Research Spotlights: April 2022

The neurons that drive competition and social behavior within groups have been identified in mice

Research, supported by the NINDS, NICHD, and others has identified neurons in the brain that influence competitive behavior and are involved in shaping social behavior of groups in a mouse model. Social interactions in people, as well as in other animals often happen in large groups, and these group interactions are important in sociology, ecology, psychology, and economics. However, the exact brain processes that are responsible for the complex dynamic behavior of social groups is not well understood, partly due to much of neuroscience research being focused on the behaviors of pairs of individuals interacting in isolation. In contrast, the current study investigated the behavior of large groups of mice during competitive group interactions.

The researchers developed a naturalistic group paradigm where mice competitively foraged for food in large cohorts while wirelessly tracking neuronal activity across thousands of unique interactions. This allowed them to follow and examine the collective behavior of the mouse groups (male mice (n = 98) aged 2 to 5 months). The data showed that the neurons in the anterior cingulate adaptively represented the social rank of the mice in relation to others in the group. The social ranking of each mouse was linked to their success, however the cells in the anterior cingulate were able to determine the relative rank of the mice from their competitive behavior, as well as incorporate information regarding available resources, the environment, and past success to influence the mice’s decisions. Using multiclass models, the researchers were able to show that these neurons tracked other individuals within the group and could accurately predict future success. Additionally, they employed neuromodulation techniques in the anterior cingulate and found that stimulating the neurons conditionally influenced the mice’s competitive effort, such that it only resulted in an increase in effort in mice if they were more dominant to their peers and decreased effort when they were subordinate.

In summary, the findings from this study indicate that competitive success is not just due to physical fitness or strength but is influenced by neuronal signals that affect competitive drive by integrating information about the individual's social ranking, social group dynamics, environment, and resources to determine the most favorable behavior for specific conditions. By understanding the neural basis of group behavior and competition in different environment, social settings, or economic situations holds the potential for better understanding instances when the brain is wired differently. For instance, several human psychological conditions exhibit alterations in social behavior such that a person’s ability to understand social norms and to display appropriate behaviors in social groups is impaired. Elucidation of the neural underpinnings of group behavior and competition may lead to a better understanding of these neurocognitive disorders.

Li SW, Zeliger O, Strahs L, Báez-Mendoza R, Johnson LM, McDonald Wojciechowski A, Williams ZM. Frontal neurons driving competitive behaviour and ecology of social groups. Nature. 2022 Mar;603(7902):661-666. doi: 10.1038/s41586-021-04000-5. Epub 2022 Mar 16. PMID: 35296863.

A parent questionnaire may help doctors track mood symptom trajectories in youth at high-risk for bipolar disorder

The U.S. Surgeon General, Dr. Vivek Murthy, has identified youth mental health as a crisis that urgently needs addressing. The recently published study supported by NIMH, NIA, and others makes an important contribution to understanding the relationship between mood instability and symptomatic, psychosocial, and family functioning among youth at high risk for bipolar disorder (BD).

The research team conducted a randomized trial of psychosocial intervention for youth at risk of BD to evaluate the presence, functional impact, and malleability of mood instability, examine the relationships level of mood instability with levels of psychosocial and family functioning, especially among those with mania symptoms, and explore whether mood instability could be modified by psychosocial interventions. Participants were recruited from outpatient clinics at the UCLA School of Medicine, University of Colorado, Boulder and Aurora, and Stanford University School of Medicine via online radio, radio, and print advertisements to their parents, or were referred by pediatricians. Participants ranged in age from 9 to 17 years at the start of the study (N = 114), and after baseline assessments were randomized to a family-focused therapy or enhanced usual care condition, each lasting four months. Mood instability was based on parent ratings, using the 2—item Children’s Affective Lability Scale. Researchers attempted to follow participants for four years, although the average length of follow-up was 104 weeks (range, 0 – 255 weeks).

Using repeated-measure mixed-effects model, researchers found the trajectory of global functioning was closely associated with the trajectory of mood instability over time. Lower global functioning scores were related to great mood instability. They also found that in the domain of family conflict, mother-rated family functioning was strongly related to mood instability of the child. Furthermore, there were significant effects of lagged mood instability scores on mother-rated functioning scores such that youth with more mood instability in one assessment interval had higher mother/offspring conflict scores in the next interval.

The study findings have some limitations including that mood instability among parents wasn’t measured, and among parents with a history of BD, current mood episodes at the times they completed the ratings of their child’s mood, was not captured.

In summary, this study provides an important examination of the role of mood instability on psychosocial and family functioning. In particular, the research team demonstrated the utility of a brief, non-diagnostic instrument for tracking symptom trajectories and psychosocial impairment. This research highlights the need for creating and validating measures that can be used by caregivers for youth mental health concerns, and for developing interventions that reduce mood instability, such as mindfulness, but are specifically tailored to the needs of youth.

Miklowitz DJ, Weintraub MJ, Singh MK, Walshaw PD, Merranko JA, Birmaher B, Chang KD, Schneck CD. Mood Instability in Youth at High Risk for Bipolar Disorder. J Am Acad Child Adolesc Psychiatry. 2022 Mar 17:S0890-8567(22)00118-6. doi: 10.1016/j.jaac.2022.03.009. Epub ahead of print. PMID: 35307538.

Sleep truncation associated with increased obesity risk and abdominal fat storage

Insufficient sleep increases the risk of multiple chronic health conditions including obesity, diabetes, depression, and premature mortality. Previous research regarding the cardiometabolic risk factor associated with sleep restriction exist, but none have made the connection to the regional distribution of body fat. Recently published research supported by the NHLBI and NCATS examined the health effects of continued sleep deficiency in conjunction with unrestricted food access on energy intake, energy output, and abdominal obesity.

To determine the influence of shortened sleep duration versus normal (control) sleep on obesity risk, a randomized, controlled 21-day in-patient study was conducted with 12 healthy, nonobese individuals. Participants were asked to adhere to an 8-hour minimum sleep-wake schedule for one week prior and refrain from caffeine, alcohol, and strenuous exercise to reduce the risk of sleep debt at study entry. The research setting allowed subjects to have free access to food and consisted of 4 days of acclimation, 14 days of experimental sleep restriction (4-hour sleep opportunity) or normal sleep (9-hour sleep opportunity), and 3 days of recovery. Real-time polysomnography monitoring ensured compliance with the study’s sleep regimens. During the inpatient protocol, research staff completed serial outcome measurements taken daily at the same time of the day to minimize circadian effects.

Increased calorie consumption, in the absence of energy expenditure, was more evident during early exposure to sleep restriction, then decreased during recovery. Protein and fat intake only increased during sleep restriction, but carbohydrate consumption increased in both study groups. Body weight increased for both sleep restriction and control conditions, but sleep curtailment resulted in a greater magnitude of increase. Furthermore, researchers observed that expansion of abdominal fat occurred only in response to 14 days of prolonged sleep restriction and changes in eating behaviors.

In summary, researchers found that shorter sleep duration combined with overeating modified subjects' lipid storage and preferential accumulation of abdominal visceral fat. They also found that sleep debt recovery on the weekends may not offset the heightened cardiometabolic risk. Therefore, following the recommended healthy range of sleep hours continues to be ideal to circumvent the negative health implications associated with sustained poor sleep habits.

Covassin N, Singh P, McCrady-Spitzer SK, St Louis EK, Calvin AD, Levine JA, Somers VK. Effects of Experimental Sleep Restriction on Energy Intake, Energy Expenditure, and Visceral Obesity. J Am Coll Cardiol. 2022 Apr 5;79(13):1254-1265. doi: 10.1016/j.jacc.2022.01.038. PMID: 35361348.