurement, and the simplicity of the apparatus permits many animals to be tested concurrently.