Experimental Brain Research

, Volume 163, Issue 3, pp 335–343 | Cite as

Modulation of intracortical excitability in human hand motor areas. The effect of cutaneous stimulation and its topographical arrangement

Research Article


Changes in afferent input can alter the excitability of intracortical inhibitory systems. For example, using paired transcranial magnetic stimulation (TMS), both electrical digital stimulation and muscle vibration have been shown to reduce short-interval intracortical inhibition (SICI). The effects following muscle vibration are confined to the corticospinal projection to the vibrated muscles. The results following digital stimulation are less clear and the relative timing of the cutaneous stimulation and TMS is critical. Here we investigated further whether changes in SICI following digit stimulation exhibit topographic specificity. Eleven normal subjects were investigated (age 28.2±7.5 years, mean±SD). Electromyographic recordings were made from the right first dorsal interosseous (FDI), abductor digiti minimi (ADM) and abductor pollicis brevis (APB) muscles. SICI was measured, with and without preceding electrical digit II or digit V cutaneous stimulation. The interval between the digital nerve stimulus and test magnetic stimulus was independently set for each subject and established by subtracting the onset latency of the motor evoked potential (MEP) from the latency of the E2 component of the cutaneomuscular reflex. Therefore, measures of intracortical excitability were made at a time at which it is known that cutaneous input is capable of modulating cortical excitability. Single digital nerve stimuli applied to digit II significantly reduced SICI in FDI but not in ADM. Single digital nerve stimuli applied to digit V significantly reduced SICI in ADM but not in FDI or APB. There was a more generalised effect on intracortical facilitation (ICF) with both digit II and digit V stimulation significantly increasing ICF in FDI and ADM. Digital stimulation (either DII or DV) did not significantly affect SICI/ICF in APB. These findings show that appropriately timed cutaneous stimuli are capable of modulating SICI in a topographically specific manner. We suggest that the selective decrease in SICI seen with cutaneous stimulation may be important for focusing of muscle activation during motor tasks.


Motor cortex Cutaneous input Cortical inhibition Human 


  1. Caccia NR, McComas AJ, Upton ARM, Blogg T (1973) Cutaneous reflexes in small muscles of the hand. J Neurol Neurosurg Psychiatr 36:960–977Google Scholar
  2. Classen J, Steinfelder B, Liepert J, Stefan K, Celnik P, Cohen LG, Hess A, Kunesch E, Chen R, Benecke R, Hallett M (2000) Cutaneomotor integration in humans is somatotopically organized at various levels of the nervous system and is task dependent. Exp Brain Res. 130:48–59Google Scholar
  3. Fisher RJ, Nakamura Y, Bestmann S, Rothwell JC, Bostock H (2002) Two phases of intracortical inhibition revealed by transcranial magnetic threshold tracking. Exp Brain Res 143:240–248CrossRefPubMedGoogle Scholar
  4. Jenner JR, Stephens JA (1982) Cutaneous reflex responses and their central nervous pathways studied in man. J Physiol (Lond) 333:405–419Google Scholar
  5. Kobayashi M, Ng J, Theoret H, Pascual-Leone A (2003) Modulation of intracortical neuronal circuits in human hand motor area by digit stimulation. Exp Brain Res 149:1–8Google Scholar
  6. Kujirai T, Caramia MD, Rothwell JC, Day BL, Thompson PD, Ferbert A, Wroe S, Asselman P, Marsden CD (1993) Corticocortical inhibition in human motor cortex. J Physiol (Lond) 471:501–519Google Scholar
  7. Lemon RN (1981) Functional properties of monkey motor cortex neurones receiving afferent input from the hand and fingers. J Physiol (Lond) 311:497–519Google Scholar
  8. Maertens de Noordhout A, Rothwell JC, Day BL, Dressler D, Nakashima K, Thompson PD, Marsden CD (1992) Effect of digital nerve stimuli on responses to electrical or magnetic stimulation of the human brain. J Physiol (Lond) 447:535–548Google Scholar
  9. Muellbacher W, Ziemann U, Boroojerdi B, Cohen L, Hallett M (2001) Role of the human motor cortex in rapid motor learning. Exp Brain Res 136:431–438CrossRefGoogle Scholar
  10. Ridding MC, Inzelberg R, Rothwell JC (1995a) Changes in excitability of motor cortical circuitry in patients with Parkinson’s disease. Ann Neurol 37:181–188CrossRefGoogle Scholar
  11. Ridding MC, Rothwell JC (1999) Afferent input and cortical organisation: a study with magnetic stimulation. Exp Brain Res 126:536–544CrossRefPubMedGoogle Scholar
  12. Ridding MC, Sheean G, Rothwell JC, Inzelberg R, Kujirai T (1995b) Changes in the balance between motor cortical excitation and inhibition in focal, task specific dystonia. J Neurol Neurosurg Psychiatr 59:493–498Google Scholar
  13. Ridding MC, Taylor JL, Rothwell JC (1995c) The effect of voluntary contraction on cortico-cortical inhibition in human motor cortex. J Physiol (Lond) 487:541–548Google Scholar
  14. Rosenkranz K, Pesenti A, Paulus W, Tergau F (2003) Focal reduction of intracortical inhibition in the motor cortex by selective proprioceptive stimulation. Exp Brain Res 149:9–16Google Scholar
  15. Rosenkranz K, Rothwell JC (2003) Differential effect of muscle vibration on intracortical inhibitory circuits in humans. J Physiol 551:649–660CrossRefGoogle Scholar
  16. Stinear CM, Byblow WD (2003) Role of intracortical inhibition in selective hand muscle activation. J Neurophysiol 89:2014–2020Google Scholar
  17. Stinear CM, Byblow WD (2004) Impaired modulation of intracortical inhibition in focal hand dystonia. Cereb Cortex 14:555–561CrossRefGoogle Scholar
  18. Tamburin S, Manganotti P, Zanette G, Fiaschi A (2001) Cutaneomotor integration in human hand motor areas: somatotopic effect and interaction of afferents. Exp Brain Res 141:232–241CrossRefGoogle Scholar
  19. Ziemann U, Chen R, Cohen LG, Hallett M (1998) Dextromethorphan decreases the excitability of the human motor cortex. Neurology 51:1320–1324PubMedGoogle Scholar
  20. Ziemann U, Lönnecker S, Paulus W (1995) Inhibition of human motor cortex by ethanol. A transcranial magnetic stimulation study. Brain 118:1437–1446PubMedGoogle Scholar
  21. Ziemann U, Lönnecker S, Steinhoff BJ, Paulus W (1996) Effects of antiepileptic drugs on motor cortex excitability in humans: a transcranial magnetic stimulation study [see comments]. Ann Neurol 40:367–378PubMedGoogle Scholar
  22. Zoghi M, Pearce SL, Nordstrom MA (2003) Differential modulation of intracortical inhibition in human motor cortex during selective activation of an intrinsic hand muscle. J Physiol 550:933–946CrossRefGoogle Scholar

Copyright information

© Springer-Verlag 2005

Authors and Affiliations

  1. 1.Discipline of Physiology, School of Molecular and Biomedical ScienceThe University of AdelaideAdelaideAustralia

Personalised recommendations