Pre-bomb marine reservoir variability in the Kimberley region, Western Australia

New ΔR values are presented for 10 known-age shells from the Kimberley region of northwest Australia. Previous estimates of ΔR for the Kimberley region are based on only 6 individual shell specimens with dates of live collection known only to within 50 yr (Bowman 1985a). Here, we describe the results of our recent attempts to constrain ΔR variability for this region by dating a suite of known-age pre-AD 1950 shell samples from the Australian Museum and Museum Victoria. A regional ΔR of 58 ± 17 14C yr for open waters between Broome and Cape Leveque is recommended based on 7 of these specimens. The criteria used to select shells for dating and inclusion in the regional mean are discussed.Copyright Information: http://www.sherpa.ac.uk/romeo/issn/0033-8222

Spatial structure normalises working memory performance in Parkinson\u27s disease

Cognitive deficits are a frequent symptom of Parkinson\u27s disease (PD), particularly in the domain of spatial working memory (WM). Despite numerous demonstrations of aberrant WM in patients, there is a lack of understanding about how, if at all, their WM is fundamentally altered. Most notably, it is unclear whether span – the yardstick upon which most WM models are built – is compromised by the disease. Moreover, it is also unknown whether WM deficits occur in all patients or only exist in a sub-group who are executively impaired. We assessed the factors that influenced spatial span in medicated patients by varying the complexity of to-be-remembered items. Principally, we manipulated the ease with which items could enter – or be blocked from – WM by varying the level of structure in memoranda. Despite having similar levels of executive performance to controls, PD patients were only impaired when remembering information that lacked spatial, easy-to-chunk, structure. Patients\u27 executive function, however, did not influence this effect. The ease with which patients could control WM was further examined by presenting irrelevant information during encoding, varying the level of structure in irrelevant information and manipulating the amount of switching between relevant and irrelevant information. Disease did not significantly alter the effect of these manipulations. Rather, patients\u27 executive performance constrained the detrimental effect of irrelevant information on WM. Thus, PD patients\u27 spatial span is predominantly determined by level of structure in to-be-remembered information, whereas their level of executive function may mitigate against the detrimental effect of irrelevant information

Self-reported intake of high-fat and high-sugar diet is not associated with cognitive stability and flexibility in healthy men

Animal studies indicate that a high-fat/high-sugar diet (HFS) can change dopamine signal transmission in the brain, which could promote maladaptive behavior and decision-making. Such diet-induced changes may also explain observed alterations in the dopamine system in human obesity. Genetic variants that modulate dopamine transmission have been proposed to render some individuals more prone to potential effects of HFS. The objective of this study was to investigate the association of HFS with dopamine-dependent cognition in humans and how genetic variations might modulate this potential association. Using a questionnaire assessing the self -reported consumption of high-fat/high-sugar foods, we investigated the association with diet by recruiting healthy young men that fall into the lower or upper end of that questionnaire (low fat/sugar group: LFS, n = 45; high fat/sugar group: HFS, n = 41) and explored the interaction of fat and sugar consumption with COMT Va1158Met and Taq1A genotype. During functional magnetic resonance imaging (fMRI) scanning, male partici-pants performed a working memory (WM) task that probes distractor-resistance and updating of WM repre-sentations. Logistic and linear regression models revealed no significant difference in WM performance between the two diet groups, nor an interaction with COMT Va1t58Met or Tag1A genotype. Neural activation in task -related brain areas also did not differ between diet groups. Independent of diet group, higher BMI was associ-ated with lower overall accuracy on the WM task. This cross-sectional study does not provide evidence for diet -related differences in WM stability and flexibility in men, nor for a predisposition of COMT Va1158Met or Tag1A genotype to the hypothesized detrimental effects of an HFS diet. Previously reported associations of BMI with WM seem to be independent of HFS intake in our male study sample.Peer reviewe

Dopamine modulates dynamic decision-making during foraging

The mesolimbic dopaminergic system exerts a crucial influence on incentive processing. However, the contribution of dopamine in dynamic, ecological situations where reward rates vary, and decisions evolve over time, remains unclear. In such circumstances, current (foreground) reward accrual needs to be compared continuously with potential rewards that could be obtained by travelling elsewhere (background reward rate), in order to determine the opportunity cost of staying versus leaving. We hypothesised that dopamine specifically modulates the influence of background – but not foreground – reward information when making a dynamic comparison of these variables for optimal behaviour. On a novel foraging task based on an ecological account of animal behaviour (marginal value theorem), human participants of either sex decided when to leave locations in situations where foreground rewards depleted at different rates, either in rich or poor environments with high or low background rates. In line with theoretical accounts, people’s decisions to move from current locations were independently modulated by changes in both foreground and background reward rates. Pharmacological manipulation of dopamine D2 receptor activity using the agonist cabergoline significantly affected decisions to move on, specifically modulating the effect of background reward rates. In particular, when on cabergoline, people left patches in poor environments much earlier. These results demonstrate a role of dopamine in signalling the opportunity cost of rewards, not value per se. Using this ecologically derived framework we uncover a specific mechanism by which D2 dopamine receptor activity modulates decision-making when foreground and background reward rates are dynamically compared

Neural mechanisms of attending to items in working memory

Working memory, the ability to keep recently accessed information available for immediate manipulation, has been proposed to rely on two mechanisms that appear difficult to reconcile: self-sustained neural firing, or the opposite-activity-silent synaptic traces. Here we review and contrast models of these two mechanisms, and then show that both phenomena can co-exist within a unified system in which neurons hold information in both activity and synapses. Rapid plasticity in flexibly-coding neurons allows features to be bound together into objects, with an important emergent property being the focus of attention. One memory item is held by persistent activity in an attended or "focused" state, and is thus remembered better than other items. Other, previously attended items can remain in memory but in the background, encoded in activity-silent synaptic traces. This dual functional architecture provides a unified common mechanism accounting for a diversity of perplexing attention and memory effects that have been hitherto difficult to explain in a single theoretical framework

Direct radiocarbon dating of fish otoliths from mulloway (Argyrosomus japonicus) and black bream (Acanthopagrus butcheri) from Long Point, Coorong, South Australia

Accelerator Mass Spectrometry (AMS) radiocarbon dates (n=20) determined on fish otoliths from mulloway (Argyrosomus japonicus) and black bream (Acanthopagrus butcheri) are reported from five sites at Long Point, Coorong, South Australia. The dates range from 2938–2529 to 326–1 cal. BP, extending the known period of occupation of Long Point. Previous dating at the sites indicated intensive occupation of the area from 2455–2134 cal. BP. Results provide a detailed local chronology for the region, contributing to a more comprehensive understanding of Aboriginal use of Ngarrindjeri lands and waters. This study validates the use of fish otoliths for radiocarbon dating and reveals how dating different materials can result in different midden chronologies

A Powassan virus domain III nanoparticle immunogen elicits neutralizing and protective antibodies in mice

Powassan virus (POWV) is an emerging tick borne flavivirus (TBFV) that causes severe neuroinvasive disease. Currently, there are no approved treatments or vaccines to combat POWV infection. Here, we generated and characterized a nanoparticle immunogen displaying domain III (EDIII) of the POWV E glycoprotein. Immunization with POWV EDIII presented on nanoparticles resulted in significantly higher serum neutralizing titers against POWV than immunization with monomeric POWV EDIII. Furthermore, passive transfer of EDIII-reactive sera protected against POWV challenge in vivo. We isolated and characterized a panel of EDIII-specific monoclonal antibodies (mAbs) and identified several that potently inhibit POWV infection and engage distinct epitopes within the lateral ridge and C-C\u27 loop of the EDIII. By creating a subunit-based nanoparticle immunogen with vaccine potential that elicits antibodies with protective activity against POWV infection, our findings enhance our understanding of the molecular determinants of antibody-mediated neutralization of TBFVs

Catecholaminergic modulation of trust decisions

Rationale: Trust is a key component of social interactions. In order to assess the trustworthiness of others, people rely on both information learned from previous encounters, as well as on implicit biases associated with specific facial features. Objective: Here, we investigated the role of catecholamine (dopamine and noradrenaline) transmission on trust decisions as a function of both experienced behavior and facial features. Methods: To increase catecholamine levels, methylphenidate (MPH, i.e., Ritalin®, 20 mg) was administered to participants (N = 24) prior to their playing a well-studied economic task, namely the Trust Game (Berg et al. 1995). We measured the amount of money invested with a variety of game partners. Across game partners, we manipulated two aspects of trust: the facial trust level (high facial trust, low facial trust, and non-social) and the likelihood of reciprocation (high, low). Results: Results demonstrated no main effect of MPH on investments, but rather a selective lowering of investments under MPH as compared with placebo with the game partners who were low on facial trustworthiness and were low reciprocators. Conclusion: These results provide evidence that MPH administration impacts social trust decision-making, but does so in a context-specific manner

An antiangiogenic neurokinin-B/thromboxane A2 regulatory axis

Establishment of angiogenic circuits that orchestrate blood vessel development and remodeling requires an exquisite balance between the activities of pro- and antiangiogenic factors. However, the logic that permits complex signal integration by vascular endothelium is poorly understood. We demonstrate that a “neuropeptide,” neurokinin-B (NK-B), reversibly inhibits endothelial cell vascular network assembly and opposes angiogenesis in the chicken chorioallantoic membrane. Disruption of endogenous NK-B signaling promoted angiogenesis. Mechanistic analyses defined a multicomponent pathway in which NK-B signaling converges upon cellular processes essential for angiogenesis. NK-B−mediated ablation of Ca2+ oscillations and elevation of 3′–5′ cyclic adenosine monophosphate (cAMP) reduced cellular proliferation, migration, and vascular endothelial growth factor receptor expression and induced the antiangiogenic protein calreticulin. Whereas NK-B initiated certain responses, other activities required additional stimuli that increase cAMP. Although NK-B is a neurotransmitter/ neuromodulator and NK-B overexpression characterizes the pregnancy-associated disorder preeclampsia, NK-B had not been linked to vascular remodeling. These results establish a conserved mechanism in which NK-B instigates multiple activities that collectively oppose vascular remodeling