Elsevier

Neuroscience Letters

Volume 340, Issue 3, 17 April 2003, Pages 181-184
Neuroscience Letters

Auditory selective attention modulated by tryptophan depletion in humans

https://doi.org/10.1016/S0304-3940(03)00102-2Get rights and content

Abstract

To elucidate serotonin modulation of selective attention, 13 volunteers (21–30 years) were studied in two sessions, 5 h after either acute tryptophan depletion (ATD) that decreases brain serotonin synthesis, or control-mixture ingestion (randomized, double-blind, cross-over design). Simultaneous electroencephalogram and magnetoencephalogram were measured during dichotic listening of two concurrent trains of standard and deviant tones. Subjects counted the deviants presented to one ear and ignored those presented to the other ear. ATD lowered plasma total tryptophan by 75% and free tryptophan by 39%. ATD suppressed the amplitude enhancement of P50 and N1 to selectively attended tones, but did not affect the later aspects of processing negativity. The P50 latencies were increased after ATD, irrespective of attention. In conclusion, serotonin may regulate attentional modulation of early cortical stimulus processing.

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Acknowledgements

This work was supported by the Helsinki University Central Hospital Research Funds, the Finnish Cultural Foundation, the Ella and Georg Ehrnrooth Foundation, and the Academy of Finland. We thank Ms Suvi Heikkilä and Mr Teemu Peltonen for their assistance in carrying out the experiments.

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