•We investigated belief updating in two tasks, with and without explicit feedback.•Model-based fMRI revealed similar confidence-encoding networks across tasks.•The anterior hippocampus led the ...confidence-encoding network, w/o feedbacks.•The medial PFC and amygdala led a confidence-encoding network, with feedbacks.
Classic decision theories typically assume the presence of explicit value-based outcomes after action selections to update beliefs about action-outcome contingencies. However, ecological environments are often opaque, and it remains unclear whether the neural dynamics underlying belief updating vary under conditions characterized by the presence or absence of such explicit value-based information, after each choice selection. We investigated this question in healthy humans (n = 28) using Bayesian inference and two multi-option fMRI tasks: a multi-armed bandit task, and a probabilistic perceptual task, respectively with and without explicit value-based feedback after choice selections. Model-based fMRI analysis revealed a network encoding belief updating which did not change depending on the task. More precisely, we found a confidence-building network that included anterior hippocampus, amygdala, and medial prefrontal cortex (mPFC), which became more active as beliefs about action-outcome probabilities were confirmed by newly acquired information. Despite these consistent responses across tasks, dynamic causal modeling estimated that the network dynamics changed depending on the presence or absence of trial-by-trial value-based outcomes. In the task deprived of immediate feedback, the hippocampus increased its influence towards both amygdala and mPFC, in association with increased strength in the confidence signal. However, the opposite causal relations were found (i.e., from both mPFC and amygdala towards the hippocampus), in presence of immediate outcomes. This finding revealed an asymmetric relationship between decision confidence computations, which were based on similar computational models across tasks, and neural implementation, which varied depending on the availability of outcomes after choice selections.
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Several decision-making vulnerabilities have been identified as underlying causes for addictive behaviours, or the repeated execution of stereotyped actions despite their adverse consequences. These ...vulnerabilities are mostly associated with brain alterations caused by the consumption of substances of abuse. However, addiction can also happen in the absence of a pharmacological component, such as seen in pathological gambling and videogaming. We use a new reinforcement learning model to highlight a previously neglected vulnerability that we suggest interacts with those already identified, whilst playing a prominent role in non-pharmacological forms of addiction. Specifically, we show that a dual-learning system (i.e. combining model-based and model-free) can be vulnerable to highly rewarding, but suboptimal actions, that are followed by a complex ramification of stochastic adverse effects. This phenomenon is caused by the overload of the capabilities of an agent, as time and cognitive resources required for exploration, deliberation, situation recognition, and habit formation, all increase as a function of the depth and richness of detail of an environment. Furthermore, the cognitive overload can be aggravated due to alterations (e.g. caused by stress) in the bounded rationality, i.e. the limited amount of resources available for the model-based component, in turn increasing the agent’s chances to develop or maintain addictive behaviours. Our study demonstrates that, independent of drug consumption, addictive behaviours can arise in the interaction between the environmental complexity and the biologically finite resources available to explore and represent it.
From flocking birds to swarming insects, interactions of organisms large and small lead to the emergence of collective dynamics. Here, we report striking collective swimming of bovine sperm in ...dynamic clusters, enabled by the viscoelasticity of the fluid. Sperm oriented in the same direction within each cluster, and cluster size and cell-cell alignment strength increased with viscoelasticity of the fluid. In contrast, sperm swam randomly and individually in Newtonian (nonelastic) fluids of low and high viscosity. Analysis of the fluid motion surrounding individual swimming sperm indicated that sperm-fluid interaction was facilitated by the elastic component of the fluid. In humans, as well as cattle, sperm are naturally deposited at the entrance to the cervix and must swim through viscoelastic cervical mucus and other mucoid secretions to reach the site of fertilization. Collective swimming induced by elasticity may thus facilitate sperm migration and contribute to successful fertilization. We note that almost all biological fluids (e.g. mucus and blood) are viscoelastic in nature, and this finding highlights the importance of fluid elasticity in biological function.
Successful reproduction in mammals requires sperm to swim against a fluid flow and through the long and complex female reproductive tract before reaching the egg in the oviduct. Millions of them do ...not make it. Despite their clinical importance, the roles played in sperm migration by the diverse biophysical and biochemical microenvironments within the reproductive tract are largely unknown. In this article, we present the development of a double layer microfluidic device that recreates two important biophysical environments within the female reproductive tract: fluid flow and surface topography. The unique feature of the device is that it enables one to study the cooperative roles of fluid flow and surface topography in guiding sperm migration. Using bull sperm as a model system, we found that microfluidic grooves embedded on a channel surface facilitate sperm migration against fluid flow. These findings suggest ways to design in vitro fertilization devices to treat infertility and to develop non-invasive contraceptives that use a microarchitectural design to entrap sperm.
This paper describes a real-time motion planning algorithm, based on the rapidly-exploring random tree (RRT) approach, applicable to autonomous vehicles operating in an urban environment. Extensions ...to the standard RRT are predominantly motivated by: 1) the need to generate dynamically feasible plans in real-time; 2) safety requirements; 3) the constraints dictated by the uncertain operating (urban) environment. The primary novelty is in the use of closed-loop prediction in the framework of RRT. The proposed algorithm was at the core of the planning and control software for Team MIT's entry for the 2007 DARPA Urban Challenge, where the vehicle demonstrated the ability to complete a 60 mile simulated military supply mission, while safely interacting with other autonomous and human driven vehicles.
Significance Mammalian females must selectively allow sperm with normal morphology and motility to ascend the reproductive tract while rejecting invasion of pathogens. By using microfluidic modeling, ...we revealed that microgrooves and gentle fluid flows, two major biophysical characteristics of the female tract, synergistically provide preferential pathways for sperm. In contrast, the sexually transmitted pathogen, Tritrichomonas foetus , is swept away from these pathways. These findings are not only valuable to dairy and beef industries for maximizing fertility and suppressing disease, but also to human medicine, because the morphology and movement of bull sperm closely resemble those of human sperm, and T. foetus closely resembles Trichomonas vaginalis , which infects 170 million people annually worldwide.
Successful mammalian reproduction requires that sperm migrate through a long and convoluted female reproductive tract before reaching oocytes. For many years, fertility studies have focused on biochemical and physiological requirements of sperm. Here we show that the biophysical environment of the female reproductive tract critically guides sperm migration, while at the same time preventing the invasion of sexually transmitted pathogens. Using a microfluidic model, we demonstrate that a gentle fluid flow and microgrooves, typically found in the female reproductive tract, synergistically facilitate bull sperm migration toward the site of fertilization. In contrast, a flagellated sexually transmitted bovine pathogen, Tritrichomonas foetus , is swept downstream under the same conditions. We attribute the differential ability of sperm and T. foetus to swim against flow to the distinct motility types of sperm and T. foetus ; specifically, sperm swim using a posterior flagellum and are near-surface swimmers, whereas T. foetus swims primarily via three anterior flagella and demonstrates much lower attraction to surfaces. This work highlights the importance of biophysical cues within the female reproductive tract in the reproductive process and provides insight into coevolution of males and females to promote fertilization while suppressing infection. Furthermore, the results provide previously unidentified directions for the development of in vitro fertilization devices and contraceptives.
Efficient contact tracing and testing are fundamental tools to contain the transmission of SARS-CoV-2. We used multi-agent simulations to estimate the daily testing capacity required to find and ...isolate a number of infected agents sufficient to break the chain of transmission of SARS-CoV-2, so decreasing the risk of new waves of infections. Depending on the non-pharmaceutical mitigation policies in place, the size of secondary infection clusters allowed or the percentage of asymptomatic and paucisymptomatic (i.e., subclinical) infections, we estimated that the daily testing capacity required to contain the disease varies between 0.7 and 9.1 tests per thousand agents in the population. However, we also found that if contact tracing and testing efficacy dropped below 60% (e.g. due to false negatives or reduced tracing capability), the number of new daily infections did not always decrease and could even increase exponentially, irrespective of the testing capacity. Under these conditions, we show that population-level information about geographical distribution and travel behaviour could inform sampling policies to aid a successful containment, while avoiding concerns about government-controlled mass surveillance.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Abstract
STUDY QUESTION
Is spermatogenesis impairment caused by Hodgkin's lymphoma (HL) itself or by the various treatments?
SUMMARY ANSWER
HL is not itself the main cause of impaired ...spermatogenesis, which is instead affected by the treatment; the extent of impairment depends on the type of treatment and the number of cycles.
WHAT IS KNOWN ALREADY
Data in the literature are contradictory, although most studies found poor semen quality in HL patients prior to treatment. The impact of therapy on spermatogenesis depends on the type of treatment, but the time needed to recover testicular function following treatment with chemotherapeutic agents inducing azoospermia is unknown.
STUDY DESIGN, SIZE, DURATION
In a retrospective study, the semen parameters of 519 patients (504 with sperm and 15 who were azoospermic) were investigated.
HL patients were analysed before therapy. A longitudinal study was also conducted of semen quality in 202 patients pre- and post-ABVD (doxorubicin, bleomycin, vinblastine and dacarbazine) at T0 (baseline) and 6 (T6), 12 (T12) and 24 (T24) months after the end of treatment, and of 42 patients pre- and post-BEACOPP (bleomycin, etoposide, doxorubicin, cyclophosphamide, vincristine, procarbazine, prednisone), COPP/ABVD (cyclophosphamide, vincristine, procarbazine, prednisone, doxorubicin, bleomycin, vinblastine and dacarbazine), OPP/ABVD (vincristine, procarbazine, prednisone, doxorubicin, bleomycin, vinblastine and dacarbazine) or MOPP (mechlorethamine, vincristine, procarbazine and prednisone) and inguinal radiotherapy at different observation times (from T0 to 16 years after treatment).
PARTICIPANTS/MATERIALS, SETTING, METHODS
Semen parameters were examined according to World Health Organization 2010 criteria, evaluating sperm concentration, total sperm number, progressive motility and morphology.
MAIN RESULTS AND THE ROLE OF CHANCE
Our data, which pertain to the largest caseload reported to date, indicate that 75% of HL patients are normozoospermic prior to treatment. The results from the HL patients studied pre- and post-therapy demonstrate that spermatogenesis recovery depends on the therapeutic regimen used. After ABVD, there was a statistically significant decrease in sperm concentration and total sperm number at T6 and T12 (P < 0.001; P < 0.01, respectively). There was a significant drop in progressive motility (P < 0.001) and a significant increase in abnormal forms (P < 0.01) at T6. The differences in sperm concentration, total sperm number and abnormal forms at T0 and T24 were not statistically significant, indicating that sperm quality had returned to pre-therapy values. The most interesting data in terms of patient management arise from the study of azoospermia induced by other chemotherapeutic agents. A high number of BEACOPP, COPP/ABVD, OPP/ABVD or MOPP cycles (≥6) induced a permanent absence of sperm in the seminal fluid, while even following a low number of cycles (<6), spermatogenesis only recovered after 3–5 years and semen quality was highly impaired.
LIMITATIONS, REASONS FOR CAUTION
The study type (retrospective) and the low caseload and varying time of the follow-up do not permit any firm conclusions to be drawn about the recovery of spermatogenesis after BEACOPP or other combined therapies, or the identification of any risk factors for testicular function in treated patients.
WIDER IMPLICATIONS OF THE FINDINGS
The pretreatment semen parameters of HL patients in this study were better than some results reported in the literature, with a higher percentage of normozoospermic patients. Strengths of this study were the large caseload of HL patients and a high degree of consistency in semen analysis, as all parameters were assessed in the same laboratory. Following the azoospermia induced by different chemotherapeutic protocols, spermatogenesis may take several years to recover. Awareness of this issue will enable oncologists to better inform patients about the possibility of recovering fertility post-treatment and also demonstrates the importance of semen cryobanking before beginning any cancer treatment.
STUDY FUNDING/COMPETING INTEREST(S)
Supported by a grant from the Italian Ministry of Education and Research (MIUR-PRIN) and the University of Rome ‘La Sapienza’ Faculty of Medicine. The authors have no conflicts of interest.
•Behavioral addictions share neurobiological and behavioral characteristics with SUDs.•Computational modeling may help clarify underlying mechanisms.•Aberrant model-based & -free control are ...presented as common computational principles.•Reinforcement learning, Bayesian inference, and neural models are introduced.•Possible extensions of models for SUDs, as well as new perspectives, are discussed.
Non-pharmacological behavioral addictions, such as pathological gambling, videogaming, social networking, or internet use, are becoming major public health concerns. It is not yet clear how behavioral addictions could share many major neurobiological and behavioral characteristics with substance use disorders, despite the absence of direct pharmacological influences. A deeper understanding of the neurocognitive mechanisms of addictive behavior is needed, and computational modeling could be one promising approach to explain intricately entwined cognitive and neural dynamics. This review describes computational models of addiction based on reinforcement learning algorithms, Bayesian inference, and biophysical neural simulations. We discuss whether computational frameworks originally conceived to explain maladaptive behavior in substance use disorders can be effectively extended to non-substance-related behavioral addictions. Moreover, we introduce recent studies on behavioral addictions that exemplify the possibility of such extension and propose future directions.
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