EFTA02672340.pdf

Cerebral Cortex Advance Access published May 14, 2009 The Truth about Lying: Inhibition of the Ahmed A. Karim", Markus Schneider", Martin Lotze". Ralf Veit', Paul Sauseng", Christoph Braun' and Anterior Prefrontal Cortex Improves Niels Birbaumer" Deceptive Behavior 'Institute of Medical Psychology and Behavioral Neurobiology. University of Tuebingen, 72074 Tuebingen, Germany, zInternational Max Planck Research School of Neural and Behavioral Sciences. 72074 TObingcn, Germany, "Department of Functional Imaging, Center for Diagnostic Radiology and Neuroradiology. University of Greifswald, 17489 Greifswald, Germany. "Department of Physiological Psychology, University of Salzburg. 5020 Salzburg, Austria and sOspedale San Camillo. IRCCS. Istituto di Ricovero c Cura a Carattcrc Scicntifico, 30126 Venezia, Italy Recent neuroimaging studies have indicated a predominant role of scat prefrontal cortex (DLPFC; BA 8) and the right aPFC. the anterior prefrontal cortex (aPFC) in deception and moral whereas the left ventromedial PFC (BA I 1) and Antygdala were cognition. yet the functional contribution of the aPFC to deceptive associated with the process of deceiving the interrogator. behavior remains unknown. We hypothesized that modulating the Funher analysis revealed that only the right aPFC was associated excitability of the aPFC by transcranial direct current stimulation with both factors of deception, indicating that this region has (tDCS) could reveal its functional contribution in generating deceitful a pivotal role in telling lies. Although these findings are quite responses. Forty-four healthy volunteers participated in a thief role- remarkable, these ncumimaging studies have at least 3 short- play in which they were supposed to steal money and then to attend comings. Firm, a general problem of neuroimaging techniques an interrogation with the Guilty Knowledge Test. During the like IMItl or PET is that they allow only correlative statements interrogation, participants received cathodal, anode], or sham tOCS. about the brain regions involved in a specific behavior (here Remarkably, inhibition of the aPFC by cathodal tOCS did not lead to deception). Causal relevance can be demonstrated with other an impairment of deceptive behavior but rather to a significant methods allowing transient inhibition of conical excitability improvement. This effect manifested in faster reaction times in such as transcranial magnetic stimulation (TMS) (Karim et at telling lies, but not in telling the truth, a decrease in sympathetic 2003; Amedi et at 200t; Karim, Schuler. et at 2004 Knoch et at skin-conductance response and feelings of guilt while deceiving the 2006) or transcranial direct current stimulation (tDCS) (Nitsche interrogator and a significantly higher lying quotient reflecting skillful and Paulus 2000, 2001; Nitsche. Schauenberg, et at 2003; Knoch lying. Increasing the excitability of the aPFC by anode] tDCS did not et al. 2008; Priori et al. 2008). Second, the functional affect deceptive behavior, confirming the specificity of the contrthution of the PIC to deception remains elusive. If, for stimulation polarity. These findings give causal support to recent instance, increased activation of the aPFC reflects cognitive correlative data obtained by functional magnetic resonance imaging processes involved in withholding the truth, suppression of this studies indicating a pivotal role of the aPFC in deception. region should impair deceptive behavior. However, if increased activation of the aPFC: rather reflects a moral conflict involved in Keywords: frontal cortex• lie detection, moral cogrXtion, neutoethics. deceiving the counterpart, then suppressing this area should conductance response (SCR), transcranial direct current stimulation 000S, have exactly the opposite effect and 'improve deceptive behavior through behasioral disinhibitlon. Neuroimaging studies Introduction on psychopaths, classified as pathological liars, have demon- Deception is a complex cognitive act, with crucial legal, moral, strated that they have significantly less gray matter in the PFC and social implications. Functional magnetic resonance imaging (Yang et aL 2005) and that they do not show moral dilemma like (fMRI) studies on neural correlates of deception have shown healthy subjects (Anderson et at 1999). Thirdly. in previous IMRE that the prefrontal cortex and the anterior cingulate cortex studies, participants were instructed when to lie and when to (ACC) were more strongly activated during lying than during say the truth. However, in cognitive processing, there is a crucial telling the truth (Lee et al. 2002; Ganis et aL 2003). Recent difference between a person who decides himself/herself knowledge about characteristic brain activation sites during whether to lie or to say the truth, and a person who merely deception enabled to recognize false statements with a pre- follows the instruction of the investigator to lie for a predefined cision between 88% and 99% (Davatzikos et al. 2(05). Canis time in the MIRI scanner and then to say the truth in order to et al. (2003) demonstrated that the anterior prefrontal cortices contrast the 2 conditions. (aPFCs; BA 9/10) were engaged during general deception, but The aim of this study was therefore I) to realize an that the right aPFC was more involved in lies that were well experimental setup, in which participants should decide rehearsed and were part of a coherent story than in themselves, which questions they would answer truthfully spontaneous. noncoherent tics, whereas the ACC was more and which ones with a lie and 2) to investigate the causal active during spontaneous generation of nonmemorized lies. In contribution of the aPFC in deceptive behavior by modulating a recent positron emission tomography (PET) study, Abe et al. the excitability of this brain region through tDCS. Three (2007) differentiated between the process of generating experiments were conducted to test the specificity of the untruthful responses and the social intention to deceive an transcranial stimulation effect. interrogator. The main effect of generating untruthful In the first experiment, 22 healthy subjects participated in responses revealed increased brain activity of the left dorsolat• a mock crime, in which they were supposed to steal money and Thc Amber 2009 Puhlbhal 1w (Wont tniveryty Prof. AN nights ment+.1 kw pcmikeuonk (taw: journahvoinliaorwetadvitioutrigaorli EFTA_R1_01945408 EFTA02672340 then to attend an interrogation with a modified version of the physiological responses to the relevant alternative are consistently larger Guilty Knowledge Test (GKT). In addition to verbal response than the COMM! alternatives. knowledge about the crime is Inferred (for (truth vs. lie) reaction time (RT). skin-conductance response a meta-amlysis on the validity of the GKT see Ben-Shakar and Ebad 2003). fi le role-play was organized as Mows: TWo subjects were asked (SCR) and feelings of guilt while deceiving the interrogator to pick I of 2 chits of paper from a cup. The subjects were told that on I were assessed In a double-blind repeated-measures design, chit was written 'thief and on the other one "innocent attendee: The subjects received cathodal or sham tDCS of their aPFC during subjects were asked to memorize their roles but not to tell the instructor the interrogation of the mock crime. Furthermore, in order to which role they had chosen. After the roles were assigned by drawing measure skillful lying. we developed a ratio called "lying lots, the subjects were told to go to an office and wait there for 20 min quotient (LQ) relating the frequency of lies to critical until the interrogation. This office consisted of a main room and an adjoining room. Both rooms were shown to the subjects before assigning questions with the frequency of lies to uncritical questions. the roles, and they were told that the innocent attendee should wait Skillful lying meant that a person intending to appear innocent during the mock crime in the main room, while the thief should go to should not simply lie on all questions, because this behavior the adjoining room and search there for money with the intention to would appear rather suspicious. Instead, as in a real criminal steal it. Money could he placed at several locations. Therefiire, the thief interrogation, the suspects had to decide themselves which should not only search for the money thoroughly hut also as quickly as questions they would answer truthfully and which ones with passible. The subjects were further told that after the money has been stolen, both subjects will be suspected to be the thief Each of them will a lie. Accordingly, a subject achieved a relatively high LQ if he/ attend independently of each other 2 interrogations with an investigator she answered all "critical items" (whose correct answer only who will play the role of a police inspector. In the interrogation. the the interrogator and the thief knew, e.g., the true color of the subjects will be asked questions, which they should answer as quickly as wallet) with a lie, but all "uncritical items" truthfully. To passible with a "yes- or a no, Additionally. the SCR and the RT will be increase motivation for deceptive hehavior, participants were recorded. The subjects were also told that during each of the 2 told that they were allowed to keep the stolen money in case interrogations. they will receive different types of tDCS. The true 'thief they could convince the interrogator that they were not guilty. should lie in such a skifilid manner that the interrogator would believe he/she is innocent. Skillful lying meant that a person intending to appear To test the specificity of the applied stimulation polarity and innocent should not simply lie on all questions. because this behavior stimulation site, we conducted a second experiment with 22 would appear rather suspicious. Instead, as in a real criminal in- healthy volunteers in which the stimulation polarity was terrogation. the suspects had to decide themselves which questions they reversed. For "anodal" tDCS of the aPFC, the anodal electrode would answer truthfully and which ones with a lie. To enhance the was placed over FP2 (international EEG 10/20 system). and the motivation of the subjects to identify themselves with their role and to cathodal electrode was placed over PO3 (left parieto-occipital make the role-play as realistic as possible, subjects were told that they were allowed to keep the stolen money in case they could convince the cortex) as a control area. In randomized order, anodal or sham interrogator that they were not guilty. However, in reality, I of the 2 tDCS of the alit was applied during the interrogation subjects was a collatorator of the experiment, a fax unknown to the Further 20 healthy subjects participated in a third experi- subject and on both pieces of paper 'thief was written. hut the ment, in which the Stroup test (Stroup 1935) was used as collaborator knew that he had to play the role 'innocent attendee: The a 'contml task' In experiments I and 2. subjects intending to goal of the investigation was to elucidate, if the subjects would show deceive the interrogator had to inhibit the truth as a prepotent during cathodal ft-mut-AMA DC stimulation of the aPFC different response and give instead a deceitful answer. The Stroop task is deceptive behavior titan during anodal or sham stimulation a widely used index of executive control (MacLeod 1991; Swick and Jovanovic 2002) that tests the ability to inhibit a prepotent Transcrankd DC Stimulation response but does not include deceiving the counterpart. Trx:s involves continuous administration of weak currents of --t mA through a pair of surface electrodes attached to the scalp (blitsche and Paulus 2000). Previous studies have demonstrated that cerebral Materials and Methods excitability was diminished by cathodal stimulation, which hyper• polarizes neurons (Terzuolo and Bullock 1956: Creutzfeldt et al. 1962: Subjects Bindmann et al. 1964: Cianside 1968). Bindmann et al. (1964) have For experiments 1-3. there were 22, 22. and 20 participants, shown that cathodal stimulation in animals can reduce or completely respectively (I3, 9, and 10 men). The mean age standard deviation inhibit spontaneous firing of conical cells. In humans, it has been was 25.6 4.9. 24.8 3.9 and 26.0 4.0. Each subject participated in shown that cathodal stimulation can decrease the excitability of the only I of the 3 experiments. All subjects were right handed according motor (Nitsche and Paulus 2000; Liebetanz et al. 2002; Nitschc, Nitsche to the Edinburgh Ilandedness Inventory (Oldfickl 1971). The study was et al 2003), visual (Antal et al. 20)1. 2004) and somatosensory convex approved by the ethics committee of the Medical Faculty of the (Dlcckh&cr et al. 2(06). University of TUbingen. Subjects were excluded if information from In the first experiment, the cathodal electrode was placed over FP2 a standardized medical questionnaire suggested prior neurological. and the anodal electrode over PO3 according to the international 10.20 psychiatric, or cardiovascular diseases or consumption of centrally EEG system (Fig. la). TICS polarity refers to the right fmntopolar acting medication. Parts of these data were previously presented at the electrode. PO3 was chosen as a reference for 2 reasons: First. to 49th Annual Meeting of the Society of Psychophysiological Research in maximize the distance between the cathodal and the modal electrode. Vancouver, Canada (Karim, Louie. et al. 2006). because current density calculations have shown that increasing the distance between the electrodes decreases the current shunted through the scalp and Increases the current density in depth (Rockstmh et al. Experimental Des(gn 1989 Miranda et at 2006) and second, because previous neumintaging Experiments I and 2 consisted of a thief role-play, in which money (X) studies did not show that the porktooccipit al cortex (RA 39)K involved Eums) was stolen and a subsequent interrogation, in which the suspects in deception (for a review. see Karim et al 2009). A constant current were asked questions about the course of the mock crime according to flow of I mA was applied through wet sponge electrodes (4 x 6 cm). and the GKT paradigm. The GKT (Lykken 1959, 1960) utilizes a series of continuous tIDCS was delivered by a battery driven, constant current multiple-choke questions. each having I true alternative and several stimulator (Schneider Electronic. Gleichen, Germany) for 13 min. The false alternatives. chosen so that an Innocent suspect would not be able interrogation started 3 min after onset of the stimulation and lasted for to discriminate them from the relevant alternative (e.g. 'the color of the 8-It) min. so that tlX3 was applied through the whole interrogation but stolen wallet was: red? black? brown? blue? gray?'). Thus. if the subject's had 3 min forerun to reach maximum effects (Nitsehe and Pat: 2000) Page 2 elf Mahn', the Wes; InrymtS DVCCPtht Dellociat • Kahn el EFTA_R1_01945409 EFTA02672341  a Cathodal IDCS of the aPFC Lying quotient (LC) 25 Ls'. 5- 0 CatfiodS Sham Figure 1. Panel A ilustrates the technique used for transuanial DC simulation. Wea drect current II mA) was applied between 2 large (24 cm). wet sponge electrodes placed over FP2 and P03 according to the iiternational 10-20 EEG system. TOGS polarity refers to the fronto.polar electrode. Panel 8 depicts the effect of cathodal WPCS on skilful ling measured by the 10. Etrot bars denote standard snot of the mean ISEM). *P < 0.05. The current was always ramped tip or down over the first and Leg 5 s of Subjects who decide simply to lie on all questions independently of stimulation, respectively. During OW'S. voltages of more than approxi- their relevance to the criminal act will have an LQ of O. A quite odd mately 10 V can induce a mild tingling sensation in the skin under the behavior would be. if a subject answers all critical questions truthfully scalp electrodes whereas t [XS at lower voltages is usually not associated hut lies on all uncritical questions. In such a case, that subject would with sensory stimulation even in experienced subjects (Hummel et at get an LQ of -100. Besides having a direct measure for skillful lying, an 2005). Skin resistance gradually declines after the first few seconds of important advantage of the I.Q Is that it enables us to control for the current application. In consequence. the voltage needed to hold subjects bias strategies or predisposition to answer almost all questions constant current decreases and becomes subthreshold for evoking in an interrogation with a lie or truthfully independently of the fact. if peripheral sensations. For slum tDC.S, placement of the electrodes. they are critical or not. A subject who deckles to lie on all questions current intensity and ramp time was identical to real tDCS: however, the would not admit knowing any critical information. but still would stimulation lasted only for 30 s. The rationale behind this sham appear dishonest. because he/she denies knowing information, which procedure was to mimic the transient skin sensation at the beginning he/she should know even as an innocent attendee. In contrast to this of real tOCS without producing any conditioning effects on the brain strategy. another subject might prefer to answer almost all questions (Skiver et al 2004: Hummel et at 2005). This method of slum truthfully. Such a subject would appear very honest; however, he/she stimulation has been shown to he reliable (Candiga et al. 2006). The would increase the passibility to he detected as the thief, because he/ interrogator and the subjects were blind to the intervention (toes or she would admit knowing a lot of informations which only the slum), which was applied by a separate investigator. delinquent could have known. In the second experiment, the stimulation polarity was reversed meaning that the anodal electrode was placed over F112 and the cathodal electrode OW! P03 according to the international 10-20 EEG Measurement q/ the RT system. Current intensity, ramp time. and duration of stimulation were RT was defined as the time between the end of the question and the identical to the firm experiment. onset of the answer. Note that the relevant information in the question In the third experiment, the stimulation parameters and stimulation was always in the last word (e.g- the mkt of the wallet was 'green.' The site were identical to the first experiment. The order of real and sham color of the wallet was law: etc.). Subjects answered the questions INS was balanced in the 3 experiments. verbally with a yes or a no. During the interrogation, the investigator and the subjects were wearing headphones with microphones, and the whole interrogation was recorded with Cool Edit Pro (Syntrillium Measurement of the LQ Software Corp.. Phoenix, United States). Acoustic information wa In order to measure skillful lying, we developed a ratio called lying digitalized at a 16-bit resolution and a sampling rate of 22 kHz. To quotient (l.Q): determine the acoustic onset of the verbal response, an amplitude filter was used that removed all acoustic signals with an amplitude of less than LQ• (I) 7.5% of the maximum sound levet The correctness of detecting the [(40t -em) IVITA l°11 min of each verbal response was checked off-line by making use of the where No, = Frequency of lies on critical questions. = Total phyhack function of the program. number of critical questions. No,,,„" • Frequency of lies on uncritical questions, and = Total number of uncritical questions. Skillful lying meant that a person intending to appear innocent Measurement °flat should not simply lie on all questions, because this behavior would SCRs were recorded at 16-Hz sampling rate with a commercial appear rather suspicious. Instead. as in a real criminal interrogation. thc ambulatory device (Varioport. Becker Meditec. Karlsruhe. Germany) suspects had to decide themselves which questions they would answer using standard Ag/AgCl electrodes filled with unibase electrolyte truthfully and which ones with a lie. affixed to the left hand. Data were processed off-line in a Matlab In the interrogation. a modified version of the GKT was applied environment (Matlab 63. The Mathworks Inc., Natick. .MA). Skin. consisting of 10 critical and 7 uncritical questions, each with 4 choices. conductance data were smoothed with a I s Gaussian kernel. The An uncritical question was a question. whose answer would be known amplitude of SCR was determined as the largest change in conductance even by an innocent attendee. who has been in the room but did not between I and 5 s after task onset, relative to the preceding smallest steal the money (e.g.. .0n the chair in the small room there was value in the interval. For statistical analysis, SCRs were log transformed a jacket. Was the color of the jacket: green? blue? black? brown?-). In (log(M:R + 1)). contrast. a critical question was a question. whose answer would he known only by the thief (e.g., in the pocket of the jacket there w wallet. Was the color of the wallet: green? blue? black? browny). Measurement of tbe Feelings of Guilt white Decent* the According to formula (I). the IQ can range from -100 to +100. A Interrogator most skillful liar would have a maximum LQ of 100, if he/she lies on all At the end of each interrogation. the subjects were asked to rate their critical questions. but answers all uncritical questions truthfully. feelings of guilt that they might have experienced while deceiving the cathni cartex Pap 3 or 9 EFTA_R1_01945410 EFTA02672342 interrogator on a scale from 0 (no feelings of guilt) to 5 (maximum a Reaction time feelings of guilt). 900 —O- Sham —6— Cathodal Stroop Task aco E To test the possible effect of cathodal tDCS on executive prefrontal E functkm (i.e.. the ability to inhibit a prepotern response), participants 700 performed the Snoop task during sham and cathodal tDCS of the aPFC. respectively. The task was conducted with a color-coxed 4-button keyboard. Participants were presented with color wonts printed in tc tc 603 colored Ink and asked to name the color of the ink as quickly as possible. 503 Thith tie Color words printed in an incongruent color (i.e., "red- printed in Noe Ink) produces slower RT known as Swoop interference (Swoop 1935). Ibe task consisted of 66 practice trials to minimize the emw rate. b Skin conductance response followed by 66 experimental trials (33 congruent and 33 fiwontntwm in randomized order). The stimulus words were: "red; "green; *bluer and -yellow: Color names appeared on the screen in I of the 4 colons 7,4 ns Preceding each trial, a fixation cross was shown Inc 2s. The trial interval o 1.2 was constant with a duration of 2 s. After the participants resistive, the a 1 screen became black fox• the n-st of tlw trial interval. 6 oti 9). 0,6 Results 0,2 0 Experiment 1 Troth W Truth 0 Shall) ■ Cath0dat Interestingly, if only the number of lies was compared between cathodal and sham tlX:S. no significant difference was found Feelings of guilt Cl between the 2 conditions (1 = 1.768, P = 0.092). However, concerning the I.Q. subjects achieved in the stimulation S FeeIn(0 of guilt condition a significantly higher LQ than in the sham condition 4 (f = 2.254, P = 0.035), meaning that the answers given in the 3 interrogation during cathodal tIXS were less likely to reveal 2 their guilt, than the answers given during slum stimulation 1 0 (HS- Sham Cathodal A repeated-measures analyses of variance (ANOVAjtm) with Figaro 2. Hens of cathodal uansaanial DC stimulation of the arrC on RI (a). Stimulation Camditiono.shoda locs,,sum ion) and Rtsponsew.„,h, smoothen SCR lei. and on feehigs of guilt (C) Mien subjects tell lies n an jk) as within-subject factors and Reaction Time as dependent intenogation of a mock crime. Eria ham denote SEM. 'P < 0.05 variable revealed no significant main effects (for Stimulation Condition: Fj,2; 2.198, P= 0.153; for Response: Fla' . 1.156. P= 0.294) but a significant interaction between the 2 factors analyses revealed a significantly negative correlation between (FL,s; = 7.037, P 0.020; Fig. 2€0. Posthoc I tests showed that the change of feelings of guilt (cathodal condition minus sham during sham tDCS. the RT for lying was significantly longer than condition) and the change of the LQ (t = -0.386, P= 0.023), for truthful responding = 2.568. P= 0.018). However, during indicating that the less feelings of guilt subjects perceived, the cathodal tDCS, the RT was significantly shorter for telling lies Os better could they deceive during the interrogation. 2.447, P= 0.02) but no for telling the truth (t= 0.611, P= 0.548). To analyze the effect of cathodal tDCS on sympathetic MS, an Experiment 2 ANOVARsj with Stimulation conditionkaihnaa tin:opium ft/CV In order to exclude the possibility that the observed effects and Responsew.,,,k,sO as within-subject factors was conducted. were only due to nonspecific effects of the electrical Again, no significant main effects were found (for Stimulation stimulation and not specific to the inhibition of the aPR: by Condition: F,.2, = 1.908, P= 0.191; for Response: Fuj = 3.216, "cathodal" DC stimulation, we conducted a second experiment P = 0.096) hut a significant interaction between the 2 factors in which the experimental design was identical to the first (Ful 6.287, P. Posthoc ttest revealed that in the sham experiment but the stimulation polarity was reversed. In condition, the SCR for lying was significantly higher than for contrast to the first experiment, anodal ti)CS of the aPFC did saying the truth (I . 3.029. P 0.008). However, in the not lead to a significant change of the LQ 0.51. Ps 0.61% stimulation condition, this difference in SCR between lies and Fig. 3). truthful responses disappeared (I= 0.626, P= 0.539; Fig. 2b). An ANOVA" with Stimulation ConditiOnommw IIXSishan IO(,) To further investigate the effect of cathodal tDCS of the and Response"„„hait) as within-subject factors and Reaction aPFC, on the subjective experience of guilt, subjects were Time as dependent variable revealed no significant main effects asked at the end of the interrogation to rate their feelings of (for Stimulation Condition: F,,21 = 0.209. P 0.652; for guilt, which they might have experienced during the in- Response: = 2.833. P = 0.107) and no significant terrogation, on a scale from 0 (no feelings of guilt) to 5 interaction between the 2 Factors (F,2, = 2.972, P = 0.099; (maximum feelings of guilt). Wilcoxon signed-rank test Fig. 4a). revealed that cathodal tIX'S of the aPR: led to significantly To analyze the effect of anodal tDCS on sympathetic sat, a lower feelings of guilt than in the sham condition (r. -1.986, further ANOVARm with Stimulation Conditionowaat ants, tots) P 0.047; Fig. 2c). Moreover, a Kendall•s tau correlation and Responsew.,,,no as within-subject factors was conducted. Page a of 9 leheition of the OH: Imisnonlkeeptto: Stlaallar • 'Calla al al EFTA_R1_01945411 EFTA02672343  a Anode] tDCS or the aPFC Lying quotient (LQ) ns 25 20. 8 15- co 10 a 5t. 5- 0 Modal Sham Figure 3. PanelA Austrates anode! transcranial DC stimulatien al the oPEC. TOGS polarity refers to the frontopolar electrode. Panel B depicts the effect of anodal tDCS an skillful (sing measured by the LO. Error bars denote SEM. a Reaction time Experiment 3 900 We tested a possible impact of cathodal tDCS of the aPFC on Sham general prefrontal executive function by using the Stroop test I 800 - 0 A octal as a control task. An ANOVA" with StimulatkniCondition(„ h,44 imsy mni in", and Stroop Conditiorkamgmenyhwonwom, ) as within- 700 - • subject factors revealed a significant main effect of the Stroup Condition on RT = 46.109, P < 0.001). However, the ti 600 Stimulation Condition had no effect on RT (Fit%) = 1.050. P= 3.18), and no significant interaction (F1,,9 = 1.593, P1222) 503 Truth Lie was found between Stimulation Condition and Strom) Condition (see Fig. 5). b Skin conductance response ns 1,4 Discussion ea r This study demonstrates for the first time that cathodal co 12 - a transcranial DC stimulation, which has been repeatedly shown 5to OA - to suppress conical excitability (Nitsche, Nitsche. et aL 2003: 4. - Antal et al. 2004; DieckhOfer et at 2OO6) can modulate OA - deceptive behavior. Moreover, our findings give causal support 1° 02 - to recent correlative data obtained by neuroimaging studies 0 indicating a predominant role of the aPFC in deceptive Truth Lie Trutt Lie O Sham ■ Modal behavior (Lee et al. 2002: Ganis ct al. 2003; Abe et al. 2007). Whereas in previous studies on neural correlates of deception C Feelings of guilt participants were instructed when to lie and when to say the truth, in the present study, subjects could decide themselves Feelings of guilt ns which questions they would answer truthfully and which ones 54I 3 2 with a lie, taking into account the difference in cognitive processing for cued and unwed lying. Must remarkably, we observed that inhibiting the excitability of the aPFC with 0 cathodal tDCS did not lead to impairment but rather to Sham Modal a significant within-subject improvement of deceptive behav- Figure 4. fleets of anodal transcranal DC stimulation of the aPEC on AT ior. This effect was expressed in faster RTs for telling lies, but sympathetic SCR Oh and on feelings of guilt (c) when subjects tee lies in an not for telling the truth, a decrease in sympathetic SCR and interrogation al a mock crime. Error bars denote SEM sP < 0.05. feelings of guilt white deceiving the interrogator and a signif- icantly higher EQ. which reflects skillful lying. The Response (lie vs. truth) revealed a significant main effect In order to exclude the possibility that the observed effects on SCR (Pia, = 38.190. P < 0.001); however, the Stimulation were only due to nonspecific effects of the electrical Condition (anodal tDCS vs. sham tDCS) had no effect on SCR stimulation and not specific to the inhibition of the OR: by (Fin = 1.164. P= 0.298), and no significant interaction (Al , = cathodal DC stimulation, we conducted a control experiment 0.009, P= 0.926) was found between Stimulation Condition and in which the stimulation polarity was reversed. Our data show Response (Fig. 4b). Also concerning the feelings of guilt that that shorter RTs in telling lies compared with telling the truth subjects might have experienced while deceiving the in- and the absence of increased SCR while deceiving the terrogator, in contrast to the first experiment, anodal tDCS interrogator were confined to cathodal UM'S of the aPH: and did not lead to a significant change of the subjective were not detectable during sham tDCS or anodal tDCS. Because experience of guilt (z = -1.89, P= 0.05% Fig. 4c). subjects were blinded to the stimulation condition and could ("Antral ("Ann Pep 5 al 9 EFTA_R1_01945412 EFTA02672344  antisocial and moral behavior. In respect to our study, 1— As — I pco ns deceiving another person in order to obtain personal profit seems to create a moral conflict, and if a person is relieved from poo this moral conflict, he/she might be able to deceive unhinder- ed!), with faster RT, less feelings of guilt and less sympathetic 700 arousal as demonstrated here. Suppressing conical excitability by cathodal tDCS or low-frequency repetitive transcranial re 600 magnetic stimulation (rTMS) has previously been shown to Sham Cathodal Sham Cathodal Congruent Incongruent induce so-called paradoxical improvement of performance through "disinhibition" processes (11ilgetag et al. 2001; Figure 5. Cathodal transcianal OC stimulation of the aPIC has no effect on RT in the Kobayashi et al. 2004: Fecteau et al. 2007). Kobayashi et al. Snoop task. Error tars denote SEM. (2004) have, for example, demonstrated that suppression of the primary motor cortex by low-frequency (EMS enhances motor performance with the ipsilateral hand by releasing the not differentiate between the stimulation polarities. nonspe- contralateral motor cortex from transcallosal inhibition. Using cific effects of the stimulation or higher awareness because of tDCS, Fecteau et al. (2007) have recently shown that enhancing stimulation cannot explain the observed effects. DLPFC activity diminished risk-taking behavior, but only when An alternative explanation for the observed effects in coupled with inhibitory modulation over the contralateral experiment I can he stated as follows: Cathodal tDCS of the DLPFC. Intriguingly, Koenigs et al. (2007) have also shown that aPFC did not have an effect on deception per se but on a lesion of the PFC. leads to an increase of utilitarian moral cognitively demanding tasks in general. Because telling lies is decisions. An increase in antisocial behavior following PFC cognitively more demanding than telling the truth, one might impairment is supposed to result from a release of limbic areas suspect that this is the main reason why an effect was found. from PFC executive control (Moll et al. 2005). However, it is Thus. DC stimulation