title: Human amygdala responses during presentation of happy and neutral faces: correlations with state anxiety.
abstract: BACKGROUND
  Previous functional imaging studies demonstrating amygdala response to happy facial expressions have all included the presentation of negatively valenced primary comparison expressions within the experimental context. This study assessed amygdala response to happy and neutral facial expressions in an experimental paradigm devoid of primary negatively valenced comparison expressions.
  
  
  METHODS
  Sixteen human subjects (eight female) viewed 16-sec blocks of alternating happy and neutral faces interleaved with a baseline fixation condition during two functional magnetic resonance imaging scans.
  
  
  RESULTS
  Within the ventral amygdala, a negative correlation between happy versus neutral signal changes and state anxiety was observed. The majority of the variability associated with this effect was explained by a positive relationship between state anxiety and signal change to neutral faces.
  
  
  CONCLUSIONS
  Interpretation of amygdala responses to facial expressions of emotion will be influenced by considering the contribution of each constituent condition within a greater subtractive finding, as well as 1) their spatial location within the amygdaloid complex; and 2) the experimental context in which they were observed. Here, an observed relationship between state anxiety and ventral amygdala response to happy versus neutral faces was explained by response to neutral faces.
authors.affiliation: W.M. Keck Laboratory for Functional Brain Imaging and Behavior, University of Wisconsin, Madison, Wisconsin 53705, USA.
authors.forename: Leah H
authors.initials: LH
authors.lastname: Somerville
authors.forename: Hackjin
authors.initials: H
authors.lastname: Kim
authors.forename: Tom
authors.initials: T
authors.lastname: Johnstone
authors.forename: Andrew L
authors.initials: AL
authors.lastname: Alexander
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Whalen
mesh_terms: D000328:Adult; D000339:Affect; D000679:Amygdala / Q000502:physiology*; D001008:Anxiety Disorders / Q000175:diagnosis / Q000523:psychology*; D005149:Facial Expression; D005260:Female; D006240:Happiness; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D012720:Severity of Illness Index