EC Neurology

Introduction: The strength of the transcallosal fibers connecting the two primary motor cortices (M1) seems to depend on the motor activity of the controlled limb and its contralateral counterpart. This study verifies cortical excitability in healthy subjects with the right hand immobilized for ten hours and the left hand free.

Objectives: The activity of the cerebral cortex M1 was analyzed in two different groups of subjects: the G1 subjected to prolonged immobilization without activity and/or stimuli and the G2 subjected to prolonged immobilization during which stimuli were provided at predefined intervals.

Materials: The study participants were divided into two groups (G1 and G2) that differed in that in G2, during the hours of immobilization, a vibration protocol was also applied. The vibration protocol stabilizes transcallosal inhibitions by simulating the normal use of the immobilized upper limb.

Results: In G1 and G2, after immobilization, the excitability of the left and right motor cortex changed, but in very different percentages depending on the type of activity carried out during the immobilization period.

Conclusion: The non-use caused by immobilization reduces the excitability of the left M1 and decreases the inhibitory effect on the right M1 but by applying a vibration, transcallosal inhibitions stabilize simulating normal use of the arm.

Keywords: Transcallosal Inhibition; Immobilization; Vibration

1. Wahl M., et al. “Human motor corpus callosum: topography, somatotopy, and link between microstructure and function”. The Journal of Neuroscience 27 (2007): 12132-12138.
2. Ferbert A., et al. “Interhemispheric inhibition of the human motor cortex”. The Journal of Physiology 453 (1992): 525-546.
3. Asanuma H and Okuda O. “Effects of transcallosal volleys on pyramidal tract cell activity of cat”. Journal of Neurophysiology 25 (1962): 198-208.
4. Jenny AB. “Commissural projections of the cortical hand motor area in monkeys”. The Journal of Comparative Neurology 188 (1979): 137-145.
5. Duque J., et al. “Intermanual differences in movement related interhemispheric inhibition”. Journal of Cognitive Neuroscience 19 (2007): 204-213.
6. Liepert J., et al. “Inhibition of ipsilateral motor cortex during phasic generation of low force”. Clinical Neurophysiology 112 (2001): 114-121.
7. Liepert J., et al. “Motor cortex disinhibition of the unaffected hemisphere after acute stroke”. Muscle and Nerve 23 (2000): 1761-1763.
8. Murase N., et al. “Influence of interhemispheric interactions on motor function in chronic stroke”. Annals of Neurology 55 (2004): 400-409.
9. Hummel FC and Cohen LG. “Non-invasive brain stimulation: a new strategy to improve neurorehabilitation after stroke?” Lancet Neurology 5 (2006): 708-712.
10. Gilio F., et al. “Effects on the right motor hand-area excitability produced by low-frequency rTMS over human contralateral homologous cortex”. The Journal of Physiology 551 (2003): 563-573.
11. Kobayashi M., et al. “Repetitive TMS of the motor cortex improves ipsilateral sequential simple finger movements”. Neurology 62 (2004): 91-98.
12. Avanzino L., et al. “1-Hz repetitive TMS over ipsilateral motor cortex influences the performance of sequential finger movements of different complexity”. European Journal of Neuroscience 27 (2008): 1285-1291.
13. Huber R., et al. “Arm immobilization causes cortical plastic changes and locally decreases sleep slow wave activity”. Nature Neuroscience 9 (2006): 1169-1176.
14. Oldfield RC. “The assessment and analysis of handedness: the Edinburgh inventory”. Neuropsychology 9 (1971): 97-113.
15. Werhahn KJ., et al. “The effect of magnetic coil orientation on the latency of surface EMG and single motor unit responses in the first dorsal interosseous muscle”. Electroencephalography and Clinical Neurophysiology 93 (1994): 138-146.
16. Liepert J., et al. “Changes of cortical motor area size during immobilization”. Electroencephalography and Clinical Neurophysiology 97 (1995): 382-386.
17. Zanette G., et al. “Reversible changes of motor cortical outputs following immobilization of the upper limb”. Electroencephalography and Clinical Neurophysiology 105 (1997): 269-279.
18. Zanette G., et al. “Modulation of motor cortex excitability after upper limb immobilization”. Clinical Neurophysiology 115 (2004): 1264-1275.
19. Porters S., et al. “Time-related changes of excitability of the human motor system contingent upon immobilisation of the ring and little fingers”. Clinical Neurophysiology 113 (2002): 367-375.
20. Trompetto C., et al. “Suppression of the transcallosal motor output: a transcranial magnetic stimulation study in healthy subjects”. Brain Research 158 (2004): 133-140.
21. Avanzino L., et al. “Intracortical circuits modulate transcallosal inhibition in humans”. The Journal of Physiology 583 (2007): 99-114.
22. Pal PK., et al. “Effect of low-frequency repetitive transcranial magnetic stimulation on interhemispheric inhibition”. Journal of Neurophysiology 94 (2005): 1668-1675.
23. Rizzo V., et al. “Paired associative stimulation of left and right human motor cortex shapes interhemispheric motor inhibition based on a Hebbian mechanism”. Cerebral Cortex 19 (2009): 907-915.
24. Rizzo V., et al. “Associative corticocortical plasticity may affect ipsilateral finger opposition movements”. Behavioural Brain Research 216 (2011): 433-439.
25. Werhahn KJ., et al. “Cortical excitability changes induced by deafferentation of the contralateral hemisphere”. Brain 125 (2002a): 1402-1413.
26. Werhahn KJ., et al. “Enhanced tactile spatial acuity and cortical processing during acute hand deafferentation”. Nature Neuroscience 5 (2002b): 936-938.
27. Floel A., et al. “Influence of somatosensory input on interhemispheric interactions in patients with chronic stroke”. Neurorehabilitation and Neural Repair 22 (2008): 477-485.
28. Allison T., et al. “The relationship between human long-latency somatosensory evoked potentials recorded from the cortical surface and from the scalp”. Electroencephalography and Clinical Neurophysiology 84 (1992): 301-314.
29. Heath CJ., et al. “Inputs from low threshold muscle and cutaneous afferents of hand and forearm to areas 3a and 3b of baboon's cerebral cortex”. The Journal of Physiology 257 (1976): 199-227.
30. Hore J., et al. “Responses of cortical neurons (areas 3a and 4) to ramp stretch of hind limb muscles in the baboon”. Journal of Neurophysiology 39 (1976): 484-500.
31. Naito E., et al. “I feel my hand moving: a new role of the primary motor cortex in somatic perception of limb movement”. Neuron 36 (2002): 979-988.
32. Rosenkranz K and Rothwell JC. “Differential effect of muscle vibration on intracortical inhibitory circuits in humans”. The Journal of Physiology 551 (2003): 649-660.
33. Swayne O., et al. “Transcallosal sensorimotor integration: effects of sensory input on cortical projections to the contralateral hand”. Clinical Neurophysiology 117 (2006): 855-863.