Motor control of the costal and crural diaphragm--insights from transcranial magnetic stimulation in man.
The costal and crural parts of the diaphragm differ in their embryological development and physiological function. It is not known if this is reflected in differences in their motor cortical representation. We compared the response of the costal and crural diaphragms using varying intensities of transcranial magnetic stimulation of the motor cortex at rest and during submaximal and maximal inspiratory efforts. The costal and crural motor evoked potential recruitment curves during submaximal inspiratory efforts were similar. The response to stimulation before, during and at 10 and 30 min after 44 consecutive maximal inspiratory efforts was also the same. Using paired stimulations to investigate intra-cortical facilitatory and inhibitory circuits we found no difference between the costal and crural response with varying interstimulus intervals, or when conditioning and test stimulus intensity were varied. We conclude that supraspinal control of the costal and crural diaphragm is identical during inspiratory tasks.
Sharshar
Tarek
T
Respiratory Muscle Laboratory, Royal Brompton and Harefield NHS Trust, Fulham Road, London, SW3 6NP, UK.
Hopkinson
Nicholas S
NS
Ross
Ewen T
ET
Jonville
Sophie
S
Dayer
Mark J
MJ
Nickol
Annabel H
AH
Lofaso
Frédéric
F
Moxham
John
J
Polkey
Michael I
MI
D000200:Action Potentials / Q000528:radiation effects; D000328:Adult; D000704:Analysis of Variance; D003964:Diaphragm / Q000033:anatomy & histology / Q000502:physiology* / Q000528:radiation effects; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation / Q000379:methods; D004576:Electromyography / Q000379:methods; D019054:Evoked Potentials, Motor / Q000502:physiology / Q000528:radiation effects; D005260:Female; D006801:Humans; D001239:Inhalation / Q000528:radiation effects; D008297:Male; D009044:Motor Cortex / Q000502:physiology / Q000528:radiation effects*; D011999:Recruitment, Neurophysiological / Q000528:radiation effects; D012063:Relaxation / Q000502:physiology; D013997:Time Factors; D050781:Transcranial Magnetic Stimulation