EXECUTIVE FUNCTIONS IN PATIENTS WITH CHRONIC LOW BACK PAIN: A BEHAVIORAL AND EVOKED RELATED POTENTIAL STUDY

Converging functional neuroimaging and neurophysiological evidence indicates distinct patterns and long-term changes in the activation of pain-related brain areas, i.e. the so-called pain matrix, in chronic pain. These areas include prefrontal cortices, in particular the dorsolateral prefrontal cortex (dlPFC), where MRI morphometric studies showed decreased gray matter in chronic pain patients. Despite these data, the correlation between chronic pain and cognitive functions, in particular executive functions (EFs), has scantily been explored. The aims of this study are 1) to explore meta-cognitive EFs in chronic LBP and controls with a battery of neuropsychological tests; 2) to explore the emotional-motivational EFs in chronic LBP and controls using the Iowa Gambling Task (IGT) in order to examine the costs that chronic pain may impose on emotional decision making; 3) to explore the neural correlates of emotional-motivational EFs mechanisms with ERPs during the IGT in order to better understand the mechanisms underlying feedback elaboration and subsequent learning processes in chronic LBP. We collected 24 patients with chronic LBP and 24 normal volunteers matched with the patients for age, sex and educational level. Changes in executive functions have been explored with a battery of neuropsychological tests (Iowa Gambling Task, Trail Making Test, Stroop Test, Modified Card Sorting Test, Digit Span Forward and Backward, Memory Interference Test). ERPs have been recorded during IGT in a subgroup of patients and controls. We found significant differences between the two groups in the MCST right categories, which were significantly lower in patients vs. controls and in MCST perseverative errors that were significantly higher in patients vs. controls. IGT data showed an impairment of both the total amount of money and the learning strategy. ERPs findings suggest a differential behavior of brain responses during IGT. The feedback related negativity (FRN) amplitude was higher to positive than negative feedback in controls, while the opposite happened in patients. The P300 amplitude was higher to positive than negative feedback in control, while this difference was absent in patients, being the P300 amplitude similarly high for both types of feedback. Our evidence indicates that chronic pain is associated with a deficit in feedback processing both for meta-cognitive and emotional-motivational components of EFs. These abnormalities may negatively influence everyday behavior.