Hypnosis and memory: two hundred years of adventures and still going!

One of the most persistent beliefs about hypnosis is its ability to transcend mnemonic abilities. This belief has paved the way to the use of hypnosis in the clinical and legal arenas. The authors review the phenomena of hypnotic hypermnesia, pseudo-memories, and amnesia in light of current knowledge of hypnosis and memory. The investigation of the relation between hypnosis and memory processes has played an important role in our understanding of memory in action. Hypnosis provides a fertile field to explore the social, neuropsychological, and cognitive variables at play when individuals are asked to remember or to forget their past. We suggest promising avenues of research that may further our knowledge of the building blocks of memories and the mechanisms that leads to forgetfulness

Does Clinical Hypnosis Have Anything to Do with Experimental Hypnosis?

Hypnosis originated as a healing practice and its historical roots can be traced back to the ideas and methods of the physician Franz Anton Mesmer in 18th century Europe. As we now understand it hypnosis is a normal psychological phenomenon that can be investigated in the laboratory and understood in terms of mainstream psychology and the neurosciences. Normally one would expect there to be continuity between experimental research and theory on the one hand and the practical application of hypnosis on the other. In this paper it is suggested that there is reason to question how much the clinical application of hypnosis is informed by the non-clinical scientific evidence and even whether clinicians can be said to be using hypnosis as it is now defined and understood in the academic literature. These matters are also briefly addressed by reference to certain other contexts in which hypnosis is applied

Low surface gravitational acceleration of Mars results in a thick and weak lithosphere : implications for topography, volcanism, and hydrology

The first author acknowledges funding from an Initiative d’Excellence (IDEX) “Attractivité” grant (VOLPERM), funded by the University of Strasbourg. M.H. also acknowledges support from the CNRS (INSU 2016-TelluS-ALEAS).Surface gravitational acceleration (surface gravity) on Mars, the second-smallest planet in the Solar System, is much lower than that on Earth. A direct consequence of this low surface gravity is that lithostatic pressure is lower on Mars than on Earth at any given depth. Collated published data from deformation experiments on basalts suggest that, throughout its geological history (and thus thermal evolution), the Martian brittle lithosphere was much thicker but weaker than that of present-day Earth as a function solely of surface gravity. We also demonstrate, again as a consequence of its lower surface gravity, that the Martian lithosphere is more porous, that fractures on Mars remain open to greater depths and are wider at a given depth, and that the maximum penetration depth for opening-mode fractures (i.e., joints) is much deeper on Mars than on Earth. The result of a weak Martian lithosphere is that dykes—the primary mechanism for magma transport on both planets—can propagate more easily and can be much wider on Mars than on Earth. We suggest that this increased the efficiency of magma delivery to and towards the Martian surface during its volcanically active past, and therefore assisted the exogeneous and endogenous growth of the planet's enormous volcanoes (the heights of which are supported by the thick Martian lithosphere) as well as extensive flood-mode volcanism. The porous and pervasively fractured (and permeable) nature of the Martian lithosphere will have also greatly assisted the subsurface storage of and transport of fluids through the lithosphere throughout its geologically history. And so it is that surface gravity, influenced by the mass of a planetary body, can greatly modify the mechanical and hydraulic behaviour of its lithosphere with manifest differences in surface topography and geomorphology, volcanic character, and hydrology.PostprintPeer reviewe

Microstructural Controls on the Uniaxial Compressive Strength of Porous Rocks Through the Granular to Non‐Granular Transition

Under uniaxial compression, a porous rock fails by coalescence of stress‐induced microcracks. The micromechanical models developed to analyze uniaxial compressive strength data consider a single mechanism for the initiation and propagation of microcracks and a fixed starting microstructure. Because the microstructure of clastic porous rock transitions from granular to non‐granular as porosity decreases during diagenesis, their strength cannot be captured by a single model. Using synthetic samples with independently controlled porosity and initial grain radius we show that high‐porosity granular samples, where microcracks grow at grain‐to‐grain contacts, are best described by a grain‐based model. Low‐porosity non‐granular samples, where microcracks grow from pores, are best described by a pore‐based model. The switch from one model to the other depends on porosity and grain radius. We propose a regime plot that indicates which micromechanical model may be more suitable to predict strength for a given porosity and grain radius

The effects of planetary and stellar parameters on brittle lithospheric thickness

P.K.B. acknowledges support from North Carolina State University. Funding for S.M. was provided by NERC standard grant NE/PO12167/1 and UK Space Agency Aurora grant ST/T001763/1. M.J.H. thanks the Institut Universitaire de France (IUF) for support.The thickness of the brittle lithosphere—the outer portion of a planetary body that fails via fracturing—plays a key role in the geological processes of that body. The properties of both a planet and its host star can influence that thickness, and the potential range of those properties exceeds what we see in the Solar System. To understand how planetary and stellar parameters influence brittle lithospheric thickness generally, we modeled a comprehensive suite of combinations of planetary mass, surface and mantle temperature, heat flux, and strain rate. Surface temperature is the dominant factor governing the thickness of the brittle layer: smaller and older planets generally have thick brittle lithospheres, akin to those of Mercury and Mars, whereas larger, younger planets have thinner brittle lithospheres that may be comparable to the Venus lowlands. But certain combinations of these parameters yield worlds with exceedingly thin brittle layers. We predict that such bodies have little elevated topography and limited volatile cycling and weathering, which can be tested by future telescopic observations of known extrasolar planets.Publisher PDFPeer reviewe

Hot climate inhibits volcanism on Venus : constraints from rock deformation experiments and argon isotope geochemistry

M.J. Heap acknowledges funding from an Initiative d’Excellence (IDEX) “Attractivité” grant (VOLPERM), funded by the University of Strasbourg.The disparate evolution of sibling planets Earth and Venus has left them markedly different. Venus’ hot (460 °C) surface is dry and has a hypsometry with a very low standard deviation, whereas Earth’s average temperature is 4 °C and the surface is wet and has a pronounced bimodal hypsometry. Counterintuitively, despite the hot Venusian climate, the rate of intraplate volcano formation is an order of magnitude lower than that of Earth. Here we compile and analyse rock deformation and atmospheric argon isotope data to offer an explanation for the relative contrast in volcanic flux between Earth and Venus. By collating high-temperature, high-pressure rock deformation data for basalt, we provide a failure mechanism map to assess the depth of the brittle–ductile transition (BDT). These data suggest that the Venusian BDT likely exists between 2–12 km depth (for a range of thermal gradients), in stark contrast to the BDT for Earth, which we find to be at a depth of ~25-27 km using the same method. The implications for planetary evolution are twofold. First, downflexing and sagging will result in the sinking of high-elevation structures, due to the low flexural rigidity of the predominantly ductile Venusian crust, offering an explanation for the curious coronae features on the Venusian surface. Second, magma delivery to the surface—the most efficient mechanism for which is flow along fractures (dykes; i.e., brittle deformation)—will be inhibited on Venus. Instead, we infer that magmas must stall and pond in the ductile Venusian crust. If true, a greater proportion of magmatism on Venus should result in intrusion rather than extrusion, relative to Earth. This predicted lower volcanic flux on Venus, relative to Earth, is supported by atmospheric argon isotope data: we argue here that the anomalously unradiogenic present-day atmospheric 40Ar/36Ar ratio for Venus (compared with Earth) must reflect major differences in 40Ar degassing, primarily driven by volcanism. Indeed, these argon data suggest that the volcanic flux on Venus has been three times lower than that on Earth over its 4.56 billion year history. We conclude that Venus’ hot climate inhibits volcanism.PostprintPeer reviewe

The Influence of Grain Size Distribution on Mechanical Compaction and Compaction Localization in Porous Rocks

The modes of formation of clastic rocks result in a wide variety of microstructures, from poorly-sorted heterogeneous rocks to well-sorted and nominally homogeneous rocks. The mechanical behavior and failure mode of clastic rocks is known to vary with microstructural attributes such as porosity and grain size. However, the influence of the grain size distribution, in particular the degree of polydispersivity or modality of the distribution, is not yet fully understood, because it is difficult to study experimentally using natural rocks. To better understand the influence of grain size distribution on the mechanical behavior of porous rocks, we prepared suites of synthetic samples consisting of sintered glass beads with polydisperse grain size distributions. We performed hydrostatic compression experiments and found that, all else being equal, the onset of grain crushing occurs much more progressively and at lower pressure in polydisperse synthetic samples than in monodisperse samples. We conducted triaxial experiments in the regime of shear-enhanced compaction and found that the stress required to reach inelastic compaction was lower in polydisperse samples compared to monodisperse samples. Further, our microstructural observations show that compaction bands developed in monomodal polydisperse samples while delocalized cataclasis developed in bimodal polydisperse samples, where small grains were systematically crushed while largest grains remained intact. In detail, as the polydispersivity increases, microstructural deformation features appear to transition from localized to delocalized through a hybrid stage where a compaction front with diffuse bands propagates from both ends of the sample toward its center with increasing bulk strain