Table 3

Factor loadings

Factor 1Factor 2Factor 3Factor 4Factor 5Rep score
Maximum of radial velocity (with respect to operandum)0.940.250.160.01−0.030.55
SD of radial velocity (with respect to operandum)0.920.140.130.300.000.36
SD of speed0.880.100.370.220.000.18
Maximum speed0.880.240.39−
Move duration0.090.950.06−
Path length0.340.820.290.330.05−0.18
Latency to maximum speed0.040.770.09−0.08−0.020.73
Latency to maximum acceleration0.040.750.08−
Maximum deviation from direct path0.210.660.280.580.10−0.50
SD of angular velocity (with respect to operandum)0.390.120.870.170.000.19
Maximum of angular velocity (with respect to operandum)0.450.230.82−0.020.19−0.02
Mean of angular velocity (with respect to operandum)−0.380.26
Turn efficiency0.010.040.04−0.200.02NA
Mean radial velocity (with respect to operandum)0.540.200.140.770.20−0.30
Mean speed0.490.240.370.750.01−0.36
Path efficiency−0.03−−0.020.43
Movement onset latency−0.120.01−0.04−0.150.01NA
Net change in heading−0.01−0.030.00−0.010.01NA
  • PCA followed by FA was used as the basis to select a subset of variables for subsequent use as regressors in GLMs to detect correlation with neuronal activity. Variables used as regressors are shown in bold. We selected a representative variable for each factor based on high loading onto its representative factor and low co-loading onto other factors (which together are represented by the rep score, the variable’s highest factor loading minus the sum of its loadings onto all other factors). These representative variables were: factor 1, maximum of radial velocity with respect to operandum; factor 2, move duration; factor 3: SD of angular velocity with respect to operandum; factor 4, path efficiency. Additionally, we selected three “independent” variables that did not load strongly onto any one factor (turn efficiency, net heading change, and movement onset latency). NA, not applicable.