Outcome contingency selectively affects the neural coding of outcomes but not of tasks

Value-based decision-making is ubiquitous in every-day life, and critically depends on the contingency between choices and their outcomes. Only if outcomes are contingent on our choices can we make meaningful value-based decisions. Here, we investigate the effect of outcome contingency on the neural coding of rewards and tasks. Participants performed a reversal-learning paradigm in which reward outcomes were contingent on trial-by-trial choices, and performed a ‘free choice’ paradigm in which rewards were random and not contingent on choices. We hypothesized that contingent outcomes enhance the neural coding of rewards and tasks, which was tested using multivariate pattern analysis of fMRI data. Reward outcomes were encoded in a large network including the striatum, dmPFC and parietal cortex, and these representations were indeed amplified for contingent rewards. Tasks were encoded in the dmPFC at the time of decision-making, and in parietal cortex in a subsequent maintenance phase. We found no evidence for contingency-dependent modulations of task signals, demonstrating highly similar coding across contingency conditions. Our findings suggest selective effects of contingency on reward coding only, and further highlight the role of dmPFC and parietal cortex in value-based decision-making, as these were the only regions strongly involved in both reward and task coding

Interfacial tension behavior of binary and ternary mixtures of partially miscible Lennard-Jones fluids: a molecular dynamics simulation

By means of extensive equilibrium molecular dynamics simulations we have investigated, the behavior of the interfacial tension $\gamma$ of two immiscible symmetrical Lennard-Jones fluids. This quantity is studied as function of reduced temperature $T^{*}={{k_{_B} T}\over \epsilon}$ in the range $0.6 \leq T^{*} \leq 3.0$. We find that, unlike the monotonic decay obtained for the liquid-vapor interfacial tension, for the liquid-liquid interface, $\gamma (T)$ has a maximum at a specific temperature. We also investigate the effect that surfactant-like particles has on the thermodynamic as well as the structural properties of the liquid-liquid interface. It is found that $\gamma$ decays monotonically as the concentration of the surfactant-like particles increases.Comment: LaTeX-Revtex file with 7 encapsulated postscript figures. Accepted for publication in Journal of Chemical Physic

Psychedelic use predicts objective knowledge about climate change via increases in nature relatedness

Lifetime psychedelic substance use has previously been linked to nature relatedness and pro-environmental behaviour. Yet, participants’ responses to the self-report measures in these studies may have been affected by stereotypical associations or confirmation bias. We therefore re-examined this link by measuring three pro-environmental dependent variables: nature relatedness, concerns about climate change, and objective knowledge about climate change. Additionally assessing lifetime experience with 30 psychoactive substances, we collected an international convenience sample for an online survey ( n = 641), Controlling for age, educational attainment, and covariation in substance use indicators, psychedelic use (primarily the use of psilocybin) predicted objective knowledge about climate change directly, and indirectly via nature relatedness. Further, it predicted concern about climate change indirectly via nature relatedness. The results suggest that the relationship of psychedelics with pro-environmental variables is not due to psychological biases, but manifests in variables as diverse as emotional affinity towards nature as well as knowledge about climate change

How exerting control over outcomes affects the neural coding of tasks and outcomes

Humans make choices every day, which are often intended to lead to desirable outcomes. While we often have some degree of control over the outcomes of our actions, in many cases this control remains limited. Here, we investigate the effect of control over outcomes on the neural correlates of outcome valuation and implementation of behavior, as desired outcomes can only be reached if choices are implemented as intended. In a value-based decision-making task, reward outcomes were either contingent on trial-by-trial choices between two different tasks, or were unrelated to these choices. Using fMRI, multivariate pattern analysis, and model-based neuroscience methods, we identified reward representations in a large network including the striatum, dorso-medial prefrontal cortex (dmPFC) and parietal cortex. These representations were amplified when rewards were contingent on subjects’ choices. We further assessed the implementation of chosen tasks by identifying brain regions encoding tasks during a preparation or maintenance phase, and found them to be encoded in the dmPFC and parietal cortex. Importantly, outcome contingency did not affect neural coding of chosen tasks. This suggests that controlling choice outcomes selectively affects the neural coding of these outcomes, but has no effect on the means to reach them. Overall, our findings highlight the role of the dmPFC and parietal cortex in processing of value-related and task-related information, linking motivational and control-related processes in the brain. These findings inform current debates on the neural basis of motivational and cognitive control, as well as their interaction

Snell's law for surface electrons: Refraction of an electron gas imaged in real space

On NaCl(100)/Cu(111) an interface state band is observed that descends from the surface-state band of the clean copper surface. This band exhibits a Moire-pattern-induced one-dimensional band gap, which is accompanied by strong standing-wave patterns, as revealed in low-temperature scanning tunneling microscopy images. At NaCl island step edges, one can directly see the refraction of these standing waves, which obey Snell's refraction law.Comment: 4 pages, 4 figure