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Eunice Yang, David Zald, Randolph Blake; Processing of fearful faces outside of awareness. Journal of Vision 2007;7(9):64. doi: https://doi.org/10.1167/7.9.64.
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© ARVO (1962-2015); The Authors (2016-present)
Being able rapidly to register the presence of potentially threatening objects or events is obviously highly adaptive. It is no surprise, therefore, that sensory processing of affectively charged stimuli can occur automatically and, at least initially, outside of conscious awareness (Wiens, 2006). Results from neuroimaging studies and from lesion studies implicate amygdala responsivity to fearful faces in the absence of awareness (Pasley et al., 2004; Williams et al., 2004, Jiang & He, 2006). Intrigued by those observations, we have investigated whether fearful faces rendered invisible by continuous flash suppression (CFS: Tsuchiya et al, JOV, 2006) emerge from suppression into awareness more quickly than do pictures of faces with neutral or happy expressions. With the aid of a mirror stereoscope, naïve observers (n = 7) dichoptically viewed dissimilar images displayed on the two halves of a calibrated video monitor. On each trial, one eye initially viewed a high contrast CFS display (dynamic Mondrian), and on most but not all trials the other eye viewed a face image ramped up in contrast to a fixed value (thereby avoiding abrupt transients). The contrast of the CFS target then gradually decreased until the observers indicated by button press the detection of the face; if no face was seen, observers withheld their response. Reaction times for detecting fearful faces were reliably shorter than those for detecting neutral faces, happy faces or inverted fearful faces (thus ruling out low-level features as the salient quality of the fearful faces); false alarm rate (response on trials when no face was presented) was negligible. These results point to some degree of processing of the affective content of a visual image presented outside of awareness. We are now exploring the involvement of limbic structures in this processing by administering this task to patients with amygdala damage.
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