Electrophysiological assessment of impulsive behavior in healthy subjects

The different concepts of impulsivity cover a wide range of divergent behaviors. In clinical terms, aspects of impulsivity are both an important feature in several psychiatric conditions related to a low central serotonergic neurotransmission like aggressive behavior and suicidality, and a core symptom of frontal lobe syndromes of various etiologies. Assessment of the different forms of impulsivity so far relies on clinical observations and self-rating questionnaires. Measurements of a distinct brain function associated with impulsive behavior are not available yet, however, electrophysiological parameters of cognitive response control elicited with the execution (Go-condition) and the inhibition (NoGo-condition) of a prepared motor response within the Continuous Performance Test (CPT) might be suitable candidates. By means of a spatial analysis method the centers of gravity (centroids) of the brain electrical fields evoked with Go- and NoGo-responses can be localized and quantified. In the present study, the Go- and NoGo-centroids and the impulsivity score in Eysenck's I(7)-scale were determined in 22 healthy subjects (10 women, 12 men, mean age 42.0+/-10.1 years). Impulsivity was correlated with both, a more anterior location of the Go- (r=0.58, P<0.01) and the NoGo-centroid (r=0.53, P=0.01). These results indicate, that in healthy subjects the amount of I(7)-impulsivity is associated with differences in the prefrontal brain activation pattern during cognitive response control. However, a replication study with a larger sample and an investigation of psychiatric patients with pathological levels of impulsivity are necessary to qualify these topographical ERP-parameters of cognitive response control as valid measures of the brain electrical basis of impulsive behavior.