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Three-layer model with absorption for conservative estimation of the maximum acoustic transmission coefficient through the human skull for transcranial ultrasound stimulation.
Transcranial ultrasound stimulation (TUS) has been shown to be a safe and effective technique for non-invasive superficial and deep brain stimulation. Safe and efficient translation to humans requires estimating the acoustic attenuation of the human skull. Nevertheless, there are no international guidelines for estimating the impact of the skull bone. A tissue independent, arbitrary derating was developed by the U.S. Food and Drug Administration to take into account tissue absorption (0.3 dB/cm-MHz) for diagnostic ultrasound. However, for the case of transcranial ultrasound imaging, the FDA model does not take into account the insertion loss induced by the skull bone, nor the absorption by brain tissue. Therefore, the estimated absorption is overly conservative which could potentially limit TUS applications if the same guidelines were to be adopted. Here we propose a three-layer model including bone absorption to calculate the maximum pressure transmission through the human skull for frequencies ranging between 100 kHz and 1.5 MHz. The calculated pressure transmission decreases with the frequency and the thickness of the bone, with peaks for each thickness corresponding to a multiple of half the wavelength. The 95th percentile maximum transmission was calculated over the accessible surface of 20 human skulls for 12 typical diameters of the ultrasound beam on the skull surface, and varies between 40% and 78%. To facilitate the safe adjustment of the acoustic pressure for short ultrasound pulses, such as transcranial imaging or transcranial ultrasound stimulation, a table summarizes the maximum pressure transmission for each ultrasound beam diameter and each frequency.
The role of the human hippocampus in decision-making under uncertainty
AbstractThe role of the hippocampus in decision-making is beginning to be more understood. Because of its prospective and inferential functions, we hypothesized that it might be required specifically when decisions involve the evaluation of uncertain values. A group of individuals with autoimmune limbic encephalitis—a condition known to focally affect the hippocampus—were tested on how they evaluate reward against uncertainty compared to reward against another key attribute: physical effort. Across four experiments requiring participants to make trade-offs between reward, uncertainty and effort, patients with acute limbic encephalitis demonstrated blunted sensitivity to reward and effort whenever uncertainty was considered, despite demonstrating intact uncertainty sensitivity. By contrast, the valuation of these two attributes (reward and effort) was intact on uncertainty-free tasks. Reduced sensitivity to changes in reward under uncertainty correlated with the severity of hippocampal damage. Together, these findings provide evidence for a context-sensitive role of the hippocampus in value-based decision-making, apparent specifically under conditions of uncertainty.
The Hopkins-Oxford Psychedelics Ethics (HOPE) Working Group Consensus Statement
The first Hopkins-Oxford Psychedelic Ethics (HOPE) workshop convened to discuss ethical matters relating to psychedelics in August of 2023 at the University of Oxford. The organizers (BDE, DBY, EJ) aimed for a diversity of participant backgrounds and perspectives. The keynotes were given by an Indigenous scholar and a psychiatrist; other attendees included lawyers and ethicists, psychedelic scientists, anthropologists, philosophers, entrepreneurs and harm reduction actors. The workshop was organized out of a recognition that the field of psychedelics is at a pivotal point in its history: research, clinical applications, and policy initiatives are quickly scaling up. The use of psychedelics is expanding, and the development of new systems governing their use is already underway. These changes are happening while substantial uncertainty remains, both about the effects of psychedelics and about the ethical dimensions surrounding their use. We recognize that there is a significant risk of harms as well as potential benefits. Participants at the workshop discussed the ethical aspects of psychedelics, including research methods, clinical practices, history, law and society, spirituality, community, culture and politics that arise in relation to psychedelics. Despite the value of these discussions, the group remains mindful that relatively few voices could be included compared to the scope of those thinking about psychedelics, and those who will be impacted by psychedelics in the coming years. Participants resolved that improving outcomes will require us to make special efforts to further increase the diversity of participant perspectives and backgrounds at future events, including patients and users (not only those who have been benefited by psychedelics, but also those who have been harmed), biopharmaceutical companies, Indigenous communities with established histories of psychedelic use, and law and policy makers. Workshop participants discussed a draft of the current document. This document is intended to summarize our shared understanding of some of the central ethical considerations relating to psychedelics and a few recommendations to the field. Of course, on some points, there is no consensus yet, and there may never be. Further, there are matters on which the group was agnostic, matters which split the room, and matters which we agreed required more evidence and more discussion between the full breadth of stakeholders. Nonetheless, the signatories endorse the sentiments below and believe they are worth conveying to the field at large. More broadly, we hope that this statement is a useful contribution: to those who work with, research, or use psychedelics, as well as anyone interested in the field.
SOME WRITING TIPS FOR PHILOSOPHY
If you grade enough papers, you will find some consistent pitfalls, especially in the writing of students who are coming to philosophy for the first time. I wrote up the following tips a couple of years ago when I was a teaching assistant for an introductory philosophy class at Yale led by Daniel Greco called 'Problems in Philosophy'. The tips were intended, then, for college students, many of them right out of high school, and most of whom had never written a philosophy paper before. So the focus is on clarity and mastering the basics. With that in mind, I hope you will find these tips helpful for teaching or writing in philosophy (or any other relevant field or discipline).
DEBATING GENDER
There is an ongoing public debate about sex, gender and identity that is often quite heated. This is an edited transcript of an informal lecture I recorded in 2019 to serve as a friendly guide to these complex issues. It represents my best attempt, not to score political points for any particular side, but to give an introductory map of the territory so that you can think for yourself, investigate further, and reach your own conclusions about such controversial questions as 'What does mean to be a man or a woman?'
The past, present, and future of the brain imaging data structure (BIDS)
Abstract The Brain Imaging Data Structure (BIDS) is a community-driven standard for the organization of data and metadata from a growing range of neuroscience modalities. This paper is meant as a history of how the standard has developed and grown over time. We outline the principles behind the project, the mechanisms by which it has been extended, and some of the challenges being addressed as it evolves. We also discuss the lessons learned through the project, with the aim of enabling researchers in other domains to learn from the success of BIDS.
Developing psychological treatments for psychosis.
Evidence shows that talking with patients about psychotic experiences can be beneficial. The key question is therefore: which psychological methods can help patients most? This editorial presents ten principles for the design and development of effective psychological treatments. These principles are perceptible characteristics of successful interventions.
Structural and Cognitive Mechanisms of Group Cohesion in Primates.
Group-living creates stresses that, all else equal, naturally lead to group fragmentation, and hence loss of the benefits that group-living provides. How species that live in large stable groups counteract these forces is not well understood. I use comparative data on grooming networks and cognitive abilities in primates to show that living in large, stable groups has involved a series of structural solutions designed to create chains of 'friendship' (friends-of-friends effects), increased investment in bonding behaviours (made possible by dietary adjustments) to ensure that coalitions work effectively, and neuronally expensive cognitive skills of the kind known to underpin social relationships in humans. The first ensures that individuals synchronise their activity cycles; the second allows the stresses created by group-living to be defused; and the third allows a large number of weak ties to be managed. Between them, these create a form of multilevel sociality based on strong versus weak ties similar to that found in human social networks. In primates, these strategies appear successively at quite specific group sizes, suggesting that they are solutions to 'glass ceilings' that would otherwise limit the range of group sizes that animals can live in (and hence the habitats they can occupy). This sequence maps closely onto the grades now known to underpin the Social Brain Hypothesis and the fractal pattern that is known to optimise information flow round networks.
EXPRESS: Uncertain World: How Children's Curiosity and Intolerance of Uncertainty Relate to their Behaviour and Emotion under Uncertainty.
Curiosity and intolerance of uncertainty (IU) are both thought to drive information seeking but may have different affective profiles; curiosity is often associated with positive affective responses to uncertainty and improved learning outcomes, whereas IU is associated with negative affective responses and anxiety. Curiosity and IU have not previously been examined together in children but may both play an important role in understanding how children respond to uncertainty. Our research aimed to examine how individual differences in parent-reported curiosity and IU were associated with behavioural and emotional responses to uncertainty. Children aged 8-12 (n=133) completed a game in which they were presented with an array of buttons on the screen that, when clicked, played neutral or aversive sounds. Children pressed buttons (information seeking) and rated their emotions and worry under conditions of high and low uncertainty. Facial expressions were also monitored for affective responses. Analyses revealed that children sought more information under high uncertainty than low uncertainty trials and that more curious children reported feeling happier. Contrary to expectations, IU and curiosity were not related to the number of buttons children pressed, nor to their self-reported emotion or worry. However, exploratory analyses suggest that children who are high in IU may engage in more information seeking that reflects checking or safety-seeking than those who are low in IU. Additionally, our findings suggest that there may be age-related change in the effects of IU on worry, with IU more strongly related to worry in uncertain situations for older children than younger children.