Modulation of neural response to happy and sad faces by acute tryptophan depletion.
BACKGROUND
Central serotonin (5HT) plays a major role in emotional processing. We used functional neuroimaging (fMRI) to investigate the effects of experimental manipulation of central 5HT levels on the regional neural response to happy and sad facial expressions.


METHODS
Ten healthy participants (eight men and two women) were scanned during an implicit emotional processing task after receiving a tryptophan-free (acute tryptophan depletion, ATD) or a balanced amino acid drink in a double-blind design.


RESULTS
ATD lowered total plasma tryptophan concentration by 80%. There was no significant effect on subjective mood ratings, on response accuracy and on reaction times. Compared to sham depletion, ATD attenuated activation in the right medial/inferior frontal gyrus, the posterior cingulate cortex, the occipital and parietal cortex bilaterally, the right hippocampus, claustrum and insula. Conversely, ATD was associated with relatively increased activation in the left inferior frontal gyrus. ATD had differential effects on activation during the processing of happy and sad faces in the right putamen and in the left superior temporal gyrus.


CONCLUSIONS
In both cortical and sub-cortical regions, the neural response associated with processing emotional faces is significantly modulated by 5HT manipulation resulting from ATD. Moreover, in certain areas, this effect of 5HT depends on the emotional valence of the stimulus.
Fusar-Poli
Paolo
P
Department of Applied and Psychobehavioural Health Sciences, University of Pavia, via Bassi 21, 27100, Pavia, Italy. p.fusar@libero.it
Allen
Paul
P
Lee
Francis
F
Surguladze
Simon
S
Tunstall
Nigel
N
Fu
Cynthia H Y
CH
Brammer
Michael J
MJ
Cleare
Anthony J
AJ
McGuire
Philip K
PK
D000328:Adult; D000596:Amino Acids / Q000008:administration & dosage; D001921:Brain / Q000378:metabolism / Q000502:physiology*; D001931:Brain Mapping; D004311:Double-Blind Method; D004644:Emotions / Q000502:physiology*; D005149:Facial Expression; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D011569:Psychiatric Status Rating Scales; D012701:Serotonin / Q000378:metabolism; D014364:Tryptophan / Q000097:blood / Q000172:deficiency*
D000596:Amino Acids; D012701:Serotonin; D014364:Tryptophan