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Corticospinal excitability modulation in resting digit muscles during cyclical movement of the digits of the ipsilateral limb

View Article: PubMed Central

ABSTRACT

We investigated how corticospinal excitability of the resting digit muscles was modulated by the digit movement in the ipsilateral limb. Subjects performed cyclical extension-flexion movements of either the right toes or fingers. To determine whether corticospinal excitability of the resting digit muscles was modulated on the basis of movement direction or action coupling between ipsilateral digits, the right forearm was maintained in either the pronated or supinated position. During the movement, the motor evoked potential (MEP) elicited by transcranial magnetic stimulation (TMS) was measured from either the resting right finger extensor and flexor, or toe extensor and flexor. For both finger and toe muscles, independent of forearm position, MEP amplitude of the flexor was greater during ipsilateral digit flexion as compared to extension, and MEP amplitude of the extensor was greater during ipsilateral digit extension as compared to flexion. An exception was that MEP amplitude of the toe flexor with the supinated forearm did not differ between during finger extension and flexion. These findings suggest that digit movement modulates corticospinal excitability of the digits of the ipsilateral limb such that the same action is preferred. Our results provide evidence for a better understanding of neural interactions between ipsilateral limbs, and may thus contribute to neurorehabilitation after a stroke or incomplete spinal cord injury.

No MeSH data available.


Typical example of MEP of toe extensor and flexor. Mean and SD of 20 trials for each task from one subject. The arrows indicate the timing of the TMS. The toe extensor is the extensor digitorum brevis (EDB) and the flexor is the flexor digitorum brevis (FDB).
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Figure 4: Typical example of MEP of toe extensor and flexor. Mean and SD of 20 trials for each task from one subject. The arrows indicate the timing of the TMS. The toe extensor is the extensor digitorum brevis (EDB) and the flexor is the flexor digitorum brevis (FDB).

Mentions: The MEPs in EDB and FDB taken from a single subject are shown in Figure 4. The MEPs amplitudes of EDB and FDB tended to be greater when they were elicited during finger extension and flexion with the forearm in the pronated position, respectively. The average MEPs amplitudes in 17 subjects are shown in Figure 5. Statistical analysis revealed that there was a significant main effect of movement (F(1,16) = 8.25, p = 0.011) on MEP amplitude of the toe extensor, whereas neither a main effect of forearm position nor an interaction between movement × forearm position was significant (F(1,16) = 0.12, p = 0.737 and F(1,16) = 2.44, p = 0.137, respectively). This indicates that MEP amplitude of EDB was greater during finger extension than during finger flexion. There was a significant main effect of movement on MEP amplitude of the toe flexor (F(1,16) = 6.43, p = 0.022) and a significant interaction between movement × forearm position (F(1,16) = 5.22, p = 0.036). Further analysis for movement in each forearm position showed that MEP amplitude of FDB was significantly greater during finger flexion than during finger extension with the forearm in the pronated position (t(16) = 2.81, corrected p = 0.026), but not in the supinated position (t(16) = 0.61, uncorrected p = 0.546). No significant main effect of forearm position on MEP amplitude of the toe flexor was observed (F(1,16) = 0.18, p = 0.675).


Corticospinal excitability modulation in resting digit muscles during cyclical movement of the digits of the ipsilateral limb
Typical example of MEP of toe extensor and flexor. Mean and SD of 20 trials for each task from one subject. The arrows indicate the timing of the TMS. The toe extensor is the extensor digitorum brevis (EDB) and the flexor is the flexor digitorum brevis (FDB).
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Related In: Results  -  Collection

License
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Figure 4: Typical example of MEP of toe extensor and flexor. Mean and SD of 20 trials for each task from one subject. The arrows indicate the timing of the TMS. The toe extensor is the extensor digitorum brevis (EDB) and the flexor is the flexor digitorum brevis (FDB).
Mentions: The MEPs in EDB and FDB taken from a single subject are shown in Figure 4. The MEPs amplitudes of EDB and FDB tended to be greater when they were elicited during finger extension and flexion with the forearm in the pronated position, respectively. The average MEPs amplitudes in 17 subjects are shown in Figure 5. Statistical analysis revealed that there was a significant main effect of movement (F(1,16) = 8.25, p = 0.011) on MEP amplitude of the toe extensor, whereas neither a main effect of forearm position nor an interaction between movement × forearm position was significant (F(1,16) = 0.12, p = 0.737 and F(1,16) = 2.44, p = 0.137, respectively). This indicates that MEP amplitude of EDB was greater during finger extension than during finger flexion. There was a significant main effect of movement on MEP amplitude of the toe flexor (F(1,16) = 6.43, p = 0.022) and a significant interaction between movement × forearm position (F(1,16) = 5.22, p = 0.036). Further analysis for movement in each forearm position showed that MEP amplitude of FDB was significantly greater during finger flexion than during finger extension with the forearm in the pronated position (t(16) = 2.81, corrected p = 0.026), but not in the supinated position (t(16) = 0.61, uncorrected p = 0.546). No significant main effect of forearm position on MEP amplitude of the toe flexor was observed (F(1,16) = 0.18, p = 0.675).

View Article: PubMed Central

ABSTRACT

We investigated how corticospinal excitability of the resting digit muscles was modulated by the digit movement in the ipsilateral limb. Subjects performed cyclical extension-flexion movements of either the right toes or fingers. To determine whether corticospinal excitability of the resting digit muscles was modulated on the basis of movement direction or action coupling between ipsilateral digits, the right forearm was maintained in either the pronated or supinated position. During the movement, the motor evoked potential (MEP) elicited by transcranial magnetic stimulation (TMS) was measured from either the resting right finger extensor and flexor, or toe extensor and flexor. For both finger and toe muscles, independent of forearm position, MEP amplitude of the flexor was greater during ipsilateral digit flexion as compared to extension, and MEP amplitude of the extensor was greater during ipsilateral digit extension as compared to flexion. An exception was that MEP amplitude of the toe flexor with the supinated forearm did not differ between during finger extension and flexion. These findings suggest that digit movement modulates corticospinal excitability of the digits of the ipsilateral limb such that the same action is preferred. Our results provide evidence for a better understanding of neural interactions between ipsilateral limbs, and may thus contribute to neurorehabilitation after a stroke or incomplete spinal cord injury.

No MeSH data available.