Structural asymmetries in the human forebrain and the forebrain of non-human primates and rats.

Possible asymmetries of the following structures were studied: volumes of total human hemispheres, cortex and white matter volumes in post-mortem- (unknown handedness) and living brains (male right-handers); volumes of the rat primary visual cortex, its mon- and binocular subfields, its layer iv and the density of myelinated fibres in layer iv; transmitter receptor densities (NMDA, AMPA, kainate and GABAA receptors) in sensorimotor regions of the rat cortex; volume of the motor cortex and the 3D-extent of the central sulcus in the post-mortem- (unknown handedness) and living human brain (male right-handers); petalia of the hemispheres in human (male right- and left-handers) and chimpanzee brains. Histological, MRI and receptor autoradiographic techniques were used. With the notable exceptions of the transmitter receptors and the total primary visual cortex in rats and the hemispheres in chimpanzees, which do not show any significant directional asymmetry, all other parameters studied are asymmetrically distributed between the right- and left hemispheres. The regional distribution pattern and the degree of asymmetry of frontal and occipital petalia in living human brains differ between right- and left-handers.