title: Lateralized α-motoneuron excitabilities during lying and standing of healthy individuals in relation to parkinsonian rigidity.
abstract: OBJECTIVE
  To elucidate mechanisms of Parkinsonian rigidity by assessing excitability of alpha-motoneurons innervating right and left soleus muscles in healthy controls and Parkinson's disease (PD) patients with rigidities in the right, left and both  legs.
  
  
  METHODS
  One group of 45 controls was recruited and 60 PD patients in three groups: rigidities, predominantly in the right, left and both legs. H-reflex (H) and muscle response (M) were recorded from right and left soleus muscles during stimulations of the posterior tibial  nerve at the popliteal fossa while lying and standing. The H/M ratio was taken as an index for motoneuron excitability.
  
  
  RESULTS
  Mean H/M ratios were significantly different on the right and left sides, modified by postural changes in controls and PD patients. Analysis of variance  showed that in healthy subjects the H/M ratio was: standing>lying (right), lying>standing (left). In right leg rigidity patients, the H/M ratio was greatest during standing, and smallest during lying. In left leg rigidity patients, the H/M ratios on the right and left sides were equally  independent of posture. In controls, left H/M>right while lying, <right while standing. In right leg rigidity patients, right H/M>left, but <right in left leg rigidity patients, independent of posture. There was no side difference in patients with rigidity in both legs.
  
  
  CONCLUSIONS
  (i) motoneuron excitability may show side and postural differences in healthy individuals and PD patients; (ii) posture may be associated with lateralized motoneuron excitability in these subjects; and (iii) Parkinsonian rigidity may have spinal motor origins.
authors.affiliation: Department of Neurology, Adana Teaching and Research Center, Faculty of Medicine, Baskent University, Adana, Turkey.
authors.forename: Sibel
authors.initials: S
authors.lastname: Karaca
authors.forename: Meliha
authors.initials: M
authors.lastname: Tan
authors.forename: Uner
authors.initials: U
authors.lastname: Tan
mesh_terms: D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006181:H-Reflex / Q000502:physiology*; D006801:Humans; D008297:Male; D009046:Motor Neurons / Q000502:physiology*; D009127:Muscle Rigidity / Q000209:etiology / Q000503:physiopathology*; D018482:Muscle, Skeletal / Q000294:innervation; D010300:Parkinson Disease / Q000150:complications / Q000503:physiopathology*; D011187:Posture / Q000502:physiology*