A Hypothesis as to the Organization of Cerebral Cortex in the Common Amniote Ancestor of Modern Reptiles and Mammals

  1. Gregory R. Bock and
  2. Gail Cardew
  1. Anton J. Reiner

Published Online: 29 APR 2008

DOI: 10.1002/0470846631.ch7

Evolutionary Developmental Biology of the Cerebral Cortex: Novartis Foundation Symposium 228

Evolutionary Developmental Biology of the Cerebral Cortex: Novartis Foundation Symposium 228

How to Cite

Reiner, A. J. (2008) A Hypothesis as to the Organization of Cerebral Cortex in the Common Amniote Ancestor of Modern Reptiles and Mammals, in Evolutionary Developmental Biology of the Cerebral Cortex: Novartis Foundation Symposium 228 (eds G. R. Bock and G. Cardew), John Wiley & Sons, Ltd, Chichester, UK. doi: 10.1002/0470846631.ch7

Author Information

  1. Department of Anatomy and Neurobiology, College of Medicine, University of Tennessee, Memphis, USA

Publication History

  1. Published Online: 29 APR 2008
  2. Published Print: 22 MAY 2000

Book Series:

  1. Novartis Foundation Symposia

Book Series Editors:

  1. Novartis Foundation

ISBN Information

Print ISBN: 9780471979784

Online ISBN: 9780470846636

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Keywords:

  • cerebral cortex;
  • neocortex;
  • dorsal ventricular ridge;
  • evolution;
  • amniotes;
  • mammal;
  • V1;
  • V2

Summary

Opinions on the evolutionary origins of mammalian neocortex have divided into two camps:

  • (1)
    antecedents of the superior neocortex (i.e. occipital, parietal and frontal lobes) and temporal neocortex (i.e. temporal lobe) were present in stem amniotes, and these antecedent regions gave rise to dorsal cortex and dorsal ventricular ridge (DVR), respectively, in living reptiles; and
  • (2)
    the stem amniote antecedent of mammalian superior neocortex gave rise to dorsal cortex in the reptilian lineage, while the stem amniote antecedent of mammal claustrum, endopiriform region and/or basolateral/basomedial amygdala gave rise to DVR in reptiles, with mammalian temporal neocortex being a newly evolved structure with no reptilian homologue.

The latter hypothesis has the merit of being more consistent with some current homeobox gene data, but it has the disadvantages of positing that mammalian temporal neocortex arose de novo. It also assumes that the high similarity between DVR and temporal neocortex in the organization of thalamic sensory input and corticostriatal projections and in the topology of sensory areas is coincidental. If one assumes that the antecedent of superior and temporal neocortex in stem amniotes was one continuous field that histologically resembled dorsal cortex in living reptiles, the first hypothesis provides basis for a parsimonious account of the origin of superior and temporal neocortex and their considerable resemblance to dorsal cortex and DVR in reptiles, as well as to Wulst and DVR in birds.