5 71 0.87 66 71 66 57 0.59 5 41 0.91 5 41 0.84 5 34 – 6 – 6 – 25 – 5 – 25 – Results scale. An additional point was added to include the

172 G Table 1 a Summary of correlations of different behavioral tests in rats Characteristic vs. Characteristic Hemisection Contusion BBB score Kinematic analysis F 0.32 6 – BBB score Kinematic analysis E1 0.02 6 – BBB score Kinematic analysis E2 0.91 6 – BBB score Kinematic analysis E3 0.92 6 – BBB score Footprint angle of rotation 0.45 18 0.5 3 BBB score Footprint base of support 0.48 17 0.52 5 BBB score Footprint stride length 0.46 17 0.23 5 BBB score Footprint score 0.7 26

0.91 5

BBB score Grid walk errors

0.85 71 0.87 66

BBB score Grid walk score 0.84 71 0.84 66 BBB score Narrow beam score

0.74 57 0.59 5

BBB score Exploratory activity 0.48 28 – BBB score Activity score 0.41 28 – BBB score Placing response 0.1 16 0.45 59 BBB score Placing response 0.4 16 0.57 59 Footprint angle of rotation Footprint base of support 0.55 38 0.97 3 Footprint stride length Footprint base of support 0.47 38 0.27 3 Footprint score Grid walk errors

0.73 41 0.91 5

Footprint score Grid walk score

0.72 41 0.84 5

Footprint score Narrow beam score

0.7 34 –

Grid walk errors Kinematic analysis F 0.35 6 – Grid walk errors Kinematic analysis E1 0.12 6 – Grid walk errors Kinematic analysis E2

0.8 6 –

Grid walk errors Kinematic analysis E3

0.81 6 –

Grid walk errors Footprint angle of rotation 0.37 37 0.75 3 Grid walk errors Footprint base of support 0.4 40 0.64 5 Grid walk errors Footprint stride length 0.55 38 0.06 5 Grid walk errors Narrow beam score

0.77 25 –

Grid walk errors Placing response 0.1 41 0.31 56 Grid walk score Kinematic analysis latency

0.87 5 –

Grid walk score Narrow beam score

0.75 25 –

Grid walk score Placing response 0.19 41 0.19 56 a The table shows correlation coefficients r-value and significance levels, and the correlation coefficients are noted with asterisks: P0.05; P0.01; P0.001. The number of animals per correlation is given in parentheses. The best correlations, indicated by the correlation coefficient, are marked in boldface. individual animals with the same BBB score also differed 4. Discussion in a broad range in the placing response. The aim of the present study was to compare outcome and relationships of different locomotor tests in order to 3.3.2. Grid walk performance establish an efficient testing procedure for spinal cord The number of errors made while crossing the grid as injured rats. We collected data from experiments in adult well as the grid walk score were highly correlated with the rats after dorsal hemisection or contusion lesion using parameters obtained by kinematic analysis, especially with several motor tasks and scaling systems. The results of the the joint angles in the E2 and E3-phase Table 1. different motor tests were correlated to evaluate the extent Correlations to the parameters obtained by footprint analy- to which the parameters relate to each other. The per- sis were weaker and revealed a heterogeneous result for formance of animals with high locomotor performance the different lesion types: a close relationship was found to showed a close relationship between tests requiring sup- angles of foot rotation and base of support in contusion raspinal motor control such as grid walk or narrow beam. animals, but not in animals with dorsal hemisection. On In contrast, animals with low locomotor capacity showed a the other hand, the correlation to stride length was better in closer relationship between the BBB score and activity in animals with a hemisection lesion. In comparison to other the open field. motor tasks, a close relationship to the narrow beam score was found in animals with dorsal hemisection data for 4.1. Methodological considerations contusion lesion injury were not obtained whereas the relationship to placing responses was very weak for both 4.1.1. Open field locomotion lesion types and locomotor outcome groups Table 2. A straightforward way to evaluate over-ground locomo- G .A.S. Metz et al. Brain Research 883 2000 165 –177 173 tion is the use of rating scales, based on observations of defined leg movements. This provides information on the activation of spinal networks that are able to produce a coordinated stepping pattern [24,25,43]. These pattern generating networks are activated by the ventrally located reticulospinal tract [11,30]. Therefore, lesions restricted to dorsal tracts of rat spinal cords, such as the corticospinal tract, result in almost complete recovery of hindlimb function [35,38]. In order to allow inter-laboratory comparisons of results, various rating systems were developed. One of the most commonly used scales was the Tarlov score [46,47], which ranks hindlimb movements and weight support in five categories. However, this method has been described to be more sensitive when the animal is capable of hindlimb weight support and is less reliable when used to score hindlimb movements without weight support [10]. This scale was improved by increasing the number of categories for all hindlimb motor features in the BBB score [4]. The BBB score is now widely used and has been shown to provide reproducible results [5]. One advantage of this scale is that preoperative training of the animals is not necessary. It was originally designed for contusion injuries and is thought to be less sensitive to clip compression injuries [48]. However, for spinal hemisection we found that the BBB score is sensitive as well. Potential limita- tions of the BBB score are due to the subjective scoring system, e.g. for determination of forelimb–hindlimb coordination [10]. An important drawback is the fact that the ordinal BBB rating system is not linear: the lower part of the scale concerns gross aspects of locomotion, while the upper part of the scale includes rather discrete movement aspects that do not represent major improvements for the animal’s motor ability. Motor training usually performed by the animals in the cages and during the tests may affect motor improvement especially in the lower part of the scale. This may be one of the reasons why the BBB score correlates closely to exploratory activity for animals with low motor ability. In the upper part of the scale 13 points, the sequence of recovery is often not related to the scaling hierarchy. If animals reach this level of performance, we suggest the addition of points for single features like toe clearance and tail position independently. Also, the motor recovery after any different lesion type and treatment strategies may require a new order of the scaling hierarchy. Fig. 3. Correlations of behavioral parameters. A Scattergram of a Especially in animals with a high locomotor outcome correlation between the BBB score and the number of errors produced on BBB score.13 and a stable degree of performance, the a grid in animals with hemisection DHX or contusion injury CONT. difference between single animals is very subtle. There- B Correlation between the BBB score and the footprint score. C fore, for detailed inter-individual differences, additional Scattergram showing the correlation between BBB score and the number of placing responses in animals with dorsal hemisection and contusion appropriate motor tests have to be used. lesion. The correlation reveals a positive relationship between both paradigms, although the distribution of single values was very inhomoge- 4.1.2. Footprint analysis neous. For both lesion types, the distribution was similar. All these graphs Different methods were previously used to measure the illustrate that the inter-animal variation was larger in animals with low placement of the hind paws [16,50]. In addition to the BBB scores ,13 points than in animals with high BBB scores 13 points. criteria plantar stepping and toe clearance, footprint analy- 174 G Table 2 a Summary of the two animal groups, subdivided into low and high locomotor outcome based on the BBB score Characteristic vs. Characteristic Correlation coefficient BBB,13 Correlation coefficient BBB13 BBB score Footprint score 0.51 4 0.65 20 BBB score Grid walk errors 0.63 17

0.82 80