The effects of serotonin versus catecholamine depletion on emotional processing: an event-related potential study on the International Affective Picture System

This study examined the effects of serotonin, catecholamine, and combined serotonin and catecholamine depletion on attentional biases associated with emotional processing. The sample comprised ten healthy male participants aged between 22 and 42 years. Depletion, or reduction of neurotransmitter function, was achieved by administering an amino acid mixture that was lacking in the precursor necessary for the production of the corresponding neurotransmitter. Emotional processing was assessed by the early attention event-related potential component, the P100, to photographs from the International Affective Picture System. Mood was rated on the quick wittedmentally slow, happy-sad, and amicable-antagonistic scales of the Visual Analogue Mood Scale. Unexpectedly, the amplitude of the P100 was larger for positive stimuli than for negative or neutral stimuli. Also contrary to expectations, there were no differences among treatment conditions in terms of the P100 to any of the emotional stimuli. Consistent with expectations, serotonin depletion and catecholamine depletion did not have any effects on subjective ratings of mood. In contrast to expectations, however, combined serotonin and catecholamine depletion failed to have any effect on mood. These findings suggest that the neurotransmitters serotonin and dopamine do not affect attentional bias in the processing of emotional stimuli.