Individual differences in threat sensitivity predict serotonergic modulation of amygdala response to fearful faces.
BACKGROUND
In this study we used functional magnetic resonance imaging (fMRI) to examine the effects of acute tryptophan depletion (ATD), a well-recognised method for inducing transient cerebral serotonin depletion, on brain activation to fearful faces.


OBJECTIVE
We predicted that ATD would increase the responsiveness of the amygdala to fearful faces as a function of individual variation in threat sensitivity.


METHODS
Twelve healthy male volunteers received a tryptophan depleting drink or a tryptophan balancing amino acid drink (placebo) in a double-blind crossover design. Five hours after drink ingestion participants were scanned whilst viewing fearful, happy and neutral faces.


RESULTS
Consistent with previous findings, fearful faces induced significant signal change in the bilateral amygdala/hippocampus as well as the fusiform face area and the right dorsolateral prefrontal cortex. Furthermore, ATD modulated amygdala/hippocampus activation in response to fearful relative to happy faces as a function of self-reported threat sensitivity (as measured with the Behavioral Inhibition Scale; Carver CS, White TL (1994) Behavioral inhibition, behavioral activation, and affective responses to impending reward and punishment: the BIS/BAS scales. J Pers Soc Psychol 67:319-333).


CONCLUSIONS
The data support the hypothesis that individual variation in threat sensitivity interacts with manipulation of 5-HT function to bias the processing of amygdala-dependent threat-relevant stimuli.
Cools
Roshan
R
MRC Behavioural and Clinical Neuroscience Centre. roshanco@berkeley.edu
Calder
Andy J
AJ
Lawrence
Andrew D
AD
Clark
Luke
L
Bullmore
Ed
E
Robbins
Trevor W
TW
D000293:Adolescent; D000328:Adult; D000679:Amygdala / Q000098:blood supply / Q000502:physiology*; D000704:Analysis of Variance; D001931:Brain Mapping; D018592:Cross-Over Studies; D018753:Diet, Protein-Restricted / Q000009:adverse effects; D004311:Double-Blind Method; D005149:Facial Expression; D005239:Fear / Q000502:physiology*; D007839:Functional Laterality; D006624:Hippocampus / Q000098:blood supply / Q000502:physiology; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D007206:Individuality; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D010100:Oxygen / Q000097:blood; D010147:Pain Measurement; D010775:Photic Stimulation / Q000379:methods; D011237:Predictive Value of Tests; D012701:Serotonin / Q000378:metabolism*; D014364:Tryptophan / Q000097:blood / Q000172:deficiency*
D012701:Serotonin; D014364:Tryptophan; D010100:Oxygen