The neural substrates of lexical emotional processing: An fMRI study.

摘要

The amygdala has been implicated in the perception, evaluation, memory, and early visual processing of threat-related stimuli. The current study focused on elucidating the role of the amygdala in the processing of highly unpleasant words. This study also examined other regions of interest (ROIs), including the ventromedial prefrontal, insular, and right posterior cortices, and the anterior and retrosplenial cinguli.; Unpleasant and neutral trials were presented to nine healthy adult women. During the first scan, subjects viewed sets of unpleasant or neutral words while selecting the most unpleasant or neutral word, respectively. During the second scan, subjects identified words that were presented during the first scan. Images were detrended, filtered, and co-registered to standard brain coordinates. The Talairach coordinates for the center of the amygdala were chosen before analysis. Activations in the remaining ROIs were identified on a post-hoc basis from whole brain analyses.; The right amygdala, medial frontal gyrus (BA 9), and the right middle temporal gyrus revealed a greater response to unpleasant than neutral words during Scan 1, confirmed by Word Condition x Time Course ANOVAs. Only the ROI activation site in the right middle temporal gyrus demonstrated a lateralized response, as confirmed by a Word Condition x Time Course x Hemisphere interaction. Correlational analyses further revealed a positive relationship between activation in this ROI and the right amygdala. While subjects recognized more of the unpleasant than neutral words, their memory performance was not correlated with the observed ROI activations. Finally, the selective response observed in the amygdala to unpleasant words was correlated with occipital activation to the unpleasant and neutral words.; Results agree with the view that the amygdala mediates the appraisal of threat-related stimuli, and modulates early processing of salient visual information in the occipital cortex. Activation in the medial frontal gyrus, (BA 9) supports the notion that this region is involved in the conscious monitoring of one's emotional state while making personally relevant decisions. Finally, the right lateralized response in the middle temporal gyrus; is consistent with the view that the right posterior cortex plays an important role in the perception of emotional stimuli.