The last decades of neuroscience research have produced immense progress in the methods available to understand brain structure and function. Social, cognitive, clinical, affective, economic, communication, and developmental neurosciences have begun to map the relationships between neuro-psychological processes and behavioral outcomes, yielding a new understanding of human behavior and promising interventions. However, a limitation of this fast moving research is that most findings are based on small samples of convenience. Furthermore, our understanding of individual differences may be distorted by unrepresentative samples, undermining findings regarding brain–behavior mechanisms. These limitations are issues that social demographers, epidemiologists, and other population scientists have tackled, with solutions that can be applied to neuroscience. By contrast, nearly all social science disciplines, including social demography, sociology, political science, economics, communication science, and psychology, make assumptions about processes that involve the brain, but have incorporated neural measures to differing, and often limited, degrees; many still treat the brain as a black box. In this article, we describe and promote a perspective—population neuroscience—that leverages interdisciplinary expertise to (i) emphasize the importance of sampling to more clearly define the relevant populations and sampling strategies needed when using neuroscience methods to address such questions; and (ii) deepen understanding of mechanisms within population science by providing insight regarding underlying neural mechanisms. Doing so will increase our confidence in the generalizability of the findings. We provide examples to illustrate the population neuroscience approach for specific types of research questions and discuss the potential for theoretical and applied advances from this approach across areas.

Adolescent alcohol consumption is a major public health problem in the United States and a high priority for organizations, such as the Office of the Surgeon General,¹ Centers for Disease Control and Prevention,² World Health Organization,³ American Academy of Pediatrics,⁴ and National Institute on Alcohol Abuse and Alcoholism.⁵ Approximately 5000 persons younger than 21 years die each year from alcohol-related fatalities,⁶ while problems linked to underage drinking were estimated in 2001 to cost about $62 billion.⁷ Underage drinking is also a predictor of alcohol problems and early mortality in adulthood.^8-11

Marijuana is the most commonly used illicit substance in the United States and is especially prevalent among young adults.¹ Marijuana use typically emerges during adolescence, peaking in the early 20s, with 35% of 21- and 22- year-old individuals reporting past year use.² This pervasiveness may be due to low perceptions of harm,² despite the short- and long-term negative consequences³ of marijuana use. Short-term consequences include acute anxiety, paranoia, and altered perception,⁴ as well as impaired motor coordination while driving.⁵ Deficits in academic achievement⁶ and disrupted brain structure and function^7-10 suggest long-term negative consequences of marijuana use. Of particular relevance to the present study is evidence that earlier onset of marijuana use leads to a faster transition to marijuana dependence¹¹ and increases the risk of developing other substance use disorders (SUDs).¹²

Background: Well-validated models of maternal behavior in small-brain mammals posit a central role of oxytocin in parenting, by reducing stress and enhancing the reward value of social interactions with offspring. In contrast, human studies are only beginning to gain insights into how oxytocin modulates maternal behavior and affiliation. Methods: To explore associations between oxytocin receptor genes and maternal parenting behavior in humans, we conducted a genetic imaging study of women selected to exhibit a wide range of observed parenting when their children were 4-6 years old. Results: In response to child stimuli during functional magnetic resonance imaging, hemodynamic responses in brain regions that mediate affect, reward, and social behavior were significantly correlated with observed positive parenting. Furthermore, single nucleotide polymorphisms (rs53576 and rs1042778) in the gene encoding the oxytocin receptor were significantly associated with both positive parenting and hemodynamic responses to child stimuli in orbitofrontal cortex, anterior cingulate cortex and hippocampus. Conclusions: These findings contribute to the emerging literature on the role of oxytocin in human social behavior and support the feasibility of tracing biological pathways from genes to neural regions to positive maternal parenting behaviors in humans using genetic imaging methods.

• Real-time fMRI neurofeedback is a promising tool to reduce drug cravings. • Reward- and affect-related brain function can be modulated through neurofeedback. • Long-term learning effects of neurofeedback training remain unknown. • Additional real-time fMRI neurofeedback studies relevant to addiction are warranted.