PREPROCESSING AND REGISTRATION OF MINISCOPE-BASED CALCIUM IMAGING OF THE RODENT BRAIN

Microscopic imaging is central to the brain and cognition studies in animals and often requires advanced image processing. In vivo recordings on awake behaving animals require stabilization of the images as the tissue in the images undergoes non-rigid deformations due to animal movement, pulse beat and breathing of the animal. Here we propose an approach to compensation for the tissue motion in calcium imaging data acquired with miniaturized wearable microscopes (miniscopes) from live rodent brains. Our approach includes preprocessing of the images in which we compensate for non-uniform illumination, remove calcium transients and instrument-specific noise. For image registration we use the multiscale mutual information based non-rigid algorithm with B-spline transformation model. We present the preliminary results of such motion compensation approach applied to the real miniscope image stacks

Astrocytes monitor cerebral perfusion and control systemic circulation to maintain brain blood flow

Astrocytes provide neurons with essential metabolic and structural support, modulate neuronal circuit activity and may also function as versatile surveyors of brain milieu, tuned to sense conditions of potential metabolic insufficiency. Here we show that astrocytes detect falling cerebral perfusion pressure and activate CNS autonomic sympathetic control circuits to increase systemic arterial blood pressure and heart rate with the purpose of maintaining brain blood flow and oxygen delivery. Studies conducted in experimental animals (laboratory rats) show that astrocytes respond to acute decreases in brain perfusion with elevations in intracellular [Ca2+]. Blockade of Ca2+-dependent signaling mechanisms in populations of astrocytes that reside alongside CNS sympathetic control circuits prevents compensatory increases in sympathetic nerve activity, heart rate and arterial blood pressure induced by reductions in cerebral perfusion. These data suggest that astrocytes function as intracranial baroreceptors and play an important role in homeostatic control of arterial blood pressure and brain blood flow

Circadian Modulation of Neurons and Astrocytes Controls Synaptic Plasticity in Hippocampal Area CA1

Most animal species operate according to a 24-h period set by the suprachiasmatic nucleus (SCN) of the hypothalamus. The rhythmic activity of the SCN modulates hippocampal-dependent memory, but the molecular and cellular mechanisms that account for this effect remain largely unknown. Here, we identify cell-type-specific structural and functional changes that occur with circadian rhythmicity in neurons and astrocytes in hippocampal area CA1. Pyramidal neurons change the surface expression of NMDA receptors. Astrocytes change their proximity to synapses. Together, these phenomena alter glutamate clearance, receptor activation, and integration of temporally clustered excitatory synaptic inputs, ultimately shaping hippocampal-dependent learning in vivo. We identify corticosterone as a key contributor to changes in synaptic strength. These findings highlight important mechanisms through which neurons and astrocytes modify the molecular composition and structure of the synaptic environment, contribute to the local storage of information in the hippocampus, and alter the temporal dynamics of cognitive processing

Raman Scattering:From Structural Biology to Medical Applications

This is a review of relevant Raman spectroscopy (RS) techniques and their use in structural biology, biophysics, cells, and tissues imaging towards development of various medical diagnostic tools, drug design, and other medical applications. Classical and contemporary structural studies of different water-soluble and membrane proteins, DNA, RNA, and their interactions and behavior in different systems were analyzed in terms of applicability of RS techniques and their complementarity to other corresponding methods. We show that RS is a powerful method that links the fundamental structural biology and its medical applications in cancer, cardiovascular, neurodegenerative, atherosclerotic, and other diseases. In particular, the key roles of RS in modern technologies of structure-based drug design are the detection and imaging of membrane protein microcrystals with the help of coherent anti-Stokes Raman scattering (CARS), which would help to further the development of protein structural crystallography and would result in a number of novel high-resolution structures of membrane proteins—drug targets; and, structural studies of photoactive membrane proteins (rhodopsins, photoreceptors, etc.) for the development of new optogenetic tools. Physical background and biomedical applications of spontaneous, stimulated, resonant, and surface- and tip-enhanced RS are also discussed. All of these techniques have been extensively developed during recent several decades. A number of interesting applications of CARS, resonant, and surface-enhanced Raman spectroscopy methods are also discussed

26th Annual Computational Neuroscience Meeting (CNS*2017): Part 3 - Meeting Abstracts - Antwerp, Belgium. 15–20 July 2017

This work was produced as part of the activities of FAPESP Research,\ud Disseminations and Innovation Center for Neuromathematics (grant\ud 2013/07699-0, S. Paulo Research Foundation). NLK is supported by a\ud FAPESP postdoctoral fellowship (grant 2016/03855-5). ACR is partially\ud supported by a CNPq fellowship (grant 306251/2014-0)

Quantum-dimensional insulators

Background. Controlled phase transitions of the metal –insulator type, caused by some form of localization of free charge carriers in a limited area of space, are of considerable interest from the point of view of the possibilities of creating various switches, relays, logic elements and other electronic components. The purpose of the work is to study the possibilities of quantum–dimensional transition of metallic graphene nanoribbons and carbon nanotubes into ordinary (non-topological) two-dimensional insulators that do not have edge states of electrical conductivity. Materials and methods. The objects of the study were “zigzag” graphene nanoribbons and “armchair” carbon nanotubes having metallic properties. The work used well-known analytical methods of quantum physics and the band theory of a solid state in relation to nanoscale 2D crystal structures. Results. It is shown that the phase transition of these nanoconductors into insulators is observed when their transverse dimensions are smaller than a certain critical value. At temperatures close to room temperature, this value is 5.0 nm for graphene nanoribbon, and 3.2 nm for carbon nanotube. Conclusions. The ability of ultra-narrow “zigzag” graphene nanoribbons to transition into the state of a quantum-dimensional semiconductor and even a dielectric makes it possible to create a completely new class of superminiature, high-speed devices for nanoelectronics, nanophotonics and nanocomputing. Operating in the ballistic current mode at room temperature, they will not require cooling, but they will differ in low power consumption, the ability to easily integrate into two-dimensional electronic circuits with a high density of layout

Consideration of quantum-dimensional effects in designing plasmon-acoustic devices of the terahertz frequency range

Background. Graphene and boron nitride nanoribbons of hexagonal syngony are promising materials for use in nanoacoustics and nanoplasmonics as transmission lines of the terahertz frequency range. Meanwhile, their nanoscale width leads to a number of quantum-dimensional effects. There are resistances, inductances and capacitances per unit length which cannot be ignored even in the ballistic regime of the free charges transport. The aim of the study is to show the significant influence of these values on the electrical and wave parameters of such devises. Materials and methods. The objects of the study were nanoribbons made of graphene (Gr) and 2D hexagonal boron nitride (h-BN) isomorphic to it. The work used well-known analytical methods of classical microwave electronics, quantum physics and the band theory of the solid state physics in relation to nanoscale 2D crystal structures. Results. Expressions are obtained for the values of the quantum resistance, inductance, and capacitance per unit length of an electrically conductive nanoribbon of limited width depending on the corresponding quanta and the number of channels of electrical conductivity due to the width of the nanoribbon, the Fermi wave number for the free carriers, spin and valley degeneracy of their energy states. It is shown that the quantum inductance and capacitance of a nanoribbon at terahertz frequencies can exceed by two orders of magnitude the corresponding characteristics of the same nanoribbon for surface plasmon polaritons. The results are illustrated by the example of a plasmon-acoustic transducer of the terahertz frequency range on the graphene-hexagonal boron nitride structure. Conclusions. The quantum inductance and capacitance per unit length of graphene nanoribbon at terahertz frequencies can exceed their corresponding values for surface plasmon polaritons in the same nanoribbon by two orders of magnitude. This result taking into account quantum-dimensional effects when designing nanoelectromechanical devises