Experimental Brain Research

, Volume 104, Issue 1, pp 115–125 | Cite as

Influence of handedness on motor unit discharge properties and force tremor

  • John G. Semmler
  • Michael A. Nordstrom
Original Paper


Discharge properties of motor units (MUs) in the first dorsal interosseous muscle (FDI) were studied in the dominant and non-dominant hands of six right-handed (RH) and six left-handed (LH) individuals. MU discharge rates and variability were similar in each hand in RH (186 MUs) and LH (160 MUs) subjects. MU synchronization was less prominent in the dominant hand of RH subjects, with 51% (45/88) of cross-correlograms of MU discharge having significant central peaks, compared with 81% (90/111) for the non-dominant hand. The strength of MU synchronization (expressed as the frequency of extra synchronous discharges above chance) was weaker in the dominant hand of right-handers (0.23 ± 0.03 s-1 vs 0.39 ± 0.03 s-1), and synchronous peaks from that hand were slightly broader. Four of six RH subjects had significant differences in synchronization between hands (weaker in dominant hand). In contrast, left-handers had similar incidence (80 vs 82%, n = 161) and strength (0.41 ± 0.03 s-1 vs 0.37 ± 0.03 s-1) of MU synchrony in dominant and non-dominant hands. No LH subject had a significant difference in synchronization between hands. Force tremor was quantified in each hand in the same subjects during isometric abduction of FDI at 0.5 N and 3.5 N, and directly correlated with the extent of MU synchronization in the muscle. Tremor root mean square amplitude was similar in dominant and non-dominant hands. Power spectral analysis of the tremor force revealed that the peak frequency in the power spectrum was not influenced by handedness, but power at the peak frequency was higher in the non-dominant hand of RH subjects. Correlations between MU discharge variability and synchrony with measures of tremor amplitude were weak. The reduced MU synchronization in the dominant hand of right-handers may reflect a more restricted distribution of direct projections from motor cortical neurons within the FDI motoneuron pool, or reduced excitability of the cortical neurons during the task. These differences in MU synchronization, however, had an insignificant influence on the magnitude of physiological tremor in the FDI.

Key words

Short term synchronization Lateral dominance First dorsal interosseous Motor cortex Human 


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  1. Allum JH, Dietz V, Freund HJ (1978) Neuronal mechanisms underlying physiological tremor. J Neurophysiol 41:557–571PubMedGoogle Scholar
  2. Bortoff GA, Strick PL (1993) Corticospinal terminations in two new-world primates: further evidence that corticomotoneuronal connections provide part of the neural substrate for manual dexterity. J Neurosci 13:5105–5118Google Scholar
  3. Bremner FD, Baker JR, Stephens JA (1991a) Correlation between the discharges of motor units recorded from the same and from different finger muscles in man. J Physiol (Lond) 432:355–380Google Scholar
  4. Bremner FD, Baker JR, Stephens JA (1991b) Effect of task on the degree of synchronization of intrinsic hand muscle motor units in man. J Neurophysiol 66:2072–2083PubMedGoogle Scholar
  5. Christakos CN (1982) A study of the muscle force waveform using a population stochastic model of skeletal muscle. Biol Cybern 44:91–106Google Scholar
  6. Datta AK, Stephens JA (1990) Synchronization of motor unit activity during voluntary contraction in man. J Physiol (Lond) 422:397–419Google Scholar
  7. Datta AK, Harrison LM, Stephens JA (1989) Task-dependent changes in the size of response to magnetic brain stimulation in human first dorsal interosseous muscle. J Physiol (Lond) 418:13–23Google Scholar
  8. Datta AK, Farmer SF, Stephens JA (1991) Central nervous pathways underlying synchronization of human motor unit firing studied during voluntary contractions. J Physiol (Lond) 432:401–425Google Scholar
  9. De Luca CJ, Roy AM, Erim Z (1993) Synchronization of motor-unit firings in several human muscles. J Neurophysiol 70:2010–2023Google Scholar
  10. Dengler R, Wolf W, Struppler A (1984) Synchronous discharges in pairs of steadily firing motor units tend to form clusters. Neurosci Lett 47:167–172Google Scholar
  11. Dietz V, Bischofberger E, Wita C, Freund HJ (1976) Correlation between the discharges of two simultaneously recorded motor units and physiological tremor. Electroencephalogr clin Neurophysiol 40:97–105Google Scholar
  12. Elble RJ, Randall JE (1976) Motor-unit activity responsible for 8-to 12-Hz component of human physiological finger tremor. J Neurophysiol 39:370–383PubMedGoogle Scholar
  13. Elble RJ, Randall JE (1978) Mechanistic components of normal hand tremor. Electroencephalogr clin Neurophysiol 44:72–82Google Scholar
  14. Elek JM, Dengler R, Konstanzer A, Hesse S, Wolf W (1991) Mechanical implications of paired motor unit discharges in pathological and voluntary tremor. Electroencephalogr clin Neurophysiol 81:279–283Google Scholar
  15. Ellaway PH (1978) Cumulative sum technique and its application to the analysis of peristimulus time histograms. Electroencephalogr clin Neurophysiol 45:302–304CrossRefPubMedGoogle Scholar
  16. Farmer SF, Ingram DA, Stephens JA (1990) Mirror movements studied in a patient with Klippel-Feil syndrome. J Physiol (Lond) 428:467–484Google Scholar
  17. Freund HJ, Büdingen HJ, Dietz V (1975) Activity of single motor units from human forearm muscles during voluntary isometric contractions. J Neurophysiol 38:933–946Google Scholar
  18. Furness P, Jessop J, Lippold OCJ (1977) Long lasting increases in the tremor of human hand muscles following brief, strong effort. J Physiol (Lond) 265:821–831Google Scholar
  19. Galganski ME, Fuglevand AJ, Enoka RM (1993) Reduced control of motor output in a human hand muscle of elderly subjects during submaximal contractions. J Neurophysiol 69:2108–2115Google Scholar
  20. Halliday AM, Redfearn JWT (1958) Finger tremor in tabetic patients and its bearing on the mechanism producing the rhythm of physiological tremor. J Neurol Neurosurg Psychiatry 21:101–108Google Scholar
  21. Kertesz A, Geschwind N (1971) Patterns of pyramidal decussation and their relationship to handedness. Arch Neurol 24:326–332Google Scholar
  22. Kirkwood PA, Sears TA, Tuck DL, Westgaard RH (1982) Variations in the time course of the synchronization of intercostal motoneurones in the cat. J Physiol (Lond) 327:105–135Google Scholar
  23. Kuypers HGJM (1981) Anatomy of the descending pathways. In: Brooks VB (ed) Handbook of physiology, sect 1, The nervous system, vol II, Motor control, part I. American Physiological Society, Bethesda, MD, pp 597–666Google Scholar
  24. Lemon RN (1993) Cortical control of the primate hand. Exp Physiol 78:263–301Google Scholar
  25. Lippold OCJ, Redfearn JWT, Vuço J (1957) The rhythmical activity of groups of motor units in the voluntary contraction of muscle. J Physiol (Lond) 137:473–487Google Scholar
  26. Logigian EL, Wierzbicka MM, Bruyninckx F, Wiegner AW, Shahahi BT, Young RR (1988) Motor unit synchronization in physiologic, enhanced physiologic, and voluntary tremor in man. Ann Neurol 23:242–250Google Scholar
  27. Löscher WN, Gallasch E (1993) Myo-electric signals from two extrinsic hand muscles and force tremor during isometric handgrip. Eur J Appl Physiol 67:99–105Google Scholar
  28. Marsden CD, Meadows JC, Lange GW, Watson RS (1969) The relation between physiological tremor of the two hands in healthy subjects. Electroencephalogr clin Neurophysiol 27:179–185CrossRefPubMedGoogle Scholar
  29. Nathan PW, Smith MC, Deacon P (1990) The corticospinal tracts in man. Course and location of fibres at different segmental levels. Brain 113:303–324PubMedGoogle Scholar
  30. Nordstrom MA, Fuglevand AJ, Enoka RM (1992) Estimating the strength of common input to human motoneurons from the cross-correlogram. J Physiol (Lond) 453:547–574Google Scholar
  31. Nordstrom MA, Semmler JG, Miles TS (1994) Handedness, motor unit discharge properties and force tremor. Soc Neurosci Abstr 20:338Google Scholar
  32. Oldfield RC (1971) The assessment and analysis of handedness: the Edinburgh inventory. Neuropsychologia 9:97–113CrossRefPubMedGoogle Scholar
  33. Pascual-Leone A, Cammarota A, Wassermann EM, Brasil-Neto JP, Cohen LG, Hallett M (1993) Modulation of motor cortical outputs to the reading hand of Braille readers. Ann Neurol 34:33–37Google Scholar
  34. Provins KA, Magliaro J (1993) The measurement of handedness by preference and performance tests. Brain Cogn 22:171–181Google Scholar
  35. Schmied A, Vedel JP, Pagni S (1994) Human spinal lateralization assessed from motoneurone synchronization: dependence on handedness and motor unit type. J Physiol (Lond) 480:369–387Google Scholar
  36. Sears TA, Stagg D (1976) Short-term synchronization of intercostal motoneurone activity. J Physiol (Lond) 263:357–381Google Scholar
  37. Semmler JG, Nordstrom MA (1993) Handedness and motor unit discharge properties in human first dorsal interosseous. Proc Aust Physiol Pharmacol Soc 23:231PGoogle Scholar
  38. Stein RB, Lee RG (1981) Tremor and clonus. In: Brooks VB (ed) Handbook of Physiology, Sect. 1. The nervous system, Vol. II. Motor control, Part I. American Physiological Society, Bethesda, MD, pp 325–343Google Scholar
  39. Stephens JA, Taylor A (1974) The effect of visual feedback on physiological muscle tremor. Electroencephalogr clin Neurophysiol 36:457–464CrossRefPubMedGoogle Scholar
  40. Stiles RN (1980) Mechanical and neural feedback factors in postural hand tremor of normal subjects. J Neurophysiol 44:40–59Google Scholar
  41. Tanaka M, McDonagh MJN, Davies CTM (1984) A comparison of the mechanical properties of the first dorsal interosseous in the dominant and non-dominant hand. Eur J Appl Physiol 58:17–20Google Scholar
  42. Taylor A (1962) The significance of grouping of motor unit activity. J Physiol (Lond) 162:259–269Google Scholar
  43. Triggs WJ, Calvanio R, Macdonell RAL, Cros D, Chiappa KH (1994) Physiological motor asymmetry in human handedness-evidence from transcranial magnetic stimulation. Brain Res 636:270–276Google Scholar
  44. Wiegner AW, Wierzbicka MM (1987) A method for assessing significance of peaks in cross-correlation histograms. J Neurosci Methods 22:125–131Google Scholar

Copyright information

© Springer-Verlag 1995

Authors and Affiliations

  • John G. Semmler
    • 1
  • Michael A. Nordstrom
    • 1
  1. 1.Department of PhysiologyUniversity of AdelaideAdelaideAustralia

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