About 18 months ago, researchers from MIT reported that our sense of morality can be manipulated using transcranial magnetic stimulation of the right temporo-paietal junction: http://bit.ly/cZc2xf
Now, Estonian researchers report that TMS targeted to the dorsolateral prefrontal cortex can also influence our willingness to tell spontaneous lies: http://gu.com/p/328bf/tw
Here's more from Talis Bachmann, senior author of the study (lightly edited for clarity). According to his website (http://www.bachmannlab.com/?page_id=34
), Bachmann pioneered investigations of the neural correlates of consciousness back in the mid-1980s.Mo Costandi: You observed inter-hemispheric differences in the effects of DLPFC stimulation. How do you explain these differences?Talis Bachmann
: Indeed, although the effect was quite weak, there were differences suggesting that slow-paced rTMS directed at left DLPFC slightly increased the relative share of the untruthful responses and right DLPFC stimulation decreased "lying" a bit. Unfortunately we do not have any good explanation and one can only speculate. I doubt that we targeted the cortical "mechanism of lying" in the right hemisphere; this would be highly unlikely. First, lying behaviour is a varied, context-dependent behaviour, involving activity in many different functional subsystems. A small localized "spot" in brain could not be responsible. Second, before we complete additional necessary experiments to see whether the effect is unilateral (right or left) or depends on bilateral interaction, we cannot restrict our list of possible explanations. Third, the sample was small (16) and in a small experiment we cannot fully exclude some "fluke" effect. Additionally, as the left brain is the verbally talking brain, direct left-DLPFC efects and/or inter-hemispheric carry over effects between right and left cortex may have lead to easier untruthful verbalizations in one experimental condition. MC: Do your findings tell us any more about the neural circuitry involved in deception?TB
: Maybe the useful tip from our study is that when we further study the DLPFC effect with various different tasks and deception contexts then we will see what role the circuitry subserving simple, perception based counterfactual statements might play among the other brain mechanisms involved in deceptive behaviour. In these studies, in addition to stimulation protocols also 3D brain-imaging (fMRI, MEG, LFP or other invasive electrode methods with neurological patients) should be used to really see what and where happens in response to the stimulus and in preparation of the deceitful versus truthful response. As fMRI may be too slow, a combined MEG/TMS study would be good. However, unfortunately, and almost by definition combining MEG and magnetic brain stimulation is a tricky business, if at all possible in a fruitful way. But if you allow me to speculate again, our pet (not intended!) explanation is something like this: as earlier research has shown that subduing functionality of the right DLPFC impairs cognitive control then automaticity of responding to stimuli might be increased. As a result more overlearned, "easy" responses are utteres. By all means, people tend to be earnest rather than liars. (Of course, if a sample of pathological liars with "automatism of lying" could be available, an interesting repeat of our experiment would be in the order of the day.MC: How are you continuing with this work?TB
: The obvious experiments are (1) a replication study; (2) instead of the inhibitory TMS effects use excitatory stimulation to hope reverse the results;(3) change the lying contexts and motivation burden to test for the generality of the effect; (4) vary stimulation intensities; and (5) cortical targets to see functional and neuroanatomical peculiarities of the putative effect, etc.MC: Your findings suggest that TMS could be used to increase the likelihood of truth-telling in the courtroom, or when someone is being interrogated. Could it be applied in this way in the near future? And would it be ethical to use the technology in this way?TB
: Unless the legal regulations are worked out, harmonized also in legislation internationally, and until the effects of TMS on lying will be reliable and methods standardized, and before the brain mechanisms plus possible adverse effects are thoroughly established and systematized, I do not see this method is ready or should be allowed to be used. Let it remain an interesting topic of basic science just now. Provided that in future the method is validated and reliable and legal norms and limitations are established for the procedures, it could be perhaps allowed and justified to use this method. But this should not be a routine, massively used technique. The public interest and threat level of the case under investigation or at the court stage of proceedings should be unusually high in order to allow this kind of methods used. So in the near future it would not be the best thing to do. Moreover, basic human rights include cognitive privacy and there's a clear infringement with these when we change the mind by physical manipulations. However, if a subject freely agrees with this kind of procedure, maybe it would make sense in police work. But I foresee heated debates among lawyers on whether "knocking truth out of the fellow" can be legalized in principle. At the same time, there are enough interested parties who would develop such techniques even if it is not a legalized practice.