Contribution of the idiothetic and the allothetic information to the hippocampal place code

Hippocampal cells exhibit preference to be active at a specific place in a familiar environment, enabling them to encode the representation of space within the brain at the population level (J. O’Keefe and Dostrovsky 1971). These cells rely on the external sensory inputs and self-motion cues, however, it is still not known how exactly these inputs interact to build a stable representation of a certain location (“place field”). Existing studies suggest that both proprioceptive and other idiothetic types of information are continuously integrated to update the self-position (e.g. implementing “path integration”) while other stable sensory cues provide references to update the allocentric position of self and correct it for the collected integration-related errors. It was shown that both allocentric and idiothetic types of information influence positional cell firing, however in most of the studies these inputs were firmly coupled. The use of virtual reality setups (Thurley and Ayaz 2016) made it possible to separate the influence of vision and proprioception for the price of not keeping natural conditions - the animal is usually head- or body-fixed (Hölscher et al. 2005; Ravassard A. 2013; Jayakumar et al. 2018a; Haas et al. 2019), which introduces vestibular motor- and visual- conflicts, providing a bias for space encoding. Here we use the novel CAVE Virtual Reality system for freely-moving rodents (Del Grosso 2018) that allows to investigate the effect of visual- and positional- (vestibular) manipulation on the hippocampal space code while keeping natural behaving conditions. In this study, we focus on the dynamic representation of space when the visual- cue-defined and physical-boundary-defined reference frames are in conflict. We confirm the dominance of one reference frame over the other on the level of place fields, when the information about one reference frame is absent (Gothard et al. 2001). We show that the hippocampal cells form adjacent categories by their input preference - surprisingly, not only that they are being driven either by visual / allocentric information or by the distance to the physical boundaries and path integration, but also by a specific combination of both. We found a large category of units integrating inputs from both allocentric and idiothetic pathways that are able to represent an intermediate position between two reference frames, when they are in conflict. This experimental evidence suggests that most of the place cells are involved in representing both reference frames using a weighted combination of sensory inputs. In line with the studies showing dominance of the more reliable sensory modality (Kathryn J. Jeffery and J. M. O’Keefe 1999; Gothard et al. 2001), our data is consistent (although not proving it) with CA1 cells implementing an optimal Bayesian coding given the idiothetic and allocentric inputs with weights inversely proportional to the availability of the input, as proposed for other sensory systems (Kate J. Jeffery, Page, and Simon M. Stringer 2016). This mechanism of weighted sensory integration, consistent with recent dynamic loop models of the hippocampal-entorhinal network (Li, Arleo, and Sheynikhovich 2020), can contribute to the physiological explanation of Bayesian inference and optimal combination of spatial cues for localization (Cheng et al. 2007)

On the massive young stellar object AFGL4176: High-spatial-resolution multi-wavelength observations and modeling

Deeply embedded and at distances of several kiloparsecs, massive young stellar objects (MYSOs) present numerous challenges for observation and study. In this work, we present spatially-resolved observations of one MYSO, AFGL 4176, together with survey and literature data, ranging from interferometric observations with VLTI/MIDI in the mid-infrared, to single-dish Herschel measurements in the far-infrared, and sub-millimeter data from APEX. We consider this spatially-resolved, multi-wavelength data set in terms of both radiative transfer and geometric models. We find that the observations are well described by one-dimensional models overall, but there are also substantial deviations from spherical symmetry at scales of tens to hundreds of astronomical units, which are revealed by the mid-infrared interferometric measurements. We use a multiple-component, geometric modeling approach to explain the mid-infrared emission on scales of tens to hundreds of astronomical units, and find the MIDI measurements are well described by a model consisting of a one-dimensional Gaussian halo and an inclined (\theta=60 deg) circumstellar disk extending out to several hundred astronomical units along a position angle of 160 deg. Finally, we compare our results both with previous models of this source, and with those of other MYSOs, and discuss the present situation with mid-infrared interferometric observations of massive stars.Comment: 15 pages, 14 figures. Accepted to Astronomy and Astrophysic

Modification of fluid lipid and mobile protein fractions of reticulocyte plasma membranes affects agonist-stimulated adenylate cyclase. Application of the percolation theory

AbstractThe technique of fluorescence recovery after photobleaching was used to measure the lateral mobility of membrane integral proteins in reticulocyte plasma membranes which were treated to modify the ‘fluid’ lipid or immobilized protein fractions, hence increasing the relative prevalence of obstacles to protein lateral motion. This was achieved by either: (1) treating the plasma membranes with phospholipase A2 followed by extraction of the hydrolysis products using fatty-acid-free bovine serum albumin, resulting in a decrease in the membrane ‘fluid’ lipid portion; or (2) preincubating the plasma membranes with polylysines, resulting in plasma membrane protein aggregation and immobilization. As the prevalence of obstacles to lateral motion increased in plasma membranes through the treatments described above, the mobility of the membrane integral proteins diminished. Experimental results for the dependence of protein mobility on the prevalence of obstacles to lateral motion were compared to theoretical data in order to verify the applicability of the percolation theory to reticulocyte plasma membranes. The influence of a decrease in the ‘fluid’ lipid and an increase in the immobilized membrane protein fractions upon the hormone-stimulated adenylate cyclase activity has been studied as well. As the ‘solid’ lipid and immobilized membrane protein fractions decreased, both the hormone-stimulated adenylate cyclase activity and the fraction of β-adrenergic receptors with high affinity to hormone diminished. It was shown that this correlation can be caused by a decrease in membrane fraction accessible to the movement of the interacting proteins of the adenylate cyclase complex. Hormonal stimulation of adenylate cyclase is discussed in terms of the percolation theory

Enriched, HIMU-type peridotite and depleted recycled pyroxenite in the Canary plume : a mixed-up mantle

Author Posting. © Elsevier B.V., 2009. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Earth and Planetary Science Letters 277 (2009): 514-524, doi:10.1016/j.epsl.2008.11.013.The Earth’s mantle is chemically and isotopically heterogeneous, and a component of recycled oceanic crust is generally suspected in the convecting mantle [Hofmann and White, 1982. Mantle plumes from ancient oceanic crust. Earth Planet. Sci. Lett. 57, 421-436]. Indeed, the HIMU component (high μ = 238U/204Pb), one of four isotopically distinct end-members in the Earth’s mantle, is generally attributed to relatively old (≥1-2 Ga) recycled oceanic crust in the form of eclogite/pyroxenite, e.g. [Zindler and Hart, 1986. Chemical geodynamics. Ann. Rev. Earth Planet. Sci. 14, 493-571]. Although the presence of the recycled component is generally supported by element and isotopic data, little is known about its physical state at mantle depths. Here we show that the concentrations of Ni, Mn and Ca in olivine from the Canarian shield stage lavas, which can be used to asses the physical nature of the source material (peridotite versus olivine-free pyroxenite) [Sobolev et al., 2007. The amount of recycled crust in sources of mantle-derived melts. Science 316, 412-417], correlate strongly with bulk rock Sr, Nd and Pb isotopic ratios. The most important result following from our data is that the enriched, HIMU-type (having higher 206Pb/204Pb than generally found in the other mantle endmembers) signature of the Canarian hotspot magmas was not caused by a pyroxenite/eclogite constituent of the plume but appears to have been primarily hosted by peridotite. This implies that the old (older than ~1 Ga) ocean crust, which has more evolved radiogenic isotope compositions, was stirred into/reacted with the mantle so that there is not significant eclogite left, whereas younger recycled oceanic crust with depleted MORB isotopic signature (<1 Ga) can be preserved as eclogite, which when melted can generate reaction pyroxenite.This work was supported by Wolfgang Paul Award, Alexander von Humboldt Foundation, to AVS, the Max Planck Society, DFG grants SCHM 250/64 and 82-1, HA3097/2 to HUS, KH and FH, NSF Grant EAR-9105113 to KH, Russian Basic Research Foundation and Russian Academy of Sciences

Data management routines for reproducible research using the G-Node Python Client library

Structured, efficient, and secure storage of experimental data and associated meta-information constitutes one of the most pressing technical challenges in modern neuroscience, and does so particularly in electrophysiology. The German INCF Node aims to provide open-source solutions for this domain that support the scientific data management and analysis workflow, and thus facilitate future data access and reproducible research. G-Node provides a data management system, accessible through an application interface, that is based on a combination of standardized data representation and flexible data annotation to account for the variety of experimental paradigms in electrophysiology. The G-Node Python Library exposes these services to the Python environment, enabling researchers to organize and access their experimental data using their familiar tools while gaining the advantages that a centralized storage entails. The library provides powerful query features, including data slicing and selection by metadata, as well as fine-grained permission control for collaboration and data sharing. Here we demonstrate key actions in working with experimental neuroscience data, such as building a metadata structure, organizing recorded data in datasets, annotating data, or selecting data regions of interest, that can be automated to large degree using the library. Compliant with existing de-facto standards, the G-Node Python Library is compatible with many Python tools in the field of neurophysiology and thus enables seamless integration of data organization into the scientific data workflow