Sept 12, 2011 (New Scientist/TSR) – YOU will tell the truth. Applying a magnetic field to the brain seems to hamper our ability to tell lies.
Lying is thought to involve inhibiting our normal propensity to truth-telling, so Talis Bachmann’s team at the University of Tartu in Estonia reasoned that dampening brain activity in the dorsolateral prefrontal cortex (DLPFC) – which is involved in cognitive control – might alter the likelihood of lying.
The researchers asked 16 volunteers to name the colour of a disc on a computer screen after receiving transcranial magnetic stimulation (TMS) to dampen activity in their DLPFC. They were given the option to lie or answer honestly. The task was then repeated following TMS of the parietal cortex – a part of the brain unassociated with cognitive control. The volunteers gave significantly fewer truthful answers after TMS of the left DLPFC – but suppressing the right DLPFC increased the number of true responses (Behavioural Brain Research, DOI: 10.1016/j.bbr.2011.07.028).
Brain-process foundations of deceptive behaviour have become a subject of intensive study both in fundamental and applied neuroscience. Recently, utilization of transcranial magnetic stimulation has enhanced methodological rigour in this research because in addition to correlational studies causal effects of the distinct cortical systems involved can be studied. In these studies, dorsolateral prefrontal cortex has been implied as the brain area involved in deceptive behaviour. However, combined brain imaging and stimulation research has been concerned mostly with deceptive behaviour in the contexts of mock thefts and/or denial of recognition of critical objects. Spontaneous, “criminally decontextuated” propensity to lying and its dependence on the activity of selected brain structures has remained unexplored. The purpose of this work is to test whether spontaneous propensity to lying can be changed by brain stimulation. Here, we show that when subjects can name the colour of presented objects correctly or incorrectly at their free will, the tendency to stick to truthful answers can be manipulated by stimulation targeted at dorsolateral prefrontal cortex. Right hemisphere stimulation decreases lying, left hemisphere stimulation increases lying. Spontaneous choice to lie more or less can be influenced by brain stimulation.
“DLPFC seems to be involved in deception, but its exact role remains unclear,” says Bruno Verschuere at the University of Amsterdam in the Netherlands. He says it is difficult to draw firm conclusions from a small sample.
SOURCE: New Scientist
