Elsevier

Neuroscience

Volume 210, 17 May 2012, Pages 110-117
Neuroscience

Cognitive, Behavioral, and Systems Neuroscience
Research Paper
Changes in corticomotor excitability and inhibition after exercise are influenced by hand dominance and motor demand

https://doi.org/10.1016/j.neuroscience.2012.03.021Get rights and content

Abstract

Previous studies on handedness have often reported functional asymmetries in corticomotor excitability (CME) associated with voluntary movement. Recently, we have shown that the degree of post-exercise corticomotor depression (PED) and increase in short-interval cortical inhibition (SICI) after a repetitive finger movement task was less when the task was performed at a maximal voluntary rate (MVR) than when it was performed at a submaximal sustainable rate (SR). In the current study, we have compared the time course of PED and SICI in the dominant (DOM) and nondominant (NDOM) hands after an MVR and SR finger movement task to determine the influence of hand dominance and task demand. We tracked motor-evoked potential (MEP) amplitude from the first dorsal interosseous muscle of the DOM and NDOM hand for 20 min after a 10-s index finger flexion-extension task at MVR and SR. For all hand-task combinations, we report a period of PED and increased SICI lasting for up to 8 min. We find that the least demanding task, one that involved index finger movement of the DOM hand at SR, was associated with the greatest change in PED and SICI from baseline (63.6±5.7% and 79±2%, P<0.001, PED and SICI, respectively), whereas the most demanding task (MVR of the NDOM hand) was associated with the least change from baseline (PED: 88.1±3.6%, SICI: 103±2%; P<0.001). Our findings indicate that the changes in CME and inhibition associated with repetitive finger movement are influenced both by handedness and the degree of demand of the motor task and are inversely related to task demand, being smallest for an MVR task of the NDOM hand and greatest for an SR task of the DOM hand. The findings provide additional evidence for differences in neuronal processing between the dominant and nondominant hemispheres in motor control.

Highlights

▶Cortico-motor excitability and cortical inhibition were measured after hand tasks. ▶We compared motor demand (rate of movement) and hand (dominant vs. nondominant). ▶Excitability was reduced and cortical inhibition increased after all tasks. ▶The most demanding task had the least post-exercise effect, and vice-versa. ▶The effect of exercise on excitability and inhibition is inverse to motor demand.

Section snippets

Subjects

Ten healthy right-handed subjects (4F, 21–30 years of age) were recruited with the approval of the University of Western Australia Human Research Ethics Committee and in conformity with the Declaration of Helsinki. Before the experiment, all subjects completed an Edinburgh Handedness Inventory assessment and provided written informed consent to partake in the study, which consisted of three testing sessions each lasting between 45 and 60 min. No subjects reported any discomfort or ill effects

Movement kinematics

Fig. 2 summarises the group mean data for movement rate and amplitude (START vs. END) for the MVR and SR tasks when performed with the DOM and NDOM hands. Statistical analysis revealed an effect for rate (F(3,72)=20.02, P<0.001; F(1,72)=4.56, P<0.05; TASK and TIME, respectively) but not amplitude. START rate for the MVR task was less for the NDOM compared with the DOM hand (5.8±0.22 Hz vs. 6.26±0.16 Hz; P<0.05), but no difference was found between the END rates for each hand (5.19±0.22 Hz vs.

Discussion

We have studied the changes in CME and SICI after a short 10-s period of cyclical finger movement in a 2×2 design comparing hand dominance and movement sustainability. For all hand-task combinations, we report a period of PED and increased SICI lasting for up to 8 min after task completion. We find that the least demanding task, one that involved index finger movement of the DOM hand at a submaximal rate, was associated with the greatest degree of PED and SICI increase, whereas the most

Conclusion

Our current findings show that undemanding motor tasks can be associated with relatively profound and lasting changes in CME and inhibition, which are in fact reduced with increasing task demand, such as maximum movement rate, or the use of the nonpreferred hand. Studies of CME after effortful exercise would benefit not only by comparison to baseline levels, but also to comparable and more sustainable exercise protocols. Such comparisons may reveal central processes in primary motor cortex,

Acknowledgments

We thank all of the participants in the study and Jonathan Green for designing and developing the data acquisition program in LabVIEW. W.P.T. was supported by a Scholarship for International Research Fees, University of Western Australia Postgraduate Award and the Enid and Arthur Home Memorial Scholarship. The authors also acknowledge support from the Neuromuscular Foundation and Muscular Dystrophy Association of Western Australia.

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