Neurochemical compartmentalization within the pigeon basal ganglia.

The goals of this study were to use multiple informative markers to define and characterize the neurochemically distinct compartments of the pigeon basal ganglia, especially striatum and accumbens. To this end, we used antibodies against 12 different neuropeptides, calcium-binding proteins or neurotransmitter-related enzymes that are enriched in the basal ganglia. Our results clarify boundaries between previously described basal ganglia subdivisions in birds, and reveal considerable novel heterogeneity within these previously described subdivisions.

Development of the Avian Dorsal Thalamus: Patterns and Gradients of Neurogenesis.

The dorsal thalamus is a region of the diencephalon that relays sensory and motor information between areas of the brain stem and the telencephalon. Although a dorsal thalamic region is recognized in all vertebrates and believed to be homologous, little is known about how the regions within it evolved and whether some or all regions within the dorsal thalamus are homologous among different vertebrate species. To characterize the gradients and patterns of neurogenesis of the avian dorsal thalamus, a single application of a low dose of bromodeoxyuridine (BrdU) was delivered to each chick between embryonic day (E)3 and E8 (stages 21 and 34), and chicks were followed up to E8 or E10 (stage 34 or 36).

Orbital spaceflight during pregnancy shapes function of mammalian vestibular system.

Pregnant rats were flown on the NASA Space Shuttle during the early developmental period of their fetuses' vestibular apparatus and onset of vestibular function. The authors report that prenatal spaceflight exposure shapes vestibular-mediated behavior and central morphology. Postflight testing revealed (a) delayed onset of body righting responses, (b) cardiac deceleration (bradycardia) to 70 degrees head-up roll, (c) decreased branching of gravistatic afferent axons, but (d) no change in branching of angular acceleration receptor projections with comparable synaptogenesis of the medial vestibular nucleus in flight relative to control fetuses.

Migratory routes and fates of cells transcribing the Wnt-1 gene in the murine hindbrain.

To investigate the origins, migrations, and fates of Wnt-1-expressing cells in the murine hindbrain, mice carrying a Wnt-1 enhancer/lacZ transgene were observed from embryonic day (E) 8 through postnatal day 18. The transgene-stained ventricular layer waxed and waned prior to and following migrations from it. Stained cells migrated first external to the hindbrain as neural crest and then within it to form typical populations of the rhombic lip, as well as others not recognized as lip derivatives.

Revised nomenclature for avian telencephalon and some related brainstem nuclei.

The standard nomenclature that has been used for many telencephalic and related brainstem structures in birds is based on flawed assumptions of homology to mammals. In particular, the outdated terminology implies that most of the avian telencephalon is a hypertrophied basal ganglia, when it is now clear that most of the avian telencephalon is neurochemically, hodologically, and functionally comparable to the mammalian neocortex, claustrum, and pallial amygdala (all of which derive from the pallial sector of the developing telencephalon). Recognizing that this promotes misunderstanding of the functional organization of avian brains and their evolutionary relationship to mammalian brains, avian brain specialists began discussions to rectify this problem, culminating in the Avian Brain Nomenclature Forum held at Duke University in July 2002, which approved a new terminology for avian telencephalon and some allied brainstem cell groups.

The Avian Brain Nomenclature Forum: Terminology for a New Century in Comparative Neuroanatomy.

Many of the assumptions of homology on which the standard nomenclature for the cell groups and fiber tracts of avian brains have been based are in error, and as a result that terminology promotes misunderstanding of the functional organization of avian brains and their evolutionary relationship to mammalian brains. Recognizing this problem, a number of avian brain researchers began an effort to revise the terminology, which culminated in the Avian Brain Nomenclature Forum, held at Duke University from July 18 to 20, 2002. In the new terminology approved at this Forum, the flawed conception that the telencephalon of birds consists nearly entirely of a hypertrophied basal ganglia has been purged from the telencephalic terminology, and the actual parts of the basal ganglia and its brainstem afferent cell groups have been given names reflecting their now evident homologies.

Comparison of thalamic populations in mammals and birds: expression of ErbB4 mRNA.

The expression of ErbB4 mRNA was examined in dorsal thalamic regions of chicks and rats. In rats, ErbB4 expression was observed in the habenular nuclei, the paraventricular nucleus, intermediodorsal nucleus, the central medial thalamic nucleus, the posterior nucleus, the parafascicular nucleus, the subparafascicular nucleus, the suprageniculate nucleus, the posterior limitans nucleus, the medial part of the medial geniculate nucleus, the peripeduncular nucleus, the posterior intralaminar nucleus, the lateral subparafascicular nucleus, the lateral posterior nucleus, and all ventral thalamic nuclei. In chicks, expression was observed in the subhabenular nucleus, the dorsomedialis posterior nucleus, the dorsointermedius posterior nucleus, the nucleus of the septomesencephalic tract, and areas surrounding the rotundus and ovoidalis nuclei, including the subrotundal and suprarotundal areas, and all ventral thalamic nuclei.