Is motor cortex excitability associated with personality factors? A replication study.

In a previous study an association has been reported between motor cortex excitability, as measured by paired-pulse transcranial magnetic stimulation (TMS) and neuroticism of the NEO personality inventory; this correlation was carried by the men. The aim of the present study was to replicate these findings in a larger sample and with additional measures of motor cortex excitability. Eighty-nine healthy volunteers filled in the NEO-FFI and underwent several measures of motor cortex excitability (resting and active motor thresholds, double-pulse TMS with interstimulus intervals of 1-20ms, and cortical silent period). We did not find any systematic significant correlations of personality factors with motor cortex excitability. Dividing the samples by sex or controlling for confounders such as age, sex and education level by partial correlations did not reveal any significant associations either. Reasons for the failure of replication may include differences in sample characteristics, personality measures, and TMS methodology. However, synopsis of literature indicates that association of personality and motor cortex excitability might be mediated rather by state than by trait factors.