The cerebrum and cerebellum of the fixed human brain: efficient and unbiased estimates of volumes and cortical surface areas.

Extremely old and relatively new stereological methods for the efficient and unbiased estimation of volumes and surface areas were applied to fixed human brains. Brains from twelve subjects (six males aged 76-81 years, six females aged 70-98 years) were hemisected. Cerebral hemispheres and cerebellar halves from both sides were sliced systematic randomly for Cavalieri estimates of volume and vertical sectioning estimates of cortical surface area. Weights and linear dimensions were also recorded. It took less than 30 minutes per cerebral hemisphere to estimate total volume and cortical surface area. Cerebellar halves were analysed even more quickly. No significant differences between brain sides and no interaction effects were found but sex differences were confirmed. For male cerebrum (both hemispheres combined), the average volume was 840 cm3 and cortical surface area was 1640 cm2. Two thirds of this surface was hidden within sulci and in the insula. Cortical volume was 320 cm2 with an arithmetic mean thickness of 2.2 mm. In females the cerebral hemisphere was smaller and the cortex was less extensive but just as voluminous. In males, the cerebellum occupied 70 cm3 with a cortical surface of 550 cm2 of which 86% was hidden in fissures. Values were not significantly different from those found in females.