Abstract
Taste perception has been reported to vary with changes in affective state. Distortions of taste perception, including blunted recognition thresholds, intensity and hedonic ratings have been identified in those suffering from depressive disorders. Serotonin is a key neurotransmitter implicated in the aetiology of anxiety and depression; systemic and peripheral manipulations of serotonin signalling have previously been shown to modulate taste detection. However, the specific effects of central serotonin function on taste processing have not been widely investigated. Here, in a double-blind placebo-controlled study, acute tryptophan depletion was used to investigate the effect of reduced central serotonin function on taste perception. 25 female participants aged 18-28 attended the laboratory on 2 occasions at least 1 week apart. On one visit they received a tryptophan depleting drink and on the other a control drink was administered. Approximately 6 hours after drink consumption they completed a taste perception task which measured detection thresholds and supra-threshold perceptions of the intensity and pleasantness of four basic tastes (sweet, sour, bitter and salt). While acutely reducing central levels of serotonin had no effect on the detection thresholds of sweet, bitter or sour tastes it significantly enhanced detection of salt. For supra-threshold stimuli, acutely reduced serotonin levels significantly enhanced the perceived intensity of both bitter and sour tastes and blunted pleasantness ratings of bitter quinine. These findings show manipulation of central serotonin levels can modulate taste perception and are consistent with previous reports that depletion of central serotonin levels enhances neural and behavioural responsiveness to aversive signals.
Effects of Acute Tryptophan Depletion on Human Taste Perception