Comparative anatomy of the pig brain

For this study the healthy brains of the domestic pigs are examined post mortem. MRI (magnetic resonance imaging) scans in transverse, sagittal and dorsal orientation (native and formalin fixed) are produced with a 1.0 Tesla scanner. 12 sagittal, 13 dorsal and 22 transverse scans are selected and labelled to produce a MRI picture atlas of the porcine brain. With the aid of the graphical software programs AMIRA® and AVIZO® (Mercury Computer Systems Inc.) it was possible to identify brain structures (like nuclei) and to locate and describe the sulci of the porcine brain in MRI. These graphical software programs make it possible to construct a three dimensional model of the porcine brain and to facilitate simultaneous identification of morphological features in dorsal, transverse and sagittal scans. In addition to the atlas, MRI scans of a wild boar, a Wiesenauer minipig and a babirusa are produced and compared with the scans of the domestic pig. An important result of this study is a summary and discussion of the nomenclature of the sulci of the porcine cortex. It is now easier to match functional areas of the cortex with the corresponding structure in the MRI scan, because a standardized nomenclature for the sulci of the porcine brain does not exist so far. This study also describes special features of the porcine brain. The porcine brain has less gyri than the brains of a variety of other ungulates. The position of the pig’s forebrain in relation to the brain stem, the strongly developed pars olfactoria of the rhinencephalon in relation to the limbic system and the topography of the pituitary gland in relation to the diencephalon, are also different from the other featured species. It is furthermore possible to identify a physiological aplasia of the cerebellar cortex of the tuber region in the MRI scans of the porcine brain. In the featured members of the suidae (pigs and babirusa) the system of gyri and sulci shows little variation. Most sulci and their position are constant. The shape of the brain differs between the brachycephalic breeds (such as the Wiesenauer minipig) and the dolichocephalic hybrid pigs (bread for meat production). The brain of the Wiesenauer minipig is shorter and rounder compared with the brains of the scanned hybrid pigs. However, the surface structures of brachycephalic and dolichocephalic pig brains show only little difference.