Sensitivity and specificity in affective and social learning in adolescence

Adolescence is a period of heightened affective and social sensitivity. In this review we address how this increased sensitivity influences associative learning. Based on recent evidence from human and rodent studies, as well as advances in computational biology, we suggest that, compared to other age groups, adolescents show features of heightened Pavlovian learning but tend to perform worse than adults at instrumental learning. Because Pavlovian learning does not involve decision-making, whereas instrumental learning does, we propose that these developmental differences might be due to heightened sensitivity to rewards and threats in adolescence, coupled with a lower specificity of responding. We discuss the implications of these findings for adolescent mental health and education.     

The adolescent brain

Adolescence is a developmental period characterized by suboptimal decisions and actions that give rise to an increased incidence of unintentional injuries and violence, alcohol and drug abuse, unintended pregnancy and sexually transmitted diseases. Traditional neurobiological and cognitive explanations for adolescent behavior have failed to account for the nonlinear changes in behavior observed during adolescence, relative to childhood and adulthood. This review provides a biologically plausible conceptualization of the neural mechanisms underlying these nonlinear changes in behavior, as a heightened responsiveness to incentives while impulse control is still relatively immature during this period. Recent human imaging and animal studies provide a biological basis for this view, suggesting differential development of limbic reward systems relative to top-down control systems during adolescence relative to childhood and adulthood. This developmental pattern may be exacerbated in those adolescents with a predisposition toward risk-taking, increasing the risk for poor outcomes.     

A time of change: Behavioral and neural correlates of adolescent sensitivity to appetitive and aversive environmental cues

Adolescence is a developmental period that entails substantial changes in affective and incentive-seeking behavior relative to both childhood and adulthood, including a heightened propensity to engage in risky behaviors and experience persistent negative and labile mood states. This review discusses the emotional and incentive-driven behavioral changes in adolescents and their associated neural mechanisms, focusing on the dynamic interactions between the amygdala, ventral striatum, and prefrontal cortex. Common behavioral changes during adolescence may be associated with a heightened responsiveness to incentives and emotional cues while the capacity to effectively engage in cognitive and emotion regulation is still relatively immature. We highlight empirical work in humans and animals that addresses the interactions between these neural systems in adolescents relative to children and adults, and propose a neurobiological model that may account for the nonlinear changes in adolescent behavior. Finally, we discuss other influences that may contribute to exaggerated reward and emotion processing associated with adolescence, including hormonal fluctuations and the role of the social environment.     

Salience network response to changes in emotional expressions of others is heightened during early adolescence: relevance for social functioning

Adolescence is a unique developmental period when the salience of social and emotional information becomes particularly pronounced. Although this increased sensitivity to social and emotional information has frequently been considered with respect to risk behaviors and psychopathology, evidence suggests that increased adolescent sensitivity to social and emotional cues may confer advantages. For example, greater sensitivity to shifts in the emotions of others is likely to promote flexible and adaptive social behavior. In this study, a sample of 54 children and adolescents (age 8–19 years) performed a delayed match‐to‐sample task for emotional faces while undergoing fMRI scanning. Recruitment of the anterior cingulate and anterior insula when the emotion of the probe face did not match the emotion held in memory followed a quadratic developmental pattern that peaked during early adolescence. These findings indicate meaningful developmental variation in the neural mechanisms underlying sensitivity to changes in the emotional expressions. Across all participants, greater activation of this network for changes in emotional expression was associated with less social anxiety and fewer social problems. These results suggest that the heightened salience of social and emotional information during adolescence may confer important advantages for social behavior, providing sensitivity to others’ emotions that facilitates flexible social responding.     

Adolescents' Reward‐related Neural Activation: Links to Thoughts of Nonsuicidal Self‐Injury

Adolescence is a critical developmental period marked by an increase in risk behaviors, including nonsuicidal self‐injury (NSSI). Heightened reward‐related brain activation and relatively limited recruitment of prefrontal regions contribute to the initiation of risky behaviors in adolescence. However, neural reward processing has not been examined among adolescents who are at risk for future engagement for NSSI specifically, but who have yet to actually engage in this behavior. In the current fMRI study (N = 71), we hypothesized that altered reward processing would be associated with adolescents' thoughts of NSSI. Results showed that NSSI youth exhibited heightened activation in the bilateral putamen in response to a monetary reward. This pattern of findings suggests that heightened neural sensitivity to reward is associated with thoughts of NSSI in early adolescence. Implications for prevention are discussed.     

The Adolescent Brain and the Emergence and Peak of Psychopathology

Adolescence is a period of heightened emotionality and increased risk for mental illness, affecting as many as one in five persons. This article reviews recent human imaging and animal studies that demarcate adolescent specific changes in brain and behavior that may help to explain this period of increased risk for psychopathology. We highlight adolescence as a sensitive period when: 1) the environment has particularly strong influences on brain and behavior and 2) normative changes in brain development can lead to an imbalance between rapidly changing limbic circuitry and relatively slower developing prefrontal circuitry. This imbalance can be exacerbated by both genetic and environmental influences leading to less capacity to regulate emotions and higher risk for psychopathology. We discuss these findings in the context of understanding who may be at greatest risk for psychopathology and when and how to best treat symptoms of emotional dysregulation.     

Theoretical underpinnings of a need-supportive intervention to address sustained healthy lifestyle changes in overweight and obese adolescents

ObjectivesRecent figures indicate that nearly a quarter of Australian adolescents are overweight or obese. Despite the well-established role of physical activity and healthy eating in reducing prevalence of obesity, there remains a lack of effective interventions that promote sustained behavior engagement. This paper aims to describe the theory-based integration and implementation of self-determination theory and goal setting theory in a family-based lifestyle intervention. Although these theories have been shown to independently predict motivation for behavior, a limited number of studies have described behavior-change techniques at a level to allow for effective evaluation and replication, and no studies have combined the theories in a healthy lifestyle behavior intervention.MethodsBehavior change techniques and the associated change mediators are described in relation to need-supportive environments provided by instructors and extended to parents in the home environment. Methods for motivating and promoting sustained engagement in adolescent physical activity and healthy eating and parent behaviors to support these lifestyle changes are discussed within the context of need-satisfaction and goal setting.ConclusionsThis study will contribute to understanding processes for developing and implementing behavior-change techniques based on the integration of two theories of motivation. Future interventions aimed at promoting maintenance of physical activity and healthy eating behaviors in overweight and obese adolescents will benefit by being informed of which techniques are effective at enhancing motivation within the intervention context and home environment.     

Changing brains, changing perspectives: the neurocognitive development of reciprocity

Adolescence is characterized by the emergence of advanced forms of social perspective taking and significant changes in social behavior. Yet little is known about how changes in social cognition are related to changes in brain function during adolescence. In this study, we investigated the neural correlates of social behavior during three phases of adolescence, carrying out functional magnetic resonance imaging of participants' brains while they were Player 2 in the Trust Game. We found that with age, adolescents were increasingly sensitive to the perspective of the other player, as indicated by their reciprocal behavior. These advanced forms of social perspective-taking behavior were associated with increased involvement of the left temporo-parietal junction and the right dorsolateral prefrontal cortex. In contrast, young adolescents showed more activity in the anterior medial prefrontal cortex, a region previously associated with self-oriented processing and mentalizing. These findings suggest that the asynchronous development of these neural systems may underlie the shift from thinking about self to thinking about the other.     

A systems approach to the cellular analysis of associative learning in the pond snail Lymnaea

We show that appetitive and aversive conditioning can be analyzed at the cellular level in the well-described neural circuitries underlying rhythmic feeding and respiration in the pond snail, Lymnaea stagnalis. To relate electrical changes directly to behavior, the snails were first trained and the neural changes recorded at multiple sites in reduced preparations made from the same animals. Changes in neural activity following conditioning could be recorded at the level of motoneurons, central pattern generator interneurons and modulatory neurons. Of significant interest was recent work showing that neural correlates of long-term memory could be recorded in the feeding network following single-trial appetitive chemical conditioning. Available information on the synaptic connectivity and transmitter content of identified neurons within the Lymnaea circuits will allow further work on the synaptic and molecular mechanisms of learning and memory.     

Developmental imaging genetics: Linking dopamine function to adolescent behavior

Adolescence is a period of development characterized by numerous neurobiological changes that significantly influence behavior and brain function. Adolescence is of particular interest due to the alarming statistics indicating that mortality rates increase two to three-fold during this time compared to childhood, due largely to a peak in risk-taking behaviors resulting from increased impulsivity and sensation seeking. Furthermore, there exists large unexplained variability in these behaviors that are in part mediated by biological factors. Recent advances in molecular genetics and functional neuroimaging have provided a unique and exciting opportunity to non-invasively study the influence of genetic factors on brain function in humans. While genes do not code for specific behaviors, they do determine the structure and function of proteins that are essential to the neuronal processes that underlie behavior. Therefore, studying the interaction of genotype with measures of brain function over development could shed light on critical time points when biologically mediated individual differences in complex behaviors emerge. Here we review animal and human literature examining the neurobiological basis of adolescent development related to dopamine neurotransmission. Dopamine is of critical importance because of (1) its role in cognitive and affective behaviors, (2) its role in the pathogenesis of major psychopathology, and (3) the protracted development of dopamine signaling pathways over adolescence. We will then focus on current research examining the role of dopamine-related genes on brain function. We propose the use of imaging genetics to examine the influence of genetically mediated dopamine variability on brain function during adolescence, keeping in mind the limitations of this approach.     

Changes in Sleep as a Function of Adolescent Development

Adolescence is marked by dramatic changes in sleep. Older adolescents go to bed later, have an increased preference for evening activities, and sleep less than younger adolescents. This behavior change is driven by external factors, notably increased pressures from academic, social, and extracurricular activities and by biological circadian factors. There are also substantial changes in sleep architecture across adolescence, with dramatic declines in slow wave sleep, and slow wave activity (delta, ~ 0.5–4.5 Hz). These changes are associated with underlying changes in brain structure and organization, with a decrease in synaptic density likely underlying the reduction in high amplitude slow waveforms. While changes in sleep across adolescence are a normal part of development, many adolescents are getting insufficient sleep and are consequently, less likely to perform well at school, more likely to develop mood-related disturbances, be obese, and are at greater risk for traffic accidents, alcohol and drug abuse.     

Eye blink rate predicts reward decisions in adolescents

The ventral striatum displays hyper‐responsiveness to reward in adolescents relative to other age groups, and animal research on the developmental trajectory of the dopaminergic system suggests that dopamine may underlie adolescent sensitivity to reward. However, practical limitations prevent the direct measurement of dopamine in healthy adolescents. Eye blink rate (EBR) shows promise as a proxy measure of striatal dopamine D2 receptor function. We investigated developmental differences in the relationship between EBR and reward‐seeking behavior on a risky decision‐making task. Increasing EBR was associated with greater reward maximization on the task for adolescent but not adult participants. Furthermore, adolescents demonstrated greater sensitivity to reward value than adults, as evinced by shifts in decision patterns based on increasing potential reward. These findings suggest that previously observed adolescent behavioral and neural hypersensitivity to reward may in fact be due to greater dopamine receptor activity, as represented by the relationship of blink rate and reward‐seeking behavior. They also demonstrate the feasibility and utility of using EBR as a proxy for dopamine in healthy youth in whom direct measurements of dopamine are prohibitively invasive.     

Neural response to prosocial scenes relates to subsequent giving behavior in adolescents: A pilot study

Adolescence is characterized by extensive neural development and sensitivity to social context, both of which contribute to engaging in prosocial behaviors. Although it is established that prosocial behaviors are linked to positive outcomes in adulthood, little is known about the neural correlates of adolescents’ prosociality. Identifying whether the brain is differentially responsive to varying types of social input may be important for fostering prosocial behavior. We report pilot results using new stimuli and an ecologically valid donation paradigm indicating (1) brain regions typically recruited during socioemotional processing evinced differential activation when adolescents evaluated prosocial compared with social or noninteractive scenes (N = 20, ages 13–17 years, M_Age = 15.30 years), and (2) individual differences in temporoparietal junction recruitment when viewing others’ prosocial behaviors were related to adolescents’ own charitable giving. These novel findings have significant implications for understanding how the adolescent brain processes prosocial acts and for informing ways to support adolescents to engage in prosocial behaviors in their daily lives.     

Central localization of plasticity involved in appetitive conditioning in Lymnaea

Learning to associate a conditioned (CS) and unconditioned stimulus (US) results in changes in the processing of CS information. Here, we address directly the question whether chemical appetitive conditioning of Lymnaea feeding behavior involves changes in the peripheral and/or central processing of the CS by using extracellular recording techniques to monitor neuronal activity at two stages of the sensory processing pathway. Our data show that appetitive conditioning does not affect significantly the overall CS response of afferent nerves connecting chemosensory structures in the lips and tentacles to the central nervous system (CNS). In contrast, neuronal output from the cerebral ganglia, which represent the first central processing stage for chemosensory information, is enhanced significantly in response to the CS after appetitive conditioning. This demonstrates that chemical appetitive conditioning in Lymnaea affects the central, but not the peripheral processing of chemosensory information. It also identifies the cerebral ganglia of Lymnaea as an important site for neuronal plasticity and forms the basis for detailed cellular studies of neuronal plasticity.     

Opposite actions of dopamine on aversive and appetitive memories in the crab

The understanding of how the reinforcement is represented in the central nervous system during memory formation is a current issue in neurobiology. Several studies in insects provide evidence of the instructive role of biogenic amines during the learning and memory process. In insects it was widely accepted that dopamine (DA) mediates aversive reinforcements. However, the idea of DA being exclusively involved in aversive memory has been challenged in recent studies. Here, we study the involvement of DA during aversive and appetitive memories in the crab Chasmagnathus. We found that DA-receptor antagonists impair aversive memory consolidation, in agreement with previous reports in insects, while administration of DA facilitates memory formation after a weak training protocol. In contrast, DA treatment during appetitive training was found to impair formation of long-term appetitive memory. In addition, as a first step in elucidating the neuroanatomical correlates of DA action on memory, we mapped dopaminergic neurons in the central nervous system of the crab. Results of the current study, together with those obtained in a previous work about the role of octopamine (OA), suggest that both amines (DA and OA) play a dual action in memory processes. On the one hand, DA and OA mediate the aversive and the appetitive signals, respectively, throughout training, while on the other hand, they interfere with the formation of memory of the opposite sign (DA in appetitive and OA in aversive). Our results support a new understanding about the way appetitive and aversive stimuli are processed during memory formation to ensure adaptive behavior.     

Adolescent pregnancy: contributing factors, consequences, treatment, and plausible solutions

Adolescence, although not always necessarily a period of extreme stress, is a time of profound physical changes which increase the adolescent's awareness of and interest in sexual behavior. This issue of sexuality, which begins in early adolescence, creates new challenges to personal and gender identity formation as the person matures. Sexual maturation is a three-fold process, requiring growth in understanding of oneself as a sexual being, in the ability to handle interpersonal relationships effectively, and in the capacity to plan behavior in view of future outcomes and present problems. A current concern is that today's adolescents, including early adolescents, may be making important life choices such as parenthood before they are developmentally ready for such roles (Chilman, 1980). This paper deals with pregnancy in adolescents and modes of responding to this phenomenon by those in the counseling and other helping professions.     

家庭功能对青少年疏离感的预测:同伴接纳的调节作用及性别差异

对608名初一至高二城市青少年进行问卷调查,考察同伴接纳在家庭功能对疏离感预测中的调节作用及其性别差异。结果表明,家庭功能健康水平较低的青少年,其疏离感较高;同伴接纳对家庭功能与疏离感之间的关系起调节作用;同伴接纳对家庭功能与青少年疏离感之间关系的调节存在显著的性别差异,高水平的同伴接纳可以调节不健康的家庭功能对男青少年疏离感的影响,而在女青少年中,这种调节作用不显著。     

Motivational systems in adolescence: Possible implications for age differences in substance abuse and other risk-taking behaviors

Adolescence is an evolutionarily conserved developmental phase characterized by hormonal, physiological, neural and behavioral alterations evident widely across mammalian species. For instance, adolescent rats, like their human counterparts, exhibit elevations in peer-directed social interactions, risk-taking/novelty seeking and drug and alcohol use relative to adults, along with notable changes in motivational and reward-related brain regions. After reviewing these topics, the present paper discusses conditioned preference and aversion data showing adolescents to be more sensitive than adults to positive rewarding properties of various drugs and natural stimuli, while less sensitive to the aversive properties of these stimuli. Additional experiments designed to parse specific components of reward-related processing using natural rewards have yielded more mixed findings, with reports of accentuated positive hedonic sensitivity during adolescence contrasting with studies showing less positive hedonic affect and reduced incentive salience at this age. Implications of these findings for adolescent substance abuse will be discussed.     

Reinforcement in an in vitro analog of appetitive classical conditioning of feeding behavior in Aplysia: blockade by a dopamine antagonist

In a recently developed in vitro analog of appetitive classical conditioning of feeding in Aplysia, the unconditioned stimulus (US) was electrical stimulation of the esophageal nerve (En). This nerve is rich in dopamine (DA)-containing processes, which suggests that DA mediates reinforcement during appetitive conditioning. To test this possibility, methylergonovine was used to antagonize DA receptors. Methylergonovine (1 nM) blocked the pairing-specific increase in fictive feeding that is usually induced by in vitro classical conditioning. The present results and previous observation that methylergonovine also blocks the effects of contingent reinforcement in an in vitro analog of appetitive operant conditioning suggest that DA mediates reinforcement for appetitive associative conditioning of feeding in Aplysia.     

基于神经成像技术的青少年大脑发育研究

大脑成熟是一个动态过程, 高级神经活动的发育主要集中于个体发展的第二个10年：青少年时期。青少年时期是行为、认知和脑迅速发展的时期。青少年普遍表现出来的注意、冲动控制、计划、决策等认知能力的提高都是基于神经系统的成熟发展起来的。运用神经成像等技术的研究指出, 大脑在青少年时期的发展经历着突触精简以及髓鞘化的过程; 白质、灰质在青少年时期的成熟有不同的发展轨迹。青少年大脑皮层的成熟顺序与认知功能的发展相联系, 人脑的高级认知功能在青少年时期发展完成。在这一过程中, 脑的发展会受到情绪、环境以及经验等因素的影响。