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 re-action 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 pro-cessing depth of emotional information
in patients with comorbid depression.
