Decision Salience Signals in Posterior Cingulate Cortex

Despite its phylogenetic antiquity and clinical importance, the posterior cingulate cortex (CGp) remains an enigmatic nexus of attention, memory, motivation, and decision making. Here we show that CGp neurons track decision salience – the degree to which an option differs from a standard – but not the subjective value of a decision. To do this, we recorded the spiking activity of CGp neurons in monkeys choosing between options varying in reward-related risk, delay to reward, and social outcomes, each of which varied in level of decision salience. Firing rates were higher when monkeys chose the risky option, consistent with their risk-seeking preferences, but were also higher when monkeys chose the delayed and social options, contradicting their preferences. Thus, across decision contexts, neuronal activity was uncorrelated with how much monkeys valued a given option, as inferred from choice. Instead, neuronal activity signaled the deviation of the chosen option from the standard, independently of how it differed. The observed decision salience signals suggest a role for CGp in the flexible allocation of neural resources to motivationally significant information, akin to the role of attention in selective processing of sensory inputs

Ambiguity Aversion in Rhesus Macaques

People generally prefer risky options, which have fully specified outcome probabilities, to ambiguous options, which have unspecified probabilities. This preference, formalized in economics, is strong enough that people will reliably prefer a risky option to an ambiguous option with a greater expected value. Explanations for ambiguity aversion often invoke uniquely human faculties like language, self-justification, or a desire to avoid public embarrassment. Challenging these ideas, here we demonstrate that a preference for unambiguous options is shared with rhesus macaques. We trained four monkeys to choose between pairs of options that both offered explicitly cued probabilities of large and small juice outcomes. We then introduced occasional trials where one of the options was obscured and examined their resulting preferences; we ran humans in a parallel experiment on a nearly identical task. We found that monkeys reliably preferred risky options to ambiguous ones, even when this bias was costly, closely matching the behavior of humans in the analogous task. Notably, ambiguity aversion varied parametrically with the extent of ambiguity. As expected, ambiguity aversion gradually declined as monkeys learned the underlying probability distribution of rewards. These data indicate that ambiguity aversion reflects fundamental cognitive biases shared with other animals rather than uniquely human factors guiding decisions

Syn-kinematic hydration reactions, grain size reduction, and dissolution-precipitation creep in experimentally deformed plagioclase-pyroxene mixtures

Source at https://doi.org/10.5194/se-9-985-2018 .It is widely observed that mafic rocks are able to accommodate high strains by viscous flow. Yet, a number of questions concerning the exact nature of the involved deformation mechanisms continue to be debated. In this contribution, rock deformation experiments on four different water-added plagioclase–pyroxene mixtures are presented:(i) plagioclase(An60–70)–clinopyroxene–orthopyroxene,(ii) plagioclase(An60)–diopside,(iii) plagioclase(An60)–enstatite,and iv) plagioclase(An01)–enstatite. Samples were deformed in general shear at strain rates of 3×10−5 to 3×10−6 s−1, 800°C, and confining pressure of 1.0 or 1.5GPa. Results indicate that dissolution–precipitation creep (DPC) and grain boundary sliding (GBS) are the dominant deformation mechanisms and operate simultaneously. Coinciding with sample deformation, syn-kinematic mineral reactions yield abundant nucleation of new grains; the resulting intense gray size reduction is considered crucial for the activity of DPC and GBS. In high strain zones dominated by plagioclase, a weak, nonrandom, and geometrically consistent crystallographic preferred orientation (CPO) is observed. Usually, a CPO is considered a consequence of dislocation creep, but the experiments presented here demonstrate that a CPO can develop during DPC and GBS. This study provides new evidence for the importance of DPC and GBS in mid-crustal shear zones within mafic rocks, which has important implications for understanding and modeling mid-crustal rheology and flow

A type VII-secreted lipase toxin with reverse domain arrangement

Funding: This study was supported by the Wellcome Trust (through Investigator Awards 10183/Z/15/Z and 224151/Z/21/Z to TP), the Intramural Research Program of the NIH, NCI, Center for Cancer Research (awarded to SML), the German Centre of Infection Research (DZIF) to SH (TTU 08.708). NM holds a Walter Benjamin Fellowship (M2871/1-1), funded by the DFG (German Research Foundation). Additionally, we acknowledge infrastructural funding by the DFG in the frame of Germany's Excellence Strategy—EXC 2124—390838134 (SH). SG is funded by the Newcastle-Liverpool-Durham BBSRC DTP2 Training Grant, project reference number BB/M011186/1 and YY by the China Scholarship Council.The type VII protein secretion system (T7SS) is found in many Gram-positive bacteria and in pathogenic mycobacteria. All T7SS substrate proteins described to date share a common helical domain architecture at the N-terminus that typically interacts with other helical partner proteins, forming a composite signal sequence for targeting to the T7SS. The C-terminal domains are functionally diverse and in Gram-positive bacteria such as Staphylococcus aureus often specify toxic anti-bacterial activity. Here we describe the first example of a class of T7 substrate, TslA, that has a reverse domain organisation. TslA is widely found across Bacillota including Staphylococcus, Enterococcus and Listeria. We show that the S. aureus TslA N-terminal domain is a phospholipase A with anti-staphylococcal activity that is neutralised by the immunity lipoprotein TilA. Two small helical partner proteins, TlaA1 and TlaA2 are essential for T7-dependent secretion of TslA and at least one of these interacts with the TslA C-terminal domain to form a helical stack. Cryo-EM analysis of purified TslA complexes indicate that they share structural similarity with canonical T7 substrates. Our findings suggest that the T7SS has the capacity to recognise a secretion signal present at either end of a substrate.Publisher PDFPeer reviewe

Water redistribution in experimentally deformed natural milky quartz single crystals-Implications for H2O-weakening processes

Natural quartz single crystals were experimentally deformed in two orientations: (1) ⊥ to one prism plane and (2) in O+ orientation at 900 and 1000°C, 1.0 and 1.5 GPa, and strain rates of ~1 × 10−6 s−1. In addition, hydrostatic and annealing experiments were performed. The starting material was milky quartz, which consisted of dry quartz with a large number of fluid inclusions of variable size up to several 100 µm. During pressurization fluid inclusions decrepitated producing much smaller fluid inclusions. Deformation on the sample scale is anisotropic due to dislocation glide on selected slip systems and inhomogeneous due to an inhomogeneous distribution of fluid inclusions. Dislocation glide is accompanied by minor dynamic recovery. Strongly deformed regions show a pointed broad absorption band in the ~3400 cm−1 region consisting of a superposition of bands of molecular H2O and three discrete absorption bands (at 3367, 3400, and 3434 cm−1). In addition, there is a discrete absorption band at 3585 cm−1, which only occurs in deformed regions and reduces or disappears after annealing, so that this band appears to be associated with dislocations. H2O weakening in inclusion-bearing natural quartz crystals is assigned to the H2O-assisted dislocation generation and multiplication. Processes in these crystals represent recycling of H2O between fluid inclusions, cracking and crack healing, incorporation of structurally bound H in dislocations, release of H2O from dislocations during recovery, and dislocation generation at very small fluid inclusions. The H2O weakening by this process is of disequilibrium nature because it depends on the amount of H2O available.The financial support of NF project NF200020.119878 is gratefully acknowledged

The Hide-and-Seek of Grain Boundaries from Moire Pattern Fringe of Two-Dimensional Graphene

Grain boundaries (GBs) commonly exist in crystalline materials and affect various properties of materials. The facile identification of GBs is one of the significant requirements for systematical study of polycrystalline materials including recently emerging two-dimensional materials. Previous observations of GBs have been performed by various tools including high resolution transmission electron microscopy. However, a method to easily identify GBs, especially in the case of low-angle GBs, has not yet been well established. In this paper, we choose graphene bilayers with a GB as a model system and investigate the effects of interlayer rotations to the identification of GBs. We provide a critical condition between adjacent moire fringe spacings, which determines the possibility of GB recognition. In addition, for monolayer graphene with a grain boundary, we demonstrate that low-angle GBs can be distinguished easily by inducing moire patterns deliberately with an artificial reference overlayopen0

Unraveling quantum Hall breakdown in bilayer graphene with scanning gate microscopy

We use low-temperature scanning gate microscopy (SGM) to investigate the breakdown of the quantum Hall regime in an exfoliated bilayer graphene flake. SGM images captured during breakdown exhibit intricate patterns of "hotspots" where the conductance is strongly affected by the presence of the tip. Our results are well described by a model based on quantum percolation which relates the points of high responsivity to tip-induced scattering between localized Landau levels.Comment: 6 pages, 4 figure

How do African grey parrots (Psittacus erithacus) perform on a delay of gratification task?

Humans and other animals often find it difficult to choose a delayed reward over an immediate one, even when the delay leads to increased pay-offs. Using a visible incremental reward procedure, we tested the ability of three grey parrots to maintain delay of gratification for an increasingly valuable food pay-off. Up to 5 sunflower seeds were placed within the parrot’s reach, one at a time, at a rate of 1 seed per second. When the parrot took a seed the trial was ended and the birds consumed the accumulated seeds. Parrots were first tested in daily sessions of 10 trials and then with single daily trials. For multiple trial sessions, all three parrots showed some limited improvement across 30 sessions. For single trial sessions, only one parrot showed any increase in seed acquisition across trials. This parrot was also able to consistently obtain two or more seeds per trial (across both multiple and single trial conditions) but was unable to able to wait 5 seconds to obtain the maximum number of seeds. This parrot was also tested on a slower rate of seed presentation, and this significantly reduced her mean seed acquisition in both multiple and single trial conditions, suggesting that both value of reward available and delay duration impact upon self-control. Further manipulation of both the visibility and proximity of seeds during delay maintenance had little impact upon tolerance of delays for both parrots tested in this condition. This task demanded not just a choice of delayed reward but the maintenance of delayed gratification and was clearly difficult for the parrots to learn; additional training or alternative paradigms are required to better understand the capacity for self-control in this species