Comparison of two methods for quantitative assessment of unrestrained locomotion in the rat.

Changes in locomotor movements induced by central and peripheral nerve injury or obtained as a result of pharmacological treatment are increasingly being investigated in rats. Several methods have been used to assess changes in the main locomotor indices, most of which are based on video recordings, usually with low time resolution, or on X-ray cinematographic recordings. Other methods are based on qualitative visual locomotor scoring systems like the BBB scale. We have analyzed locomotor indices in freely moving rats using two methods that can give quantitative results and which may be readily automated. One is based on detecting the onsets of swing and stance phases with contact electrodes (CE), while the second is based on recording the bursts of electromyographic activity (EMG) from the flexor and extensor muscles of each limb during the swing and stance phases, respectively. Besides the investigation of spontaneous locomotion in intact rats, our study also included an examination of locomotion on a ladder using EMG recording and analysis of locomotor disturbances following spinal cord hemisection, for which combined application of the two methods appeared to be useful. Overall, the EMG method appears to be more versatile than the CE method, although the use of both methods in parallel is recommended.