Delay discounting demonstrates lower impulsivity linked to a higher likelihood of succeeding at smoking cessation

Sixty-eight percent of smokers want to quit, but only one in 10 are successful at smoking cessation. Recently, impulsivity has been studied in relation to smoking cessation with measures like the delay discounting task (DDT). We aimed to build on the robust literature that has already revealed the association between impulsivity and smoking cessation, as well as look at the differences between sexes for which there is conflicting evidence. We hypothesized that lower impulsivity would be positively associated with cessation success. In the parent cessation trial, participants were randomized to 12 weeks of progesterone or placebo. Participants were asked to quit smoking, and their smoking status was monitored via expired carbon monoxide throughout the study. Participants completed a DDT at screening, week 4, and week 8 using the 27-item Monetary Choice Questionnaire, where participants decided between a small immediate reward or a larger delayed reward (LDR). The effective delay 50 (ED50), which is the delay at which the LDR loses half its value, was analyzed. To estimate the association between ED50 and cessation, a logistic mixed model with a participant random intercept was fit, controlling for study week, randomization, sex, and age. For the 181 participants, a doubling of the ED50 was associated with an 18% increase in the odds of tobacco cessation (95% confidence interval: 0.2-38% increase; p=0.05). In agreement with our hypothesis, lower impulsivity correlated to greater tobacco cessation success. Our study also showed no evidence of sex differences in the association between ED50 and smoking cessation.

Avoid-approach conflict behaviors differentially affected by anxiolytics: implications for a computational model of risky decision-making

Whether fear or anxiety is expressed is thought to depend on an animal's proximity to threat. In general, fear is elicited when threat is proximal, while anxiety is a response to threat that is distal and uncertain. This threat gradient model suggests that fear and anxiety involve non-overlapping neural circuitry, yet few behavioral paradigms exist that elicit both states. We studied avoid-approach conflict in rats that were behaving in a predator-inhabited foraging arena task that involved tangible threat and reward incentives. In the task, rats exhibited a variety of both fearful and anxious behaviors corresponding to proximal and distal threat, respectively. We then administered ethanol or diazepam to the rats in order to study how anxiolytics affected these fear and anxiety behaviors. We discovered that both ethanol and diazepam attenuated proximal-threat fear-like behaviors. Furthermore, we found that diazepam, but not ethanol, increased distal-threat anxiety-like behavior but also made rats less risk-averse. Finally, we describe how decisional conflict can be modeled as a partially observable Markov decision process and characterize a potential relationship between anxious behavior, diazepam's ability to suppress hippocampal theta oscillations, and hippocampal representations of the future.