title: Examining the effects of former cannabis use on cerebellum-dependent eyeblink conditioning in humans.
abstract: BACKGROUND
  Previous work in humans has shown that chronic cannabis users exhibit disruptions in classical eyeblink conditioning (EBC), a form of associative learning that is known to be dependent on the cerebellum. Based upon previous work in animals, it was hypothesized that these learning deficits were related to cannabinoid receptor (CB1R) downregulation. However, it remains unclear whether there is a recovery of cerebellum-dependent learning after the cessation of cannabis use.
  
  
  METHODS
  Therefore, former cannabis users (n=10), current cannabis users (n=10), and cannabis-naïve controls (n=10), all free of DSM-IV Axis-I or -II disorders, were evaluated. A standard delay EBC procedure was utilized in which paired presentations of a conditioned stimulus (CS; e.g., tone) and a co-terminating unconditioned stimulus (US; e.g., ocular airpuff) were administered, thus eliciting a conditioned eyeblink response (CR). The primary dependent measures were percentage of CRs and CR latency across conditioning blocks.
  
  
  RESULTS
  Similar to prior studies, current cannabis users exhibited marked impairments in both the acquisition and timing of CRs compared to controls. Although former cannabis users showed intact CR acquisition compared to controls, they exhibited significantly impaired (shorter) CR latencies. In both cannabis groups, UR amplitude did not differ from controls, indicating normal US processing.
  
  
  CONCLUSIONS
  These data suggest that a recovery of function has occurred for the learning of the CS-US association, while the accurate timing of the CR shows lasting impairments. Taken together, these results suggest that heavy cannabis use can disrupt timing-related synaptic plasticity within the cerebellum, even after the cessation of cannabis use.
authors: Department of Psychology, University of Iowa, Iowa City, IA 52242, USA.
authors: Adam B
authors: AB
authors: Steinmetz
authors: Chad R
authors: CR
authors: Edwards
authors: Jennifer M
authors: JM
authors: Vollmer
authors: Molly A
authors: MA
authors: Erickson
authors: Brian F
authors: BF
authors: O'Donnell
authors: William P
authors: WP
authors: Hetrick
authors: Patrick D
authors: PD
authors: Skosnik
mesh_terms: D000328:Adult; D001767:Blinking / Q000187:drug effects / Q000502:physiology*; D016022:Case-Control Studies; D002531:Cerebellum / Q000187:drug effects / Q000503:physiopathology*; D003214:Conditioning, Classical / Q000187:drug effects / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D002189:Marijuana Abuse / Q000503:physiopathology*; D011930:Reaction Time