Any substantial change in brain size requires a change in the number of neurons and their supporting elements in the brain, which in turn requires an alteration in either the rate, or the duration of neurogenesis. The schedule of neurogenesis is surprisingly stable in mammalian brains, and increases in the duration of neurogenesis have predictable outcomes: late-generated structures become disproportionately large. The olfactory bulb and associated limbic structures may deviate in some species from this general brain enlargement: in the rhesus monkey, reduction of limbic system size appears to be produced by an advance in the onset of terminal neurogenesis in limbic system structures. Not only neurogenesis but also many other features of neural maturation such as process extension and retraction, follow the same schedule with the same predictability. Although the underlying order of event onset remains the same for all of the mammals we have yet studied, changes in overall rate of neural maturation distinguish related subclasses, such as marsupial and placental mammals, and changes in duration of neurodevelopment distinguish species within subclasses. A substantial part of the regularity of event sequence in neurogenesis can be related directly to the two dimensions of the neuraxis in a recently proposed prosomeric segmentation of the forebrain [Rubenstein et al., Science, 266: 578, 1994]. Both the spatial and temporal organization of development have been highly conserved in mammalian brain evolution, showing strong constraint on the types of brain adaptations possible. The neural mechanisms for integrative behaviors may become localized to those locations that have enough plasticity in neuron number to support them.

Keywords:
Neurogenesis, Neurodevelopment, Brain size, Allometry, Marsupial mammals, Placental mammals, Prosomere
1.
Aboitiz, F. (1996) Does bigger mean better? Evolutionary determinants of brain size and structure. Brain Behav. Evol., 47: 225–245.
2.
Armstrong, E., M.R. Clarke, and E.M. Hill (1987) Relative size of the anterior thalamic nuclei distinguishes anthropoids by social system. Brain Behav. Evol., 30: 263–271.
3.
Ashwell, K.W.S., P.M.E. Waite, and L. Marotte (1996) Ontogeny of the projection tracts and commissural fibres in the forebrain of the tammar wallaby (Macropus eugenii): timing in comparison with other mammals. Brain Behav. Evol., 47: 8–22.
4.
Baron, G., H.D. Frahm, K.P. Bhatnagar, and H. Stephan (1983) Comparison of brain structure volumes in insectivora and primates: main olfactory bulb (MOB). J. Hirnforsch., 24: 551–558.
5.
Barton, R.A. (1996) Neocortex size and behavioural ecology in primates. Proc. R. Soc. Lond. (Biol.), 263: 173–177.
6.
Barton, R.A., A. Purvis, and P.H. Harvey (1995) Evolutionary radiation of visual and olfactory brain systems in primates, bats and insectivores. Philos. Trans. Roy. Soc. Lond. (B), 348: 381–392.
7.
Chalupa, L.M., and B. Dreher (1991) High precision systems require high precision blueprints – a new view regarding the formation of connections in the mammalian visual system. J. Cog. Neurosci., 3: 209–219.
8.
Chesselet, M.-F., C. Gonzales, and P. Levitt (1991) Heterogeneous distribution of the limbic system-associated membrane protein in the caudate nucleus and substantia nigra in the cat. Neuroscience, 40: 725–733.
9.
Coté, P.-Y., P. Levitt, and A. Parent (1995) Distribution of limbic system-associated membrane protein immunoreactivity in primate basal ganglia. Neuroscience, 69: 71–81.
10.
Coté, P.-Y., P. Levitt, and A. Parent (1996) Limbic system associated membrane protein (LAMP) in primate amygdala and hippocampus. Hippocampus, 6: 483–494.
11.
Dunlop, S.A., I.B.G. Tee, R.D. Lund, and L.D. Beazley (1997) Development of primary visual projections occurs entirely postnatally in the fat-tailed dunnart, a marsupial mouse, Sminthopsis crassicaudata. J. Comp. Neurol., 384: 26–40.
12.
Eagleson, K.L., L. Lillien, A. V. Chan, and P. Levitt (1997) Mechanisms specifying area fate in cortex include cell-cycle-dependent decisions and the capacity of progenitors to express phenotype memory. Development, 124: 1623–1630.
13.
Eisenberg, J.F. (1981) The Mammalian Radiations: An Analysis of Trends in Evolution, Adaptation and Behavior. The University of Chicago Press, Chicago.
14.
Eisthen, H.L. (1997) Evolution of vertebrate olfactory systems. Brain Behav. Evol., 50: 222–233.
15.
Finlay, B.L., and R.B. Darlington (1995) Linked regularities in the development and evolution of mammalian brains. Science, 268: 1578–1584.
16.
Fox, J.H., and W. Wilczynski (1986) Allometry of major CNS divisions: towards a reevaluation of somatic brain-body scaling. Brain Behav. Evol., 28: 157–169.
17.
Gaillaird, J.M., D. Pontier, D. Allaine, A. Loison, J.C. Herve, and A. Heizmann (1997) Variation in growth form and precocity at birth in eutherian mammals. Proc. R. Soc. Lond. (Biol.), 264: 859–868.
18.
Gerhart, J., and M. Kirschner (1997) Cells, Embryos and Evolution. Blackwell Science, Inc., Malden, Massachusetts.
19.
German, R.Z., D.W. Hertweck, J.E. Sirianni, and D.R. Swindler (1994) Heterochrony and sexual dimorphism in the pigtailed macaque (Macaca nemestrina). Am. J. Phys. Anthropol., 93: 373–380.
20.
Gittleman, J.L. (1991) Carnivore olfactory brain size; allometry, phylogeny and ecology. J. Zool. Lond., 225: 253–272.
21.
Gittleman, J.L. (1994) Female brain size and parental care in carnivores. Proc. Natl. Acad. Sci. USA, 91: 5495–5497.
22.
Gittleman, J.L. (1995) Carnivore brain size, behavioral ecology and phylogeny. J. Mammol., 67: 23–36.
23.
Gould, S.J. (1975) Allometry in primates with emphasis on scaling and the evolution of the brain. Cont. Primatol., 5: 244–292.
24.
Gould, S.J. (1980) The Panda’s Thumb. W.W. Norton, New York.
25.
Harman, A.M., and L.D. Beazley (1986) Development of visual projections in the marsupial, Setonix brachyurus. Anat. Embryol., 175: 181–188.
26.
Harman, A.M., N.J. Eastough, and L.D. Beazley (1995) Development of the visual cortex in a wallaby – phylogenetic implications. Brain Behav. Evol., 45: 138–152.
27.
Jerison, H.J. (1973) Evolution of the Brain and Intelligence. Academic Press, New York.
28.
Jolicoeur, P., P. Pirlot, G. Baron, and H. Stephan (1984) Brain structure and correlation patterns in insectivora, chiroptera and primates. Syst. Zool., 33: 14–29.
29.
Kageyama, G.H., and R.T. Robertson (1993) Development of geniculocortical projections to visual cortex in rat – evidence for early ingrowth and synaptogenesis. J. Comp. Neurol., 335: 123–148.
30.
Karten, H.J. (1997) Evolutionary developmental biology meets the brain: the origins of mammalian cortex. Proc. Natl. Acad. Sci. USA, 94: 2800–2804.
31.
Krause, W.J., and N.R. Saunders (1994) Brain growth and neocortical development in the opossum. Ann. Anat., 176: 395–407.
32.
Kuan, C.Y., E.A. Elliott, R.A. Flavell, and P. Rakic (1997) Restrictive clonal allocation in the chimeric mouse brain. Proc. Natl. Acad. Sci. USA, 94: 3374–3379.
33.
Laird, A.K., S.A. Tyler, and A.D. Barton (1965) Dynamics of normal growth. Growth, 29: 233–238.
34.
Miller, B., L. Chou, and B.L. Finlay (1993) The early development of thalamocortical and corticothalamic projections. J. Comp. Neurol., 335: 16–41.
35.
Murre, J.M.J., and D.P.F. Sturdy (1995) The connectivity of the brain: multi-level quantitative analysis. Biol. Cybern., 73: 529–545.
36.
Pirlot, P., and P. Jolicoeur (1982) Correlations between major brain regions in Chiroptera. Brain Behav. Evol., 20: 172–181.
37.
Puelles, L. (1995) A segmental morphological paradigm for understanding vertebrate forebrains. Brain Behav. Evol., 46: 319–337.
38.
Purves, D. (1988) Body and Brain: A Trophic Theory of Neural Connections. Harvard University Press, Cambridge, Massachusetts.
39.
Reynolds, M.L., M.E. Cavanagh, K.M. Dziegielewska, L.A. Hinds, N.R. Saunders, and C.H. Tyndale-Biscoe (1985) Postnatal development of the telencephalon of the tammar wallaby (Macropus eugenii): an accessible model of neocortical differentiation. Anat. Embryol., 173: 81–94.
40.
Robinson, S.R., and B. Dreher, B. (1990) The visual pathway of eutherian mammals and marsupials develop according to a common timetable. Brain Behav. Evol., 36: 177–195.
41.
Rubenstein, J.L.R., S. Martinez, K. Shimamura and L. Puelles (1994) The embryonic vertebrate forebrain: the prosomeric model. Science, 266: 578–579.
42.
Rubenstein, J.L.R., and K. Shimamura (1997) Regulation of patterning and differentiation of the embryonic vertebrate forebrain. In Molecular and Cellular Approaches to Neural Development (ed. by W.M. Cowan, S.L. Zipursky, and T.M. Jessel), Plenum Press, New York.
43.
Sacher, G.A. (1982) The role of brain maturation in the evolution of the primates. In Primate Brain Evolution: Methods and Concepts (ed. by E. Armstrong and D. Falk). Plenum, New York.
44.
Stephan, H., G., B., and H.D. Frahm. (1988) Comparative size of brain and brain components. In Comparative Primate Biology (Vol. 4) Alan R. Liss.
45.
Takahashi, T., R.S. Nowakowski, and V.S. Caviness (1993) Cell cycle parameters and patterns of nuclear movement in the neocortical proliferative zone of the fetal mouse. J. Neurosci, 13: 820–833.
46.
Takahashi, T., R.S. Nowakowski, and V.S. Caviness (1994) Mode of cell proliferation in the developing mouse neocortex. Proc. Natl. Acad. Sci. USA, 91: 375–379.
47.
Turner, D.L., E.Y. Snyder, and C.L. Cepko (1990) Lineage independent determination of cell type in the embryonic mouse retina. Neuron, 4: 833–845.
1998
Copyright / Drug Dosage / Disclaimer
Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher.
Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug.
Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.
You do not currently have access to this content.