title: Discharge patterns of human tensor palatini motor units during sleep onset.
abstract: OBJECTIVE
  Upper airway muscles such as genioglossus (GG) and tensor palatini (TP) reduce activity at sleep onset. In GG reduced muscle activity is primarily due to inspiratory modulated motor units becoming silent, suggesting reduced respiratory pattern generator (RPG) output. However, unlike GG, TP shows minimal respiratory modulation and presumably has few inspiratory modulated motor units and minimal input from the RPG. Thus, we investigated the mechanism by which TP reduces activity at sleep onset.
  
  
  METHODS
  The activity of TP motor units were studied during relaxed wakefulness and over the transition from wakefulness to sleep.
  
  
  METHODS
  Sleep laboratory.
  
  
  METHODS
  Nine young (21.4 ± 3.4 years) males were studied on a total of 11 nights.
  
  
  METHODS
  Sleep onset.
  
  
  RESULTS
  Two TP EMGs (thin, hooked wire electrodes), and sleep and respiratory measures were recorded. One hundred twenty-one sleep onsets were identified (13.4 ± 7.2/subject), resulting in 128 motor units (14.3 ± 13.0/subject); 29% of units were tonic, 43% inspiratory modulated (inspiratory phasic 18%, inspiratory tonic 25%), and 28% expiratory modulated (expiratory phasic 21%, expiratory tonic 7%). There was a reduction in both expiratory and inspiratory modulated units, but not tonic units, at sleep onset. Reduced TP activity was almost entirely due to de-recruitment.
  
  
  CONCLUSIONS
  TP showed a similar distribution of motor units as other airway muscles. However, a greater proportion of expiratory modulated motor units were active in TP and these expiratory units, along with inspiratory units, tended to become silent over sleep onset. The data suggest that both expiratory and inspiratory drive components from the RPG are reduced at sleep onset in TP.
authors.affiliation: School of Psychological Science, University of Melbourne, Parkville, Australia.
authors.forename: Christian L
authors.initials: CL
authors.lastname: Nicholas
authors.forename: Amy S
authors.initials: AS
authors.lastname: Jordan
authors.forename: Leila
authors.initials: L
authors.lastname: Heckel
authors.forename: Christopher
authors.initials: C
authors.lastname: Worsnop
authors.forename: Bei
authors.initials: B
authors.lastname: Bei
authors.forename: Julian P
authors.initials: JP
authors.lastname: Saboisky
authors.forename: Danny J
authors.initials: DJ
authors.lastname: Eckert
authors.forename: David P
authors.initials: DP
authors.lastname: White
authors.forename: Atul
authors.initials: A
authors.lastname: Malhotra
authors.forename: John
authors.initials: J
authors.lastname: Trinder
mesh_terms: D004569:Electroencephalography; D004576:Electromyography; D006801:Humans; D008297:Male; D009046:Motor Neurons / Q000502:physiology*; D017286:Polysomnography; D012132:Respiratory Muscles / Q000294:innervation / Q000502:physiology*; D012143:Respiratory Physiological Phenomena; D012894:Sleep Stages / Q000502:physiology*; D055815:Young Adult