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The following are three types of proposals that can be considered for nomenclature change:

1) Homology. The existing avian brain nomenclature is based upon inferred homology. Even the name "avian telencephalon" is based upon homology with other vertebrates. As such, some nomenclature change proposals will be based upon homology. This includes the cortex-layered hypothesis (Fig. 3) and the claustrum-amygdala hypothesis (Fig. 4). If by the time of the forum evidence strongly favors one of these homology hypotheses or modifications of them, new names based upon mammalian layers, such as avian regions 1-5, and/or the mammalian claustrum-amygdala, will be implemented. The advantages of renaming structures based upon mammalian or even reptilian homology, is that scientist can more readily translate information discovered in one system to another. A disadvantage of homology-based nomenclature is that it may take a number of years to sort out homologous brain regions. Another disadvantage is that if an agreed upon hypothesis in the future ended up being incorrect then neurobiologists will be stuck with inaccurate names, as they are today. To circumvent these potential problems for homology based nomenclatures, it would be necessary to convene future forums and make periodic updates.

2) Transitional. An alternative is to use transitional names until an agreed upon homology based nomenclature can be implemented. The advantages of such transitional names are that they can be implemented relatively quickly, incorporate changes that maintain abbreviations of the structures, and remove inaccurate nomenclature that leads to comparative mistakes. This allows time for homology studies to mature so that correct homologies can be established. The disadvantage is that they limit the types of names and meaning that can be given to different brain regions.

3) Neutral. Another alternative is to rename the avian telencephalic structures with mammalian- and reptilian-independent terminologies. Mammalian neurobiologists have named mammalian structures with avian- and reptilian-independent terminologies. For the avian brain, the extreme version of this approach will be to keep only one structural name similar, the "telencephalon," and then to rename of all its components. The divisions can be based upon cytoarchitectonic features, much like Rose' 1914 treatise, or other types of features. The advantages of neutral names is that, similar to transitional ones, they can be implemented relatively quickly by the time of the forum, they remove the inaccurate nomenclature that often leads to comparative mistakes, and unlike the transitional ones, they can be given relevant topographical and/or functional meaning based upon known properties of the avian telencephalon. The disadvantage is that neutral names are not as user friendly for transferring information between different vertebrate systems.

In each of the above scenarios, the advantages outweigh the disadvantages. In different degrees, each scenario prevents current comparative mistakes allowing easier transfer of information between vertebrate systems. One or more of the above alternatives are possible to resolve by the time of the forum. That is, it is not necessary to identify all homologies between the avian and mammalian telencephalon in a 2-year period to change avian nomenclature by 2002, as for instance proposals 2 and 3 do not require resolution on such comparisons.

First posted 10/24/2000
Last updated 11/10/2000

Erich Jarvis

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