title: Internally vs. externally triggered movements in patients with major depression.
abstract: BACKGROUND
  Psychomotor retardation is a prominent clinical feature of major depression. While several studies investigated these deficits, differences between internally and externally triggered response selection and initiation are less well understood. In the current study, we delineate internally vs. externally driven response selection and initiation in depression and their relation to basic psychomotor functioning.
  
  
  METHODS
  20 inpatients diagnosed with a (unipolar) major depression and 20 closely matched healthy controls performed a computerized motor paradigm assessing differences between internally and externally cued movements. Psychomotor performance and basic memory functions were assessed using a neuropsychological test-battery. To examine within group homogeneity a multivariate clustering approach was applied.
  
  
  RESULTS
  Patients featured a global slowing of internally and externally cued response selection compared to controls, as well as impairments in basic psychomotor functioning. Yet, basic motor speed was preserved. Furthermore, patients were more severely impaired when movements involved internal response selection. The data-driven clustering revealed two patient subgroups, which both showed psychomotor disturbances, while only one featured slowing of response selection.
  
  
  CONCLUSIONS
  The results suggest a differential rather than a global psychomotor slowing in major depression with specific impairments of visuospatial and attentional processing as cognitive aspects of psychomotor functioning. As found for depression, in Parkinson's disease internally cued movements are more severely affected than externally cued reactions. Both may therefore be caused by dopaminergic deregulation due to frontostriatal deficits. Finally, multivariate clustering of behavioral data may be a promising future approach to identify subtypes of psychomotor or cognitive disturbances in different patient populations.
authors.affiliation: Department of Psychiatry, Psychotherapy and Psychosomatics, RWTH Aachen University, Aachen, Germany.
authors.forename: Felix
authors.initials: F
authors.lastname: Hoffstaedter
authors.forename: Jan
authors.initials: J
authors.lastname: Sarlon
authors.forename: Christian
authors.initials: C
authors.lastname: Grefkes
authors.forename: Simon B
authors.initials: SB
authors.lastname: Eickhoff
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000928:Antidepressive Agents / Q000494:pharmacology / Q000627:therapeutic use; D001077:Aptitude Tests / Q000706:statistics & numerical data; D016022:Case-Control Studies; D003463:Cues; D003865:Major Depressive Disorder / Q000175:diagnosis / Q000188:drug therapy / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009068:Movement / Q000187:drug effects / Q000502:physiology*; D009483:Neuropsychological Tests / Q000706:statistics & numerical data; D011597:Psychomotor Performance / Q000187:drug effects / Q000502:physiology*; D012720:Severity of Illness Index
chemical_list: D000928:Antidepressive Agents