title: Does interhemispheric communication relate to the bilateral function of muscles? A study of scapulothoracic muscles using transcranial magnetic stimulation.
abstract: Interhemispheric connections have been demonstrated between the motor cortex controlling muscle pairs. However, these investigations have tended to concentrate upon hand muscles. We have extended these investigations to proximal muscles that control the scapula upon the trunk and help to move and stabilise the shoulder. Using a paired pulse transcranial magnetic stimulation protocol, the interhemispheric interactions between different shoulder girdle muscle pairs, serratus anterior, upper trapezius and lower trapezius were investigated. Test motor evoked potentials were conditioned using conditioning pulse intensities of 80% and 120% of active motor threshold at three different condition-test intervals, during three different tasks. Interhemispheric inhibition was observed in upper trapezius using a conditioning intensity of 120% and condition-test interval of 8 ms (17 ± 18%, p < 0.007). A trend towards inhibition was observed in lower trapezius and serratus anterior using a conditioning intensity of 120% and a condition-test interval of 8 ms (13 ± 22%; p < 0.07 and 10 ± 19% respectively; p < 0.07). No interhemispheric facilitation was evoked. The study demonstrates that a low level of interhemispheric inhibition rather than interhemispheric facilitation could be evoked between these muscle pairs.
authors: Department of Physiotherapy, Kings College London, University of London, United Kingdom; Department of Physiotherapy, Imperial College Healthcare NHS Trust, United Kingdom. Electronic address: davidmatthews2@nhs.net.
authors: D
authors: D
authors: Matthews
authors: P
authors: P
authors: Murtagh
authors: A
authors: A
authors: Risso
authors: G
authors: G
authors: Jones
authors: C M
authors: CM
authors: Alexander
mesh_terms: D000328:Adult; D004576:Electromyography; D019054:Evoked Potentials, Motor / Q000502:physiology; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006225:Hand / Q000502:physiology; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D009068:Movement / Q000502:physiology*; D053580:Muscle Strength / Q000502:physiology; D018482:Muscle, Skeletal / Q000502:physiology*; D009433:Neural Inhibition / Q000502:physiology; D011930:Reaction Time / Q000502:physiology; D012540:Scapula / Q000502:physiology; D013909:Thorax / Q000502:physiology; D060726:Torso / Q000502:physiology; D050781:Transcranial Magnetic Stimulation / Q000379:methods*
keywords: AMT; C-T interval; FDI; IHF; IHI; Interhemispheric facilitation; Interhemispheric inhibition; M1; MEP; MVC; Motor control; TMS; Transcranial magnetic stimulation; Trunk muscles; active motor threshold; condition-test interval; first dorsal interossei; interhemispheric facilitation; interhemispheric inhibition; maximum voluntary contraction; motor evoked potential; primary motor cortex; transcranial magnetic stimulation