Figure 1.

The effect of acute treatment with three antidepressants on behaviour and modelling of judgement bias. Fluoxetine (0.3, 1.0 mg/kg), reboxetine (0.3, 1.0 mg/kg), venlafaxine (1.0, 3.0 mg/kg) or saline vehicle (0.0 mg/kg) were administered acutely prior to testing on the judgement bias task. (A) None of the antidepressants tested at any dose induced a positive change in cognitive bias index (CBI) for the midpoint tone. Although not significant, reboxetine (0.3 mg/kg) showed a tendency to cause a negative change in CBI. (B/C/D) Behavioural data were modelled using the diffusion model and parameters corresponding to the relative starting point (zr), drift rate (v) and boundary separation (a) were analysed. (B) The higher doses of reboxetine (1.0 mg/kg) and venlafaxine (3.0 mg/kg) caused a positive change in zr. (C) There were no effects on v. (D) The higher dose of reboxetine (1.0 mg/kg) only caused a significant increase in a. Change from baseline (vehicle session) measures were calculated to take into account individual differences in underlying bias. Data shown are for the midpoint tone only, and represent mean ± SEM. n=9, 30 min pre-treatment. *p<0.05, ^#p≤0.07. Veh – vehicle; Flu – fluoxetine; Reb – reboxetine; Ven – venlafaxine.