It is well known that electroencephalographic event related potential component P300 is sensitive to perception of critical items in a concealed information test. However, it is not known whether the relative level of expression of P300 as a neural marker of deception can be manipulated by means of non-invasive neuromodulation. Here, we show that while P300 exhibited systematic amplitude differences in response to the more as well as the less significant stimuli items encountered at the “crime scene” compared to neutral items, offline rTMS to dorsolateral prefrontal cortex attenuated P300 amplitude in response to the critical items. Yet, the individual subjects showed different sensitivity of the P300 as the marker of concealment. We conclude that rTMS can be used for subduing electrophysiological markers of deception, but this effect depends on whether the subject belongs to the group of CIT-sensitive individuals.

Dorsolateral prefrontal cortex (DLPFC) participates in many mental functions involving cognitive control. This also applies to processes underlying deception. Recently it was shown that, compared to the opposite effect found with left-hemisphere 1-Hz repetitive transcranial magnetic stimulation of the DLPFC, right-hemisphere stimulation decreased the propensity to produce untruthful responses in a subsequent task where subjects had freedom to name presented stimulus-objects either veridically or nonveridically. In a similar experiment, the purpose of the present study was to test whether changing the rTMS protocol from the disrupting to facilitatory type can lead to opposite results. When trains of 10-Hz pulses were delivered to the right DLPFC, propensity to lie increased while similar left-hemisphere DLPFC stimulation did not change the rate of untruthful responses. We can conclude that the way how right DLPFC and other areas functionally associated with it are involved in producing truthful or deliberately deceptive statements about perceived objects considerably depends on what are the parameters of stimulation by which functionality of this system is manipulated.

Knowing the brain processes involved in lying is the key point in today's deception detection studies. We have previously found that stimulating the dorsolateral prefrontal cortex (DLPFC) with repetitive transcranial magnetic stimulation (rTMS) affects the rate of spontaneous lying in simple behavioural tasks. The main idea of this study was to examine the role of rTMS applied to the DLPFC in the behavioural conditions where subjects were better motivated to lie compared to our earlier studies and where all possible conditions (inhibition of left and right DLPFC with 1-Hz and sham; excitation of left and right DLPFC with 10-Hz and sham) were administered to the same subjects. It was expected that excitation of the left DLPFC with rTMS decreases and excitation of the right DLPFC increases the rate of lying and that inhibitory stimulation reverses the effects. As was expected, excitation of the left DLPFC decreased lying compared to excitation of the right DLPFC, but contrary to the expectation, inhibition had no different effects. These findings suggest that propensity to lie can be manipulated by non-invasive excitatory brain stimulation by TMS targeted at DLPFC and the direction of the effect depends on the cortical target locus.

Brain-process foundations of deceptive behaviour have become a subject of intensive study both in fundamental and applied neuroscience. Recently, utilization of transcranial magnetic stimulation has enhanced methodological rigour in this research because in addition to correlational studies causal effects of the distinct cortical systems involved can be studied. In these studies, dorsolateral prefrontal cortex has been implied as the brain area involved in deceptive behaviour. However, combined brain imaging and stimulation research has been concerned mostly with deceptive behaviour in the contexts of mock thefts and/or denial of recognition of critical objects. Spontaneous, "criminally decontextuated" propensity to lying and its dependence on the activity of selected brain structures has remained unexplored. The purpose of this work is to test whether spontaneous propensity to lying can be changed by brain stimulation. Here, we show that when subjects can name the colour of presented objects correctly or incorrectly at their free will, the tendency to stick to truthful answers can be manipulated by stimulation targeted at dorsolateral prefrontal cortex. Right hemisphere stimulation decreases lying, left hemisphere stimulation increases lying. Spontaneous choice to lie more or less can be influenced by brain stimulation.