Functional correlates of structural asymmetries in the human brain

摘要: The human brain is both structurally and functionally asymmetric. However, there have been relatively few studies assessing both structural and functional asymmetries in the same subject population. One behavioral asymmetry of particular interest to human evolution is handedness, which is much more pronounced at the population level in humans than in other species. It has been postulated that this may be related to the evolution of tool manufacturing and use, as well as language. The development of tool use may have selected for lateralized cognitive and motor functions that provided a foundation for the later left‐lateralization of speech and language in humans (Bradshaw 1993).Analyses of fossil hominin endocasts have revealed anatomical asymmetries that are assumed to reflect asymmetries in underlying brain regions. Handedness has been shown to be associated with brain petalias (the greater protrusion of the right frontal and left occipital lobes), the motor cortex, and the planum temporale (Amunts et al. 1996, Foundas et al. 1995) but its association with other structural areas of the brain have not been extensively investigated. Knowing the extent to which neuroanatomical asymmetries in different regions of the brain are associated with handedness will allow better assessment of handedness in fossil specimens. Using the MRI scans of 71 healthy, female subjects we assessed the degree of association between handedness and structural asymmetry. Interesting areas of association include the hand region of the motor and somatosensory cortexes, planum temporale, fusiform gyrus, and Broca’s area.