In this study, the investigators examine the effects of low-dose ketamine on different oculomotor, perceptual and cognitive functions. They also examine effects on concurrent brain activity using blood oxygen level dependent (BOLD) functional magnetic resonance imaging (fMRI). A sample of N=25 healthy, male participants is required to complete the study. The design is within-subjects, placebo-controlled, double-blind and cross-over. A targeted ketamine level in plasma of 100ng/ml is applied. It is hypothesised that ketamine, compared to placebo, will lead to changes in task performance and brain activity similar to those observed in patients with schizophrenia.