Glutamine-to-glutamate ratio in the nucleus accumbens predicts effort-based motivated performance in humans

Substantial evidence implicates the nucleus accumbens in motivated performance, but very little is known about the neurochemical underpinnings of individual differences in motivation. Here, we applied 1H magnetic resonance spectroscopy (1H-MRS) at ultra-high-field in the nucleus accumbens and inquired whether levels of glutamate (Glu), glutamine (Gln), GABA or their ratios predict interindividual differences in effort-based motivated task performance. Given the incentive value of social competition, we also examined differences in performance under self-motivated or competition settings. Our results indicate that higher accumbal Gln-to-Glu ratio predicts better overall performance and reduced effort perception. As performance is the outcome of multiple cognitive, motor and physiological processes, we applied computational modeling to estimate best-fitting individual parameters related to specific processes modeled with utility, effort and performance functions. This model-based analysis revealed that accumbal Gln-to-Glu ratio specifically relates to stamina; i.e., the capacity to maintain performance over long periods. It also indicated that competition boosts performance from task onset, particularly for low Gln-to-Glu individuals. In conclusion, our findings provide novel insights implicating accumbal Gln and Glu balance on the prediction of specific computational components of motivated performance. This approach and findings can help developing therapeutic strategies based on targeting metabolism to ameliorate deficits in effort engagement

Equilibrium moisture content of radiata pine at elevated temperature and pressure reveals measurement challenges

Relatively few studies have been performed on the equilibrium moisture content (EMC) of wood under conditions of elevated temperature and pressure. Eight studies indicated that EMC near saturation decreased between 100 and 150 A degrees C, whilst five studies indicated that EMC increased. The aim of this study was to identify the likely source of the disagreement using radiata pine (Pinus radiata D. Don) sapwood which was conditioned to a moisture content of around 3 % and then exposed for 1 h at 150 A degrees C and relative humidities of either 50, 70 or 90 %. Mean values of EMC, obtained through in situ gravimetric analyses, were 5.7, 7.6 and 12.6 % with 95 % confidence intervals of the order of 1 %. In two further experiments, the humidity was allowed to rise briefly above 90 % and the moisture content after 1 h was found to be > 30 % as in the five studies that indicated EMC increased above 100 A degrees C. The high moisture contents were attributed to condensation of liquid water on the specimen with subsequent evaporation at a rate that was too slow for the moisture content to reach equilibrium before it was measured. Reliable EMC data at elevated temperatures require (1) tight process control of experimental conditions with minimal standard error, (2) specimens with low initial moisture content to avoid unwanted wood mass loss over time, (3) a relative humidity upper limit that avoids drift above 95 %, and (4) extrapolation of data to humidity approaching 100 %

The Central Atlantic Magmatic Province (CAMP): A Review

The Central Atlantic magmatic province (CAMP) consists of basic rocks emplaced as shallow intrusions and erupted in large lava flow fields over a land surface area in excess of 10 million km2 on the supercontinent Pangaea at about 201 Ma. The peak activity of the CAMP straddled the Triassic-Jurassic boundary and probably lasted less than 1 million years, while late activity went on for several Ma more into the Sinemurian. Emission of carbon and sulfur from the CAMP magmas and from intruded sediments probably caused extinctions at the end-Triassic. Intrusive rocks are represented by isolated dykes up to 800 km-long, by dense dyke swarms and by extremely voluminous sills and a few layered intrusions. Lava fields were erupted as short-lived pulses and can be traced over distances of several hundred km within sedimentary basins. They consist of either compound or simple pahoehoe flows. Globally, the intrusive and effusive rocks are estimated to represent an original magmatic volume of at least 3 million km3. Herein we subdivide the CAMP basalts for the first time into six main geochemical groups, five represented by low-Ti and one by high-Ti rocks. Except for one low-Ti group, which is ubiquitous throughout the entire province, all other groups occur in relatively restricted areas and their compositions probably reflect contamination from the local continental lithosphere. Major and trace elements and Sr-Nd-Pb-Os isotopic compositions indicate that the basaltic magmas had an enriched composition compared to Mid-Ocean Ridge basalts and different from Atlantic Ocean Island basalts. The enriched composition of CAMP basalts is only in part attributable to crustal contamination. It also probably requires subducted upper and lower continental crust material that enriched the shallow upper mantle from which CAMP basalts were generated. A contribution from a deep mantle-plume is not required by geochemical and thermometric data, but it remains unclear what other possible heat source caused mantle melting on the scale required to form CAMP