title: Modulation of neural response to happy and sad faces by acute tryptophan depletion.
abstract: 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.
authors: Department of Applied and Psychobehavioural Health Sciences, University of Pavia, via Bassi 21, 27100, Pavia, Italy. p.fusar@libero.it
authors: Paolo
authors: P
authors: Fusar-Poli
authors: Paul
authors: P
authors: Allen
authors: Francis
authors: F
authors: Lee
authors: Simon
authors: S
authors: Surguladze
authors: Nigel
authors: N
authors: Tunstall
authors: Cynthia H Y
authors: CH
authors: Fu
authors: Michael J
authors: MJ
authors: Brammer
authors: Anthony J
authors: AJ
authors: Cleare
authors: Philip K
authors: PK
authors: McGuire
mesh_terms: 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*
chemical_list: D000596:Amino Acids; D012701:Serotonin; D014364:Tryptophan