Central nervous activity during a dot probe task with facial expressions in fibromyalgia

Abstract

Fibromyalgia syndrome (FMS) is a chronic pain condition accompanied by affective symptoms and cognitive impairments. This study investigated central nervous correlates of attentional and emotional processing in FMS. Therefore, event-related potentials were recorded in 26 FMS patients and 26 healthy controls during a dot probe task, which required participants to decide which side of the screen an asterisk was displayed on; the asterisk was immediately preceded by a facial expression (anger, pain, happiness, neutral) on the left or right side. Comorbid depression was also assessed. In patients, N170 amplitude was smaller for anger and pain expressions than for happy expressions, and P2 was greater for pain expressions than for happy expressions. N170 and P2 were unaffected by emotional expressions in controls. LPC was smaller overall in patients than controls. Though reaction times were longer overall in patients than controls, no behavioral effects of emotional stimuli arose in these groups. In contrast, FMS patients with comorbid depression showed less attentional interference due to emotional expressions, and less difficulty disengaging from these stimuli than patients without depression. While the observations concerning N170 suggested facilitated encoding of facial features representing negative rather than positive emotions in FMS and more automatized processing of pain expressions, those for P2 indicated increased attentional resource allocation to pain-related information. Reduced LPC reflects nonspecific deficits in sustained attention in FMS, which is in line with the longer reaction times. Behavioral data suggest lower processing depth of emotional information in patients with comorbid depression.