Figure 2.

The effect of acute treatment with ketamine on behaviour and modelling of judgement bias. Ketamine (0.0, 0.3, 1.0, 3.0 mg/kg) was administered acutely prior to testing on the task. 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. (A) Acute treatment with ketamine (1.0 mg/kg), a rapid acting antidepressant, induced a positive bias at the midpoint tone. (B) Ketamine had no effect on zr. (C) The positive bias induced by 1.0 mg/kg ketamine is reflected by a more positive drift rate (v). (D) Acute treatment with ketamine did not alter (a). Change from baseline (0.0 mg/kg 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=13, 60 min pre-treatment. *p<0.05.