Table 2.
Results of the 2factorial repeated measurement ANOVAs conducted for experiments 1–4
| Expt no. | Variables | d.f. | F values | P values |
|---|---|---|---|---|
| 1 | Current flow | 1 | 2.427 | 0.1579 |
| Electrode position | 5 | 0.560 | 0.7299 | |
| Polarity of current stimulation | 1 | 1.502 | 0.2552 | |
| Current flow × electrode position | 5 | 0.827 | 0.5383 | |
| Current flow × polarity of current stimulation | 1 | 7.744 | 0.0238 * | |
| Electrode position × polarity of current stimulation | 5 | 2.613 | 0.0389 * | |
| Current flow × electrode position × polarity of current stimulation | 5 | 0.650 | 0.6633 | |
| 2 | Time course | 10 | 1.442 | 0.1658 |
| Polarity of current stimulation | 1 | 48.875 | < 0.0001 * | |
| Polarity of current stimulation × time course | 10 | 10.289 | < 0.0001 * | |
| 3 | Duration of current stimulation | 4 | 5.295 | 0.0011 * |
| Time course | 5 | 14.790 | < 0.0001 * | |
| Duration of current stimulation × time course | 20 | 2.768 | 0.0001 * | |
| 4 | Intensity of current stimulation | 4 | 6.011 | 0.004 * |
| Time course | 5 | 23.798 | < 0.0001 * | |
| Intensity of current stimulation × time course | 20 | 3.736 | < 0.0001 * |
The results of experiment 1 show that the effect of current flow depends on electrode position and polarity of current flow. For experiment 2, the ANOVA reveals a dependency of the aftereffect on polarity of current stimulation and an interaction of polarity and time course. As shown by the results of experiments 3 and 4, the independent variables – current duration, stimulation intensity and time course after current stimulation – determine the MEP size. Furthermore, the interactions between time course, stimulation duration and intensity indicate prolonged effects of longer and more intense stimulation on MEP size. d.f., degrees of freedom. *P < 0.05.