Attention gates the processing of stimuli relatively early in visual cortex. Yet, existing data suggest that emotional stimuli activate brain regions automatically, largely immune from attentional control. To resolve this puzzle, we used functional magnetic resonance imaging to first measure activation in regions that responded differentially to faces with emotional expressions (fearful and happy) compared with neutral faces. We then measured the modulation of these responses by attention, using a competing task with a high attentional load. Contrary to the prevailing view, all brain regions responding differentially to emotional faces, including the amygdala, did so only when sufficient attentional resources were available to process the faces. Thus, the processing of facial expression appears to be under top-down control.T o what extent are unattended objects processed by the visual system? Psychophysical evidence suggests that processing outside the focus of attention is attenuated and may even be eliminated under some conditions (1-4). For example, ''change blindness'' studies show that subjects may fail to report even very large changes in complex scenes (2). Even low-level tasks commonly thought to be ''preattentive,'' such as orientation pop-out, may require attention to be successfully performed (3). Likewise, at the neural level, functional MRI responses in the middle temporal area to moving stimuli are essentially eliminated when subjects are engaged in a competing task with high attentional load (4). Taken together, these studies suggest that perception and its underlying neural substrate may be abolished if attentional resources are completely consumed by a competing task.A major exception to this critical role of attention may be the neural processing of emotional stimuli, which are reported to be processed automatically, namely, without attention (5, 6). Subjects exhibit fast, involuntary autonomic responses to emotional stimuli, such as aversive pictures or faces with fearful expressions (7,8). Other behavioral studies suggest that the visual processing of facial expression occurs not only automatically but may even take place without conscious awareness (5). This conclusion is also supported by imaging studies of the amygdala, a structure important for the processing of fear (9, 10). Such studies report that the amygdala is activated not only when normal subjects view fearful faces, but even when these stimuli are masked and subjects appear to be unaware of them (11,12). The view has thus emerged that the amygdala is specialized for the fast detection of emotionally relevant stimuli in the environment, and that this can occur without attention and even without conscious awareness.In the present study, we tested the alternative possibility, namely, that the neural processing of emotional stimuli is not automatic and requires some degree of attention, similar to the processing of other stimulus categories. We hypothesized that the failure to modulate the processing of emotional stimuli by attention...

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We used fMRI to investigate how moment-to-moment neural activity contributes to success or failure on individual trials of a visual working memory (WM) task. We found that different nodes of a distributed cortical network were activated to a greater extent for correct compared to incorrect trials during stimulus encoding, memory maintenance during delays, and at test. A logistic regression analysis revealed that the fMRI signal amplitude during the delay interval in a network of frontoparietal regions predicted successful performance on a trial-by-trial basis. Differential delay activity occurred even for only those trials in which BOLD activity during encoding was strong, demonstrating that it was not a simple consequence of effective versus ineffective encoding. Our results indicate that accurate memory depends on strong sustained signals that span the delay interval of WM tasks.

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