A striking neurochemical form of compartmentalization has been found in the striatum of humans and other species, dividing it into striosomes and matrix. The function of this organization has been ...unclear, but the anatomical connections of striosomes indicate their relation to emotion-related brain regions, including the medial prefrontal cortex. We capitalized on this fact by combining pathway-specific optogenetics and electrophysiology in behaving rats to search for selective functions of striosomes. We demonstrate that a medial prefronto-striosomal circuit is selectively active in and causally necessary for cost-benefit decision-making under approach-avoidance conflict conditions known to evoke anxiety in humans. We show that this circuit has unique dynamic properties likely reflecting striatal interneuron function. These findings demonstrate that cognitive and emotion-related functions are, like sensory-motor processing, subject to encoding within compartmentally organized representations in the forebrain and suggest that striosome-targeting corticostriatal circuits can underlie neural processing of decisions fundamental for survival.
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•A specific fronto-striatal decision circuit is activated by cost-benefit conflict•It primarily targets striatal striosomes, linked to limbic functions of striatum•Its optogenetic control selectively alters decisions under cost-benefit conflict•Its corticostriatal control is exerted through a striatal inhibitory microcircuit
Optogenetic manipulation and electrophysiology of a circuit connecting the prefrontal cortex to striosomes—compartmentalized structures of the striatum—reveals that it has a selective role in influencing decision-making for choices with cost-benefit tradeoffs.
Objective
This essay aims to explain the impasse in debates concerning Confederate monuments in public spaces by noting a difference in unstated philosophical assumptions.
Method
I examine two ...positions in this debate, offering an explanation for the inability for opposing sides to engage. The analytical framework has its basis in philosophical debates regarding objectivity in scientific theory selection.
Results
Arguably, the impasse in this debate concerns underlying ethical principles: one that assesses morality based on intentions that motivate actions (namely, the motivation for erecting a monument) and one that assesses morality based on consequences of actions (namely, the consequences of removing monuments).
Conclusions
The locus of discussion can shift to these philosophical principles, offering a novel avenue for discussion and, hence, reconciliation. I suggest a fate for Confederate monuments that is responsive to both sides’ concerns and is informed by another country's attempt to reconcile with its troubled past.
High-intensity interval training (HIT) increases skeletal muscle oxidative capacity similar to traditional endurance training, despite a low total exercise volume. Much of this work has focused on ...young active individuals, and it is unclear whether the results are applicable to older less active populations. In addition, many studies have used "all-out" variable-load exercise interventions (e.g., repeated Wingate tests) that may not be practical for all individuals. We therefore examined the effect of a more practical low-volume submaximal constant-load HIT protocol on skeletal muscle oxidative capacity and insulin sensitivity in middle-aged adults, who may be at a higher risk for inactivity-related disorders.
Seven sedentary but otherwise healthy individuals (three women) with a mean ± SD age, body mass index, and peak oxygen uptake (VO(2peak)) of 45 ± 5 yr, 27 ± 5 kg·m(-2), and 30 ± 3 mL·kg(-1)·min(-1) performed six training sessions during 2 wk. Each session involved 10 × 1-min cycling at ∼60% of peak power achieved during a ramp VO(2peak) test (eliciting ∼80%-95% of HR reserve) with 1 min of recovery between intervals. Needle biopsy samples (vastus lateralis) were obtained before training and ∼72 h after the final training session.
Muscle oxidative capacity, as reflected by the protein content of citrate synthase and cytochrome c oxidase subunit IV, increased by ∼35% after training. The transcriptional coactivator peroxisome proliferator-activated receptor γ coactivator 1α was increased by ∼56% after training, but the transcriptional corepressor receptor-interacting protein 140 remained unchanged. Glucose transporter protein content increased ∼260%, and insulin sensitivity, on the basis of the insulin sensitivity index homeostasis model assessment, improved by ∼35% after training.
Constant-load low-volume HIT may be a practical time-efficient strategy to induce metabolic adaptations that reduce the risk for inactivity-related disorders in previously sedentary middle-aged adults.
The oxygenation of Earth’s surface environment dramatically altered key biological and geochemical cycles and ultimately ushered in the rise of an ecologically diverse biosphere. However, atmospheric ...oxygen partial pressures (pO₂) estimates for large swaths of the Precambrian remain intensely debated. Here we evaluate and explore the use of carbonate cerium(Ce) anomalies (Ce/Ce*) as a quantitative atmospheric pO₂ proxy and provide estimates of Proterozoic pO₂ using marine carbonates from a unique Precambrian carbonate succession—the Paleoproterozoic Pethei Group. In contrast to most previous work, wemeasure Ce/Ce* on marine carbonate precipitates that formed in situ across a depth gradient, building on previous detailed sedimentology and stratigraphy to constrain the paleo-depth of each sample. Measuring Ce/Ce* across a full platform to basin depth gradient, we found only minor depleted Ce anomalies restricted to the platform and upper slope facies. We combine these results with a Ce oxidation model to provide a quantitative constraint on atmospheric pO₂ 1.87 billion years ago (Ga). Our results suggest Paleoproterozoic atmospheric oxygen concentrations were low, near 0.1% of the present atmospheric level. This work provides another crucial line of empirical evidence that atmospheric oxygen levels returned to low concentrations following the Lomagundi Event, and remained low enough for large portions of the Proterozoic to have impacted the ecology of the earliest complex organisms.
Effective evaluation of costs and benefits is a core survival capacity that in humans is considered as optimal, “rational” decision-making. This capacity is vulnerable in neuropsychiatric disorders ...and in the aftermath of chronic stress, in which aberrant choices and high-risk behaviors occur. We report that chronic stress exposure in rodents produces abnormal evaluation of costs and benefits resembling non-optimal decision-making in which choices of high-cost/high-reward options are sharply increased. Concomitantly, alterations in the task-related spike activity of medial prefrontal neurons correspond with increased activity of their striosome-predominant striatal projection neuron targets and with decreased and delayed striatal fast-firing interneuron activity. These effects of chronic stress on prefronto-striatal circuit dynamics could be blocked or be mimicked by selective optogenetic manipulation of these circuits. We suggest that altered excitation-inhibition dynamics of striosome-based circuit function could be an underlying mechanism by which chronic stress contributes to disorders characterized by aberrant decision-making under conflict.
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•Chronic stress produces abnormal cost-benefit integration in decision-making•This reflects abnormal in-task firing dynamics of prefrontal and striatal cells•This circuit disorder leads to highly elevated firing of striosomal output neurons•Optogenetic manipulations can mimic or reverse these behavioral effects of stress
A brain circuit that connects the prefrontal cortex with striosomes in the striatum is activated in cost-benefit decision-making and becomes severely impaired after chronic stress, producing abnormal weighing of cost and benefit.
Both the abiotic environment and the composition of animal and plant communities change with elevation. For mutualistic species, these changes are expected to result in altered partner availability, ...and shifts in context-dependent benefits for partners. To test these predictions, we assessed the network structure of terrestrial ant-plant mutualists and how the benefits to plants of ant inhabitation changed with elevation in tropical forest in Papua New Guinea. At higher elevations, ant-plants were rarer, species richness of both ants and plants decreased, and the average ant or plant species interacted with fewer partners. However, networks became increasingly connected and less specialized, more than could be accounted for by reductions in ant-plant abundance. On the most common ant-plant, ants recruited less and spent less time attacking a surrogate herbivore at higher elevations, and herbivory damage increased. These changes were driven by turnover of ant species rather than by within-species shifts in protective behaviour. We speculate that reduced partner availability at higher elevations results in less specialized networks, while lower temperatures mean that even for ant-inhabited plants, benefits are reduced. Under increased abiotic stress, mutualistic networks can break down, owing to a combination of lower population sizes, and a reduction in context-dependent mutualistic benefits.
Acute kidney injury (AKI) is a common complication following cardiac surgery performed on cardiopulmonary bypass (CPB) and has important implications for prognosis. The aetiology of cardiac ...surgery‐associated AKI is complex, but renal hypoxia, particularly in the medulla, is thought to play at least some role. There is strong evidence from studies in experimental animals, clinical observations and computational models that medullary ischaemia and hypoxia occur during CPB. There are no validated methods to monitor or improve renal oxygenation during CPB, and thus possibly decrease the risk of AKI. Attempts to reduce the incidence of AKI by early transfusion to ameliorate intra‐operative anaemia, refinement of protocols for cooling and rewarming on bypass, optimization of pump flow and arterial pressure, or the use of pulsatile flow, have not been successful to date. This may in part reflect the complexity of renal oxygenation, which may limit the effectiveness of individual interventions. We propose a multi‐disciplinary pathway for translation comprising three components. Firstly, large‐animal models of CPB to continuously monitor both whole kidney and regional kidney perfusion and oxygenation. Secondly, computational models to obtain information that can be used to interpret the data and develop rational interventions. Thirdly, clinically feasible non‐invasive methods to continuously monitor renal oxygenation in the operating theatre and to identify patients at risk of AKI. In this review, we outline the recent progress on each of these fronts.
The evolution of the global carbon and silicon cycles is thought to have contributed to the long-term stability of Earth's climate
. Many questions remain, however, regarding the feedback mechanisms ...at play, and there are limited quantitative constraints on the sources and sinks of these elements in Earth's surface environments
. Here we argue that the lithium-isotope record can be used to track the processes controlling the long-term carbon and silicon cycles. By analysing more than 600 shallow-water marine carbonate samples from more than 100 stratigraphic units, we construct a new carbonate-based lithium-isotope record spanning the past 3 billion years. The data suggest an increase in the carbonate lithium-isotope values over time, which we propose was driven by long-term changes in the lithium-isotopic conditions of sea water, rather than by changes in the sedimentary alterations of older samples. Using a mass-balance modelling approach, we propose that the observed trend in lithium-isotope values reflects a transition from Precambrian carbon and silicon cycles to those characteristic of the modern. We speculate that this transition was linked to a gradual shift to a biologically controlled marine silicon cycle and the evolutionary radiation of land plants
.