Comparing movement-related cortical potential between real and simulated movement tasks from an ecological validity perspective

IntroductionConcerns regarding the ecological validity of movement-related cortical potential (MRCP) experimental tasks that are related to motor learning have recently been growing. Therefore, we compared MRCP during real movement task (RMT) and simulated movement task (SMT) from an ecological validity perspective.MethodsThe participants performed both RMT and SMT, and MRCP were measured using electroencephalogram (EEG). EEG was based on the 10-20 method, with electrodes placed in the motor cortex (C3 and C4) and supplementary motor cortex (FCz [between Fz and Cz] and Cz) areas. This experiment examined the MRCP using Bereitschaftspotential (BP) and negative slope (NS’) onset times, and BP, NS’, and motor potential (MP) amplitudes during the task.ResultsThe results revealed that the SMT exhibited later BP and NS’ onset times and smaller BP, NS’, and MP amplitudes than the RMT. Furthermore, in RMT, the onset time of MRCP was delayed, and the amplitude of MRCP was smaller in the second half of the 200 times task than in the first half, whereas in SMT, there was no change in onset time and amplitude. The SMT showed a different MRCP than the RMT, suggesting that the ecological validity of the task should be fully considered when investigating the cortical activity associated with motor skill learning using MRCP.ConclusionEcological validity of the study should be fully considered when investigating the cortical activity associated with motor skill learning using MRCP. Moreover, it is important to understand the differences between the two methods when applied clinically

Real-Time Changes in Corticospinal Excitability during Voluntary Contraction with Concurrent Electrical Stimulation

<div><p>While previous studies have assessed changes in corticospinal excitability <em>following</em> voluntary contraction coupled with electrical stimulation (ES), we sought to examine, for the first time in the field, <em>real-time</em> changes in corticospinal excitability. We monitored motor evoked potentials (MEPs) elicited by transcranial magnetic stimulation and recorded the MEPs using a mechanomyogram, which is less susceptible to electrical artifacts. We assessed the MEPs at each level of muscle contraction of wrist flexion (0%, 5%, or 20% of maximum voluntary contraction) during voluntary wrist flexion (flexor carpi radialis (FCR) voluntary contraction), either with or without simultaneous low-frequency (10 Hz) ES of the median nerve that innervates the FCR. The stimulus intensity corresponded to 1.2× perception threshold. In the FCR, voluntary contraction with median nerve stimulation significantly increased corticospinal excitability compared with FCR voluntary contraction without median nerve stimulation (<em>p</em><0.01). In addition, corticospinal excitability was significantly modulated by the level of FCR voluntary contraction. In contrast, in the extensor carpi radialis (ECR), FCR voluntary contraction with median nerve stimulation significantly decreased corticospinal excitability compared with FCR voluntary contraction without median nerve stimulation (<em>p</em><0.05). Thus, median nerve stimulation during FCR voluntary contraction induces reciprocal changes in cortical excitability in agonist and antagonist muscles. Finally we also showed that even mental imagery of FCR voluntary contraction with median nerve stimulation induced the same reciprocal changes in cortical excitability in agonist and antagonist muscles. Our results support the use of voluntary contraction coupled with ES in neurorehabilitation therapy for patients.</p> </div

Changes in MMG-MEPs during rest or during FCR voluntary muscle contraction, with and without median nerve stimulation.

<p>Data are presented as the mean ± standard error (n = 15). Asterisks indicate significant differences between tasks by post-hoc testing with a Bonferroni correction (*<i>p</i><0.05; **<i>p</i><0.01). (A) MMG-MEPs from the FCR during 0, 5, and 20% of the FCR MVC with median nerve stimulation (open square) and without median nerve stimulation (filled square). (B) Effects of FCR voluntary contraction strength on corticospinal excitability measured in the FCR. The data from FCR voluntary contraction without median nerve stimulation was subtracted from the data from FCR voluntary contraction with median nerve stimulation. The FCR results are displayed as a white bar. (C) MMG-MEPs from the ECR during 0, 5, and 20% of the FCR MVC with median nerve stimulation (open square) and without median nerve stimulation (filled square). (D) Effects of FCR voluntary contraction strength on corticospinal excitability measured in the ECR. The data from FCR voluntary contraction without median nerve stimulation was subtracted from the data from FCR voluntary contraction with median nerve stimulation. The ECR results are displayed as a gray bar.</p

An example of MMG-MEPs during FCR voluntary contraction with and without median nerve stimulation in a single subject.

<p>The MMG-MEPs responses from FCR muscle during FCR voluntary contraction without median nerve stimulation (A) and with median nerve stimulation (B). (C) and (D) show the MMG-MEPs from ECR muscles during FCR voluntary contraction without median nerve stimulation and with median nerve stimulation, respectively. Left: Wave forms of MMG-MEPs during 0% maximum FCR voluntary contraction (at rest). Middle: Wave forms of MMG-MEPs during 5% of the MVC. Right: Wave forms of MMG-MEPs during 20% of the MVC. Black vertical lines show the trigger of TMS.</p

Changes in MMG-MEPs during rest or during mental imagery of FCR voluntary muscle contraction, with or without median nerve stimulation.

<p>Data are presented as the mean ± standard error (n = 7). Asterisks indicate significant differences between tasks after post-hoc testing with a Bonferroni correction (*<i>p</i><0.05; **<i>p</i><0.01). (A) MMG-MEPs from the FCR during mental imagery of 0, 5, and 20% of the MVC with median nerve stimulation (open triangle) or without median nerve stimulation (filled triangle). (B) Effects of mental imagery of FCR voluntary contraction strength on corticospinal excitability measured in the FCR. The data from mental imagery without median nerve stimulation were subtracted from those from mental imagery with median nerve stimulation. The FCR results are displayed as a white bar. (C) MMG-MEPs from the ECR during the mental imagery of 0, 5, and 20% of the MVC with median nerve stimulation (open triangle) or without median nerve stimulation (filled triangle). (D) Effects of mental imagery of FCR voluntary contraction strength on corticospinal excitability measured in the ECR. The data from mental imagery without median nerve stimulation were subtracted from data of mental imagery with median nerve stimulation. The ECR results are displayed as a gray bar.</p