Morphological characteristics and electrophysiological responses of visceral nociceptive neurons in somatosensory cerebral cortex of cat

The cerebellar anatomy of red junglefowl and white leghorn chickens: insights into the effects of domestication on the cerebellum

Domestication is the process by which wild organisms become adapted for human use. Many phenotypic changes are associated with animal domestication, including decreases in brain and brain region sizes. In contrast with this general pattern, the chicken has a larger cerebellum compared with the wild red junglefowl, but what neuroanatomical changes are responsible for this difference have yet to be investigated. Here, we quantified cell layer volumes, neuron numbers and neuron sizes in the cerebella of chickens and junglefowl. Chickens have larger, more folded cerebella with more and larger granule cells than junglefowl, but neuron numbers and cerebellar folding were proportional to cerebellum size. However, chickens do have relatively larger granule cell layer volumes and relatively larger granule cells than junglefowl. Thus, the chicken cerebellum can be considered a scaled-up version of the junglefowl cerebellum, but with enlarged granule cells. The combination of scaling neuron number and disproportionate enlargement of cell bodies partially supports a recent theory that domestication does not affect neuronal density within brain regions. Whether the neuroanatomical changes we observed are typical of domestication or not requires similar quantitative analyses in other domesticated species and across multiple brain regions.

The fusogen EFF-1 controls sculpting of mechanosensory dendrites

The mechanisms controlling the formation and maintenance of neuronal trees are poorly understood. We examined the dynamic development of two arborized mechanoreceptor neurons (PVDs) required for reception of strong mechanical stimuli in Caenorhabditis elegans. The PVDs elaborated dendritic trees comprising structural units we call "menorahs." We studied how the number, structure, and function of menorahs were maintained. EFF-1, an essential protein mediating cell fusion, acted autonomously in the PVDs to trim developing menorahs. eff-1 mutants displayed hyperbranched, disorganized menorahs. Overexpression of EFF-1 in the PVD reduced branching. Neuronal pruning appeared to involve EFF-1-dependent branch retraction and neurite-neurite autofusion. Thus, EFF-1 activities may act as a quality control mechanism during the sculpting of dendritic trees.

Dendritic morphology of callosal and ipsilateral projection neurons in monkey prefrontal cortex

Subpopulations of cortical pyramidal neurons have been distinguished based on the projection target of their principal axons or by their dendritic morphology. In this study, we sought to test the hypothesis that pyramidal neurons in monkey prefrontal cortex that furnish callosal or ipsilateral projections have distinctive dendritic morphologies. Retrogradely-labeled, Fast Blue-containing callosal and ipsilateral neurons were intracellularly filled with Lucifer Yellow, immunoconverted, and reconstructed. Quantitative measurements of the size and complexity of the dendritic arbor, including total dendritic length, horizontal extent, number of branch points, maximum branch order, and number of segments, as well as spine density, were made. In general, callosal neurons had larger and more complex dendritic arbors for both apical and basilar dendritic trees than did ipsilateral neurons. The greatest difference was in total dendritic length; the apical and basilar trees of callosal neurons were 34 and 25% longer, respectively. In addition, spine density was also significantly greater on the apical and basilar dendrites of callosal neurons. These findings could not be explained by differences in somal size or completeness of dendritic filling between callosal and ipsilateral neurons. Our observations support the hypothesis that callosal and ipsilateral neurons differ on a number of measures of dendritic size and complexity. Furthermore, these findings imply that these two subpopulations of pyramidal cells differ in the number and perhaps types of excitatory inputs that they receive. Finally, differences in the dendritic morphology of callosal and ipsilateral neurons have implications for understanding the functional attributes of these two populations of cells, as well as for the characterization of pyramidal neurons in human disease states.