Towards building a more complex view of the lateral geniculate nucleus: Recent advances in understanding its role

The lateral geniculate nucleus (LGN) has often been treated in the past as a linear filter that adds little to retinal processing of visual inputs. Here we review anatomical, neurophysiological, brain imaging, and modeling studies that have in recent years built up a much more complex view of LGN . These include effects related to nonlinear dendritic processing, cortical feedback, synchrony and oscillations across LGN populations, as well as involvement of LGN in higher level cognitive processing. Although recent studies have provided valuable insights into early visual processing including the role of LGN, a unified model of LGN responses to real-world objects has not yet been developed. In the light of recent data, we suggest that the role of LGN deserves more careful consideration in developing models of high-level visual processing

The psychological and human brain effects of music in combination with psychedelic drugs

This research investigated how psychedelics and music work together in the brain and modulate subjective experience. Chapter 1 highlighted the prominent role of music in psychedelic therapy in the 1950s and 1960s, and how music continues to be used in modern psychotherapeutic trials with psychedelics. Although ‘psychedelic therapy’ shows promising findings for mental health care, little is known empirically about the therapeutic functions of music. The primary objective of this thesis was to address this knowledge gap, via studying the effects of psychedelics and music on human brain function in healthy volunteers, and via studying the subjective experience of music, both in healthy volunteers and in patients undergoing psychedelic therapy. Study 1 (Chapter 3) demonstrated intensified music-evoked emotions under the classic psychedelic LSD, including emotions of ‘wonder’ and ‘transcendence’. In subsequent work (study 2, Chapter 4), increased activation in the inferior frontal gyrus and the precuneus to the timbre features in the music, was associated with increased music-evoked emotions of wonder. Study 3 (Chapter 5) demonstrated that LSD and music interact to enhance information flow from the parahippocampus to the visual cortex, and that this effect correlated with increased complex mental imagery and autobiographical memories. Study 4 (Chapter 6), showed that music has a substantial influence on the therapeutic experience with psilocybin in patients with depression, and the quality of the music-experience predicted peak experiences and insightfulness during sessions, and reductions in depression after sessions. These findings support the hypothesis that the music-experience is intensified under psychedelics, and the widely-held view that this effect may be therapeutically significant. Possible brain mechanisms and therapeutic mechanisms are discussed in Chapter 7, but further research is warranted to better understand these mechanisms, and to learn how music can be best used in psychedelic therapy.Open Acces

Molecules in Superfluid Helium Nanodroplets

This open access book covers recent advances in experiments using the ultra-cold, very weakly perturbing superfluid environment provided by helium nanodroplets for high resolution spectroscopic, structural and dynamic studies of molecules and synthetic clusters. The recent infra-red, UV-Vis studies of radicals, molecules, clusters, ions and biomolecules, as well as laser dynamical and laser orientational studies, are reviewed. The Coulomb explosion studies of the uniquely quantum structures of small helium clusters, X-ray imaging of large droplets and electron diffraction of embedded molecules are also described. Particular emphasis is given to the synthesis and detection of new species by mass spectrometry and deposition electron microscopy

Aspects of Pacemakers

Outstanding steps forward were made in the last decades in terms of identification of endogenous pacemakers and the exploration of their controllability. New "artifical" devices were developed and are now able to do much more than solely pacemaking of the heart. In this book different aspects of pacemaker - functions and interactions, in various organ systems were examined. In addition, various areas of application and the potential side effects and complications of the devices were discussed

Population Dynamics In A Model Closed Ecosystem

For almost any species in any environment, it is nearly impossible to predict its fitness from molecular knowledge. If fitness is not to be a mere tautology, reproducible measurements of the survival and reproduction of populations are needed over many generations. Laboratory microbial ecosystems afford the short time and length scales required for such measurements. Their conventional implementations, batch cultures with period refreshment of growth medium or chemostats with continuous refreshment, have a number of disadvantages, such as the introduction of additional frequencies, selection for surface growth and the distortion of chemical interactions. In closed ecosystems free energy is instead supplied as light, allowing for simpler, replicable protocols and a consistent interpretation of interactions, independent of their mode or timescale. Here, I describe a model closed ecosystem consisting of three singlecelled microbes, Escherichia coli, Chlamydomonas reinhardtii and Tetrahymena thermophila and show that these species can coexist for hundreds of days under closure. Using a custom built in situ fluorescence microscopy set up, the densities of these three species can be measured automatically and noninvasively over months with low classification error and large dynamical range. When kept under identical boundary conditions, these ecosystems reproducibly diverge in composition, with characteristic divergence times of ~20 days for T. thermophila, ~40 days for the other two species, and an approximately linear increase of an aggregate divergence measure over the first ~60 days. For two ecosystems, densities were measured continuously under constant conditions and their dynamics shown to be nonstationary for all three species \u3e100 days after closure. As a consequence, conventional time series methods assuming stationarity are inadequate and wavelet analysis is proposed as an alternative. Species-species interactions are further investigated using oscillations in illumination intensity. Densities of C. reinhardtii and, surprisingly, E. coli respond to modest perturbations of light intensity. Variation of the modulation frequency strongly implicates the circadian clock of C. reinhardtii in its response. The nonlinearity of the E. coli response suggests that it depends on C. reinhardtii density or spatial distribution rather than directly responds to the modulation of illumination. Further improvements in the detection of interactions are proposed

Hydrogen bond rearrangements and the motion of charge defects in water viewed using multidimensional ultrafast infrared spectroscopy

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, February 2010."December 2009." Cataloged from PDF version of thesis. Vita.Includes bibliographical references.Compared with other molecular liquids, water is highly structured due to its ability to form up to four hydrogen bonds to its nearest neighbors, resulting in a tetrahedral network of molecules. However, this network is highly dynamic, exhibiting fluctuations and rearrangements that take place on femtosecond to picosecond time scales. The transport of excess protons and proton holes in water makes exclusive use of water's hydrogen bonding network. Compared to ions of similar size and charge density, both hydronium and hydroxide ions exhibit anomalously high diffusion rates due to the fact that water molecules that neighbor these ions can undergo a proton transfer reaction with the ion. This allows the structural diffusion of the ion to occur apart from the displacement of individual water molecules. In this thesis we adopt a joint experimental and theoretical approach to characterize the fluctuations of water's hydrogen bonding network and how these fluctuations act to drive the structural diffusion of the aqueous hydroxide ion. The experimental data that we present consists of a series of ultrafast nonlinear infrared spectroscopies, in particular two-dimensional infrared spectroscopy (2D IR), applied to the O-H stretching transition of a dilute solution of HOD in NaOD/D20. The frequency of the O-H stretch, (OH, is highly sensitive to the configuration of its hydrogen bonding partner. 2D IR spectroscopy allows us to measure rapid shifts in OH that reveal time scales for changes in the local environment of the HOD molecule.(cont.) The calculation of 2D IR spectra from molecular dynamics simulations then allows us to make a direct connection between the results of our experiments and the underlying dynamics of the system that drive both hydrogen bond exchange and the structural diffusion of the hydroxide ion. 2D IR spectra recorded for dilute HOD in D20 show a strong asymmetry, preferentially broadening in the frequency region indicative of strained or broken hydrogen bonds, indicating that these configurations are unstable and quickly return to a hydrogen bond. The time scale over which the 2D spectra broaden, ~60 fs, is similar to the librational period of water and suggests that molecules exchange hydrogen bonding partners though rapid, large amplitude rotations. Molecular dynamics simulations find that the transition state for hydrogen bond exchange resembles a bifurcated hydrogen bond. In roughly half of the examined exchange events, a second solvation shell water molecule inserts across the breaking hydrogen bond. This suggests that hydrogen bond rearrangements are tied to the restructuring of a water molecule's solvation shell. Upon the addition of NaOD to HOD/D20 solution, a large absorption continuum appears to the low frequency side of the O-H stretch due to the formation of strong hydrogen bonds between HOD molecules and OD ions. At early waiting times, 2D IR spectra show large, offdiagonal intensity in this frequency range that rapidly relaxes within ~110 fs.(cont.) Modeling using an empirical valence bond simulation (MS-EVB) model of aqueous NaOH suggests that as the 0-H stretching potential symmetrizes during proton transfer events, overtone transitions of the shared proton contribute strongly to 2D spectra. The rapid loss of offdiagonal intensity results from the spectral sweeping of these vibrational overtones as the solvent modulates the motion of the shared proton. The collective electric field of the solvent is found to be an appropriate reaction coordinate for the formation and modulation of shared proton states. Over picosecond waiting times, spectral features appear in the 2D IR spectra that are indicative of the exchange of population between OH~ ions and HOD molecules due to proton transfer. The construction of a spectral fitting model gives a lower bound of 3 ps for this exchange. Calculations of structural parameters following proton exchange using the MS-EVB simulation model suggest that the observed exchange process corresponds to the formation and breakage of hydrogen bonds donated by the HOD/OD~ pair formed as a result of the proton transfer. A full description of the structural diffusion of the hydroxide ion requires both a description of the local hydrogen bonding structure of the ion as well as the dielectric fluctuations of the surrounding solvent.by Sean T. Roberts.Ph.D

Physics at BES-III

This physics book provides detailed discussions on important topics in $\tau$-charm physics that will be explored during the next few years at \bes3 . Both theoretical and experimental issues are covered, including extensive reviews of recent theoretical developments and experimental techniques. Among the subjects covered are: innovations in Partial Wave Analysis (PWA), theoretical and experimental techniques for Dalitz-plot analyses, analysis tools to extract absolute branching fractions and measurements of decay constants, form factors, and CP-violation and \DzDzb-oscillation parameters. Programs of QCD studies and near-threshold tau-lepton physics measurements are also discussed.Comment: Edited by Kuang-Ta Chao and Yi-Fang Wan

Topological Signatures and Quenches in One Dimensional Fermionic Systems

L'abstract è presente nell'allegato / the abstract is in the attachmen

Humanoid Robots

For many years, the human being has been trying, in all ways, to recreate the complex mechanisms that form the human body. Such task is extremely complicated and the results are not totally satisfactory. However, with increasing technological advances based on theoretical and experimental researches, man gets, in a way, to copy or to imitate some systems of the human body. These researches not only intended to create humanoid robots, great part of them constituting autonomous systems, but also, in some way, to offer a higher knowledge of the systems that form the human body, objectifying possible applications in the technology of rehabilitation of human beings, gathering in a whole studies related not only to Robotics, but also to Biomechanics, Biomimmetics, Cybernetics, among other areas. This book presents a series of researches inspired by this ideal, carried through by various researchers worldwide, looking for to analyze and to discuss diverse subjects related to humanoid robots. The presented contributions explore aspects about robotic hands, learning, language, vision and locomotion