ANATOMICAL COMPARISON OF THE MACAQUE AND MARSUPIAL VISUAL-CORTEX - COMMON FEATURES THAT MAY REFLECT RETENTION OF ESSENTIAL CORTICAL ELEMENTS

This study identifies fundamental anatomical features of primary visua l cortex, area V1 of macaque monkey cerebral cortex, i.e., features th at are present in area V1 of phylogenetically distant mammals of quite different lifestyle and features that are common to other regions of cortex. We compared anatomical constituents of macaque V1 with V1 of m embers of the two principal marsupial lines, the dunnart and the quokk a, that diverged from the eutherian mammalian line over 135 million ye ars ago. Features of V1 common to both macaque and marsupials were the n compared with anatomical features we have previously described for m acaque prefrontal cortex. Despite large differences in overall area an d thickness of V1 cortex between these animals, the absolute size of p yramidal neurons is remarkably similar, as are their specific dendriti c branch patterns and patterns of distribution of intrinsic axons. Pyr amidal neuron patchy connections exist in the supragranular V1 in both the marsupial quokka and macaque as well as in macaque prefrontal cor tex. Several specific types of aspinous interneurons are common to are a V1 in both marsupial and macaque and are also present in macaque pre frontal cortex. Spiny stellate cells are a common feature of the thala mic-recipient, mid-depth lamina 4 of V1 in all three species. Because these similarities exist despite the very different Lifestyles and evo lutionary histories of the animals compared, this finding argues for a highly conserved framework of cellular detail in macaque primary visu al cortex rather than convergent evolution of these features. (C) 1998 Wiley-Liss, Inc.