A role for attentional bias in cognitive deficits in chronic pain?
This thesis extends current understanding of cognitive deficits in people with chronic pain, specifically those related to attention. Researchers have proposed that attentional capacity is allocated to pain sensation, and away from current tasks and goals, leading to broad cognitive deficits (deficit-view). However, an attentional bias to pain-related information has also been observed in people with chronic pain, suggesting that attention is motivated towards information in the environment that is pain-related, and away from information that is not. Such an attentional bias away from information not related to pain may contribute to the cognitive deficits observed on tasks using neutral stimuli (motivated attention hypothesis). In testing the deficit-view and motivated attention accounts of cognitive deficits in chronic pain, I focused on how people attend to rapidly presented information (temporal attention) and the ability to control attention in the face of distraction. To assess how chronic pain affects temporal attention, I used a phenomenon known as the attentional blink, which is a failure to detect a second target that appears soon after a first. Participants viewed a stream of briefly displayed words in which two target words (indicated by their colour) were embedded, with a manipulation of the time between the first and second target. They were required to report the two targets. In one experiment the first target was either pain-related or neutral (to assess how pain-relatedness affects the induction of the blink), and in other experiments this manipulation was applied to the second target (to assess how pain-relatedness affects how targets overcome the blink). In undergraduate participants, both induction and overcoming of the attentional blink was modulated by pain-relatedness. I then compared the effects of manipulating the second target in people with and without chronic pain. If people with chronic pain have general deficits in temporal attention, a deeper attentional blink (relative to control participants) for both kinds of targets should be observed. If motivated attention describes processing in people with chronic pain, a shallower attentional blink for pain related targets than neutral targets (an attentional bias) should be observed. Critically, this bias should be larger in participants with chronic pain. Contrary to both the deficit and motivated attention views, the attentional blink in participants with chronic pain did not differ from that in controls for either pain-related or neutral targets. Furthermore, neither group showed an attentional bias for pain-related targets, and a follow-up experiment failed to replicate the attentional bias observed in undergraduate students as well. Collectively, these findings suggested that attentional bias, as assessed by modulation of the attentional blink, was not reliable. A stronger test of the deficit-view and motivated attention hypothesis was needed. I shifted focus to another attentional domain, the control of distraction. To assess how chronic pain affects attentional control, I used an emotional distraction task, in which participants identified a target letter in an array that flanked irrelevant distractor images that were either intact or scrambled. Intact images depicted either extreme threat to body-tissue, or benign scenes. Distraction is indicated by slowing on intact relative to scrambled distractor trials. If people with chronic pain have general deficits in attentional control, they should show greater distraction from both kinds of images (relative to controls). If motivated attention describes processing in people with chronic pain, greater distraction from body-threat images than neutral images (relative to controls) should be observed. While all participants were more distracted by images depicting extreme threat to body-tissue, people with chronic pain were not more distracted than control participants for either image type. Findings fail to support either a deficit or motivated attention view of attentional control in chronic pain. Although these experiments do not provide evidence that chronic pain affects attentional processing, across experiments people with chronic pain reported that they experience deficits in attention, and they showed behavioural evidence of psychomotor slowing. These findings suggest that, as is repeatedly reported in the literature, people in chronic pain feel like they have attentional deficits, and that some aspects of cognitive and/or motor processing are impacted. Careful consideration is given to what specific cognitive functions might be impaired in chronic pain. The outcome of this discussion suggests pertinent research directions to further understanding of cognition in chronic pain experience.