Aggression and violent behaviour are often noticed as a threat of society. Therefore, the understanding of violent behaviour has high social relevance.

The investigation sample comprised 80 right-handers: 40 prisoners who committed severe violent crimes and 40 controls with no history of violence. All subjects were male and matched for age.

We performed a study with transcranial magnetic stimulation (TMS) in a sample of violent offenders in order to measure cortical inhibition in the motoneural system which is part of the frontal cortex.

To investigate the intracortical inhibition and the intracortical facilitation we conducted paired-pulse stimulation according to the technique of Kujirai et al. (1993). The investigation sample comprised 80 right-handers: 40 prisoners who committed severe violent crimes and 40 controls with no history of violence. All subjects were male and matched for age.

Using the paired-pulse paradigm with interstimulus intervals (ISI) of 1–15 ms, a reduced cortical inhibition (ISI 3 ms) was found in violent offenders compared with control subjects in the left cortex.

These findings corroborate the hypothesis of inhibition deficits in violent offenders when compared with control subjects due to a lack of impulsive control.