Ventral prefrontal cortex activity correlates with suppression of amygdala reactivity to emotionally challenging stimuli, presumably reflecting higher-order cognitive evaluation of negative stimuli being brought into play. (The amygdala influences a broad range of physiological and behavioral responses associated with emotion, with the left amygdala being particularly responsive to negative facial expressions.) Foland-Ross et al. have now shown that prefrontal grey matter (nerve cell containing cortical layer) thickness inversely correlates with amygdala reactivity. Greater ventromedial prefrontal cortical gray matter thickness was associated with greater reduction of activation in the left amygdala during affect labeling, a cognitive task that had previously been shown to dampen amygdala response.
In other words, if you have a thicker layer of prefrontal nerve cells, you might be less prone to emotional upset from unpleasant stimuli.