Hippocampal and amygdalar volumes in relation to handedness in adults aged 60-64

We evaluated the association between handedness and manual tracings of hippocampal and amygdalar volumes. Brain MRI and handedness data were obtained for 441 community dwelling participants aged 60-64 years of whom 31 were left-handed. Both absolute and normalized hippocampal volumes were larger in left-handed women than right-handed women. Hippocampal volume was not associated with handedness in men, and amygdalar volume was not associated with handedness in men or women. There was no right-left asymmetry in hippocampal or amygdalar volumes in either gender. We conclude that volumetric differences by handedness must be taken into account where hippocampal volumes are of clinical importance. Our results may also explain reports of lower rates of dementia in left-handed individuals.