The Morphological Substrate of Cerebral Asymmetry: the Problem of Its Measurement The Morphological Substrate of Cerebral Asymmetry: the Problem

problem is the definition of unequivo¬ cal constant reference points or lines for the subsequent measurements. Since the variation of gyri and sulci is very high this has not been followed and thus unbiased results could be achieved. Tracing the contours of brain struc¬ tures (planimetry) leads to two-di¬ mensional results. The measured pro¬ file area of a structure in one slice of one hemisphere was related to that of the other hemisphere.3910 However, the results are biased due to the fact that the sectioning plane is mostly not identical on the left and right side. This holds for brains obtained at au¬ topsy, as well as for computed tomo¬ graphic or magnetic resonance images. Surface area (a two-dimensional pa¬ rameter) and volume (a three-dimen¬ sional parameter) can easily be esti¬ mated by stereology. It does not re¬ quire complicated handling of brain material as described by Albanese and coworkers.1 Serial sections through the whole brain or through one struc¬ ture of interest are used for the eval¬ uation.1617 Applying stereological methods we could only find slight differences be¬ tween the two hemispheres.12 The vol¬ ume of the orbital part of the frontal cortex, the rhinencephalon, and the hippocampus showed, in the right hemisphere, a distinctly increased volume.12 Morphometry gives objective, reli¬ able, and reproducible results. The aim of forthcoming investigations on structural brain asymmetries should be directed toward the application of these techniques; then the results of different research groups can be com¬ pared with each other. Furthermore, clear criteria of the boundaries of dif¬ ferent brain regions must be defined in order to avoid one main source of