Time course of corticospinal excitability in reaction time and self‐paced movements

Abstract

We used transcranial magnetic stimulation (TMS) to study the time course of corticospinal excitability before and after brisk thumb abduction movements, either in a simple reaction time (RT) paradigm or self-paced. Premovement increase in corticospinal excitability began about 20 msec earlier for self-paced compared with simple RT movements. For both simple RT and self-paced movements after electromyographic (EMG) offset, there was a first period of increased excitability from 0 to 100 msec, followed by a second period from 100 to 160 msec. Corticospinal excitability was decreased from about 500 to 1,000 msec after EMG offset for both types of movements. Our results show that motor preparation that begins 1.5 to 2 seconds before self-paced movement is not associated with increased corticospinal excitability. The first phase of increased corticospinal excitability after EMG offset may be due to activity of motor cortex neuron subthreshold for activating spinal motor neurons, and the second phase may reflect a subthreshold second agonist burst. The period of decreased corticospinal excitability after movement corresponds to the onset of event-related synchronization (ERS) of electroencephalographic signals in the 20-Hz band, and supports the hypothesis that ERS may be related to an inactive, idling state of the motor cortex.

Age-related differences in corticospinal excitability during a choice reaction time task

“…Levels of facilitation were rather feeble (110 % to 120 % of MEP amplitude at the onset of the IS) and not significantly different in both age groups. This result was in line with previous studies reporting increased CS excitability in the agonist muscle of the selected hand towards voluntary EMG onset in young adults (Chen et al 1998;Chen and Hallett 1999;Leocani et al 2000). In addition, no correlations were found between individual levels of facilitation at the 75 % PreMT and RTs (neither for older nor for young adults), indicating that higher facilitation of MEPs in the selected FDI did not necessarily predict faster RTs.…”

“…It is assumed that suppression of CS excitability is necessary to prevent erroneous premature responding (Davranche et al 2007;Duque and Ivry 2009;Touge et al 1998). During response generation, however, it has been reported that CS excitability is increased in the agonist muscle of the selected hand towards voluntary electromyographical (EMG) signal onset (Chen et al 1998;Chen and Hallett 1999;Leocani et al 2000).…”

Abnormal corticomotor excitability assessed in biceps brachii preceding pronator contraction post-stroke

“…A number of studies have previously demonstrated that stimulus intensities below resting motor threshold detected increases in CM excitability of an agonist during preparation for a motor action (Chen et al, 1998;MacKinnon and Rothwell, 2000;Pascual-Leone et al, 1992;Tomberg and Caramia, 1991). Indeed, in the present study, application of subthreshold TMS prior to intended muscle contractions in healthy subjects revealed that agonist BB CM excitability increased, because the stimulus intensities used were below rest threshold.…”

“…Therefore, pre-contraction changes in CM excitability of the antagonist BB were assessed in the present study using stimulus intensities below resting threshold. Subthreshold TMS has been previously used to examine changes in CM excitability during preparation for a motor action in a number of studies (Chen et al, 1998;MacKinnon and Rothwell, 2000;Pascual-Leone et al, 1992;Tomberg and Caramia, 1991).…”

Influence of task-related ipsilateral hand movement on motor cortex excitability

“…Motor cortex excitability is in¯uenced by multiple inputs that may vary depending on the task (Chen et al, 1998;Seyal et al, 1999), preparation for voluntary movement (Hoshiyama and Kakigi, 1999) and sensory input (Furubayashi et al, 2000;Tokimura et al, 2000). Electroencephalographic (Pfurtscheller et al, 1996;Leocani et al, 1997), magnetoencephalographic (Nagamine et al, 1994(Nagamine et al, , 1996 and event-related potentials (Shibasaki and Rothwell, 1999;Hoshiyama and Kakigi, 1999) evidence suggest premovement changes (bilateral in case of ERPs) hundreds of ms before and after a voluntary response.…”