title: Corticospinal interaction during isometric compensation for modulated forces with different frequencies.
abstract: BACKGROUND
  During isometric compensation of modulated low-level forces corticomuscular coherence (CMC) has been shown to occur in high-beta or gamma-range. The influence of the frequency of force modulation on CMC has up to now remained unexplored. We addressed this question by investigating CMC, motor performance, and cortical spectral power during a visuomotor task in which subjects had to compensate a modulated force of 8% of the maximum voluntary contraction exerted on their right index finger. The effect of three frequencies of force modulation (0.6, 1.0 and 1.6 Hz) was tested. EEG, EMG from first dorsal interosseus, hand flexor and extensor muscles, and finger position were recorded in eight right-handed women.
  
  
  RESULTS
  Five subjects showed CMC in gamma- (28-45 Hz) and three in beta-range (15-30 Hz). Beta- and gamma-range CMC and cortical motor spectral power were not modulated by the various frequencies. However, a sharp bilateral CMC peak at 1.6 Hz was observed, but only in the five gamma-range CMC subjects. The performance error increased linearly with the frequency.
  
  
  CONCLUSIONS
  Our findings suggest that the frequency of force modulation has no effect on the beta- and gamma-range CMC during isometric compensation for modulated forces at 8% MVC. The beta- and gamma-range CMC may be related to interindividual differences and possibly to strategy differences.
authors.affiliation: Institute of Neuroinformatics, University of Zürich and ETH Zürich, Switzerland.
authors.forename: José R
authors.initials: JR
authors.lastname: Naranjo
authors.forename: Xi
authors.initials: X
authors.lastname: Wang
authors.forename: Jürgen
authors.initials: J
authors.lastname: Schulte-Mönting
authors.forename: Frank
authors.initials: F
authors.lastname: Huethe
authors.forename: Christoph
authors.initials: C
authors.lastname: Maurer
authors.forename: Marie-Claude
authors.initials: MC
authors.lastname: Hepp-Reymond
authors.forename: Rumyana
authors.initials: R
authors.lastname: Kristeva
mesh_terms: D000293:Adolescent; D000328:Adult; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D009044:Motor Cortex / Q000502:physiology*; D053580:Muscle Strength / Q000502:physiology*; D018482:Muscle, Skeletal / Q000294:innervation / Q000502:physiology*; D011712:Pyramidal Tracts / Q000502:physiology*; D055815:Young Adult