The growth of the feline brain from fetal into adult life II. A morphometric study of subcortical nuclei

As a continuation of the morphometric studies on the preceding paper, here we report on the rate of growth of the caudate nucleus (n.). thalamus, red n., and the substantia (s.) nigra using, with few exceptions, the same coho rt of cats. The same previously used brains (n = 64 cats were allocated to the following age groups: fetal (E) 59 days, postnatal (P) days 1, 7, 15, 3 0, 45, 60, 90, 120, and 180. Sixteen additional cats, interspersed within t he groups, were substituted for the red n, and a. nigra studies. There were six subjects per group (except for E59, n = 4). Using a projection microsc ope and cytochrome oxidase-stained coronal sections, a combined (left plus right sides) total of 4693, 3822, 1636, and 1180 sections were drawn for th e caudate, thalamus, a, nigra, and red n., respectively. With computer assi stance, the drawings were digitized to calculate mean cross-sectional areas and then the mean volume of each structure per group. The growth time tabl es for the caudate n., thalamus and s. nigra were fairly synchronous. In te rms of percentage of the adult volume, for the left side (both sides grew a t a similar rate), the three structures grew at a fast pace between E59 and P30. Thus, at E59 their respective percentages relative to adult volume we re 23.7, 29.8 and 22.6% and by P30 the percentages were within adult range (85.2, 115.1 and 87.5%, respectively). Starting at P30, for the thalamus an d at P45 for the caudate n., there was a consistent tendency to an overgrow which ranged between 4.3 and 30.9% (at P180, P<0.5) for the caudate and be tween 0.3 and 15.1% for the thalamus. In addition, starting at P30, the rig ht thalamus tended to be consistently larger than the left by a margin rang ing between 0.5 and 11.2% (P120. P<0.05). The red n. grew at a different, s lower pace. Starting from a fetal volume equivalent to an 18.6% of adult si ze, its volume was only a 61.0% of the adult value at P30 and came within r ange of adulthood size only by P60 (81.3%). Neither the s, nigra nor the re d n, showed any consistent tendency to overgrow or to asymmetry. These find ings are discussed in the context of the literature. Furthermore, we discus s general conclusions and considerations pertaining to both papers as well as draw comparisons with the maturational time tables of other developmenta l landmarks in cats, Finally, in a comparison with growth of human brain st ructures, we point at the limitations and complexities involved in studying human material and, noting interspecies similarities, we propose that the present data from an advanced gyrencephalic mammal may form the bases for a model of structures maturation in humans. (C) 2000 Elsevier Science B.V. A ll rights reserved.