Differential effects of indoleamines on auditory choice reaction, selective attention, and pitch discrimination

The indoleamines serotonin and melatonin (MT) affected visual processing such as choice reaction. This study determined whether the indoleamines influence the processing of auditory stimuli. Serotonergic activity was increased using citalopram (CIT). We compared effects of single doses of 40 mg CIT, 1 mg MT, and placebo (randomized double-blind, cross-over design) in 18 healthy men. The applied tests assessed auditory choice reaction, selective attention, and serial discrimination using pitch variations as stimuli in each task. CIT reduced the performance in choice reaction and selective attention but not discrimination. MT tended to reduce selective attention and to improve discrimination. The findings suggest that indoleamines had different effects on distinct kinds of auditory processing. Serotonergic activation improved visual choice reaction, whereas the opposite effect was found in the auditory domain. We conclude that disorders and drugs affecting the indoleamines must be considered differentially in the auditory and the visual system.