MOLECULES AND COGNITION - THE LATTERDAY LESSONS OF LEVELS, LANGUAGE, AND LAC - EVOLUTIONARY OVERVIEW OF BRAIN STRUCTURE AND FUNCTION IN SOME VERTEBRATES AND INVERTEBRATES

The characteristics of the nervous systems of a number of organisms in different phyla are examined at the recombinant DNA, protein, neuroan atomic, neurophysiological, and cognitive levels. Among the invertebra tes, special attention is paid to the advantages as well as the shortc omings of the fly Drosophila melanogaster, the worm Caenorhabditis ele gans, the honey bee Apis mellifera, the sea hare Aplysia californica, the octopus Octopus vulgaris, and the squid Loligo pealei. Among verte brates, the focus is on Homo sapiens, the mouse Mus musculus, the rat Rattus norvegicus, the cat Felis catus, the macaque monkey Macaca fasc icularis, the barn owl Tyto alba, and the zebrafish Brachydanio rerio. Vertebrate nervous systems have also been compared in fossil vs. exta nt organisms. I conclude that complex nervous systems arose in the Ear ly Cambrian via a big bang that was underpinned by a modular method of construction involving massive pleiotropy of gene circuits. This rapi dity of construction had enormous implications for the degrees of free dom that were subsequently available to evolving nervous systems. I al so conclude that at the level of neuronal populations and interactions of neuropiles there is no model system between phyla except at the ba sic macromolecular level. Further, I argue that to achieve a significa nt understanding of the functions of extant nervous systems we need to concentrate on fewer organisms in greater depth and manipulate genome s via transgenic technologies to understand the behavioral outputs tha t are possible from an organism. Finally, I analyze the concepts of '' perceptual categorization'' and ''information processing'' and the dif ficulties involved in the extrapolation of computer analogies to sophi sticated nervous systems.