Brain sizes, surfaces, and neuronal sizes of the cortex cerebri: A stereological investigation of man and his variability and a comparison with some mammals (primates, whales, marsupials, insectivores, and one elephant)

Abstract

This study deals with the stereological estimation of macroscopic sizes of brain and cortex, i.e., volume, surface, and folding, and of microscopic neuronal sizes, i.e., density, mean size, size distribution, and number of neurons. The results show that the degree of variability in man amounts to about 15%. A decrease in volume of the different gray structures can be observed in man after the age of 65 years. The surface, folding index, and length of convolution do not alter with aging. The comparison with mammals of various sizes allows the conclusion that there is a high correlation to brain size for nearly all macroscopic values. Man and elephant, however, have a cortical surface which is, in comparison with whales, relatively small. In contrast, whales have very small cortices compared with man. At the cytoarchitectonic level, the neuronal density has a correlation to brain size. Contrary to other mammals, the primates and man have a high fraction of small granular neurons, especially in layer 4. The assumption that the number of cortical neurons beneath a given surface area of cortex is the same in all mammals cannot be verified, especially in those with large brains. The allometric connection between brain size and parameters is not valid for all measurements (e.g., thickness of cortex, mean size of neurons, perikaryal size distribution, and glial density). Yet some other measurements are well correlated.

The CBF Threshold and Dynamics for Focal Cerebral Infarction in Spontaneously Hypertensive Rats

“…12, No.3, 1992 Tower and Young, 1973). Important changes in cor tical cytoarchitectonics accompany this species ef fect on metabolism (Haug, 1987;Stolzenberg et aI., 1989). As the average species brain weight declines, the density of neurons in the neocortex (excepting area 17) increases (Cragg, 1967;Haug, 1987), while mean perikaryal volume (Bok, 1959) and glia per neuron decrease (Tower and Elliot, 1952;Sharif, 1953;Friede, 1954;Hawkins and Olszewski, 1957;Tower, 1967;Tower and Young, 1973).…”

“…Important changes in cor tical cytoarchitectonics accompany this species ef fect on metabolism (Haug, 1987;Stolzenberg et aI., 1989). As the average species brain weight declines, the density of neurons in the neocortex (excepting area 17) increases (Cragg, 1967;Haug, 1987), while mean perikaryal volume (Bok, 1959) and glia per neuron decrease (Tower and Elliot, 1952;Sharif, 1953;Friede, 1954;Hawkins and Olszewski, 1957;Tower, 1967;Tower and Young, 1973). Depending on the species, methodology, and region of neo cortex selected, 1 mm3 of primate cortex contains 20,000-60,000 neurons and 22,000-66,000 glia while the rat has 91,000-132,000 neurons and 40,000-53,000 glia/mm3 (Tower and Elliot, 1952;Tower, 1954;Brizzie et aI., 1964;Bass et aI., 1971;Hess and Thalheimer, 1971;Haug, 1987).…”

“…As the average species brain weight declines, the density of neurons in the neocortex (excepting area 17) increases (Cragg, 1967;Haug, 1987), while mean perikaryal volume (Bok, 1959) and glia per neuron decrease (Tower and Elliot, 1952;Sharif, 1953;Friede, 1954;Hawkins and Olszewski, 1957;Tower, 1967;Tower and Young, 1973). Depending on the species, methodology, and region of neo cortex selected, 1 mm3 of primate cortex contains 20,000-60,000 neurons and 22,000-66,000 glia while the rat has 91,000-132,000 neurons and 40,000-53,000 glia/mm3 (Tower and Elliot, 1952;Tower, 1954;Brizzie et aI., 1964;Bass et aI., 1971;Hess and Thalheimer, 1971;Haug, 1987). The higher cel lular packing density in the rat brain has been used to explain the higher rate of cerebral (giucose and oxygen) metabolism in the rat vs. primate (Nilsson and Siesj6, 1976;Kennedy et aI., 1978;Siesj6, 1978).…”

Neuroanatomy of the common dolphin (Delphinus delphis) as revealed by magnetic resonance imaging (MRI)

“…As there is a 55-60 million year divergence between cetaceans and the phylogenetically closest group (the artiodactyls), odontocete brains represent a blend of early mammalian and uniquely derived features (Ridgway, 1986;Glezer et al, 1988;Ridgway, 1990;Manger et al, 1998). The differences between cetacean and other mammalian brains of similar size have been noted at the level of cortical cytoarchitecture and histochemistry (Garey et al, 1985;Garey and Leuba, 1986;Glezer et al, , 1992aGlezer et al, , b, 1993Glezer et al, , 1998Hof et al, 1992Hof et al, , 1995, cortical surface configuration (Jacobs et al, 1979;Morgane et al, 1980;Haug, 1987), and subcortical structural morphology (Tarpley and Ridgway, 1994;Glezer et al, 1995a, b). These differences are also manifest during ontogeny (Oelschlager and Buhl, 1985;Buhl and Oelschlager, 1988;Oelschlager and Kemp, 1998).…”

Multivariate Pattern Recognition for Diagnosis and Prognosis in Clinical Neuroimaging: State of the Art, Current Challenges and Future Trends

“…There is substantial normal inter-individual variation in brain morphology even in healthy volunteers, for example, approximately 15 % variability in cortical thickness (Haug 1987). In contrast, there is less variability in the interhemispheric difference between homologous brain regions.…”