Brain asymmetry
In human neuroanatomy, brain asymmetry can refer to at least two quite distinct findings: Neuroanatomical differences themselves exist on different scales, from neuronal densities, to the size of regions such as the planum temporale, to—at the largest scale—the torsion or "wind" in the human brain, reflected shape of the skull, which reflects a backward (posterior) protrusion of the left occipital bone and a forward (anterior) protrusion of the right frontal bone.
Rightward asymmetry can be seen in the right central sulcus (potentially suggesting increased connectivity between motor and somatosensory cortices in the left side of the brain), lateral ventricle, entorhinal cortex, amygdala and temporo-parieto-occipital area.
Others were convinced by experiments such as those conducted by Marie-Jean-Pierre Flourens, in which he demonstrated lesions to bird brains caused irreparable damage to vital functions.
[8] Flourens's methods, however, were not precise; the crude methodology employed in his experiments actually caused damage to several areas of the tiny brains of the avian models.
As Broca continued to study similar patients, he made the connection that all of the cases involved damage to the left hemisphere, and in 1864 noted the significance of these findings—that this must be a specialized region.
In addition to studies on human patients with various diseases of the brain, much of what is understood today about asymmetries and lateralization of function has been learned through both invertebrate and vertebrate animal models, including zebrafish, pigeons, rats, and many others.
[13] The corpus callosum is the largest collective pathway of white matter tissue in the body that is made of more than 200 million nerve fibers.
For right handed individuals, since the brain operates the contralateral side of the body, they could have a more induced motor cortex in the left hemisphere.
Lateralization of function and asymmetry in the human brain continues to propel a popular branch of neuroscientific and psychological inquiry.
[9] As more information emerges, researchers are finding insights into how and why early human brains may have evolved the way that they did to adapt to social, environmental and pathological changes.
[28] As has been the case in the past, studies on language processing and the implications of left- and right- handedness also dominate current research on brain asymmetry.
