title: The influence of glutamatergic antagonism on motor variability, and comparison to findings in schizophrenia patients.
abstract: OBJECTIVE
  The primary aim of this explorative study was to investigate the influence of the glutamatergic N-methyl-d-aspartate (NMDA) receptor antagonist memantine on motor activity in healthy subjects. Secondarily, we wanted to compare these data to findings in a sample of schizophrenia patients.
  
  
  METHODS
  The healthy subjects acted as their own controls in an open-within-subject design. Motor activity was recorded with an actigraph worn for 24 h in the drug-free, and steady-state memantine conditions, respectively. Motor activity levels for 1-min intervals were analysed by means of both linear and nonlinear methods. The schizophrenia patients were monitored only once, without memantine manipulation.
  
  
  RESULTS
  The root mean square successive differences (RMSSD) and the RMSSD/SD ratio were increased by memantine, and memantine was also associated with lower autocorrelation (lag 1) but in recordings from the right arm only. These movement patterns partly corresponded to those found in a sample of drug-treated schizophrenia patients. Total activity level, standard deviation (SD) and sample entropy were not significantly different in the memantine versus drug-free condition.
  
  
  CONCLUSIONS
  The findings suggest a role for the NMDA receptor in the regulation of motor activity in healthy individuals as memantine increased the variability in the motor recordings and the alterations between adjacent motor recordings. It is suggested that the findings may be relevant to the role played by glutamate and the NMDA receptor functioning to the motor disturbances in schizophrenia.
authors.affiliation: 1 Division of Psychiatry, Haukeland University Hospital, Bergen, Norway.
authors.forename: Erik
authors.initials: E
authors.lastname: Johnsen
authors.affiliation: 1 Division of Psychiatry, Haukeland University Hospital, Bergen, Norway.
authors.forename: Ole Bernt
authors.initials: OB
authors.lastname: Fasmer
authors.affiliation: 3 Department of Biological and Medical Psychology, University of Bergen, Bergen, Norway.
authors.forename: Heidi
authors.initials: H
authors.lastname: van Wageningen
authors.affiliation: 1 Division of Psychiatry, Haukeland University Hospital, Bergen, Norway.
authors.forename: Kenneth
authors.initials: K
authors.lastname: Hugdahl
authors.affiliation: 4 Olaviken Psychiatric Hospital, Bergen, Norway.
authors.forename: Erik
authors.initials: E
authors.lastname: Hauge
authors.affiliation: 2 Department of Clinical Medicine, Section for Psychiatry, University of Bergen, Bergen, Norway.
authors.forename: Hugo A
authors.initials: HA
authors.lastname: Jørgensen