Trait anxiety and impoverished prefrontal control of attention

  • Bishop S
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Abstract

Many neurocognitive models of anxiety emphasize the importance of a hyper-responsive threat-detection system centered on the amygdala, with recent accounts incorporating a role for prefrontal mechanisms in regulating attention to threat. Here we investigated whether trait anxiety is associated with a much broader dysregulation of attentional control. Volunteers performed a response-conflict task under conditions that posed high or low demands on attention. High trait-anxious individuals showed reduced prefrontal activity and slower target identification in response to processing competition when the task did not fully occupy attentional resources. The relationship between trait anxiety and prefrontal recruitment remained after controlling for state anxiety. These findings indicate that trait anxiety is linked to impoverished recruitment of prefrontal attentional control mechanisms to inhibit distractor processing even when threat-related stimuli are absent. Notably, this deficit was observed when ongoing task-related demands on attention were low, potentially explaining the day-to-day difficulties in concentration that are associated with clinical anxiety. National surveys suggest that nearly 20% of the adult US population will meet criteria for one or more anxiety disorders in a 12-month period 1 . Anxiety is hugely disruptive to everyday life, placing an emotional burden on both individuals and their families. Conse-quently, there is a great deal of interest in advancing our understanding of the mechanisms underlying anxiety and developing new approaches for treating it. Cognitive studies from the 1980s and 1990s suggest that anxiety is characterized by increased attentional capture by threat-related stimuli 2,3 . The predominant theoretical stance has been that this arises as a result of a hyper-responsive pre-attentive threat-detection system centered on the amygdala 4 . This account has been modified in recent years to incorporate an influence of prefrontal cortical mechanisms in the top-down control of selective attention to threat 5,6 . However, these models have retained an emphasis on the need for competition between the processing of threat-related and neutral stimuli to be present for anxiety-related cognitive biases to be observed. Here we test a more radical account; namely that trait anxiety may be characterized by impaired recruitment of prefrontal mechanisms that are critical to the active control of attention when the task at hand does not fully govern the allocation of attention. It is proposed that this deficit does not arise as a result of current or state levels of anxiety, but instead reflects an underlying trait characteristic that influences atten-tional processing regardless of the presence or absence of threat-related stimuli. This may interact with state anxiety influences on subcortical threat detection mechanisms 7,8 to account for the threat-related atten-tional biases associated with clinical anxiety. It may, however, also account for observations that anxious individuals show deficits across a range of non-affective tasks that place demands on attentional or cognitive control 9–11 . Neural models of attentional or cognitive control have implicated the dorsolateral prefrontal cortex (DLPFC) in both the sustained and flexible control of attention. In regards to the former, DLPFC is thought to support the establishment and maintenance of 'attentional sets' , with sustained representation of current goals and task rules being used to facilitate task-related performance 12,13 . DLPFC recruitment is also thought to be important in the active re-allocation of attentional resources in response to trial-by-trial changes in processing competi-tion, with these changes being signaled by input from regions that are thought to monitor the occurrence of such competition, in particular dorsal anterior cingulate cortex (ACC) 14 . DLPFC involvement in the online trial-to-trial adjustment of attentional control has been demon-strated through tasks manipulating response conflict, where task-irrelevant stimuli promote a response that is either congruent (low conflict) or incongruent (high conflict) with that required by the current target 15,16 . Proponents of the load theory of selective atten-tion 17,18 have argued that active recruitment of attentional control mechanisms is required, in particular, in response to processing competition under conditions of low perceptual load. When the perceptual load or processing requirements of the primary task is high, the task is thought to fully occupy attentional resources, with the processing of distractors being terminated at an early stage before they can compete for further processing, such as response selection and entry into working memory. Under conditions of low perceptual load, however, attentional resources are thought to be only partially occu-pied, allowing salient distractors to compete for further processing

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Authors

  • Sonia J. Bishop

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