Responses to threat-related stimuli are influenced by conscious and unconscious processes, but the neural systems underlying these processes and their relationship to anxiety have not been clearly delineated. Using fMRI, we investigated the neural responses associated with the conscious and unconscious (backwardly masked) perception of fearful faces in healthy volunteers who varied in threat sensitivity (Spielberger trait anxiety scale). Unconscious processing modulated activity only in the basolateral subregion of the amygdala, while conscious processing modulated activity only in the dorsal amygdala (containing the central nucleus). Whereas activation of the dorsal amygdala by conscious stimuli was consistent across subjects and independent of trait anxiety, activity in the basolateral amygdala to unconscious stimuli, and subjects' reaction times, were predicted by individual differences in trait anxiety. These findings provide a biological basis for the unconscious emotional vigilance characteristic of anxiety and a means for investigating the mechanisms and efficacy of treatments for anxiety.
Bibliographical noteFunding Information:
We would like to thank Kevin LaBar, Daniel Salzman, Jonathan Polan, Tor Wager, and Brad Peterson for their helpful discussion of the data or the manuscript. This work was funded (in part) by the Howard Hughes Medical Insittute, the Kavli Institute for Brain Sciences, the Neurobiology and Behavior Research Training Program (NICHD HD 07430), an NIMH MD/PhD NRSA fellowship to A.E., NSF graduate research fellowships to K.C.K. and J.T.D., and by Johnson & Johnson (J.H.). The authors of this paper have declared a conflict of interest. For details, go to http://www.neuron.org/cgi/content/full/44/6/1043 .