Electrocortical markers of lying: When truthful people are taken for mendacious

The capacity to deceive others is a complex, multicomponential and typically human cognitive ability, which requires higher-order cognitive functions and the ability to suppress truthful information. Nothwithstanding the polygraph is widely used in countries such as USA to detect deception, not much is known about the role of emotional processes (such as the fear of being considered guilty while being innocent) in affecting physiological responses used as lie indicators. The aim of this study was to investigate the time course and neural correlates of untruthful behaviour in response to visually presented neutral and affective questions through the analysis of electro-cortical potentials; the questions could also be inherently true or false and ERP were recorded from 128 scalp sites in 23 volunteers. Behavioural and ERP responses indicated that when one is lying there is an increased need for executive functions, namely working memory, inhibition and task switching processes. Deceptive responses elicited a more negative N400 over the prefrontal regions and a smaller late positivity (LP 550-750 ms) over the prefrontal and frontal areas. However, such a reduction in LP amplitude was elicited also by truthful affective responses, thus resulting in a lack of difference between mendacious and truthful responses to emotional questions. A swLORETA inverse solution was applied to the N400 component (300-400 ms) that indeed would represent the neural marker of deception (difference-wave: untruthful-truthful). The results showed the activation of the precentral gyrus (BA6), of the superior, medial, middle and inferior frontal gyrus (BA9, 11, 47), and of the anterior cingulate cortex during deceptive responding.