Hippocampal volume is positively associated with behavioural inhibition (BIS) in a large community-based sample of mid-life adults: the PATH through life study.

The fields of personality research and neuropsychology have developed with very little overlap. Gray and McNaughton were among the first to recognize that personality traits must have neurobiological correlates and developed models relating personality factors to brain structures. Of particular note was their description of associations between conditioning, inhibition and activation of behaviours, and specific neural structures such as the hippocampus, amygdala and the prefrontal cortex. The aim of this study was to determine whether personality constructs representing the behavioural inhibition and activation systems (BIS/BAS) were associated with volumetric measures of the hippocampus and amygdala in humans. Amygdalar and hippocampal volumes were measured in 430 brain scans of cognitively intact community-based volunteers. Linear associations between brain volumes and the BIS/BAS measures were assessed using multiple regression, controlling for age, sex, education, intra-cranial and total brain volume. Results showed that hippocampal volumes were positively associated with BIS sensitivity and to a lesser extent with BAS sensitivity. No association was found between amygdalar volume and either the BIS or BAS. These findings add support to the model of Gray and McNaughton, which proposes a role of the hippocampus in the regulation of defensive/approach behaviours and trait anxiety but suggest an absence of associations between amygdala volume and BIS/BAS measures.