*2.1.5. F-wave data analysis*

All recorded F-wave data were analyzed for the persistence, F/M amplitude ratio, and latency in each trial. The minimum of F-wave peak-to-peak amplitude was at least 20 μV [21]. The persistence was defined as the number of detected F-wave responses divided by 30 supramaximal electrical stimuli. The F/M amplitude ratio was defined as the mean amplitude of all responses divided by the M-wave amplitude. The amplitude measured individually for each F-wave and then the mean calculated. The latency was defined as the mean latency from the time of electrical stimulation to onset of detected F-waves. The persistence reflects the number of backfiring spinal anterior horn cells [22, 23]. The F/M amplitude ratio reflects the number of backfiring spinal anterior horn cells and the individual cells excitability [22, 23]. Thus, these parameters are considered the indices of the spinal motor neuron excitability.

#### *2.1.6. Statistical analysis*

The normality of F-wave data was not confirmed by using the Kolmogorov-Smirnov and Shapiro-Wilk tests. We used a nonparametric method in this research. The persistence, F/M amplitude ratio, and latency among three trials (rest, MI, post) under each MI conditions (10% MI, 30% MI, 50% MI, and 70% MI conditions) were compared using the Friedman test and Scheffe's post hoc test.

We also calculated the relative value obtained by dividing F-wave data during MI under four MI conditions by that at rest. The relative values among four MI conditions were compared using the Friedman test. We used SPSS statistics ver. 19 (IBM Corp., USA) for statistical analysis. The threshold for statistical significance was set to p = 0.05.

#### *2.1.7. Results*

The persistence during MI under all MI conditions was significantly greater than that at rest (10% MI vs. Rest, 70% MI vs. Rest, \*\**p* < 0.01; 30% MI vs. Rest, 50% MI vs. Rest, \**p* < 0.05) (**Tables 1**–**4**). The persistence immediately after MI under all MI conditions was reduced to rest level (**Tables 1**–**4**).

The F/M amplitude ratio during MI under 10, 30, and 50% MI conditions was significantly greater than that at rest (10% MI vs. Rest, 50% MI vs. Rest, \*\**p* < 0.01; 30% MI vs. Rest, \**p* < 0.05) (**Tables 1**–**3**). The F/M amplitude ratio during MI under 70% MI condition was tended to be increased than that at rest (p ≒ 0.082) (**Table 4**). The F/M amplitude ratio immediately after MI under all MI conditions was reduced to rest level (**Tables 1**–**4**).

No significantly differences in the latency were observed among three trials (rest, MI, post)

Persistence (%) 55.9 ± 17.6 88.1 ± 10.8\*\* 65.3 ± 19.9 F/M amplitude ratio (%) 0.94 ± 0.33 1.79 ± 1.23 1.11 ± 0.44 Latency (ms) 24.4 ± 1.37 24.1 ± 1.27 24.3 ± 1.15

Persistence (%) 62.7 ± 22.3 94.0 ± 9.40\* 65.5 ± 27.0 F/M amplitude ratio (%) 1.08 ± 0.28 2.60 ± 2.30\*\* 0.98 ± 0.40 Latency (ms) 24.5 ± 1.61 24.3 ± 1.82 24.5 ± 1.58

Persistence (%) 61.2 ± 19.5 88.0 ± 12.2\*\* 60.0 ± 18.7 F/M amplitude ratio (%) 1.00 ± 0.94 2.92 ± 2.95\*\* 1.11 ± 0.52 Latency (ms) 24.9 ± 1.16 24.6 ± 0.99 24.9 ± 1.14

**Rest 70% MI post**

**Rest 50% MI post**

**Rest 30% MI post**

**Rest 10% MI post**

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Persistence (%) 61.8 ± 12.6 91.9 ± 9.70\*\* 73.1 ± 20.7 F/M amplitude ratio (%) 0.90 ± 0.35 2.46 ± 2.61\*\* 1.18 ± 0.67 Latency (ms) 25.3 ± 0.98 25.2 ± 1.25 25.5 ± 0.99

\*\**p* < 0.01; significant difference between rest and 10% MI trial.

\*\**p* < 0.05; significant difference between rest and 30% MI trial.

**Table 2.** Changes in F-wave under 30% MI condition.

**Table 1.** Changes in F-wave under 10% MI condition.

The relative values of the persistence, F/M amplitude ratio, and latency did not exhibit signifi-

under all MI conditions (**Tables 1**–**4**).

cant differences among all MI conditions (**Table 5**).

\*\**p* < 0.01; significant difference between rest and 70% MI trial.

*p* < 0.05; significant difference between rest and 50% MI trial. \*\**p* < 0.01; significant difference between rest and 50% MI trial.

**Table 3.** Changes in F-wave under 50% MI condition.

**Table 4.** Changes in F-wave under 70% MI condition.

\*

#### The Application of Motor Imagery to Neurorehabilitation http://dx.doi.org/10.5772/intechopen.75411 57


\*\**p* < 0.01; significant difference between rest and 10% MI trial.

**Table 1.** Changes in F-wave under 10% MI condition.

participants press the sensor of pinch meter by left thumb and index finger at 50% MVC) for 1 min. They were instructed to keep the 50% MVC value (kgf) measured numerically on the display of pinch meter. For the MI trial, participants performed MI of isometric thenar muscle activity at 50% MVC for 1 min. F-waves were recorded during MI (50% MI). Immediately after 50% MI trial (post), F-waves were recorded during relaxation for 1 min. The above process was defined as the MI at 50% MVC condition (50% MI condition). This protocol was repeated for 10, 30, and 70% MI conditions. Each condition was performed randomly on dif-

All recorded F-wave data were analyzed for the persistence, F/M amplitude ratio, and latency in each trial. The minimum of F-wave peak-to-peak amplitude was at least 20 μV [21]. The persistence was defined as the number of detected F-wave responses divided by 30 supramaximal electrical stimuli. The F/M amplitude ratio was defined as the mean amplitude of all responses divided by the M-wave amplitude. The amplitude measured individually for each F-wave and then the mean calculated. The latency was defined as the mean latency from the time of electrical stimulation to onset of detected F-waves. The persistence reflects the number of backfiring spinal anterior horn cells [22, 23]. The F/M amplitude ratio reflects the number of backfiring spinal anterior horn cells and the individual cells excitability [22, 23]. Thus, these

The normality of F-wave data was not confirmed by using the Kolmogorov-Smirnov and Shapiro-Wilk tests. We used a nonparametric method in this research. The persistence, F/M amplitude ratio, and latency among three trials (rest, MI, post) under each MI conditions (10% MI, 30% MI, 50% MI, and 70% MI conditions) were compared using the Friedman test and

We also calculated the relative value obtained by dividing F-wave data during MI under four MI conditions by that at rest. The relative values among four MI conditions were compared using the Friedman test. We used SPSS statistics ver. 19 (IBM Corp., USA) for statistical analy-

The persistence during MI under all MI conditions was significantly greater than that at rest (10% MI vs. Rest, 70% MI vs. Rest, \*\**p* < 0.01; 30% MI vs. Rest, 50% MI vs. Rest, \**p* < 0.05) (**Tables 1**–**4**). The persistence immediately after MI under all MI conditions was reduced to

The F/M amplitude ratio during MI under 10, 30, and 50% MI conditions was significantly greater than that at rest (10% MI vs. Rest, 50% MI vs. Rest, \*\**p* < 0.01; 30% MI vs. Rest, \**p* < 0.05) (**Tables 1**–**3**). The F/M amplitude ratio during MI under 70% MI condition was tended to be increased than that at rest (p ≒ 0.082) (**Table 4**). The F/M amplitude ratio immediately after MI

parameters are considered the indices of the spinal motor neuron excitability.

sis. The threshold for statistical significance was set to p = 0.05.

under all MI conditions was reduced to rest level (**Tables 1**–**4**).

ferent days.

*2.1.5. F-wave data analysis*

56 Evolving BCI Therapy - Engaging Brain State Dynamics

*2.1.6. Statistical analysis*

Scheffe's post hoc test.

rest level (**Tables 1**–**4**).

*2.1.7. Results*


**Table 2.** Changes in F-wave under 30% MI condition.


\* *p* < 0.05; significant difference between rest and 50% MI trial. \*\**p* < 0.01; significant difference between rest and 50% MI trial.

**Table 3.** Changes in F-wave under 50% MI condition.


**Table 4.** Changes in F-wave under 70% MI condition.

No significantly differences in the latency were observed among three trials (rest, MI, post) under all MI conditions (**Tables 1**–**4**).

The relative values of the persistence, F/M amplitude ratio, and latency did not exhibit significant differences among all MI conditions (**Table 5**).


After all F-wave recordings, F-wave data was analyzed with respect to the persistence, F/M

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The normality of F-wave data was not confirmed by using the Kolmogorov-Smirnov and Shapiro-Wilk tests. We used a nonparametric method in this research. The persistence, F/M amplitude ratio, and latency among three trials (rest, MI, post) under two MI conditions (50% MI and 100% MI conditions) were compared using the Friedman test and Scheffe's post hoc test. We also calculated the relative value obtained by dividing F-wave data during MI under four MI conditions by that at rest. The relative values among two MI conditions were compared using the Wilcoxon signed rank test. We used SPSS statistics ver. 19 (IBM Corp., USA) for

The persistence during MI under two MI conditions was significantly greater than that at rest (50% MI vs. Rest, 100% MI vs. Rest, \*\**p* < 0.01) (**Tables 6**, **7**). The persistence immediately after

The F/M amplitude ratio during MI under two MI conditions was significantly greater than that at rest (50% MI vs. Rest, 100% MI vs. Rest, \*\**p* < 0.01) (**Tables 6**, **7**). The F/M amplitude ratio immediately after MI under two MI conditions was reduced to rest level (**Tables 6**, **7**). No significantly differences in the latency were observed among three trials (rest, MI, post)

The relative values of the persistence, F/M amplitude ratio, and latency did not exhibit signifi-

From results of our previous works, it is suggested that MI of isometric thenar muscle activity at 10, 30, 50, 70, and 100% can facilitate the spinal motor neuron excitability. About this, it is considered to be influence of descending pathways corresponding to thenar muscle. Previous researches have demonstrated the activation of diverse brain area contribute to motor preparation and planning during MI [9–13]. The excitatory and inhibitory inputs modulate the spinal motor neuron excitability via the corticospinal and/or extrapyramidal tract [30]. Thus, it is plausibly that the activation of central nervous system contributes to motor preparation and planning during MI facilitated the spinal motor neuron excitability via the corticospinal

Furthermore, all subjects participated in our previous works were instructed to perform MI with holding the sensor of a pinch meter. Mizuguchi et al. [31] reported that corticospinal excitability during MI utilizing an object was modulated by a combination of tactile and proprioceptive inputs while holding an object. We previously reported that the spinal motor neuron

*2.3.1. The spinal motor neuron excitability during MI of isometric thenar muscle activity*

statistical analysis. The threshold for statistical significance was set to p = 0.05.

MI under two MI conditions was reduced to rest level (**Tables 6**, **7**).

under two MI conditions (**Tables 6**, **7**).

cant differences between two MI conditions (**Table 8**).

amplitude ratio, and latency.

*2.2.5. Statistical analysis*

*2.2.6. Results*

**2.3. Discussion**

and/or extrapyramidal tract.

**Table 5.** Comparison of F-wave among 10% MI, 30% MI, 50% MI, and 70% MI condition.
