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presented discrepant findings regarding the presence of stages in brain and cognitive maturation, as described in Piagetian theory. This article questions whether their variables (e.g., skull circumference and global mental test scores) are appropriate indices from which to make such conclusions. Evidence from direct brain measurements (e.g., the quantitative electroencephalogram [QEEG]) and other neurobiological indices provides stronger support for the conclusion that regional brain maturation exhibits growth spurts and plateaus. The specific neuropsychological functions represented by regional QEEG maturation data give a composite picture of brain growth that is consistent with Piagetian theory.

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Abstract:The spatial locations of several forebrain and midbrain fibre tracts have been compared across seven commonly used inbred, hybrid and outbred mouse strains using a series of electrolytic lesions of known positions with respect to a stereotaxic instrument. Highly significant genetic variation was found in the positions of lambda, bregma and several major fibre tracts with respect to interaural zero; in the locations of fibre tracts with respect to bregma; and in the location of fibre tracts with respect to each other. It was demonstrated that stereotaxic coordinates of a structure for one strain could not be used for other strains. Errors resulting from improper alignment of the head in the instrument and histological artifact were also determined. These errors showed no significant group differences, but they revealed that within-group variation was substantially affected by such imperfections.

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