Activation of the amygdala and anterior cingulate during nonconscious processing of sad versus happy faces
Section snippets
Subjects
Twelve healthy right-handed female adults, ranging in age from 21 to 28 years (M = 23.7, SD = 2.1), underwent functional magnetic resonance imaging (fMRI) using blood oxygenation level dependent (BOLD) contrast. Participants, recruited from the local community and the staff of McLean Hospital, were without history of psychiatric or neurological illness according to a structured clinical interview, and all had normal or corrected–normal vision. Subjects were naı̈ve to the face stimuli and
Masked happiness
Presentation of happy faces masked by neutral faces yielded significant activation within the left (P < 0.005) and right (P < 0.05) amygdala (see Fig. 3 and Table 1). Several clusters of suprathreshold activation were also observed within the left (P < 0.01) and right (P < 0.01) anterior cingulate gyrus.
Masked sadness
Presentations of masked sad faces were not associated with any suprathreshold clusters of activation within either the left or right amygdala relative to the fixation baseline (see Fig. 3 and
Discussion
Subjects were presented with photographs of happy and sad faces in a manner that minimized or eliminated conscious visual perception of the presented affect. Despite being presented below the threshold of conscious awareness, these “unseen” emotional stimuli yielded specific patterns of activation within the amygdala and anterior cingulate gyrus that differed as a function of the emotional valence of the masked facial expression. Masked happiness was associated with significant bilateral
Conclusion
This is the first fMRI study to use backward masking of facial stimuli to demonstrate differential regional activation associated with nonconscious processing of happy versus sad facial affect. While the cingulate gyrus demonstrated relative consistency across affect conditions, the amygdala showed clearly distinct patterns of activation depending on whether the nonconscious stimuli depicted happy or sad expressions. These findings suggest a role for the amygdala in processing nonconscious
Acknowledgements
This material has been reviewed by the Walter Reed Army Institute of Research. There is no objection to its presentation and/or publication. The opinions or assertions contained herein are the private views of the authors, and are not to be construed as official, or as reflecting true views of the Department of the Army or the Department of Defense. This work was supported by a grant from the National Institute of Child Health and Human Development (NICHD) to William D. Killgore, PhD, NIH grant
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