Comparative cellular analysis of motor cortex in human, marmoset and mouse

The primary motor cortex (M1) is essential for voluntary fine-motor control and is functionally conserved across mammals(1). Here, using high-throughput transcriptomic and epigenomic profiling of more than 450,000 single nuclei in humans, marmoset monkeys and mice, we demonstrate a broadly conserved cellular makeup of this region, with similarities that mirror evolutionary distance and are consistent between the transcriptome and epigenome. The core conserved molecular identities of neuronal and non-neuronal cell types allow us to generate a cross-species consensus classification of cell types, and to infer conserved properties of cell types across species. Despite the overall conservation, however, many species-dependent specializations are apparent, including differences in cell-type proportions, gene expression, DNA methylation and chromatin state. Few cell-type marker genes are conserved across species, revealing a short list of candidate genes and regulatory mechanisms that are responsible for conserved features of homologous cell types, such as the GABAergic chandelier cells. This consensus transcriptomic classification allows us to use patch-seq (a combination of whole-cell patch-clamp recordings, RNA sequencing and morphological characterization) to identify corticospinal Betz cells from layer 5 in non-human primates and humans, and to characterize their highly specialized physiology and anatomy. These findings highlight the robust molecular underpinnings of cell-type diversity in M1 across mammals, and point to the genes and regulatory pathways responsible for the functional identity of cell types and their species-specific adaptations.Cardiovascular Aspects of Radiolog

Computational modeling of spanwise flexibility effects on flapping wing aerodynamics

The implications of spanwise flexibility on flapping wing aerodynamics are investigated numerically for a rectangular wing in pure heave. A computational framework for fluid-structural interactions has been developed based on a direct coupling procedure between (i) a pressure-based finite-volume fluid flow solver based on the Navier-Stokes equations, and (ii) a quasi-3D finite element structural dynamics solver based on a geometrically nonlinear composite beam-like and linear plate-like formulations. The computational results are first correlated with available experimental data. It is shown that two key factors associated with spanwise wing deformation affect thrust generation, namely, in-phase motion between the wing tip and root, and the increased effective angle of attack of the deformed wing. If the wing motions resulting from both prescribed motion and deformation are correlated, the increased effective angle of attack at the tip could enhance the aerodynamic performance. If the flexibility is too high, then the wing tip and root could move in inconsistent directions, resulting in deteriorated aerodynamic performance. Copyright © 2009 by the American Institute of Aeronautics and Astronautics, Inc