The Human Homologue of Macaque Area V6A

In macaque monkeys, V6A is a visuomotor area located in the anterior bank of the POs, dorsal and anterior to retinotopically-organized extrastriate area V6 (Galletti et al 1996). Unlike V6, V6A represents both contra- and ipsilateral visual fields and is broadly retinotopically organized (Galletti et al 1999b). The contralateral lower visual field is over-represented in V6A. The central 20°-30° of the visual field are mainly represented dorsally (V6Ad) and the periphery ventrally (V6Av), at the border with V6. Both sectors of area V6A contain arm movement-related cells, active during spatially-directed reaching movements (Gamberini et al., 2011). In humans, we previously mapped the retinotopic organization of area V6 (Pitzalis et al., 2006). Here, using phase-encoded fMRI, cortical surface-based analysis and wide-field retinotopic mapping, we define a new cortical region that borders V6 anteriorly and shows a clear over-representation of the contralateral lower visual field and of the periphery. As with macaque V6A, the eccentricity increases moving ventrally within the area. The new region contains a non-mirror-image representation of the visual field. Functional mapping reveals that, as in macaque V6A, the new region, but not the nearby area V6, responds during finger pointing and reaching movements. Based on similarity in position, retinotopic properties, functional organization and relationship with the neighbouring extrastriate visual areas, we propose that the new cortical region is the human homologue of macaque area V6A

Stabilization of Ion Concentration Polarization Using a Heterogeneous Nanoporous Junction

We demonstrate a recycled ion-flux through heterogeneous nanoporous junctions, which induce stable ion concentration polarization with an electric field. The nanoporous junctions are based on integration of ionic hydrogels whose surfaces are negatively or positively charged for cationic or anionic selectivity, respectively. Such heterogeneous junctions can be matched up in a way to achieve continuous ion-flux operation for stable concentration gradient or ionic conductance. Furthermore, the combined junctions can be used to accumulate ions on a specific region of the device.Korea Research Foundation (Grant MOEHRD: KRF-2007-331-D00040)Korean Science and Engineering Foundation (Grant MOST: R01-2007-000-20675-0)Korea Research Foundation (Grant MOEHRD: KRF-J03000)National Research Foundation of Korea (Grant NRF-2009- 352-D00034)National Institutes of Health (U.S.) (EB005743)National Science Foundation (U.S.). (CBET-0347348

Ultrathin Silicon Membranes for Wearable Dialysis

The development of wearable or implantable technologies that replace center-based hemodialysis (HD) hold promise to improve outcomes and quality of life for patients with ESRD. A prerequisite for these technologies is the development of highly efficient membranes that can achieve high toxin clearance in small-device formats. Here we examine the application of the porous nanocrystalline silicon (pnc-Si) to HD. pnc-Si is a molecularly thin nanoporous membrane material that is orders of magnitude more permeable than conventional HD membranes. Material developments have allowed us to dramatically increase the amount of active membrane available for dialysis on pnc-Si chips. By controlling pore sizes during manufacturing, pnc-Si membranes can be engineered to pass middle-molecular-weight protein toxins while retaining albumin, mimicking the healthy kidney. A microfluidic dialysis device developed with pnc-Si achieves urea clearance rates that confirm that the membrane offers no resistance to urea passage. Finally, surface modifications with thin hydrophilic coatings are shown to block cell and protein adhesion

Cerebellar Asymmetry and Cortical Connectivity in Monozygotic Twins with Discordant Handedness

Handedness differentiates patterns of neural asymmetry and interhemispheric connectivity in cortical systems that underpin manual and language functions. Contemporary models of cerebellar function incorporate complex motor behaviour and higher-order cognition, expanding upon earlier, traditional associations between the cerebellum and motor control. Structural MRI defined cerebellar volume asymmetries and correlations with corpus callosum (CC) size were compared in 19 pairs of adult female monozygotic twins strongly discordant for handedness (MZHd). Volume and asymmetry of cerebellar lobules were obtained using automated parcellation.CC area and regional widths were obtained from midsagittal planimetric measurements. Within the cerebellum and CC, neurofunctional distinctions were drawn between motor and higher-order cognitive systems. Relationships amongst regional cerebellar asymmetry and cortical connectivity (as indicated by CC widths) were investigated. Interactions between hemisphere and handedness in the anterior cerebellum were due to a larger right-greater-than-left hemispheric asymmetry in right-handed (RH) compared to left-handed (LH) twins. In LH twins only, anterior cerebellar lobule volumes (IV, V) for motor control were associated with CC size, particularly in callosal regions associated with motor cortex connectivity. Superior posterior cerebellar lobule volumes (VI, Crus I, Crus II, VIIb) showed no correlation with CC size in either handedness group. These novel results reflected distinct patterns of cerebellar-cortical relationships delineated by specific CC regions and an anterior-posterior cerebellar topographical mapping. Hence, anterior cerebellar asymmetry may contribute to the greater degree of bilateral cortical organisation of frontal motor function in LH individuals

Influence of silicon dioxide capping layers on pore characteristics in nanocrystalline silicon membranes

Abstract Porous nanocrystalline silicon (pnc-Si) membranes are a new class of membrane material with promising applications in biological separations. Pores are formed in a silicon film sandwiched between nm thick silicon dioxide layers during rapid thermal annealing. Controlling pore size is critical in the size-dependent separation applications. In this work, we systematically studied the influence of the silicon dioxide capping layers on pnc-Si membranes. Even a single nm thick top oxide layer is enough to switch from agglomeration to pore formation after annealing. Both the pore size and porosity increase with the thickness of the top oxide, but quickly reach a plateau after 10 nm of oxide. The bottom oxide layer acts as a barrier layer to prevent the a-Si film from undergoing homo-epitaxial growth during annealing. Both the pore size and porosity decrease as the thickness of the bottom oxide layer increases to 100 nm. The decrease of the pore size and porosity is correlated with the increased roughness of the bottom oxide layer, which hinders nanocrystal nucleation and nanopore formation