A cytoarchitectonic volumetric comparison of brains in wild and domestic sheep
By means of allometric methods it is possible to determine the intraspecific relation between brain weight and body weight in wild European sheep (Ovis ammon musimon) and two breeds of domesticated sheep (Ovis ammon f. aries). A reduction in total brain weight of 24% is observed which is due to domestication.
The following reductions of the five brain subdivisions are determined for domesticated sheep: telencephalon 26%, diencephalon 21%, mesencephalon 22%, cerebellum 16% and medulla oblongata 13%.
In the telencephalon the greatest reduction is found in the allocortex (29%), followed by the neocortex (26%) and corpus striatum (21%).
The allocortex is subdivided cytoarchitectionically and functionally into olfactory and limbic structures. There is less reduction in olfactory (22%) than in limbic (35%) components. Within the limbic structures the hippocampus with 41% shows the highest rate of reduction.
There are racial differences in brain volume by 8% between North German Moorland Sheep (Heidschnucke) and Blackhead Sheep (Schwarzkopffleischschaf). The sizes and volumes of corresponding brain parts of these two breeds did not differ significantly.