Increasing data indicate that emotional stimuli gain preferential access to attentional resources. This effect can be instantiated as improved detection time, enhanced cortical responses, and greater disruption of the processing of concurrent or immediately subsequent stimuli. The amygdala has been hypothesized to play a critical role in the emotional guidance of attention. This influence figures prominently in several neuro-behavioral models of anxiety disorders. However, direct evidence for this hypothesis is extremely limited, and little is known regarding the aspects of attentional modulation that are affected by selective lesions of the amygdala. Preliminary data from our laboratory indicate that patients who have undergone selective unilateral removal of the amygdala and anterior hippocampus for intractable epilepsy show deficits in specific attentional tasks. These deficits include a failure to show an attentional blink in response to aversive emotional pictures, a slowed visual search for emotional stimuli, and a failure to show any slowing of performance during presentation of emotional words in the Emotional Stroop paradigm. The present proposal aims to elucidate the specific components of attention that are affected by amygdala lesions in humans. Additionally, we propose to test recent theories that posit that the left and right amygdala are differentially involved in processing conscious vs. unconscious stimuli and conditioned vs. innately emotional stimuli. Towards this end, we propose to study 38 patients before and after they undergo unilateral (half right-half left) amygdalohippocampectomies for intractable epilepsy. We will additionally study 38 age-, gender-, handedness- and education-matched controls, and 38 nonsurgical epilepsy patients who are matched with the amygdalohippocampectomy patients for anticonvulsant usage. Participants will receive a battery of tests to determine the specific effects of amygdala lesions on attentional guidance in response to different types of emotional stimuli. The study represents the first research to thoroughly examine the role of selective amygdala lesions on different tasks of attention modulation. It is unique in the emotion literature in its examination of patients both pre- and post-surgery and its ability to rule out confounds of anticonvulsant medications. Thus, the study will be able to address the effects of amygdala lesions with a degree of precision that has been unattainable in previous research on the human amygdala.
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