Subdivisions of the Auditory Midbrain (N. Mesencephalicus Lateralis, pars dorsalis) in Zebra Finches Using Calcium-Binding Protein Immunocytochemistry

The midbrain nucleus mesencephalicus lateralis pars dorsalis (MLd) is thought to be the avian homologue of the central nucleus of the mammalian inferior colliculus. As such, it is a major relay in the ascending auditory pathway of all birds and in songbirds mediates the auditory feedback necessary for the learning and maintenance of song. To clarify the organization of MLd, we applied three calcium binding protein antibodies to tissue sections from the brains of adult male and female zebra finches. The staining patterns resulting from the application of parvalbumin, calbindin and calretinin antibodies differed from each other and in different parts of the nucleus. Parvalbumin-like immunoreactivity was distributed throughout the whole nucleus, as defined by the totality of the terminations of brainstem auditory afferents; in other words parvalbumin-like immunoreactivity defines the boundaries of MLd. Staining patterns of parvalbumin, calbindin and calretinin defined two regions of MLd: inner (MLd.I) and outer (MLd.O). MLd.O largely surrounds MLd.I and is distinct from the surrounding intercollicular nucleus. Unlike the case in some non-songbirds, however, the two MLd regions do not correspond to the terminal zones of the projections of the brainstem auditory nuclei angularis and laminaris, which have been found to overlap substantially throughout the nucleus in zebra finches

Women have greater density of neurons in posterior temporal cortex

Cytoarchitectonic area TA1 (von Economo) in the cortex of the planum temporale within the Sylvian fissure, which is auditory association cortex and documented to be part of the neural substrate of language functions, was studied quantitatively in the brain specimens of five women and four men (mean age of 50 year). All cases were documented to be medically and cognitively normal, and consistently right-handed. We investigated the possibility that the difference in brain size between men and women is reflected in differences in the numerical density of neurons in area TA1, an area associated with morphologic and psychological sex differences. Neuron counts were made directly through cell differentiation under the microscope from Nissl-stained sections. Cortical depth, the number of neurons through the depth of cortex under 1 mm2 of cortical surface (Nc), and the number of neurons per unit volume (Nv) were obtained for the total cortex and for each of the six layers in each hemisphere. For total cortex in both hemispheres, depth and Nc were similar, but Nv was greater by 11% in women, with no overlap of scores between the sexes. The sex difference in Nv was attributable to layers II and IV; in contrast, Nv did not differ between the sexes in layers III, V, and VI. This is the first report of such a sex difference in human cortex. The results suggest that the cortical functional unit has a different ratio of input and output components in men and women which could have implications for the sex differences in cognition and behavior. Due to the small sample size and the homogeneity of the cases studied, generalizability of the results requires replication by other studies. In addition, cytoarchitectonic mapping indicated that area TA1 also occurs in the vertical posterior wall of the Sylvian fissure, providing evidence that anatomical definition of the planum temporale should include the posterior vertical wall of the superior temporal gyrus.</jats:p

The Claustrum of the Pig: An Immunohistochemical and a Quantitative Golgi Study

Despite increasing interest in the claustrum (Cl) over the last decades, its function is still a puzzling problem. Among the experimental species of potential use in Cl research, the pig is considered an interesting model, because of the similarities of its brain with the corresponding cortical and subcortical human structures. The swine Cl presents a peculiar morphology, characterized by a wide posterior enlargement, ideal for physiological investigations. There is a wealth of data on general anatomy, cytoarchitecture, and chemo architecture of the Cl, but much less is known about the dendritic morphometry of its neurons. Dendritic length and branching pattern are key features to understand the organization of the microcircuitry, and thus the delineation of the structure\u2013function relationships of the Cl. To this effect, we undertook (a) a quantitative study of the dendrites of the spiny neurons of the swine Cl, employing the Golgi staining; and (b) an immunohistochemical analysis to describe the distribution of the parvalbumin (PV)-immunoreactive interneurons throughout the same nucleus. Taken together, the results that we report here show that the dendritic architecture and the distribution of the PV expressing interneurons change when the Cl of this species changes its shape along the rostro-caudal axis, thus suggesting a potentially specific function for the large posterior puddle. Anat Rec, 2019. \ua9 2019 Wiley Periodicals, Inc