Objective The ability to inhibit motor responses has recently been linked to risk-taking behaviour, including gambling. This suggests that those with high trait levels of sensation seeking, the major personality determinant of risk taking, may have poorer response inhibition. We provide converging evidence to support this: first by testing whether performance on a stop-signal response inhibition task is related to levels of sensation seeking, and second, by assessing whether variation in sensation seeking is associated with variation in grey matter volumes of a brain region causally implicated in response inhibition, the right inferior frontal gyrus.

Method For study one, 87 healthy subjects (25 males) completed a measure of sensation seeking together with a stop-signal task. For study two, 152 healthy subjects (45 males) completed the sensation seeking measure and underwent T1-weighted MRI at 3 T. We carried out a voxel-based morphometry analysis using diffeomorphic anatomical registration through exponentiated lie (DARTEL) algebra to examine grey matter volumes, with a region of interest centred on the right inferior frontal gyrus.

Results UPPS Sensation Seeking, but not other impulsivity facets, correlated with performance on the Stop-Signal task, with higher sensation seeking associated with poorer response inhibition, indexed by larger mean stop signal reaction time. The DARTEL analysis revealed significant negative associations between sensation seeking and grey matter volumes in the right inferior frontal gyrus, as well as the right orbitofrontal cortex and right middle temporal gyrus.

Conclusion These findings provide converging evidence to support the link between risk taking and motor inhibition, both at a psychological level and at a biological level. These findings may explain why individuals with disinhibitory disorders sharing genetic variation with sensation seeking show poor response inhibition and suggest a key role of the right inferior frontal gyrus in self-control.