EFTA02672340

Cerebral Cortex Advance Access published May 14, 2009 The Truth about Lying: Inhibition of the Anterior Prefrontal Cortex Improves Deceptive Behavior Recent neuroimaging studies have indicated a predominant role of the anterior prefrontal cortex (aPFC) in deception and moral cognition. yet the functional contribution of the aPFC to deceptive behavior remains unknown. We hypothesized that modulating the excitability of the aPFC by transcranial direct current stimulation (tDCS) could reveal its functional contribution in generating deceitful responses. Forty-four healthy volunteers participated in a thief role- play in which they were supposed to steal money and then to attend an interrogation with the Guilty Knowledge Test. During the interrogation, participants received cathodal, anode], or sham tOCS. Remarkably, inhibition of the aPFC by cathodal tOCS did not lead to an impairment of deceptive behavior but rather to a significant improvement. This effect manifested in faster reaction times in telling lies, but not in telling the truth, a decrease in sympathetic skin-conductance response and feelings of guilt while deceiving the interrogator and a significantly higher lying quotient reflecting skillful lying. Increasing the excitability of the aPFC by anode] tDCS did not affect deceptive behavior, confirming the specificity of the stimulation polarity. These findings give causal support to recent correlative data obtained by functional magnetic resonance imaging studies indicating a pivotal role of the aPFC in deception. Keywords: frontal cortex• lie detection, moral cogrXtion, neutoethics. conductance response (SCR), transcranial direct current stimulation 000S, Introduction Deception is a complex cognitive act, with crucial legal, moral, and social implications. Functional magnetic resonance imaging (fMRI) studies on neural correlates of deception have shown that the prefrontal cortex and the anterior cingulate cortex (ACC) were more strongly activated during lying than during telling the truth (Lee et al. 2002; Ganis et aL 2003). Recent knowledge about characteristic brain activation sites during deception enabled to recognize false statements with a pre- cision between 88% and 99% (Davatzikos et al. 2(05). Canis et al. (2003) demonstrated that the anterior prefrontal cortices (aPFCs; BA 9/10) were engaged during general deception, but that the right aPFC was more involved in lies that were well rehearsed and were part of a coherent story than in spontaneous. noncoherent tics, whereas the ACC was more active during spontaneous generation of nonmemorized lies. In a recent positron emission tomography (PET) study, Abe et al. (2007) differentiated between the process of generating untruthful responses and the social intention to deceive an interrogator. The main effect of generating untruthful responses revealed increased brain activity of the left dorsolat• Ahmed A. Karim", Markus Schneider", Martin Lotze". Ralf Veit', Paul Sauseng", Christoph Braun' and Niels Birbaumer" '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 scat prefrontal cortex (DLPFC; BA 8) and the right aPFC. whereas the left ventromedial PFC (BA I 1) and Antygdala were associated with the process of deceiving the interrogator. Funher analysis revealed that only the right aPFC was associated with both factors of deception, indicating that this region has a pivotal role in telling lies. Although these findings are quite remarkable, these ncumimaging studies have at least 3 short- comings. Firm, a general problem of neuroimaging techniques like IMItl or PET is that they allow only correlative statements about the brain regions involved in a specific behavior (here deception). Causal relevance can be demonstrated with other methods allowing transient inhibition of conical excitability such as transcranial magnetic stimulation (TMS) (Karim et at 2003; Amedi et at 200t; Karim, Schuler. et at 2004 Knoch et at 2006) or transcranial direct current stimulation (tDCS) (Nitsche and Paulus 2000, 2001; Nitsche. Schauenberg, et at 2003; Knoch et al. 2008; Priori et al. 2008). Second, the functional contrthution of the PIC to deception remains elusive. If, for instance, increased activation of the aPFC reflects cognitive processes involved in withholding the truth, suppression of this region should impair deceptive behavior. However, if increased activation of the aPFC: rather reflects a moral conflict involved in deceiving the counterpart, then suppressing this area should have exactly the opposite effect and 'improve deceptive behavior through behasioral disinhibitlon. Neuroimaging studies on psychopaths, classified as pathological liars, have demon- strated that they have significantly less gray matter in the PFC (Yang et aL 2005) and that they do not show moral dilemma like healthy subjects (Anderson et at 1999). Thirdly. in previous IMRE studies, participants were instructed when to lie and when to say the truth. However, in cognitive processing, there is a crucial difference between a person who decides himself/herself whether to lie or to say the truth, and a person who merely follows the instruction of the investigator to lie for a predefined time in the MIRI scanner and then to say the truth in order to contrast the 2 conditions. The aim of this study was therefore I) to realize an experimental setup, in which participants should decide themselves, which questions they would answer truthfully and which ones with a lie and 2) to investigate the causal contribution of the aPFC in deceptive behavior by modulating the excitability of this brain region through tDCS. Three experiments were conducted to test the specificity of the transcranial stimulation effect. In the first experiment, 22 healthy subjects participated in 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 Guilty Knowledge Test (GKT). In addition to verbal response (truth vs. lie) reaction time (RT). skin-conductance response (SCR) and feelings of guilt while deceiving the interrogator were assessed In a double-blind repeated-measures design, subjects received cathodal or sham tDCS of their aPFC during the interrogation of the mock crime. Furthermore, in order to measure skillful lying. we developed a ratio called "lying quotient (LQ) relating the frequency of lies to critical questions with the frequency of lies to uncritical questions. Skillful lying meant that a person intending to appear innocent should not simply lie on all questions, because this behavior would appear rather suspicious. Instead, as in a real criminal interrogation, the suspects had to decide themselves which questions they would answer truthfully and which ones with a lie. Accordingly, a subject achieved a relatively high LQ if he/ she answered all "critical items" (whose correct answer only the interrogator and the thief knew, e.g., the true color of the wallet) with a lie, but all "uncritical items" truthfully. To increase motivation for deceptive hehavior, participants were told that they were allowed to keep the stolen money in case they could convince the interrogator that they were not guilty. To test the specificity of the applied stimulation polarity and stimulation site, we conducted a second experiment with 22 healthy volunteers in which the stimulation polarity was reversed. For "anodal" tDCS of the aPFC, the anodal electrode was placed over FP2 (international EEG 10/20 system). and the cathodal electrode was placed over PO3 (left parieto-occipital cortex) as a control area. In randomized order, anodal or sham tDCS of the alit was applied during the interrogation Further 20 healthy subjects participated in a third experi- ment, in which the Stroup test (Stroup 1935) was used as a 'contml task' In experiments I and 2. subjects intending to deceive the interrogator had to inhibit the truth as a prepotent response and give instead a deceitful answer. The Stroop task is a widely used index of executive control (MacLeod 1991; Swick and Jovanovic 2002) that tests the ability to inhibit a prepotent response but does not include deceiving the counterpart. Materials and Methods Subjects For experiments 1-3. there were 22, 22. and 20 participants, respectively (I3, 9, and 10 men). The mean age standard deviation was 25.6 4.9. 24.8 3.9 and 26.0 4.0. Each subject participated in only I of the 3 experiments. All subjects were right handed according to the Edinburgh Ilandedness Inventory (Oldfickl 1971). The study was approved by the ethics committee of the Medical Faculty of the University of TUbingen. Subjects were excluded if information from a standardized medical questionnaire suggested prior neurological. psychiatric, or cardiovascular diseases or consumption of centrally acting medication. Parts of these data were previously presented at the 49th Annual Meeting of the Society of Psychophysiological Research in Vancouver, Canada (Karim, Louie. et al. 2006). Experimental Des(gn Experiments I and 2 consisted of a thief role-play, in which money (X) Eums) was stolen and a subsequent interrogation, in which the suspects were asked questions about the course of the mock crime according to the GKT paradigm. The GKT (Lykken 1959, 1960) utilizes a series of multiple-choke questions. each having I true alternative and several false alternatives. chosen so that an Innocent suspect would not be able to discriminate them from the relevant alternative (e.g. 'the color of the stolen wallet was: red? black? brown? blue? gray?'). Thus. if the subject's physiological responses to the relevant alternative are consistently larger than the COMM! alternatives. knowledge about the crime is Inferred (for 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 to pick I of 2 chits of paper from a cup. The subjects were told that on I chit was written 'thief and on the other one "innocent attendee: The subjects were asked to memorize their roles but not to tell the instructor which role they had chosen. After the roles were assigned by drawing lots, the subjects were told to go to an office and wait there for 20 min until the interrogation. This office consisted of a main room and an adjoining room. Both rooms were shown to the subjects before assigning the roles, and they were told that the innocent attendee should wait during the mock crime in the main room, while the thief should go to the adjoining room and search there for money with the intention to steal it. Money could he placed at several locations. Therefiire, the thief should not only search for the money thoroughly hut also as quickly as 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 attend independently of each other 2 interrogations with an investigator who will play the role of a police inspector. In the interrogation. the subjects will be asked questions, which they should answer as quickly as passible with a "yes- or a no, Additionally. the SCR and the RT will be recorded. The subjects were also told that during each of the 2 interrogations. they will receive different types of tDCS. The true 'thief 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 innocent should not simply lie on all questions. because this behavior would appear rather suspicious. Instead, as in a real criminal in- terrogation. the suspects had to decide themselves which questions they would answer truthfully and which ones with a lie. To enhance the motivation of the subjects to identify themselves with their role and to 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 interrogator that they were not guilty. However, in reality, I of the 2 subjects was a collatorator of the experiment, a fax unknown to the subject and on both pieces of paper 'thief was written. hut the collaborator knew that he had to play the role 'innocent attendee: The goal of the investigation was to elucidate, if the subjects would show during cathodal ft-mut-AMA DC stimulation of the aPFC different deceptive behavior titan during anodal or sham stimulation Transcrankd DC Stimulation 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 excitability was diminished by cathodal stimulation, which hyper• polarizes neurons (Terzuolo and Bullock 1956: Creutzfeldt et al. 1962: Bindmann et al. 1964: Cianside 1968). Bindmann et al. (1964) have shown that cathodal stimulation in animals can reduce or completely inhibit spontaneous firing of conical cells. In humans, it has been shown that cathodal stimulation can decrease the excitability of the motor (Nitsche and Paulus 2000; Liebetanz et al. 2002; Nitschc, Nitsche et al 2003), visual (Antal et al. 20)1. 2004) and somatosensory convex (Dlcckh&cr et al. 2(06). In the first experiment, the cathodal electrode was placed over FP2 and the anodal electrode over PO3 according to the international 10.20 EEG system (Fig. la). TICS polarity refers to the right fmntopolar electrode. PO3 was chosen as a reference for 2 reasons: First. to maximize the distance between the cathodal and the modal electrode. 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. 1989 Miranda et at 2006) and second, because previous neumintaging studies did not show that the porktooccipit al cortex (RA 39)K involved in deception (for a review. see Karim et al 2009). A constant current flow of I mA was applied through wet sponge electrodes (4 x 6 cm). and continuous tIDCS was delivered by a battery driven, constant current stimulator (Schneider Electronic. Gleichen, Germany) for 13 min. The interrogation started 3 min after onset of the stimulation and lasted for 8-It) min. so that tlX3 was applied through the whole interrogation but 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 25 Ls'. 5- 0 Lying quotient (LC) 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 stimulation, respectively. During OW'S. voltages of more than approxi- mately 10 V can induce a mild tingling sensation in the skin under the scalp electrodes whereas t [XS at lower voltages is usually not associated with sensory stimulation even in experienced subjects (Hummel et at 2005). Skin resistance gradually declines after the first few seconds of current application. In consequence. the voltage needed to hold constant current decreases and becomes subthreshold for evoking peripheral sensations. For slum tDC.S, placement of the electrodes. current intensity and ramp time was identical to real tDCS: however, the stimulation lasted only for 30 s. The rationale behind this sham procedure was to mimic the transient skin sensation at the beginning of real tOCS without producing any conditioning effects on the brain (Skiver et al 2004: Hummel et at 2005). This method of slum stimulation has been shown to he reliable (Candiga et al. 2006). The interrogator and the subjects were blind to the intervention (toes or slum), which was applied by a separate investigator. 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 system. Current intensity, ramp time. and duration of stimulation were identical to the firm experiment. In the third experiment, the stimulation parameters and stimulation site were identical to the first experiment. The order of real and sham INS was balanced in the 3 experiments. Measurement of the LQ In order to measure skillful lying, we developed a ratio called lying quotient (l.Q): LQ•[(40t IVITA-em) l°11 (I) where No, = Frequency of lies on critical questions. = Total 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 should not simply lie on all questions, because this behavior would appear rather suspicious. Instead. as in a real criminal interrogation. thc suspects had to decide themselves which questions they would answer truthfully and which ones with a lie. In the interrogation. a modified version of the GKT was applied consisting of 10 critical and 7 uncritical questions, each with 4 choices. An uncritical question was a question. whose answer would be known even by an innocent attendee. who has been in the room but did not steal the money (e.g.. .0n the chair in the small room there was a jacket. Was the color of the jacket: green? blue? black? brown?-). In 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). According to formula (I). the IQ can range from -100 to +100. A most skillful liar would have a maximum LQ of 100, if he/she lies on all critical questions. but answers all uncritical questions truthfully. Subjects who decide simply to lie on all questions independently of their relevance to the criminal act will have an LQ of O. A quite odd behavior would be. if a subject answers all critical questions truthfully hut lies on all uncritical questions. In such a case, that subject would get an LQ of -100. Besides having a direct measure for skillful lying, an important advantage of the I.Q Is that it enables us to control for the subjects bias strategies or predisposition to answer almost all questions in an interrogation with a lie or truthfully independently of the fact. if they are critical or not. A subject who deckles to lie on all questions would not admit knowing any critical information. but still would appear dishonest. because he/she denies knowing information, which he/she should know even as an innocent attendee. In contrast to this strategy. another subject might prefer to answer almost all questions truthfully. Such a subject would appear very honest; however, he/she would increase the passibility to he detected as the thief, because he/ she would admit knowing a lot of informations which only the delinquent could have known. Measurement q/ the RT RT was defined as the time between the end of the question and the onset of the answer. Note that the relevant information in the question was always in the last word (e.g- the mkt of the wallet was 'green.' The color of the wallet was law: etc.). Subjects answered the questions 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 Software Corp.. Phoenix, United States). Acoustic information wa digitalized at a 16-bit resolution and a sampling rate of 22 kHz. To determine the acoustic onset of the verbal response, an amplitude filter was used that removed all acoustic signals with an amplitude of less than 7.5% of the maximum sound levet The correctness of detecting the min of each verbal response was checked off-line by making use of the phyhack function of the program. Measurement °flat SCRs were recorded at 16-Hz sampling rate with a commercial ambulatory device (Varioport. Becker Meditec. Karlsruhe. Germany) using standard Ag/AgCl electrodes filled with unibase electrolyte affixed to the left hand. Data were processed off-line in a Matlab environment (Matlab 63. The Mathworks Inc., Natick. .MA). Skin. conductance data were smoothed with a I s Gaussian kernel. The amplitude of SCR was determined as the largest change in conductance between I and 5 s after task onset, relative to the preceding smallest value in the interval. For statistical analysis, SCRs were log transformed (log(M:R + 1)). Measurement of tbe Feelings of Guilt white Decent* the Interrogator At the end of each interrogation. the subjects were asked to rate their 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 feelings of guilt). Stroop Task To test the possible effect of cathodal tDCS on executive prefrontal functkm (i.e.. the ability to inhibit a prepotern response), participants 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 colored Ink and asked to name the color of the ink as quickly as possible. 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. 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 Preceding each trial, a fixation cross was shown Inc 2s. The trial interval was constant with a duration of 2 s. After the participants resistive, the screen became black fox• the n-st of tlw trial interval. Results Experiment 1 Interestingly, if only the number of lies was compared between cathodal and sham tlX:S. no significant difference was found between the 2 conditions (1 = 1.768, P = 0.092). However, concerning the I.Q. subjects achieved in the stimulation condition a significantly higher LQ than in the sham condition (f = 2.254, P = 0.035), meaning that the answers given in the interrogation during cathodal tIXS were less likely to reveal their guilt, than the answers given during slum stimulation (HS- A repeated-measures analyses of variance (ANOVAjtm) with Stimulation Camditiono.shoda locs,,sum ion) and Rtsponsew.„,h, jk) as within-subject factors and Reaction Time as dependent 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 (FL,s; = 7.037, P 0.020; Fig. 2€0. Posthoc I tests showed that during sham tDCS. the RT for lying was significantly longer than for truthful responding = 2.568. P= 0.018). However, during cathodal tDCS, the RT was significantly shorter for telling lies Os 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 ANOVARsj with Stimulation conditionkaihnaa tin:opium ft/CV and Responsew.,,,k,sO as within-subject factors was conducted. Again, no significant main effects were found (for Stimulation Condition: F,.2, = 1.908, P= 0.191; for Response: Fuj = 3.216, P = 0.096) hut a significant interaction between the 2 factors (Ful 6.287, P. Posthoc ttest revealed that in the sham condition, the SCR for lying was significantly higher than for saying the truth (I . 3.029. P 0.008). However, in the stimulation condition, this difference in SCR between lies and truthful responses disappeared (I= 0.626, P= 0.539; Fig. 2b). To further investigate the effect of cathodal tDCS of the aPFC, on the subjective experience of guilt, subjects were asked at the end of the interrogation to rate their feelings of guilt, which they might have experienced during the in- terrogation, on a scale from 0 (no feelings of guilt) to 5 (maximum feelings of guilt). Wilcoxon signed-rank test revealed that cathodal tIX'S of the aPR: led to significantly lower feelings of guilt than in the sham condition (r. -1.986, P 0.047; Fig. 2c). Moreover, a Kendall•s tau correlation a 900 aco EE tc tc b 700 603 503 Reaction time —O- Sham —6— Cathodal Thith tie Skin conductance response 7,4 o 1.2 a 1 6 oti ns 9). 0,6 0,2 0 Troth W Truth FeeIn(0 of guilt Cl S 4 3 2 1 0 0 Shall) ■ Cath0dat Feelings of guilt Sham Cathodal Figaro 2. Hens of cathodal uansaanial DC stimulation of the arrC on RI (a). smoothen SCR lei. and on feehigs of guilt (C) Mien subjects tell lies n an intenogation of a mock crime. Eria ham denote SEM. 'P < 0.05 analyses revealed a significantly negative correlation between the change of feelings of guilt (cathodal condition minus sham condition) and the change of the LQ (t = -0.386, P= 0.023), indicating that the less feelings of guilt subjects perceived, the better could they deceive during the interrogation. Experiment 2 In order to exclude the possibility that the observed effects were only due to nonspecific effects of the electrical stimulation and not specific to the inhibition of the aPR: by "cathodal" DC stimulation, we conducted a second experiment in which the experimental design was identical to the first experiment but the stimulation polarity was reversed. In contrast to the first experiment, anodal ti)CS of the aPFC did not lead to a significant change of the LQ 0.51. Ps 0.61% Fig. 3). An ANOVA" with Stimulation ConditiOnommw IIXSishan IO(,) and Response"„„hait) as within-subject factors and Reaction Time as dependent variable revealed no significant main effects (for Stimulation Condition: F,,21 = 0.209. P 0.652; for Response: = 2.833. P = 0.107) and no significant interaction between the 2 Factors (F,2, = 2.972, P = 0.099; Fig. 4a). To analyze the effect of anodal tDCS on sympathetic sat, a further ANOVARm with Stimulation Conditionowaat ants, tots) 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 25 20. 8 co 10 a 5t. 5- 15- 0 Lying quotient (LQ) ns 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 900 I 800 - 0 700 - ti 600 503 Sham A octal • Truth Lie b Skin conductance response 1,4 ea co 12 - a 5 OA - to 4. - OA - 1° 02 - 0 C Feelings of guilt r ns 45 I 3 2 0 Truth O Sham Lie Trutt Feelings of guilt ns ■ Modal Lie Sham Modal Figure 4. fleets of anodal transcranal DC stimulation of the aPEC on AT sympathetic SCR Oh and on feelings of guilt (c) when subjects tee lies in an interrogation al a mock crime. Error bars denote SEM sP < 0.05. The Response (lie vs. truth) revealed a significant main effect on SCR (Pia, = 38.190. P < 0.001); however, the Stimulation Condition (anodal tDCS vs. sham tDCS) had no effect on SCR (Fin = 1.164. P= 0.298), and no significant interaction (Al , = 0.009, P= 0.926) was found between Stimulation Condition and Response (Fig. 4b). Also concerning the feelings of guilt that subjects might have experienced while deceiving the in- terrogator, in contrast to the first experiment, anodal tDCS did not lead to a significant change of the subjective experience of guilt (z = -1.89, P= 0.05% Fig. 4c). Experiment 3 We tested a possible impact of cathodal tDCS of the aPFC on general prefrontal executive function by using the Stroop test as a control task. An ANOVA" with StimulatkniCondition(„ h,44 imsy mni in", and Stroop Conditiorkamgmenyhwonwom,) as within- subject factors revealed a significant main effect of the Stroup Condition on RT = 46.109, P < 0.001). However, the Stimulation Condition had no effect on RT (Fit%) = 1.050. P= 3.18), and no significant interaction (F1,,9 = 1.593, P1222) was found between Stimulation Condition and Strom) Condition (see Fig. 5). Discussion This study demonstrates for the first time that cathodal transcranial DC stimulation, which has been repeatedly shown to suppress conical excitability (Nitsche, Nitsche. et aL 2003: Antal et al. 2004; DieckhOfer et at 2OO6) can modulate deceptive behavior. Moreover, our findings give causal support to recent correlative data obtained by neuroimaging studies indicating a predominant role of the aPFC in deceptive behavior (Lee et al. 2002: Ganis ct al. 2003; Abe et al. 2007). Whereas in previous studies on neural correlates of deception participants were instructed when to lie and when to say the truth, in the present study, subjects could decide themselves which questions they would answer truthfully and which ones 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 cathodal tDCS did not lead to impairment but rather to a significant within-subject improvement of deceptive behav- ior. This effect was expressed in faster RTs for telling lies, but not for telling the truth, a decrease in sympathetic SCR and feelings of guilt white deceiving the interrogator and a signif- icantly higher EQ. which reflects skillful lying. In order to exclude the possibility that the observed effects were only due to nonspecific effects of the electrical stimulation and not specific to the inhibition of the OR: by cathodal DC stimulation, we conducted a control experiment in which the stimulation polarity was reversed. Our data show that shorter RTs in telling lies compared with telling the truth and the absence of increased SCR while deceiving the interrogator were confined to cathodal UM'S of the aPH: and were not detectable during sham tDCS or anodal tDCS. Because subjects were blinded to the stimulation condition and could ("Antral ("Ann Pep 5 al 9 EFTA_R1_01945412 EFTA02672344 pco poo 700 re 600 ns 1— As — I Sham Cathodal Congruent Sham Cathodal Incongruent Figure 5. Cathodal transcianal OC stimulation of the aPIC has no effect on RT in the Snoop task. Error tars denote SEM. not differentiate between the stimulation polarities. nonspe- cific effects of the stimulation or higher awareness because of stimulation cannot explain the observed effects. An alternative explanation for the observed effects in experiment I can he stated as follows: Cathodal tDCS of the aPFC did not have an effect on deception per se but on cognitively demanding tasks in general. Because telling lies is cognitively more demanding than telling the truth, one might suspect that this is the main reason why an effect was found. Thus. DC stimulation would have affected any other cognitively demanding task in a similar manner. To exclude this possibility. we conducted a third experiment with the Stroop test as a control task. Our results demonstrate that although the incongruent condition is cognitively more demanding than the congruent one. cathodal tDCS of the aPFC had no effect on performance, suggesting a specific effect on deceptive behav- ior and not on cognitively demanding tasks in general. The intriguing question that remains is why did cathodal tDCS lead to "improvement" of deceptive behavior and not to its impairment? Recent neuroimaging studies have emphasized that the aPFC (BA 9/10) plays a crucial role in moral cognition (Greene et al. 2001; Moll et al. 2002. 2005). Moll et al. (2002, 2005) found increased activation of the aPFC when a moral judgment condition was compared with a nonemotional factual judg- ment, but not when moral judgments were compared with a social emotional condition, during which a more ventral region was activated. Greene et al. (2001) used a moral judgment task that involved classic moral dilemmas (e.g., should you kill an innocent person in order to save 5 other people?) and found increased activation of the aPFC during emotionally loaded moral judgments. Moreover, neuroimaging studies have also emphasized the importance of the aPK: in social interaction (Stuss et al. 2001: Decety and Sommerville 2003; Amodio and Frith 2006; ticathenon et al 2006; Rains and Yang 2006). Ileathenon et al. (2006) have shown that making judgments about the self relative to an intimate other selectively activates the aPFC. Stuss et al. (2001) have demonstrated on patients with limited focal frontal and nonfrontal lesions that the frontal lobes are necessary for "theory of mind; which includes inferences about feelings of others and empathy for those feelings. The anterior pm:, the ventral PFC. and the amygdala are regions that have been shown to be involved in both antisocial behavior and moral decision making (Rain and Yang 2006). Taking these findings into account, the aPFC seems to he crucially involved in sock,- emotional judgments Suppressing the excitability of this region or focal lesions should therefore show an impact on antisocial and moral behavior. In respect to our study, deceiving another person in order to obtain personal profit seems to create a moral conflict, and if a person is relieved from this moral conflict, he/she might be able to deceive unhinder- ed!), with faster RT, less feelings of guilt and less sympathetic arousal as demonstrated here. Suppressing conical excitability by cathodal tDCS or low-frequency repetitive transcranial magnetic stimulation (rTMS) has previously been shown to induce so-called paradoxical improvement of performance through "disinhibition" processes (11ilgetag et al. 2001; Kobayashi et al. 2004: Fecteau et al. 2007). Kobayashi et al. (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 contralateral motor cortex from transcallosal inhibition. Using tDCS, Fecteau et al. (2007) have recently shown that enhancing DLPFC activity diminished risk-taking behavior, but only when coupled with inhibitory modulation over the contralateral DLPFC. Intriguingly, Koenigs et al. (2007) have also shown that a lesion of the PFC. leads to an increase of utilitarian moral decisions. An increase in antisocial behavior following PFC impairment is supposed to result from a release of limbic areas from PFC executive control (Moll et al. 2005). However, it is not the aim of this study to state that the aPFC is the only cortical region, whose stimulation can modulate deceptive behavior. Ncuroimaging studies have indicated that also other conical areas, especially the DLPFC (Phan et al. 2005; Abe et al. 2006, 2007) and the superior temporal sulcus (Phan et al. 2005) are also involved in deception and that in different types of deception (e.g., lies that arc rehearsed and part of a coherent story vs. spontaneous noncoherent lies) different cortical networks arc involved (Canis et al. 2003; Abe et al. 2007). Priori et al. (2008) have recently demonstrated that tDCS of the IX.PFC alters RT in deception of experienced events but had no effect on RI's in deception of new events. Thus, future studies will have to investigate the effect of stimulation of different conical areas in different types of lies and the duration of these effects in relation to the stimulation parameters. A further interesting question is, why anodal tDCS, which has been shown to increase cortical excitability (Gartskle 1968; Nitsche and Paulus 2001: Antal et al. 2004), did not lead to opposite effects compared with cathodal tlX:S resulting in an impairment of deceptive behavior and an increase of feelings of guilt while deceiving the interrogator? Although our data show that concerning the 1.Q and feelings of guilt there is a tendency toward lower LQ and higher feelings of guilt during anodal tDCS compared with sham tlX:S (cf. Figs 3h and 4c), these changes did not reach significance. It is plausible to assume that disruption of the PFC can have an effect on social cognition (Anderson et al. 1999), moral reasoning (Koenigs et al. 2007), or even on deception as shown in the present study, however, increasing the excitability in a 'normal functioning" PFC does not necessarily have to lead to opposite effects presumably due to ceiling effects. However it is tempting to test in patients with "impaired" PFC if increasing conical excitability by anodal tDCS can help to remedy functional deficits. In transcranial stimulation studies, positioning the 131S coil or the tDCS electrodes can provide a great challenge. Although in tDCS studies positioning the relatively large electrodes (about 4 x 6 cm) according to the international 10-20 EF.G system is a very common method (s. Knoch et 21 2006; Fecteau ct al. 2007: Priori et al. 2008). Herwig et at. (2003) have shown Pimps 6 al 1 histition or the est: imprints tktepthv kri/I S EFTA_R1_01945413 EFTA02672345 that for TMS studies, positioning the more focal figure-of-eight TMS coil according to the 10-20 EEG system Ls reliable when dealing with larger scale conical areas, Thus, for stimulating a relatively large and well-defined conical region u the aPFC stereotaxic neuronavigation systems are certainly not neces- sary. In a PET study, Lang et al. (2005) have placed the tDCS electrodes over the primary motor cortex (identified by inducing motor evoked potentials with TMS) and over the right fronto-polar cortex (directly above the right eyebrow) and found the highest increase in regional cerebral blood flow below the stimulating electrodes in the primary motor cortex and the aPFC. Moreover, Okamoto et at (2004) established recently for transcranial stimulation studies a correspondence between the 10-20 EEG system and magnetic resonance imaging based stereotaxic space (Talairach coordinates and the standard template of the Montreal Neurological Institute) and expressed the anatomical structures for the 10-20 conical projection points probabilistically. Their findings show that despite interindividual variance in the structure of the pre- frontal cortex, the electrode position over 172 is with a 100% probability in BA 10. Taking these findings into account. positioning the tf/CS electrode over FP2 stimulates mainly BA 10. hlowever, due to the use of relatively large electrodes (4 x 6 cm) to prevent heating artifacts, stimulation of the junction to BA9 has to be considered as well. Nitsche and Paulus (2000) have shown that a minimum current density of 0.017 mA/cm2 is necessary to modify cortical excitability by tDCS in humans. The applied current density of 0.04 mA/cm2 in this study is in accordance with several tDCS studies demonstrating functionally relevant modulating effects on cortical excitability (cf. Hummel ct al. 2005; Nitsche et al. 2007). One might further suspect that the 3D pattern of brain sulci and gyri might create an overall change in current polarity in the targeted brain areas. However, current density calculations from our laboratory (Rockstroh et al. 1989) and from other research groups (Rush and Driscoll 1968; Miranda et al 2006) as well as direct intracellular measurements of DC stimulation (Purpura and McMurtry 1965) revealed an average current flow in the expected direction independent of single sold and gyri. The findings of the present study are also particularly interesting in the light of clinical evidence suggesting that psychopaths, who arc classified as pathological liars, have significantly less gray matter in their PFC (Yang et al. 2005) and. remarkably, do not show higher SCR when telling lies (Verschuerc ct al. 2005). We have previously demonstrated that in psychopaths limbic-prefrontal regions (amygdala, orbitofrontal cortex, insula, and the anterior cingulate), and SCR during anticipation of aversive events Ls pathologically reduced (Veit et al. 2002; Birbaumer et al. 2005). In a social reactive aggression paradigm. Lour: et al. (2007) have shown that during retaliation, subjects with high psychopathic scores had less BA 9/10 activation in comparison to subjects with low psychopathic scores. These findings are in accordance with the results of other research groups reporting decreased prefrontal blood flow (for a review, see Blair 2007) and deficient autonomic responses, for example, SCR, in anticipation of threatening events (Blair et at 1997; Hare et al. 1978). Moreover, several studies (Anderson et at 1999: Moll et al. 2005) have also shown that in psychopaths and patients with aPFC lesions, moral cognition is impaired. Thus, our findings support the hypotheses that a dysfunction of the aPFC and its specific connections may underlie certain psychopathological conditions that are characterized by the absence of sympa- thetic arousal while performing a wrongful act such as deceiving in a criminal interrogation. Finally, concerning the current debate on emerging ethical issues in neuroscience (cf. Farah 2002), interdisciplinary research and communication are needed to address the following question: If neuroscientific research can demonstrate that deceptive behavior and moral cognition are not only associated with the activation of specific brain areas, but may even be modulated by noninvasive stimulation of these areas, what implications will such findings have on our concept of personal responsibility and neurocthical applications? Funding The Deutsche Forschungsgemein.schaft (DFG) and the Volks- wagen Foundation. European Platform for Life Sciences, Mind Sciences, and the Humanities. Notes We thank ). Iktx and C Sheridan fur their support and C Dockery for participating in the SCR analyses. also thank R. Sitararn and B. Kotchoubey for valuable discuz ions. Cotylla (finteresf: None declared. Address correspondence to Ahmed A. Karim, Institute of Medical Psychology and Behavioral Neurobiology. University of Tuebingen. Gartenstrasse 29, 72074 Tuebingen. Germany. Email: ahmedkarim uni-webingentle. References Abe N, Suzuki M. Mod E. Itoh M. Fujii T. 2007. Deceiving others: distinct neural responses of the prefrontal cortex and arnygdala in simple fabrication and deception with social interactions.) Cogn Neurosci. 19:287-295. Abe N. Suzuki M. Tsukiura T. Mori F. Yamaguchi K. Itoh M. Fujii T. 2006. Dissociable roles of prefrontal and anterior cingulate cortices in deception. Cereb Cortex. I6t192-199. Anted' A. noel A. Knecht S. FL. Cohen LG. 2004. Transcranial magnetic stimulation of the occipital pole Interferes with verbal processing in blind subjects. Nat Neurosci. 7:1266-1270. Amodio DA. Frith CD. 2006. Meeting of minds the medial frontal cortex and social cognition. Nat Rev Neurosci. ":268-277. Anderson SW, Bechara A, Damasio II, Tranel D, Damasio AR. 1999. Impairment of social and noel behaviour related to early damage in human prefrontal cortex. Nat Neurosci. 2:1032-1037. Antal A. Kincses TZ, Nitschc AN. Banfai 0. Paulus W. 2004. Excitability changes Induced In the human primary visual cortex by transeranial direct current stimulation: direct electrophysiological evidence. Invest Ophthalmol vis Sci. 45:702-707. Antal A, Nitsche MA. Paulus W. 2001. External modulation of visual perception in humans. NeuroReport. 12:3553-3555. Ben•Shakar G. Elaad E 2003. The validity of psychophysiological detection of information with the guilty knowledge lest; a meta. analytic review.) April PsychoL 88:131-151. Bindmann IJ. lippold OC, Redfern JW. 1964. The action of brief polarizing currents on the cerebral cortex of the rat (I) during current flow and (2) in the production of long-lasting after effects.) PhysioL 172:369-382. Birbaumer N. Veit R, 1.042C N. Erb NI, Hermann C. Grodd W. Floc It 2005. Deficient fear conditioning in pnychopathr a functional magnetic resonance imaging study. Arch Gen Psychiatry. 62:799-805. Blair RJR. 2007. The antygdakt and ventromedial prefrontal cortex In morality and psychopathy. Trends Cogn Sri. 11:387-392. Blair RJR, Jones I. Clark F, Smith N. 1997. The psychopathic Individual: a lack of responsiveness to distress cuts? Psychophysiology. 34:192-198. rattal Cain Page 7 919 EFTA_R1_01945414 EFTA02672346 Creutzfeldt ()D. Fromm GIL Kapp H. 1962. Influence of tran.sconical d•c currents on corneal neuronal activity. Exp Nemo]. 5,436-452. Davatziken C, Ruparel K. Fan Y, Shen DG. Achanya M. Loughead JW. Gur RC, Langkiwn 1)0. 2005. Classifying spatial patterns of brain activity with machine learning methods: application to lie detection. Neurolmage. 28663-6(8. Decety J, Sommerville JA. 2003. Shared representations between self and Othef: a social cognitive neuroscience view. Trends Cogn Sci. 7:527-533. DieckhOfer A. NX'aberski TI). Nitsche M. Paulus W, Buchner H, Gohhele R. 2006. Tran.scranial direct current stimulation applied over the somatosensory cortex—differential alien on low and high frequency SEPs. CAM Ncuroplusiol. 117:2221-2227. Farah Al). 2002. Emerging ethical issues in neuroscknce. Nat Neurosci. 5:1123-1129. Fectrau S. Knoch D. Fregni F. Sultani N. Bogle° P. Pascual-Leone A. 2007. Diminishing risk-taking behavior by modulating activity in the prefrontal cortex: a direct current stimulation study. J Neurosci. 27:6212-6218. Gandiga PC, Hummel R:. Cohen LG. 2006. Transcranial DC stimulation (tDCS) a tool for double-blind sham-controlled clinical studies in twain stimulation. CUM Neurophysiol. 117:845-850. Gans G. KaSSIITI SM. SCOW S. Thompson WI, Yurgelun-Todd DA. 2003. Neural correlates of different types of deception: an 1/4111 investigation. Cereb Cortex. 13:830-836. Ganslde Ili. 1968. Mechanisms of sustained increases of firing rate of neurones in the rat cerebral cortex after polarization: rote of protein synthesis. Nature. 220.383-384. Covent JD. Sommerville RB, Nystrom I.E. DarleyJNI, Cohen JD. 2001. An 111181 investigation of emotional engagement in moral judgment. Science. 293:2105-2108. Hare RD.FrazelleJ.Cos ON. 1978. Psych t ;pathy and ptivsiologjc•al responses to threat of an aversive stimulus. Psychophysiology. 15:165-172. Ileatherton T, Wykugl CL Macrae (:N. Demos KE, Denny Br, Kelley WM. 2006 Medial prefrontal activity differentiates self from close others. SCAN. 1:18-25. Ilerwig U, Satrap" P, Schoenfeldttecuona C. 2003.1).01g the 10.20 EEG system for positioning of transcranial magnetic stimulation. Brain Topogr. 1695-99. I lilgetag CC, Theme( II, Pascualleont A. 2001. Enhanced visual spatial attention imilateral to ff.MS•Indueed 'virtual lesions of human parietal cortex. Nat Neurosci 4:953-957. Hummel F, Celnik P. Giraux P. Heel A. Wu WIL Gerloff C. Cohen LG. 2005. Effects of noninvasive conical stimulation on skilled motor function in chronic stroke. Brain. 128:490-499. Karim AA. Kammer T, Loire M, Ilinterberger T. God& B, Cohen I.. Birbaumer N. 2003. Effects of repetitive transeranial magnetic stimulation (rTMS) on slow cortical potentials (SCP). Stipp' (Ain Neurophysiol. 56331-337. Karim AA. Lane Al. Schneider M. Weber C, Braun C. Birbaumer N. 2006. Inhibition of the anterior prefrontal cortex improves deceptive behavior. Psychophysiology. 43,550. Karim AA, Schneider M, Krippl M. Birbaumer N. 2009. Neurobiology of deception. In: Midler JL editor. Neurobiology of forensic disorders. Stuttgart: Flogrefe. Forthcoming. Karim AA, Schuler A, Hegner VI., Friedel E, God& B. 2006 Facilitating effect of I5-liz repetitive transcranial magnetic stimulation on tactile perceptual learning. J Cogn Neurosci. 18:1577-1585. Knoch D, Nitsche MA. Richbacher U. Elsetwgger C, Pascual-Leone A, Fehr E. 2008. Studying the neurobiology of social interaction with transcranlal direct current stimulation—the example of punishing unfairness Cereb Cortex. 181987-199). Knoch f), P-asctd.Leone A. Meyer K, Treyer V, Fchr E. 2006. Diminishing reciprocal fairness by disrupting the right prefrontal cortex. Science. 314:829-832. Kobayashi M. Hutchinson S, Theoret FL Schlaug G. Pascual.Leone A. 2004. Repetitive 'EMS of the motor cortex improves Unilateral sequential simple finger movements. Neurology. 6291-98. Koenigs M, Young I., Adolphs R. Tranel D. Cushman F. Hauser M. Danusio A. 2007. Damage to the prefrontal cortex increases utilitarian moral judgements. Nature. 446908-911. Lang N. Siebner HR. Wan) NS. Lee L. Nitsche MA. Paulus W. Rothwell)(:. Lemon RN, Frackowiak RS. 2005. How does transcranial UC stimulation of the primary motor cones alter regional normal activity in the human brain? For ) Neumsci. 22:495-504. Lee Tide,. Liu II-L, Tan 141, Chan CCI I, Mahankali S. Peng CM. lion J. Fox PT, Gao J.H. 2002. lie detection by functional magnetic resonance Imaging. Hum Brain Mapp. 15:157-164. Liebet‘uu D, Nitsche MA. Tergau E Paulus W. 2002. Pharmacological approach to the mechanisms of transcranial DC.stimulation.induced aftereffects of human motor cortex excitability. Brain. 125: 2238-2247. Laze NI, Veit R. Anders S. Birbaumer N. 2007. Evidence for a different role of the ventral and dorsal medial prefrontal cortex for social reactive aggression: an interactive 174121 study. Neurolmage. 34470-478. Lykken DT. 1959. The GSR in the detection of guilt. ) Appl Psycho. 431385-388. Lykken DT. 1960. The validity of the guilty knowledge technique: the effects of faking.) Appl Psycho'. 44:258-262. MacLeod CM. 1991. Half a century of research on the Stroop effect: an integrative review. Psychol Bull. 109:163-203. Miranda PD, 1.O111211IN NE Hallett M. 2006. Modeling the current distribution during transcranial direct current stimulation. Gin Neurophysiol. 117:1623-1629. Moll ), de Oliveira-Souza R, Eslinger PJ, Bramati MouraiMiranda J. Andrciuolo PA, Pessoa L 2002. The neural correlates of moral sensitivity: a functional magnetic resonance imaging investigation of basic and mural emotions. J Neurosci. 22:2730-2736 Moll J, Zahn R. de ()Ilveira.Soura R, Krueger F, Grafman J. 2005. The neural basis of human moral cognition. Nat Neurosci. 6799-809. Nitsche MA. Docinkes T, Karaite's*: A. Antal A. Lkbetanz D. Lang N. Tergau E Paulus VV. 2007. Shaping the effects of transcranial direct current stimulation of the human cortex. J Neurophysiol. 97:3109-3117. Nitsche MA. Nitsehe MS. Klein CC. Tergau F. Rothwell JC. Paulus W. 2003. Level of action of cathodal DC polarisation induced inhibitkm of the human motor cortex. Gin Neurophysiol 114:600.6(4. Nitsche MA. Paulus W. 2000. Excitability changes induced in the human motor cortex by weak transcranial direct current stimulation. J Physic'. 527633-639. Nitsehe MA, Paulus W. 2001. Sustained excitability elevations induced by transcranial DC motor cortex stimulation in humans. Neurology. 57:1899-1901. Nitsche MA. Schaucnburg A, Lang N. Lictocianz D, Exncr C, Paulus W. Tergau F. .B1(13. Fascilitation of implicit motor learning by weak transcranial direct current stimulation of the primary motor cortex in the human.) Cogn Neurosci. 15:619-626. Okamoto 31, Dan IL Sakamoto K. Kazuhiro T. Shimizu K, Kohono S. Oda I, Isobe S, Suzuki T. Kohayama K, et al. 2004. Three-dimensional probabilistic anatomical carnio-cerebral correlation via the in- ternational 10-20 system oriented for transcranial functional brain mapping. Neuroimage. 21:99-Ill. Oklfield R(:. 1971. The assessment and analysis of handedness: the Edinburgh Inventory. Neuropsychologia 9:97-113. Phan KL, Slat/011am A. Ziemlewicz 1). Fitzgerald DA. Green C. Smith W. 2005. Neural correlates of telling lies: a functional magnetic resonance imaging study at 4 Tesla. Acad Radio]. 12:164-172. Priori A. Mameli (:ogiamanian F. Alaneglia S. Tiriticco N. Mrakic- Sposta S. Fermi:el K. Zago S. Poleax' I). Sartori G. 2008. Lie-specific involvement of dorsolateral prefrontal cortex in deception. Cereb Cortex. 18451-455. Purpura DP. Ale:Munn JG. 1965. Intracellular activities and evoked potential changes during polarization of motor cortex, J Neuro. physiol. 28166-1'85. Raine A. Yang Y. 2006. Neural foundations to moral reasoning and antisocial behavior. SCAN. 1:203-213. Rockstroh B, Elbert T. Canavan A. Lutzenberger W. Birbaumer N. 1989. Slow conical potentials and behaviour. Baltimore (MD) Urban & Schwarzenherg, Rush S, Driscoll DA. 1968. Current distribution in the brain from surface electrodes. Anesth Anal?, 47:717-723. Pap I el Inhibition ri the 4'W sums°, necePtiw fiehmor • Katu o al EFTA_R1_01945415 EFTA02672347 Siebuer HR. Lang N. Rizzo V. Nitsche MA. Paulus W. Lemon RN. Bothwell JC. 2004. Preconditioning of low•frequency repetitive transcranial magnetic stimulation with transcranial direct current stimulation: evidence for homeostatic plasticity in the human motor cortex. J Neuronci. 24:3379-3385. Mroop JR. 1935. Studies of interference in serial verbal reactions.) Exp Psychol. 186,13-662. Muss DT, Gallup CC, Jr., Alexander MP. 2001. The frontal kites arc necessary for 'theory of mind'. Brain. 124:279-2/46. SwIck D. Joranmic J. 2002. Anterior cingulate cortex and the Strum task: ncuropsychological evidence for topographic specificity. Neuropsychologia. 40:1240-1253. Terzuolo CA. Bulkx:k M. 1956. Measurement of imposed voltage gradient adequate to modulate neuronal firing. Proc Natl Acad Sci USA. 42:687-694. Veit R. Hot H. Erb M. Hermann C, Loin M. Grodd W, Birbaumer N. 2002. Brain circuits involved in emotional learning in antisocial behavior and social phobia in humans. Neurosci Lett. 328: 233-236 Verschuere B, Cromhez De Cercry A, Koster Ell. 2005. Psychopathic traits and autonomic responding to concealed information in a prison sample. Psychophysiology. 42:239.245. Yang Y. Rains A. Lencz T. Mule 5, I:teas:4c 1, Collctti P. 2005. Prefrontal white matter in pathological liars Br J Psychiatry.. Ceitheal Conn Page 9 of 9 EFTA_R1_01945416 EFTA02672348