title: Impaired delay and trace eyeblink conditioning performance in major depressive disorder.
abstract: BACKGROUND
  Preliminary evidence obtained in our lab has revealed that depressive symptoms impair associative learning, as measured by acquisition of eyeblink classical conditioning (EBCC) tasks. The current study assesses EBCC acquisition in individuals with major depressive disorder (MDD).
  
  
  METHODS
  The 17-item Hamilton Rating Scale for Depression (HAM-D(17)) and the 30-item Inventory for Depressive Symptomatology, Self-Report (IDS-SR(30)) were used to quantify severity of depressive symptoms. Participants received 60 trials each in delay 500, trace 500, and trace 1000 conditioning paradigms. A 150-ms, 5-7 psi air puff served as the unconditioned stimulus (US), and an 80-dB, 1-kHz tone as the conditioned stimulus (CS). Mean percent conditioned responses (CRs) served as the primary measure of task acquisition.
  
  
  RESULTS
  The MDD group generated significantly fewer CRs on delay 500 and trace 500 tasks, and approached significance on the trace 1000 task compared to healthy controls. Furthermore, presentation of successive trials did not increase CR production in the depressed group, in contrast to progressive increases observed in the control group.
  
  
  CONCLUSIONS
  The presentation of multiple EBCC tasks precludes some detailed analyses of task-specific performance. Future studies may also benefit from including sufficient numbers of subjects to assess differential characteristics of depression (e.g., length of episode, depressive subtype) and treatment effects.
  
  
  CONCLUSIONS
  These data suggest that MDD impairs acquisition of EBCC, providing behavioral support for cerebellar and hippocampal dysfunction in depression. Delineating the neural substrates involved in MDD may aid in future treatment approaches for this pervasive disorder.
authors.affiliation: Department of Psychiatry, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, TX 75390-9119, USA. tracy.greer@utsouthwestern.edu
authors.forename: Tracy L
authors.initials: TL
authors.lastname: Greer
authors.forename: Madhukar H
authors.initials: MH
authors.lastname: Trivedi
authors.forename: Lucien T
authors.initials: LT
authors.lastname: Thompson
mesh_terms: D000388:Air; D001245:Association Learning; D001767:Blinking / Q000502:physiology*; D002531:Cerebellum / Q000502:physiology; D003214:Conditioning, Classical / Q000502:physiology*; D003865:Major Depressive Disorder; D006624:Hippocampus / Q000502:physiology; D006801:Humans; D010555:Personality Inventory; D010812:Physical Stimulation / Q000379:methods; D011569:Psychiatric Status Rating Scales; D012720:Severity of Illness Index