Effects of serotonin depletion and dopamine depletion on bimodal divided attention

W Königschulte,C Civai,P Hildebrand,T J Gaber,G R Fink,F D Zepf

doi:10.1080/15622975.2018.1532110

Abstract

Objectives: This study aimed to explore the effects of acute phenylalanine tyrosine depletion (APTD) and acute tryptophan depletion (ATD) on bimodal divided attention. A balanced amino acid mixture (BAL) served as control condition.Methods: Fifty-three healthy adults (final analyzed sample was N = 49, age: M = 23.8 years) were randomly assigned to APTD, ATD or BAL in a double-blind, between-subject approach. Divided attention was assessed after 4 h. Blood samples were taken before and 6 h after challenge intake.Results: Amino acid concentrations following challenge intake significantly decreased (all P ≤ 0.01). There was a significant difference in the mean reaction time (RT) towards auditory stimuli, but not towards visual stimuli between the groups. Post-hoc comparison of mean RTs (auditory stimuli) showed a significant difference between ATD (RT = 604.0 ms, SD = 56.9 ms) and APTD (RT = 556.4 ms, SD = 54.2 ms; P = 0.037), but no RT difference between ATD and BAL or APTD and BAL (RT = 573.6 ms, SD = 45.7 ms).Conclusions: The results indicate a possible dissociation between the effects of a diminished brain 5-HT and DA synthesis on the performance in a bimodal divided attention task. The difference was exclusively observed within the RT towards auditory signals.

Highlights

The ability to allocate attention simultaneously to concurrent stimuli is essential for many daily life activities
N = 53 subjects participated in the study, after screening, the data of 4 subjects were excluded for various reasons, i.e. outliers in terms of unusually high error rates during the administered attention task, one subject in the acute phenylalanine-tyrosine depletion (APTD) group was withdrawn from the study because of nausea approx. four hours after challenge-intake
To the best of our knowledge, this pilot study is the first that provides data regarding the effects of acute tryptophan depletion (ATD) and APTD on bimodal attentional performance in healthy adult participants

Summary

Introduction

The ability to allocate attention simultaneously to concurrent stimuli is essential for many daily life activities. Experimental manipulation of brain DA and 5-HT systems allows to examine the contribution of these neurotransmitter systems to the neurochemical processes underlying attention. Dietary neurotransmitter precursor depletion techniques such as acute tryptophan depletion (ATD, which leads to a decreased central nervous synthesis rate of 5-HT) or acute phenylalanine tyrosine depletion (APTD, which decreases DA synthesis in the brain) have become favorable tools in neuropsychological research (Booij et al 2003; Young 2013; Biskup et al 2015)

Methods

Results

Conclusion