Abstract
Rationale:There has recently been increasing interest in pharmacological manipulations that could potentially enhance exposure-based cognitive behaviour therapy for anxiety disorders. One such medication is the partial NMDA agonist d-cycloserine. It has been suggested that d-cycloserine enhances cognitive behaviour therapy by making learning faster. While animal studies have supported this view of the drug accelerating learning, evidence in human studies has been mixed. We therefore designed an experiment to measure the effects of d-cycloserine on human motor learning.Methods:Fifty-four healthy human volunteers were randomly assigned to a single dose of 250mg d-cycloserine versus placebo in a double-blind design. They then performed a motor sequence learning task.Results:D-cycloserine did not increase the speed of motor learning or the overall amount learnt. However, we noted that participants on d-cycloserine tended to respond more carefully (shifting towards slower, but more correct responses).Conclusion:The results suggest that d-cycloserine does not exert beneficial effects on psychological treatments via mechanisms involved in motor learning. Further studies are needed to clarify the influence on other cognitive mechanisms.
Highlights
Results have so far been mixed, with some studies reporting that DCS could enhance motor learning (Kuriyama et al, 2011), fear conditioning (Kalisch et al, 2009) or incremental learning (Forsyth et al, 2015), but others failing to find an effect on motor learning (Cherry et al, 2014; Feld et al, 2013; Kuo et al, 2008), fear extinction (Guastella et al, 2007; Klumpers et al, 2012) or reward learning (Scholl et al, 2014)
We assessed whether DCS could enhance motor learning
While participants had reaction times of 412±11ms in the first learning block, they had speeded up to 322±17ms in the last learning block. This improvement in reaction time across all 15 learning blocks did not differ between the groups (ANOVA, block (15) × group (2) interaction: F(2.2,112.9)=1.1, p=0.34), nor was there a difference in the average reaction time between groups (ANOVA, main effect of group: F(1,52)=2.10 p=0.15)
Summary
The N-methyl-D-aspartate (NMDA) receptor partial agonist d-cycloserine (DCS) has been found to enhance diverse kinds of learning in animal studies, including fear extinction (Walker et al, 2002), cocaine cue extinction (Torregrossa et al, 2010) and reward learning (Golden and Houpt, 2007; Portero-Tresserra et al, 2013). Results have so far been mixed, with some studies reporting that DCS could enhance motor learning (Kuriyama et al, 2011), fear conditioning (Kalisch et al, 2009) or incremental learning (Forsyth et al, 2015), but others failing to find an effect on motor learning (Cherry et al, 2014; Feld et al, 2013; Kuo et al, 2008), fear extinction (Guastella et al, 2007; Klumpers et al, 2012) or reward learning (Scholl et al, 2014). We tested the impact of DCS on motor learning further, in the effects of a higher dose than tested previously (Feld et al, 2013; Kuo et al, 2008; Kuriyama et al., 2011). In an exploratory analysis of nonlearning dependent effects we found that DCS led participants to shift their balance in how quickly and accurately they responded towards more careful responding compared with placebo
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
