The Journal of Neuroscience, August 1, 1998, 18(15):5839-5849
The "Neostriatum" Develops as Part of the Lateral Pallium in
Birds
Georg F.
Striedter1,
T.
Alejandro
Marchant2, and
Sarah
Beydler1
1 Department of Psychobiology and Center for the
Neurobiology of Learning and Memory and 2 Department of
Ecology and Evolutionary Biology, University of California at Irvine,
Irvine, California 92697
Telencephalic organization in birds is so unusual that many
homologies between avian and mammalian telencephalic areas remain controversial. Particularly contested is the avian
"neostriatum," which has historically been homologized to
either mammalian striatum, lateral neocortex, or endopiriform
claustrum. Because homologies between these adult structures have been
so difficult to resolve, we have begun to examine how telencephalic
development diverges between birds and other vertebrates. To this end,
biotinylated dextran was injected into the lateral telencephalon of
chick embryos at 3 d of incubation, and the distribution of
labeled cells was examined up to 14 d later. The data show that a
definite boundary to cellular migration develops just ventral to the
neostriatum between 5 and 8 d of incubation. Labeled
polyclones within the neostriatum stretch from the ventricular zone to
the brain surface and exhibit an increasingly rostrocaudal orientation
as development proceeds. Individual polyclones contribute cells to
several of the distinct auditory, visual, somatosensory, and olfactory
regions within the neostriatum. A comparative analysis suggests that
the avian neostriatum develops from a precursor region that in other vertebrates gives rise to olfactory cortex and, when present, to other
components of the piriform lobe, such as the endopiriform claustrum and
basolateral amygdala. Conclusions about lateral pallial homologies
between birds and mammals remain uncertain, however, primarily because
so little is known about the development of the lateral pallium in
mammals. This lacuna might be filled by applying to mammals the novel
fate-mapping method described in the present paper.
Key words:
neocortex; piriform cortex; chick; forebrain; development; lineage; migration
Copyright © 1998 Society for Neuroscience 0270-6474/98/18155839-11$05.00/0
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