Neurobehavioral evidence for changes in dopamine system activity during adolescence

Conspiracy theory beliefs in the adolescent population: A systematic review

INTRODUCTION

While the study of conspiracy theory beliefs is a relatively new research area, there has been a rise in academic interest in recent years. The literature provides evidence of relationships between conspiracy theory beliefs and a range of factors, but the vast majority of studies are limited to adult samples, and it is unclear how such beliefs present in adolescence.

METHODS

The systematic review was conducted according to the PRISMA-S format. Relevant databases were searched up to February 23, 2023, for quantitative studies related to adolescent conspiracy theory beliefs.

RESULTS

The six included articles show that conspiracy theory beliefs are present from the start of adolescence, and stable from age 14 upwards, with correlations reported for mistrust and paranoid thinking. Negative relationships were reported for cognitive factors such as ontological confusion, cognitive ability, and actively open-minded thinking. Health-related beliefs correlated with adverse childhood experiences, peer problems, conduct, and sociodemographic factors. Right-wing authoritarianism and anxiety positively correlated with intergroup conspiracy theory beliefs.

CONCLUSION

While some factors from adult studies are replicated in the review, there are differences between age groups. The age at which conspiracy theory beliefs begin to form indicate developmental aspects of adolescence, and possibly childhood, that require further examination. Cognitive factors show promise for interventions and should be explored further. However, the lack of studies using adolescent populations is an issue that must be resolved for a greater understanding of conspiracy theory beliefs and a move toward effective interventions.

A unique multi-synaptic mechanism involving acetylcholine and GABA regulates dopamine release in the nucleus accumbens through early adolescence in male rats

Adolescence is characterized by changes in reward-related behaviors, social behaviors, and decision-making. These behavioral changes are necessary for the transition into adulthood, but they also increase vulnerability to the development of a range of psychiatric disorders. Major reorganization of the dopamine system during adolescence is thought to underlie, in part, the associated behavioral changes and increased vulnerability. Here, we utilized fast scan cyclic voltammetry and microdialysis to examine differences in dopamine release as well as mechanisms that underlie differential dopamine signaling in the nucleus accumbens (NAc) core of adolescent (P28-35) and adult (P70-90) male rats. We show baseline differences between adult and adolescent-stimulated dopamine release in male rats, as well as opposite effects of the α6 nicotinic acetylcholine receptor (nAChR) on modulating dopamine release. The α6-selective blocker, α-conotoxin, increased dopamine release in early adolescent rats, but decreased dopamine release in rats beginning in middle adolescence and extending through adulthood. Strikingly, blockade of GABAA and GABAB receptors revealed that this α6-mediated increase in adolescent dopamine release requires NAc GABA signaling to occur. We confirm the role of α6 nAChRs and GABA in mediating this effect in vivo using microdialysis. Results herein suggest a multisynaptic mechanism potentially unique to the period of development that includes early adolescence, involving acetylcholine acting at α6-containing nAChRs to drive inhibitory GABA tone on dopamine release.

Adolescent neurocognitive development and decision-making abilities regarding gender-affirming care

Recently, politicians and legislative bodies have cited neurodevelopmental literature to argue that brain immaturity undermines decision-making regarding gender-affirming care (GAC) in youth. Here, we review this literature as it applies to adolescents' ability to make decisions regarding GAC. The research shows that while adolescence is a time of peak risk-taking behavior that may lead to impulsive decisions, neurocognitive systems supporting adult-level decisions are available given deliberative processes that minimize influence of short-term rewards and peers. Since GAC decisions occur over an extended period and with support from adult caregivers and clinicians, adolescents can engage adult-level decision-making in this context. We also weigh the benefits of providing GAC access during adolescence and consider the significant costs of blocking or delaying GAC. Transgender and non-binary (TNB) adolescents face significant mental health challenges, many of which are mitigated by GAC access. Further, initiating the GAC process during adolescence, which we define as beginning at pubertal onset, leads to better long-term mental health outcomes than waiting until adulthood. Taken together, existing research indicates that many adolescents can make informed decisions regarding gender-affirming care, and that this care is critical for the well-being of TNB youth. We highlight relevant considerations for policy makers, researchers, and clinicians.

Developmental dyslexia susceptibility genes DNAAF4, DCDC2, and NRSN1 are associated with brain function in fluently reading adolescents and young adults

Reading skills and developmental dyslexia, characterized by difficulties in developing reading skills, have been associated with brain anomalies within the language network. Genetic factors contribute to developmental dyslexia risk, but the mechanisms by which these genes influence reading skills remain unclear. In this preregistered study (https://osf.io/7sehx), we explored if developmental dyslexia susceptibility genes DNAAF4, DCDC2, NRSN1, and KIAA0319 are associated with brain function in fluently reading adolescents and young adults. Functional MRI and task performance data were collected during tasks involving written and spoken sentence processing, and DNA sequence variants of developmental dyslexia susceptibility genes previously associated with brain structure anomalies were genotyped. The results revealed that variation in DNAAF4, DCDC2, and NRSN1 is associated with brain activity in key language regions: the left inferior frontal gyrus, middle temporal gyrus, and intraparietal sulcus. Furthermore, NRSN1 was associated with task performance, but KIAA0319 did not yield any significant associations. Our findings suggest that individuals with a genetic predisposition to developmental dyslexia may partly employ compensatory neural and behavioral mechanisms to maintain typical task performance. Our study highlights the relevance of these developmental dyslexia susceptibility genes in language-related brain function, even in individuals without developmental dyslexia, providing valuable insights into the genetic factors influencing language processing.

Acculturating Systems of Care to Ensure Healthy Futures for Latine Migrant Youth

Migration across the Americas is an ever-changing process with current trends including increased migration into the United States of Latine youth. Experiences before, during, and after migration can increase the risk of psychiatric illness, including discriminatory and exclusionary experiences when accessing care. Acculturation typically focuses on the process that the immigrant group experiences when coming into contact with a host culture. Members of the host culture and systems of care can take intentional steps to acculturate themselves in an integrative manner in an effort to reduce host-immigrant friction and better coordinate care across systems.

Transcranial Magnetic Stimulation Across the Lifespan: Impact of Developmental and Degenerative Processes

Transcranial magnetic stimulation (TMS) has emerged as a pivotal noninvasive technique for investigating cortical excitability and plasticity across the lifespan, offering valuable insights into neurodevelopmental and neurodegenerative processes. In this review, we explore the impact of TMS applications on our understanding of normal development, healthy aging, neurodevelopmental disorders, and adult-onset neurodegenerative diseases. By presenting key developmental milestones and age-related changes in TMS measures, we provide a foundation for understanding the maturation of neurotransmitter systems and the trajectory of cognitive functions throughout the lifespan. Building on this foundation, the paper delves into the pathophysiology of neurodevelopmental disorders, including autism spectrum disorder, attention-deficit/hyperactivity disorder, Tourette syndrome, and adolescent depression. Highlighting recent findings on altered neurotransmitter circuits and dysfunctional cortical plasticity, we underscore the potential of TMS as a valuable tool for unraveling underlying mechanisms and informing future therapeutic interventions. We also review the emerging role of TMS in investigating and treating the most common adult-onset neurodegenerative disorders and late-onset depression. By outlining the therapeutic applications of noninvasive brain stimulation techniques in these disorders, we discuss the growing body of evidence supporting their use as therapeutic tools for symptom management and potentially slowing disease progression. The insights gained from TMS studies have advanced our understanding of the underlying mechanisms in both healthy and disease states, ultimately informing the development of more targeted diagnostic and therapeutic strategies for a wide range of neuropsychiatric conditions.

A lifetime perspective on risk factors for cognitive decline with a special focus on early events

Both Alzheimer's disease and vascular dementia are the result of disease processes that typically develop over several decades. Population studies have estimated that more than half of the risk for dementia is preventable or at least modifiable through behavioral adaptations. The association between these lifestyle factors and the risk of dementia is most evident for exposure in midlife. However, habits formed in middle age often reflect a lifetime of behavior patterns and living conditions. Therefore, individuals who, for example, are able to maintain healthy diets and regular exercise during their middle years are likely to benefit from these cognition-protective habits they have practiced throughout their lives. For numerous adult diseases, significant risks can often be traced back to early childhood. Suboptimal conditions during the perinatal period, childhood and adolescence can increase the risk of adult diseases, including stroke, heart disease, insulin resistance, hypertension and dementia. This review aims at summarizing some of the evidence for dementia risks from a life-time perspective with the goal of raising awareness for early dementia prevention and successful aging.

Effects of L-Dopa, SKF-38393, and quinpirole on exploratory, anxiety- and depressive-like behaviors in pubertal female and male mice

Adolescence is a phase of substantial changes in the brain, characterized by maturational remodeling of many systems. This remodeling allows functional plasticity to adapt to a changing environment. The dopaminergic system is under morphological and physiological changes during this phase. In the present study, we investigated if changes in the dopaminergic tone alter mice behavior in a receptor and sex-specific manner, specifically at the beginning of the puberty period. We administered L-Dopa, SKF-38393 (D1 dopamine receptor agonist), and Quinpirole (D2 dopamine receptor agonist) and tested male and female mice's motor, anxiety- and depressive-like behavior. While females displayed an impaired exploratory drive, males presented an intense depressive-like response. Our results provide insights into the function of dopaminergic development in adolescent behavior and highlight the importance of studies in this time window with male and female subjects.

The influence of screen time on behaviour and emotional problems among adolescents: A comparison study of the pre-, peak, and post-peak periods of COVID-19

The coronavirus disease 2019 (COVID-19) pandemic has brought drastic changes globally in the past three years, one of which is an increase in the use of digital media or electronic devices. Previous studies have shown that long screen time may stimulate the neurobiological system, resulting in various behavioural and emotional problems; however, there is insufficient population-based evidence. This study aimed to investigate the influence of screen time on behavioural and emotional problems in Indonesian adolescents at three time points: the pre-, peak, and post-peak periods of COVID-19. Data were collected using an online community mental health survey. This survey incorporated the Youth Screen Time Survey to gauge screen time and the adolescent version of the Strengths and Difficulties Questionnaire to assess emotional, conduct, and prosocial behaviour problems. The participants were adolescents in secondary and senior high schools, with 337, 423, and 1,096 participants from the pre-, peak-, and post-pandemic periods, respectively, included in the analysis. Daily average screen time was compared, followed by the calculation of odds ratios for screen time and mental health problems during the different periods. The results demonstrated significant differences in adolescents' total daily average screen time between the different pandemic periods. Decreased screen time was associated with reduced emotional, conduct, and prosocial behaviour problems, especially during the peak period. Thus, psychoeducation on screen time in adolescents should be considered as a point of interest for mental well-being interventions.

Abuse-like toluene exposure during early adolescence alters subsequent ethanol and cocaine behavioral effects and brain monoamines in male mice

Currently, there is a gap in understanding the neurobiological impact early adolescent toluene exposure has on subsequent actions of other drugs. Adolescent (PND 28-32) male Swiss-Webster mice (N = 210) were exposed to 0, 2000, or 4000 ppm of toluene vapor for 30 min/day for 5 days. Immediately following the last toluene exposure (PND 32; n = 15) or after a short delay (PND 35; n = 15), a subset of subjects' brains was collected for monoamine analysis. Remaining mice were assigned to one of two abstinence periods: a short 4-day (PND 36) or long 12-day (PND 44) delay after toluene exposure. Mice were then subjected to a cumulative dose response assessment of either cocaine (0, 2.5, 5, 10, 20 mg/kg; n = 60), ethanol (0, 0.5, 1, 2, 4 g/kg; n = 60), or saline (5 control injections; n = 60). Toluene concentration-dependently increased locomotor activity during exposure. When later challenged, mice exposed previously to toluene were significantly less active after cocaine (10 and 20 mg/kg) compared to air-exposed controls. Animals were also less active at the highest dose of alcohol (4 g/kg) following prior exposure to 4000 ppm when compared to air-exposed controls. Analysis of monoamines and their metabolites using High Pressure Liquid Chromatography (HPLC) within the medial prefrontal cortex (mPFC), nucleus accumbens (NAc), dorsal striatum (dSTR), and ventral tegmental area (VTA) revealed subtle effects on monoamine or metabolite levels following cumulative dosing that varied by drug (cocaine and ethanol) and abstinence duration. Our results suggest that early adolescent toluene exposure produces behavioral desensitization to subsequent cocaine-induced locomotor activity with subtle enhancement of ethanol's depressive effects and less clear impacts on levels of monoamines.

Acute and long-term effects of adolescence stress exposure on rodent adult hippocampal neurogenesis, cognition, and behaviour

Adolescence represents a critical period for brain and behavioural health and characterised by the onset of mood, psychotic and anxiety disorders. In rodents, neurogenesis is very active during adolescence, when is particularly vulnerable to stress. Whether stress-related neurogenesis changes influence adolescence onset of psychiatric symptoms remains largely unknown. A systematic review was conducted on studies investigating changes in hippocampal neurogenesis and neuroplasticity, hippocampal-dependent cognitive functions, and behaviour, occurring after adolescence stress exposure in mice both acutely (at post-natal days 21-65) and in adulthood. A total of 37 studies were identified in the literature. Seven studies showed reduced hippocampal cell proliferation, and out of those two reported increased depressive-like behaviours, in adolescent rodents exposed to stress. Three studies reported a reduction in the number of new-born neurons, which however were not associated with changes in cognition or behaviour. Sixteen studies showed acutely reduced hippocampal neuroplasticity, including pre- and post-synaptic plasticity markers, dendritic spine length and density, and long-term potentiation after stress exposure. Cognitive impairments and depressive-like behaviours were reported by 11 of the 16 studies. Among studies who looked at adolescence stress exposure effects into adulthood, seven showed that the negative effects of stress observed during adolescence on either cell proliferation or hippocampal neuroplasticity, cognitive deficits and depressive-like behaviour, had variable impact in adulthood. Treating adolescent mice with antidepressants, glutamate receptor inhibitors, glucocorticoid antagonists, or healthy diet enriched in omega-3 fatty acids and vitamin A, prevented or reversed those detrimental changes. Future research should investigate the translational value of these preclinical findings. Developing novel tools for measuring hippocampal neurogenesis in live humans, would allow assessing neurogenic changes following stress exposure, investigating relationships with psychiatric symptom onset, and identifying effects of therapeutic interventions.

The relationship between disrupted anhedonia-related circuitry and suicidal ideation in major depressive disorder: A network-based analysis

BACKGROUND

Several epidemiological studies and psychological models have suggested that major depressive disorder (MDD) with anhedonia is associated with suicidal ideation (SI). However, little is known about whether the functional network pattern and intrinsic topologically disrupted in patients with anhedonia are related to SI.

METHODS

The resting-fMRI by applying network-based statistic (NBS) and graph-theory analyses was estimated in 273 patients with MDD (144 high anhedonia [HA], 129 low anhedonia [LA]) and 150 healthy controls. In addition, we quantified the SI scores of each patient. Finally, the mediation analysis assessed whether anhedonia symptoms could mediate the relationship between anhedonia-related network metrics and SI.

RESULT

The NBS analysis demonstrated that individuals with HA have a single abnormally increased functional connectivity component in a frontal-limbic circuit (termed the "anhedonia-related network", including the frontal cortex, striatum, anterior cingulate cortex and amygdala). The graph-theory analysis demonstrated that the anhedonia-related network showed a significantly disrupted topological organization (lower gamma and lambda), which the small-world property trend randomized. Furthermore, the anhedonia symptoms could mediate the relationship between the anhedonia-related network metrics (the mean functional connectivity values, the area under the curves values of gamma and nodal local efficiency in nucleus accumbens) and SI.

CONCLUSIONS

We found that disruption of the reward-related network in MDD leads to SI through anhedonia symptoms. These findings show the abnormal topological construction of functional brain network organization in anhedonia, shedding light on the neurological processes underlying SI in MDD patients with anhedonia symptoms.

The longitudinal role of family conflict and neural reward sensitivity in youth's internalizing symptoms

Adolescence is often associated with an increase in psychopathology. Although previous studies have examined how family environments and neural reward sensitivity separately play a role in youth's emotional development, it remains unknown how they interact with each other in predicting youth's internalizing symptoms. Therefore, the current research took a biopsychosocial approach to examine this question using two-wave longitudinal data of 9353 preadolescents (mean age = 9.93 years at T1; 51% boys) from the Adolescent Brain Cognitive Development study. Using mixed-effects models, results showed that higher family conflict predicted youth's increased internalizing symptoms 1 year later, whereas greater ventral striatum (VS) activity during reward receipt predicted reduced internalizing symptoms over time. Importantly, there was an interaction effect between family conflict and VS activity. For youth who showed greater VS activation during reward receipt, high family conflict was more likely to predict increased internalizing symptoms. In contrast, youth with low VS activation during reward receipt showed high levels of internalizing symptoms regardless of family conflict. The findings suggest that youth's neural reward sensitivity is a marker of susceptibility to adverse family environments and highlight the importance of cultivating supportive family environments where youth experience less general conflict within the family.

Dopamine transporter blockade during adolescence increases adult dopamine function, impulsivity, and aggression

Sensitive developmental periods shape neural circuits and enable adaptation. However, they also engender vulnerability to factors that can perturb developmental trajectories. An understanding of sensitive period phenomena and mechanisms separate from sensory system development is still lacking, yet critical to understanding disease etiology and risk. The dopamine system is pivotal in controlling and shaping adolescent behaviors, and it undergoes heightened plasticity during that time, such that interference with dopamine signaling can have long-lasting behavioral consequences. Here we sought to gain mechanistic insight into this dopamine-sensitive period and its impact on behavior. In mice, dopamine transporter (DAT) blockade from postnatal (P) day 22 to 41 increases aggression and sensitivity to amphetamine (AMPH) behavioral stimulation in adulthood. Here, we refined this sensitive window to P32-41 and identified increased firing of dopaminergic neurons in vitro and in vivo as a neural correlate to altered adult behavior. Aggression can result from enhanced impulsivity and cognitive dysfunction, and dopamine regulates working memory and motivated behavior. Hence, we assessed these behavioral domains and found that P32-41 DAT blockade increases impulsivity but has no effect on cognition, working memory, or motivation in adulthood. Lastly, using optogenetics to drive dopamine neurons, we find that increased VTA but not SNc dopaminergic activity mimics the increase in impulsive behavior in the Go/NoGo task observed after adolescent DAT blockade. Together our data provide insight into the developmental origins of aggression and impulsivity that may ultimately improve diagnosis, prevention, and treatment strategies for related neuropsychiatric disorders.

Amphetamine disrupts dopamine axon growth in adolescence by a sex-specific mechanism in mice

Initiating drug use during adolescence increases the risk of developing addiction or other psychopathologies later in life, with long-term outcomes varying according to sex and exact timing of use. The cellular and molecular underpinnings explaining this differential sensitivity to detrimental drug effects remain unexplained. The Netrin-1/DCC guidance cue system segregates cortical and limbic dopamine pathways in adolescence. Here we show that amphetamine, by dysregulating Netrin-1/DCC signaling, triggers ectopic growth of mesolimbic dopamine axons to the prefrontal cortex, only in early-adolescent male mice, underlying a male-specific vulnerability to enduring cognitive deficits. In adolescent females, compensatory changes in Netrin-1 protect against the deleterious consequences of amphetamine on dopamine connectivity and cognitive outcomes. Netrin-1/DCC signaling functions as a molecular switch which can be differentially regulated by the same drug experience as function of an individual's sex and adolescent age, and lead to divergent long-term outcomes associated with vulnerable or resilient phenotypes.

Can antidepressant use be associated with emotional blunting in a subset of patients with depression? A scoping review of available literature

INTRODUCTION

Despite frequent recognition of emotional blunting in the published literature, either as a primary symptom of depression or as an adverse effect of antidepressants, there is no systematic synthesis on this topic to our knowledge. We undertook this scoping review to assess the prevalence, clinical features, implicated causes and management of emotional blunting, outlining the phenomenological and clinical gaps in research.

METHOD

A systematic search was done until March 15, 2022, to include all original studies (i.e., interventional trials, cohort & cross-sectional studies, case reports, and case series). All reviewed data were delineated to answer pertinent clinical, phenomenological, and management questions related to the phenomenon of emotional blunting.

RESULTS

A total of 25 original studies were included in our scoping review. Emotional blunting was described as a persistent diminution in both positive and negative feelings in depressed patients, who could subjectively differentiate it from their acute symptoms. However, the literature lacked the distinction between emotional blunting as a primary symptom of depression or an adverse effect of antidepressants. Common clinical strategies to manage antidepressant-induced emotional blunting included dose reduction or switching to a different antidepressant.

CONCLUSION

Emotional blunting was a significant patient-reported concern with antidepressants. Future research should clarify phenomenological and neurobiological constructs underlying emotional blunting to improve diagnostic and management skills.

Reappraising the role of dopamine in adolescent risk-taking behavior

Adolescence is characterized by increased risk-taking, which is often ascribed to developmental changes in dopaminergic signaling. Popular models propose that these behaviors are caused by dopamine-induced hypersensitivity to rewards, which overrides adolescents' immature self-control mechanisms. However, these models are often based on oversimplified notions about the workings and functions of dopamine. Here we discuss the relationship between changes in the dopaminergic system and adolescent behavior in light of current theories/models about the functions of dopamine. We show that dopamine is linked to learning, adaptive decision-making under uncertainty, and increased motivation to work for rewards. Thus, changes in the dopaminergic system contribute to the maturation of cognitive control through various mechanisms, contrary to the false dichotomy between reward processing and self-control. Finally, we note that dopamine interacts with a number of other neuromodulator systems, which also change during adolescence, but that have been largely ignored in the field of adolescent development. A full understanding of adolescent behavior will require these neurochemicals and their interactions with dopamine to be taken into account.

Former Training Relieves the Later Development of Behavioral Inflexibility in an Animal Model Overexpressing the Dopamine Transporter

A range of dopamine-dominating neuropsychiatric disorders present with cognitive deficits. In accordance, the dopamine transporter overexpressing rat model (DAT-tg rat) displays cognitive deficits by means of behavioral inflexibility and learning disabilities. It remains to be investigated when cognitive deficits emerge, due to the inherent DA irregularities, during the life course of the DAT-tg rat and what may relieve symptoms. The Morris water maze (MWM) was used to assess cognitive abilities in three cohorts of DAT-tg rats. In the first cohort, the development of cognitive deficits was assessed by repeatedly testing animals in the MWM at postnatal day (PND) 35, 60, and 90. In the second and third cohort, pharmacological interventions and transcranial direct current stimulation (tDCS) were tested in adult animals to understand what drives, and thus relieves, the deficits. Minor differences were observed between DAT-tg rats and control rats at PND 35 and 60, whereas cognitive deficits fully emerged at PND 90. A high dosage of methylphenidate diminished both behavioral inflexibility and improved learning abilities in adult rats. Interestingly, rats subjected early in life to the MWM also displayed improved behavioral flexibility as compared to rats naïve to the paradigm. Cognitive deficits gradually develop over time and fully emerge in adulthood. Pharmacological modulation of the ubiquitous DAT overexpression overall improves deficits in adult rats, whereas early training decreases later development of behavioral inflexibility. Thus, former training may constitute a preventive avenue that alters some aspects of cognitive deficits resulting from inherent DA abnormalities.

Development of anxiety-like behaviors during adolescence: Persistent effects of adolescent morphine exposure in male rats

Epidemiological studies show the prevalence of opioid use, misuse and abuse in adolescents, which imposes social and economic accountability worldwide. Chronic opioid exposure, especially in adolescents, may have lasting effects on emotional behaviors that persist into adulthood. The current experiments were therefore designed to study the effects of sustained opioid exposure during adolescence on anxiety-like behaviors. Adolescent male Wistar rats underwent increasing doses of morphine for 10 days (PNDs 31-40). After that the open field test (OFT) and elevated plus maze (EPM) test were performed over a 4-week postmorphine treatment from adolescence to adulthood. Moreover, the weight of the animals was measured at these time points. We found that chronic adolescent morphine exposure reduces the weight gain during the period of morphine treatment and 4 weeks after that. It had no significant effect on the locomotor activity in the animals. Moreover, anxiolytic-like behavior was observed in the rats exposed to morphine during adolescence evaluated by OFT and EPM test. Thus, long-term exposure to morphine during adolescence has the profound potential of altering the anxiety-like behavior profile in the period from adolescence to adulthood. The maturation of the nervous system can be affected by drug abuse during the developmental window of adolescence and these effects may lead to behaviorally stable alterations.

Validation of the aberrant salience inventory in a general and clinical Spanish population

BACKGROUND

The concept of aberrant salience is related to the onset of psychosis. Its study is important for early identification and possible intervention in processes activating later positive symptoms.

OBJECTIVES

This study validated the Spanish Aberrant Salience Inventory (ASI) for adult and clinical populations.

METHODS

The sample consisted of 6178 participants, of whom 4523 were adolescents, 1292 were general population adults and 363 were patients with a psychopathology.

RESULTS

The evidence provided validates the instrument's structure. Invariance of measurement suggests that both men and women, patients and nonclinical population (adults and adolescents) interpreted the items on the ASI similarly. The distribution of scores by age also suggests stabilization of the trend at about 19 years of age, showing a developmental change in motivational response. The hypothesis that patients, and in particular, those diagnosed with schizophrenia and other psychotic disorders and bipolar disorders would have the highest average scores in aberrant salience was met.

CONCLUSIONS

This is a valuable instrument for evaluating a complex process related to abnormal motivation in the development of schizophrenia.

Transitioning patients with juvenile idiopathic arthritis to adult care: the Nordic experience

BACKGROUND

With juvenile idiopathic arthritis (JIA), there are several protocols and practices used worldwide for the transition from paediatric to adult care. In this study, we examined the transferral rates and disease activity after transition, as well as the disease- and health-related outcomes. We also introduce the transition practices employed in the Nordic countries.

METHODS

The study population comprised 408 participants with a disease onset from 1997 to 2000 who attended an 18-year follow-up visit in this population-based Nordic JIA cohort study. The patients were retrospectively divided into three subgroups: Patients transferred directly from paediatric care to adult rheumatology care, patients referred there later, and patients never transferred during the 18-year follow-up period.

RESULTS

One hundred and sixty-three (40%) JIA patients had been directly transferred to an adult clinic. The cumulative transition rate was 52%, but there were significant differences between the participating centres. Fifty patients had later been referred to an adult clinic. Among the 195 patients who had never been transferred, 39% were found to have disease activity at the study visit.

CONCLUSION

This study highlights the need to reconsider transition practices to avoid our undesirable finding of patients with disease activity in JIA, but no appropriate health care follow-up.

Perceptual cognitive abilities in young athletes: A gender comparison

To achieve optimal performance in sports, it is essential to have strong perceptual cognitive abilities. Evidence suggests that athletes have superior perceptual abilities compared to nonathletes. However, gender differences in athletes’ perceptual cognitive abilities have not been previously reported. This project aims to evaluate perceptual cognitive abilities among male and female adolescents. To measure perceptual abilities, a 3-dimensional multiple-object tracking task was used. The findings confirm the superior perceptual cognitive abilities in young athletes relative to nonathletes. However, our results indicate differences in performance patterns between male and female athletes. These results demonstrate that sports engagement and perceptual cognitive abilities are strongly related during adolescence and that this relationship seems more prevalent in male athletes for this age group.

Early life stress influences basal ganglia dopamine receptors and novel object recognition of adolescent and adult rats

Environmental stimuli in early life are recognized to affect brain development and behavior. Mother-pup interaction constitutes a determinant stimulus during this critical period. It is known that the dopaminergic system undergoes significant reorganization during adolescence and that dopamine receptors are involved in recognition memory. Based on the above, we examined the effects of brief and prolonged maternal separation during the neonatal period (15 or 180 min daily) on basal ganglia dopamine receptors and on the behavior in the novel object recognition task of adolescent and adult male rats. Using the NOR task, we observed that the discrimination index (DI) was decreased in rats with brief maternal separations independent of age. Using receptor autoradiography, we observed that brief maternal separation induced decreases in D1, D2 and D4 receptor binding levels in adult basal ganglia nuclei, while prolonged maternal separation induced increases in D1 receptor binding levels in caudate - putamen (CPu) of adolescent rats. With immunoblotting experiments, we found decreases in D1 and increases in D2 total protein levels in CPu of adult rats with prolonged maternal separations. Α positive correlation was observed between DI and D1 binding levels in CPu, internal globus pallidus and substantia nigra, and D2 binding levels in nucleus accumbens core in adult rats, using the Pearson correlation coefficient. Our results indicate that the long-lasting effects of neonatal mother-offspring separation on dopamine receptors depend on the duration of maternal separation and age and that this early life experience impairs recognition memory in adolescent and adult rats. Furthermore, the present results suggest that modulation of striatal dopamine receptors might underlie the reduced recognition memory of adult rats with brief neonatal maternal separations.

The influence of reward anticipation on conflict control in children and adolescents: Evidences from hierarchical drift-diffusion model and event-related potentials

Reward is deemed a performance reinforcer. The current study investigated how social and monetary reward anticipation affected cognitive control in 39 children, 40 adolescents, and 40 adults. We found that cognitive control performance improved with age in a Simon task, and the reaction time (RT) was modulated by the reward magnitude. The conflict monitoring process (target N2 amplitudes) of adolescents and the attentional control processes (target P3 amplitudes) of adolescents and adults could be adjusted by reward magnitude, suggesting that adolescents were more sensitive to rewards compared to children. Reward magnitudes influenced the neural process of attentional control with larger P3 in congruent trails than that in incongruent trials only in low reward condition. The result of hierarchical drift-diffusion model indicated that children had slower drift rates, higher decision threshold, and longer non-decision time than adolescents and adults. Adolescents had faster drift rates in monetary task than in social task under the high reward condition, and they had faster drift rates under high reward condition than no reward condition only in the monetary task. The correlation analysis further showed that adults' non-decision time and decision threshold correlated with conflict monitoring process (N2 responses) and attentional control process on conflicts (P3 responses). Adolescents' drift rates associated with neural process of attentional control. The current study reveals that reward magnitude and reward type can modulate cognitive control process, especially in adolescents.

GENETIC AND ENVIRONMENTAL CONTRIBUTIONS TO POSITIVE AFFECT: INSIGHTS FROM ADOLESCENT TWINS

Disturbances in positive affect and reductions in social reward/interpersonal pleasure are common across a range of clinical disorders and are often related. We examined the relationship between the Anticipatory and Consummatory Interpersonal Pleasure Scale (ACIPS-A), and other measures of positive affect in adolescents in a genetically informative research design. The sample consisted of 177 MZ and 136 same sex DZ twins drawn from a study of adolescent twins (M = 16.4 ± .97 years) who were part of the Wisconsin Twin Project. The self-report questionnaires included the Behavioral Activation Scale (BAS), Psychological Well-Being Scale, revised Early Adolescent Temperament Questionnaire (EATQR) and the adolescent version of the ACIPS (ACIPS-A). Structural equation modeling estimated the relative contribution of genetic and environmental factors to the phenotypic variance in each of the measures. Follow-up bivariate analyses parsed the genetic and environmental contributions to the phenotypic covariances between the ACIPS-A and each of the other measures of positive affect. We found evidence of moderate heritability for the ACIPS-A scale scores. Overall, models specifying additive genetic and unique environmental effects (AE models) were the most parsimonious models for each of the measures. Several of the measures showed moderate positive phenotypic intercorrelations, and all but one of these intercorrelations showed significant partial genetic underpinnings. Moreover, the bivariate biometric analyses indicated that the ACIPS-A also captures unique heritable variation. Thus, the ACIPS-A captures unique heritable contributions to social/interpersonal pleasure, as well as shared genetic variance with other measures of positive affectivity.

Examining impulsivity and risky decision making among school youth in balloon analogue risk task

BACKGROUND

Impulsivity trait as a risk factor which typically displayed in risk decision among school youth. This study aims to examine behavioral and cognitive problems of risky decision among Chinese young people aged 15-25 years. The balloon analogue risk task (BART) and event-related potential (ERP) were combine used to explore the neural mechanism of risky decision process whether infected by impulsivity trait.

METHODS

A total of 31 subjects were included, including 16 experimental subjects with risk behavior (RS), and 15 health control subjects with non-risk behavior (HC). BART were used to measure risk-taking propensity and ERP were to record in real time. RS vs. HC were compared to explain the relationship between impulsivity and risky decision.

RESULTS

Behavioral data in BART task shown that the RS subjects tended to make risky decisions. ERP results illustrate that P300 in RS subjects is more significant positive-going than HC that means dysfunction of cognitive control, and FRN in RS subjects is more negative-going than HC in negative feedback condition, which means individual with high impulsive would be more sensitive to unexpected outcome.

CONCLUSIONS

Impulsiveness is a risk factor for school adolescent, because RS subjects performed more risky decision than control group, the evidence indicate that individual with high impulsiveness would lead to be less sensitive to harmful consequences and more inclination to immediate rewards. Therefore, the inclination of risk taking can be powerfully informed by different levels of impulsiveness.

Is Adolescence a Sensitive Period for the Development of Incentive-Reward Motivation?

Human adolescence is broadly construed as a time of heightened risk-taking and a vulnerability period for the emergence of psychopathology. These tendencies have been attributed to the age-related development of neural systems that mediate incentive motivation and other aspects of reward processing as well as individual difference factors that interact with ongoing development. Here, we describe the adolescent development of incentive motivation, which we view as an inherently positive developmental progression, and its associated neural mechanisms. We consider challenges in applying the sensitive period concept to these maturational events and discuss future directions that may help to clarify mechanisms of change.

Dopamine D2 receptor regulates cortical synaptic pruning in rodents

Synaptic pruning during adolescence is important for appropriate neurodevelopment and synaptic plasticity. Aberrant synaptic pruning may underlie a variety of brain disorders such as schizophrenia, autism and anxiety. Dopamine D2 receptor (Drd2) is associated with several neuropsychiatric diseases and is the target of some antipsychotic drugs. Here we generate self-reporting Drd2 heterozygous (SR-Drd2+/-) rats to simultaneously visualize Drd2-positive neurons and downregulate Drd2 expression. Time course studies on the developing anterior cingulate cortex (ACC) from control and SR-Drd2+/- rats reveal important roles of Drd2 in regulating synaptic pruning rather than synapse formation. Drd2 also regulates LTD, a form of synaptic plasticity which includes some similar cellular/biochemical processes as synaptic pruning. We further demonstrate that Drd2 regulates synaptic pruning via cell-autonomous mechanisms involving activation of mTOR signaling. Deficits of Drd2-mediated synaptic pruning in the ACC during adolescence lead to hyper-glutamatergic function and anxiety-like behaviors in adulthood. Taken together, our results demonstrate important roles of Drd2 in cortical synaptic pruning.

Primed for addiction: A critical review of the role of microglia in the neurodevelopmental consequences of adolescent alcohol drinking

Alcohol is one of the most widely used recreational substances worldwide, with drinking frequently initiated during adolescence. The developmental state of the adolescent brain makes it vulnerable to initiating alcohol use, often in high doses, and particularly susceptible to alcohol-induced brain changes. Microglia, the brain parenchymal macrophages, have been implicated in mediating some of these effects, though the role that these cells play in the progression from alcohol drinking to dependence remains unclear. Microglia are uniquely positioned to sense and respond to central nervous system insult, and are now understood to exhibit innate immune memory, or "priming," altering their future functional responses based on prior exposures. In alcohol use disorders (AUDs), the role of microglia is debated. Whereas microglial activation can be pathogenic, contributing to neuroinflammation, tissue damage, and behavioral changes, or protective, it can also engage protective functions, providing support and mediating the resolution of damage. Understanding the role of microglia in adolescent AUDs is complicated by the fact that microglia are thought to be involved in developmental processes such as synaptic refinement and myelination, which underlie the functional maturation of multiple brain systems in adolescence. Thus, the role microglia play in the impact of alcohol use in adolescence is likely multifaceted. Long-term sequelae may be due to a failure to recover from EtOH-induced tissue damage, altered neurodevelopmental trajectories, and/or persistent changes to microglial responsivity and function. Here, we review critically the literature surrounding the effects of alcohol on microglia in models of adolescent alcohol misuse. We attempt to disentangle what is known about microglia from other neuroimmune effectors, to which we apply recent discoveries on the role of microglia in development and plasticity. Considered altogether, these studies challenge assumptions that proinflammatory microglia drive addiction. Alcohol priming microglia and thereby perturbing their homeostatic roles in neurodevelopment, especially during critical periods of plasticity such as adolescence, may have more serious implications for the neuropathogenesis of AUDs in adolescents.

Critical windows of susceptibility in the association between manganese and neurocognition in Italian adolescents living near ferro-manganese industry

INTRODUCTION

Understanding the neurodevelopmental effects of manganese (Mn) is complicated due to its essentiality for growth and development. While evidence exists for the harmful effects of excess Mn, pediatric epidemiologic studies have observed inconsistent associations between Mn and child cognition.

OBJECTIVE

We sought to estimate prospective associations between Mn measured in three different early-life time windows with adolescent cognition using deciduous teeth biomarkers.

METHODS

Deciduous teeth were collected from 195 participants (ages 10-14 years) of the Public Health Impact of Manganese Exposure (PHIME) study in Brescia, Italy. Measurements of tooth Mn represented prenatal (∼14 weeks gestation - birth), early postnatal (birth - 1.5 years) and childhood (∼1.5 - 6 years) time windows. Neuropsychologists administered the Wechsler Intelligence Scale for Children, 3rd edition (WISC-III), to obtain composite IQ and subtest scores. Associations between tooth Mn at each time window and adolescent WISC-III scores were estimated using multivariable linear regression. We tested differences in associations between Mn and outcomes across time windows using multiple informant models. Sex-specific associations were explored in stratified models.

RESULTS

Adjusted associations between tooth Mn and composite IQ scores were positive in the prenatal period and negative in the childhood period. Associations were strongest for subtest scores that reflect working memory, problem solving, visuospatial ability and attention: prenatal Mn was positively associated with Digits backward [SD change in score per interquartile range increase in Mn: β = 0.20 (95 % CI: 0.02, 0.38)] and Block design [β = 0.21 (0.01, 0.41)] and early postnatal Mn was positively associated with Digits forward [β = 0.24 (0.09, 0.40)], while childhood Mn was negatively associated with Coding [β = -0.14 (-0.28, -0.001)]. Sex-stratified analyses suggested different Mn-cognition associations for boys and girls and was also dependent on the time window of exposure.

CONCLUSION

Our results suggest that exposure timing is critical when evaluating Mn associations between Mn and cognition. Higher prenatal Mn was beneficial for adolescent cognition; however, these beneficial associations shifted towards harmful effects in later time windows. Cognitive domains most sensitive to Mn across time windows included visuospatial ability, working memory, attention and problem-solving.

Association between EEG asymmetry and the error-related negativity across middle childhood

Resting frontal EEG alpha asymmetry has been extensively examined as a marker of motivational disposition. Recent research has examined how this trait-level marker of motivation influences an individual's internal error monitoring (indexed by the error-related negativity; ERN), with mixed findings as to whether more negative ERNs are associated with greater left or right alpha power. Data from 339 children who completed an incentivized Go/No-Go task annually from Kindergarten through 2nd grade were examined for an association between ERN amplitude and EEG asymmetry, and for whether the association was developmentally stable. Results indicate an association between left-dominant activation and a more negative amplitude in Kindergarten, with an inversion of this association emerging by 2nd grade, such that a more negative ERNs were associated with right-dominant activation. We suggest that the association between EEG asymmetry and ERN amplitude is likely modulated by task condition (e.g., incentivization) and experience over time (e.g., habituation).

Repetitive Transcranial Magnetic Stimulation for Adolescent Major Depressive Disorder: A Focus on Neurodevelopment

Adolescent depression is a potentially lethal condition and a leading cause of disability for this age group. There is an urgent need for novel efficacious treatments since half of adolescents with depression fail to respond to current therapies and up to 70% of those who respond will relapse within 5 years. Repetitive transcranial magnetic stimulation (rTMS) has emerged as a promising treatment for major depressive disorder (MDD) in adults who do not respond to pharmacological or behavioral interventions. In contrast, rTMS has not demonstrated the same degree of efficacy in adolescent MDD. We argue that this is due, in part, to conceptual and methodological shortcomings in the existing literature. In our review, we first provide a neurodevelopmentally focused overview of adolescent depression. We then summarize the rTMS literature in adult and adolescent MDD focusing on both the putative mechanisms of action and neurodevelopmental factors that may influence efficacy in adolescents. We then identify limitations in the existing adolescent MDD rTMS literature and propose specific parameters and approaches that may be used to optimize efficacy in this uniquely vulnerable age group. Specifically, we suggest ways in which future studies reduce clinical and neural heterogeneity, optimize neuronavigation by drawing from functional brain imaging, apply current knowledge of rTMS parameters and neurodevelopment, and employ an experimental therapeutics platform to identify neural targets and biomarkers for response. We conclude that rTMS is worthy of further investigation. Furthermore, we suggest that following these recommendations in future studies will offer a more rigorous test of rTMS as an effective treatment for adolescent depression.

Pornography Use Prevalence and Associated Factors in Arab Countries: A Multinational Cross-Sectional Study of 15,027 Individuals

BACKGROUND

There has been a tangible increase in pornography consumption during the past decade, with the absence of a large-scale study of Arab countries.

AIM

The present study aimed to assess the prevalence of pornography viewing and its associated risk factors in Arab countries.

METHODS

A large cross-sectional online survey was carried out recruiting participants without restrictions on the age, socioeconomic level, job, or educational level. Multivariable logistic regression analysis was performed to identify possible risk factors for viewing porn and results were expressed as odds ratios (ORs) and 95% confidence interval (95% CI).

OUTCOMES

Main outcomes were pornography viewing (first exposure and frequency), the perceptions of this act, use of spare time, physical activity (exercising), and frequency of psychiatrist visits.

RESULTS

The final number of participants included in the study was 15027 participants with a mean age ± standard deviation of 23.82 years ± 24.99. Most of the participants were men (84.56%), living with parents (81.71%), and 60.51% university graduates. There were statistically significant differences (P < .001) in the attitude and practice of men compared with women throughout all tested variables. Frequent pornography viewing was associated with male gender (OR [95% CI] = 7.08 [6.43 to 7.81]; P < .001) and age group ≤15 years (OR [95% CI] = 1.33 [1.01 to 1.75]; P = .044). By contrast, higher education was inversely associated with viewing rates reaching the lowest level in PhD awardees (OR [95% CI] = 0.36 [0.26 to 0.51]; P = .003). It was also noted that regular exercising (OR [95% CI] = 0.66 [0.58 to 0.74]; P < .001) was associated with a reduction in pornography viewing rates.

CLINICAL IMPLICATIONS

Young age, male gender, and lower educational level are all predictors for higher pornography viewing and should be considered when designing public health intervention in a related context.

STRENGTHS AND LIMITATIONS

This is the first large-scale multi-national survey to be conducted in Arab countries to investigate pornography viewing. The main limitations were the cross-sectional design (cannot indicate causality) and the self-report nature (liable to social desirability and recall bias).

CONCLUSION

Pornography viewing is common in Arab countries and associated with some personal and behavioral factors. Eljawad MA, Se'eda H, Ghozy S, et al. Pornography Use Prevalence and Associated Factors in Arab Countries: A Multinational Cross-Sectional Study of 15,027 Individuals. J Sex Med 2021;18:539-548.

The Brain Emotional Systems in Addictions: From Attachment to Dominance/Submission Systems

Human development has become particularly complex during the evolution. In this complexity, adolescence is an extremely important developmental stage. Adolescence is characterized by biological and social changes that create the prerequisites to psychopathological problems, including both substance and non-substance addictive behaviors. Central to the dynamics of the biological changes during adolescence are the synergy between sexual and neurophysiological development, which activates the motivational/emotional systems of Dominance/Submission. The latter are characterized by the interaction between the sexual hormones, the dopaminergic system and the stress axis (HPA). The maturation of these motivational/emotional systems requires the integration with the phylogenetically more recent Attachment/CARE Systems, which primarily have governed the subject's relationships until puberty. The integration of these systems is particularly complex in the human species, due to the evolution of the process of competition related to sexual selection: from a simple fight between two individuals (of the same genus and species) to a struggle for the acquisition of a position in rank and the competition between groups. The latter is an important evolutionary acquisition and believed to be the variable that has most contributed to enhancing the capacity for cooperation in the human species. The interaction between competition and cooperation, and between competition and attachment, characterizes the entire human relational and emotional structure and the unending work of integration to which the BrainMind is involved. The beginning of the integration of the aforementioned motivational/emotional systems is currently identified in the prepubertal period, during the juvenile stage, with the development of the Adrenarche-the so-called Adrenal Puberty. This latter stage is characterized by a low rate of release of androgens, the hormones released by the adrenal cortex, which activate the same behaviors as those observed in the PLAY system. The Adrenarche and the PLAY system are biological and functional prerequisites of adolescence, a period devoted to learning the difficult task of integrating the phylogenetically ancient Dominance/Submission Systems with the newer Attachment/CARE Systems. These systems accompany very different adaptive goals which can easily give rise to mutual conflict and can in turn make the balance of the BrainMind precarious and vulnerable to mental suffering.

Friendship stability in adolescence is associated with ventral striatum responses to vicarious rewards

An important task for adolescents is to form and maintain friendships. In this three-wave biannual study, we used a longitudinal neuroscience perspective to examine the dynamics of friendship stability. Relative to childhood and adulthood, adolescence is marked by elevated ventral striatum activity when gaining self-serving rewards. Using a sample of participants between the ages of eight and twenty-eight, we tested age-related changes in ventral striatum response to gaining for stable (n = 48) versus unstable best friends (n = 75) (and self). In participants with stable friendships, we observed a quadratic developmental trajectory of ventral striatum responses to winning versus losing rewards for friends, whereas participants with unstable best friends showed no age-related changes. Ventral striatum activity in response to winning versus losing for friends further varied with friendship closeness for participants with unstable friendships. We suggest that these findings may reflect changing social motivations related to formation and maintenance of friendships across adolescence.

White Matter Correlates of Hostility and Aggression in the Visuospatial Function Network in Patients With Schizophrenia

Background: Violent acts in patients with schizophrenia are often associated with their hostility and aggression levels. Poor visuospatial processing has been suggested as a possible risk factor of violence in schizophrenia. However, studies investigating the relationship between hostility, aggression, and the visuospatial function have been lacking. Here, we aimed to investigate brain dysconnectivity associated with hostility and aggression in schizophrenia, particularly focusing on the visuospatial function network. Methods: Eighty-eight participants with schizophrenia and 42 healthy controls were enrolled. The visuospatial function network regions of interest were analyzed using Tract-Based Spatial Statistics. The hostility item from the Positive and Negative Syndrome Scale (PANSS), aggressive, and agitated behavior item from the Scale for the Assessment of Positive Symptoms (SAPS), and the Rey Complex Figure Test (R-CFT) were measured. Results: Among the participants with schizophrenia, the SAPS aggressive and agitated behavior scores were significantly correlated with fractional anisotropies (FAs) of the white matter regions in the splenium of the corpus callosum (CC), left posterior thalamic radiations (PTR), and left posterior corona radiata (PCR). Exploratory correlational analysis revealed significant negative correlations between FAs of the splenium of the CC and R-CFT copy and immediate recall scores. In addition, three regions including CC, PTR, and PCR that significantly correlated with the aggression scores showed significant correlations with the total PANSS scores. Conclusion: Our main finding suggests that aggression of patients with schizophrenia may be associated with poor visuospatial ability and underlying white matter dysconnectivity. These may help enhance understanding aggression in patients with schizophrenia.

The association between sleep-wake ratio and overnight picture recognition is moderated by BDNF genotype

A wealth of studies supports the role of sleep in memory performance. Experimentally controlled studies indicate that prolonged wake after memory encoding is detrimental for memory outcome whereas sleep protects from wake-time interference and promotes memory consolidation. We examined how the natural distribution of wake and sleep between encoding and retrieval associated with overnight picture recognition accuracy among 161 adolescents following their typical sleep schedule with an in-home polysomnography. The memorized pictures varied in their level of arousal (calm to exciting) and valence (negative to positive). Suspecting genotypic influence on the sensitivity for sleep/wake dynamics, we also assessed if these associations were affected by known gene polymorphisms involved in neural plasticity and sleep homeostasis: brain-derived neurotrophic factor (BDNF) Val66Met and Catechol-O-methyltransferase (COMT) Val158Met. In the whole sample, overnight recognition accuracy was associated with the levels of arousal and valence of the pictures, but not with sleep percentage (i.e. the percentage of time spent asleep between memory encoding and retrieval). While the allelic status of BDNF or COMT did not have any main effect on recognition accuracy, a significant moderation by BDNF Val66Met was found (p = .004): the subgroup homozygous for valine allele showed positive association between sleep percentage and recognition accuracy. This was underlain by detrimental influence of wake, rather than by any memory benefit of sleep. Our results complement the mounting evidence that the relation between sleep and memory performance is moderated by BDNF Val66Met. Further studies are needed to clarify the specific mechanisms.

Neurobiological Sensitivity to Social Rewards and Punishments Moderates Link Between Peer Norms and Adolescent Risk Taking

Although peer influence is a strong predictor of adolescents' risk-taking behaviors, not all adolescents are susceptible to their peer group. One hundred and thirty-six adolescents (M_age  = 12.79 years) completed an fMRI scan, measures of perceived peer group norms, and engagement in risky behavior. Ventral striatum (VS) sensitivity when anticipating social rewards and avoiding social punishments significantly moderated the association between perceived peer norms and adolescents' own risk behaviors. Perceptions of more deviant peer norms were associated with increased risky behavior, but only for adolescents with high VS sensitivity; adolescents with low VS sensitivity were resilient to deviant peer norms, showing low risk taking regardless of peer context. Findings provide a novel contribution to the study of peer influence susceptibility.

Adolescents exhibit reduced Pavlovian biases on instrumental learning

Multiple learning systems allow individuals to flexibly respond to opportunities and challenges present in the environment. An evolutionarily conserved "Pavlovian" learning mechanism couples valence and action, promoting a tendency to approach cues associated with reward and to inhibit action in the face of anticipated punishment. Although this default response system may be adaptive, these hard-wired reactions can hinder the ability to learn flexible "instrumental" actions in pursuit of a goal. Such constraints on behavioral flexibility have been studied extensively in adults. However, the extent to which these valence-specific response tendencies bias instrumental learning across development remains poorly characterized. Here, we show that while Pavlovian response biases constrain flexible action learning in children and adults, these biases are attenuated in adolescents. This adolescent-specific reduction in Pavlovian bias may promote unbiased exploration of approach and avoidance responses, facilitating the discovery of rewarding behavior in the many novel contexts that adolescents encounter.

Psychological impacts of "screen time" and "green time" for children and adolescents: A systematic scoping review

Technological developments in recent decades have increased young people's engagement with screen-based technologies (screen time), and a reduction in young people's contact with nature (green time) has been observed concurrently. This combination of high screen time and low green time may affect mental health and well-being. The aim of this systematic scoping review was to collate evidence assessing associations between screen time, green time, and psychological outcomes (including mental health, cognitive functioning, and academic achievement) for young children (<5 years), schoolchildren (5-11 years), early adolescents (12-14 years), and older adolescents (15-18 years). Original quantitative studies were identified in four databases (PubMed, PsycInfo, Scopus, Embase), resulting in 186 eligible studies. A third of included studies were undertaken in Europe and almost as many in the United States. The majority of studies were cross-sectional (62%). In general, high levels of screen time appeared to be associated with unfavourable psychological outcomes while green time appeared to be associated with favourable psychological outcomes. The ways screen time and green time were conceptualised and measured were highly heterogeneous, limiting the ability to synthesise the literature. The preponderance of cross-sectional studies with broadly similar findings, despite heterogeneous exposure measures, suggested results were not artefacts. However, additional high-quality longitudinal studies and randomised controlled trials are needed to make a compelling case for causal relationships. Different developmental stages appeared to shape which exposures and outcomes were salient. Young people from low socioeconomic backgrounds may be disproportionately affected by high screen time and low green time. Future research should distinguish between passive and interactive screen activities, and incidental versus purposive exposure to nature. Few studies considered screen time and green time together, and possible reciprocal psychological effects. However, there is preliminary evidence that green time could buffer consequences of high screen time, therefore nature may be an under-utilised public health resource for youth psychological well-being in a high-tech era.

Role of genetic background in the effects of adolescent nicotine exposure on mesolimbic dopamine transmission

Smoking during adolescence may increase the likelihood to develop nicotine dependence and to abuse other drugs such as cocaine. Despite great efforts to understand underlying neurobiological mechanisms of this progression, less attention has been paid to the role of genetic factors. Here, we investigated the influence of both genetic background and age at first nicotine exposure in the long-lasting effects on mesolimbic dopamine transmission including the increased cocaine-rewarding effect. Mid-adolescent and adult rats of inbred strains Lewis (addiction prone) and Fischer 344 (addiction resistant) were administered nicotine (0.4 mg/kg) or vehicle once daily for 5 days. Changes in dopamine transmission were investigated by in vivo microdialysis and electrophysiology after 30 days of withdrawal, whereas changes in cocaine-rewarding effect were assessed via conditioned place preference paradigm. Nicotine pre-exposure differentially changed mesolimbic dopamine transmission depending on strain and age of pre-exposure. A potentiation of dopamine response to nicotine was observed in nucleus accumbens (NAc) core of both strains and age groups, whereas dopamine response in NAc shell was enhanced exclusively in Lewis rats exposed to nicotine during adolescence. A similar response was observed following cocaine challenge at adulthood. Changes in VTA dopamine cell population and activity were observed only in adolescent nicotine-pretreated Lewis rats, which also showed an increased cocaine-rewarding effect at adulthood. These results highlight the influence of genetic background in the long-lasting effects of nicotine exposure and suggest that exposure during adolescence might increase nicotine and cocaine-rewarding properties in genetically vulnerable individuals, thereby facilitating progression toward dependence.

Drug Conditioning and Sensitization in Mice: Importance of Early Voluntary Exercise

The timing of voluntary exercise relative to drug conditioning is important to its "neuroprotective" effects, though it is unclear whether the voluntary exercise needs to occur temporally contiguous with drug conditioning, or occur during an early, developmental period, but non-contiguous with drug conditioning, for its "neuroprotective" effects. To distinguish between these two ideas, the timing of voluntary exercise relative to drug conditioning on the development and extinction of conditioned hyperactivity, and induction of sensitization was manipulated in the present experiment. Specifically, half of the exercise mice were permitted access to home-cage running wheels for 6 continuous weeks (Exercise-Exercise) whereas the other half of the exercise mice were permitted access to home-cage running wheels only for the first 3  weeks and then had the wheels removed (Exercise-Sedentary). Likewise, half of the sedentary mice had no home-cage running wheels for 6 continuous weeks (Sedentary-Sedentary) whereas the other half of the sedentary mice were permitted access to the home-cage running wheels for the last 3 weeks prior to the acquisition phase (Sedentary-Exercise). Mice received vehicle or methamphetamine (Meth; 1.0 mg/kg; acquisition), followed by saline-alone sessions (extinction) and finally challenged with an escalating Meth-regimen (0.25 → 1.0 mg/kg). While all Meth-paired groups, regardless of exercise regimen, showed conditioned hyperactivity, Exercise-Exercise and Exercise-Sedentary mice were less responsive to chronic Meth exposure and showed slower extinction compared to the other Meth-paired groups. These results suggest an early exercise regimen, during a critical developmental window, protects against the stimulant properties of Meth and simultaneously facilitates contextual learning.

Post-pubertal Difference in Nigral Dopaminergic Cells Firing in the Schizophrenia Model Prepared by Perinatal Challenges of a Cytokine, EGF

Schizophrenia in humans typically develops during and after adolescence; however, the biological underpinning for the specificity of this onset time window remains to be determined. In the present study, we investigated this knowledge gap using our own animal model for schizophrenia. Rodents and monkeys challenged with a cytokine, epidermal growth factor (EGF), as neonates are known to exhibit various behavioral and cognitive abnormalities at the post-pubertal stage. We used the EGF-challenged mice as an animal model for schizophrenia to evaluate the electrophysiological impact of this modeling on nigral dopamine neurons before and after puberty. In vivo single unit recording revealed that the burst firing of putative dopamine neurons in substantia nigra pars compacta was significantly higher in the post-pubertal stage of the EGF model than in that of control mice; in contrast, this difference was not observed in the pre-pubertal stage. The increase in burst firing was accompanied by a decline in Ca²⁺-activated K⁺ (I_SK) currents, which influence the firing pattern of dopamine neurons. In vivo local application of the SK channel blocker apamin (80 μM) to the substantia nigra was less effective at increasing burst firing in the EGF model than in control mice, suggesting the pathologic role of the I_SK decrease in this model. Thus, these results suggest that the aberrant post-pubertal hyperactivity of midbrain dopaminergic neurons is associated with the temporal specificity of the behavioral deficit of this model, and support the hypothesis that this dopaminergic aberration could be implicated in the adolescent onset of schizophrenia.

Developmental trajectories to reduced activation of positive valence systems: A review of biological and environmental contributions

Reduced activation of positive valence systems (PVS), including blunted neural and physiological responses to pleasant stimuli and rewards, has been shown to prospectively predict the development of psychopathology. Yet, little is known about how reduced PVS activation emerges across development or what implications it has for prevention. We review genetic, temperament, parenting, and naturalistic and laboratory stress research on neural measures of PVS and outline developmentally-informed models of trajectories of PVS activation. PVS function is partly heritable and appears to reflect individual differences in early-emerging temperament traits. Although lab-induced stressors blunt PVS activation, effects of parenting and naturalistic stress on PVS are mixed and depend on the type of stressor, developmental timing, and interactions amongst risk factors. We propose that there may be multiple, dynamic developmental trajectories to reduced PVS activation in which combinations of genes, temperament, and exposure to severe, prolonged, or uncontrollable stress may exert direct and interactive effects on PVS function. Critically, these risk factors may alter PVS developmental trajectories and/or PVS sensitivity to proximal stressors. Distinct factors may converge such that PVS activation proceeds along a typical, accelerated, chronically low, or stress-reactive trajectory. Finally, we present directions for future research with translational implications.

Comparing dopamine release, uptake, and D2 autoreceptor function across the ventromedial to dorsolateral striatum in adolescent and adult male and female rats

Adolescence is characterized by changes in behavior, such as increases in sensation seeking and risk taking, and increased vulnerability to developing a range of psychiatric disorders, including substance abuse disorders (SUD) and mood disorders. The mesolimbic dopamine system plays an essential role in mediating these behaviors and disorders. Therefore, it is imperative to understand how the dopamine system and its regulation are changing during this period of development. Here, we used ex vivo fast scan cyclic voltammetry to compare stimulated dopamine release and its local circuitry regulation between early adolescent and adult male and female Sprague-Dawley rats. We found that, compared to adults, adolescent males have decreased stimulated dopamine release in the NAc core, while adolescent females have increased dopamine release in the NAc shell, NAc core, and DMS. We also found sex- and region-specific differences in other dopamine dynamics, including maximal dopamine uptake (Vmax), release across a range of stimulation frequencies, and autoreceptor regulation of dopamine release. Better understanding how the dopamine system develops during adolescence will be imperative for understanding what mediates adolescent vulnerability to developing psychiatric disorders and how disruptions during this period of reorganization could alter behaviors and vulnerability into adulthood.

Neural Dynamic Responses of Monetary and Social Reward Processes in Adolescents

Adolescence is an essential developmental period characterized by reward-related processes. The current study investigated the development of monetary and social reward processes in adolescents compared with that in children and adults; furthermore, it assessed whether adolescents had different levels of sensitivity to various types of rewards. Two adapted incentive delay tasks were employed for each participant, and event-related potentials (ERPs) were recorded. The behavioral results showed that both monetary and social rewards could motivate response speed, and participants were more accurate under the monetary reward condition than under the social reward condition. The behavioral performances of individuals increased with age. For the ERP data, the cue-P3, target-P2, target-P3 and feedback-related negativity (FRN) components were investigated to identify reward motivation, emotional arousal, attention allocation and feedback processing. Children and adolescents showed higher motivation (larger cue-P3) to rewards than adults. Adolescents showed larger emotional responses to rewards; that is, they had larger target-P2 amplitudes than adults and shorter target-P2 latencies than children. Children showed stronger emotional reactivity for monetary rewards than for social rewards. All age groups had stronger attentional control (larger target-P3) under the monetary reward condition than under the social reward condition. The present study sheds light on the neurodevelopment of reward processes in children, adolescents and adults and shows that various reward process stages demonstrate different age-related and reward-type-related characteristics.

Adolescence versus adulthood: Differences in basal mesolimbic and nigrostriatal dopamine transmission and response to drugs of abuse

Epidemiological studies have shown that people who begin experimenting drugs of abuse during adolescence are more likely to develop substance use disorders, and the earliest is the beginning of their use, the greatest is the likelihood to become dependent. Understanding the neurobiological changes increasing adolescent vulnerability to drug use is becoming imperative. Although all neurotransmitter systems undergo relevant developmental changes, dopamine system is of particular interest, given its role in a variety of functions related to reward, motivation, and decision making. Thus, in the present study, we investigated differences in mesolimbic and nigrostriatal dopamine transmission between adolescent (5, 6, 7 weeks of age) and adult rats (10-12 weeks of age), in basal conditions and following drug challenge, by using in vivo brain microdialysis. Although no significant difference between adolescents and adults was observed in dopamine basal levels in the nucleus accumbens (NAc)shell and core, reduced DA levels were found in the dorsolateral striatum (DLS) of early and mid-adolescent rats. Adolescent rats showed greater increase of dopamine in the NAc shell following nicotine (0.4 mg/kg), THC (1.0 mg/kg), and morphine (1.0 mg/kg), in the NAc core following nicotine and morphine, and in the DLS following THC, morphine, and cocaine (10 mg/kg). These results, while adding new insight in the development and functionality of the dopamine system during different stages of adolescence, might provide a neurochemical basis for the greater vulnerability of adolescents to drugs of abuse and for the postulated gateway effect of nicotine and THC toward abuse of other illicit substances.

Experience during adolescence shapes brain development: From synapses and networks to normal and pathological behavior

Adolescence is a period of dramatic neural reorganization creating a period of vulnerability and the possibility for the development of psychopathology. The maturation of various neural circuits during adolescence depends, to a large degree, on one's experiences both physical and psychosocial. This occurs through a process of plasticity which is the structural and functional adaptation of the nervous system in response to environmental demands, physiological changes and experiences. During adolescence, this adaptation proceeds upon a backdrop of structural and functional alterations imparted by genetic and epigenetic factors and experiences both prior to birth and during the postnatal period. Plasticity entails an altering of connections between neurons through long-term potentiation (LTP) (which alters synaptic efficiency), synaptogenesis, axonal sprouting, dendritic remodeling, neurogenesis and recruitment (Skaper et al., 2017). Although most empirical evidence for plasticity derives from studies of the sensory systems, recent studies have suggested that during adolescence, social, emotional, and cognitive experiences alter the structure and function of the networks subserving these domains of behavior. Each of these neural networks exhibits heightened vulnerability to experience-dependent plasticity during the sensitive periods which occur in different circuits and different brain regions at specific periods of development. This report will summarize some examples of adaptation which occur during adolescence and some evidence that the adolescent brain responds differently to stimuli compared to adults and children. This symposium, "Experience during adolescence shapes brain development: from synapses and networks to normal and pathological behavior" occurred during the Developmental Neurotoxicology Society/Teratology Society Annual Meeting in Clearwater Florida, June 2018. The sections will describe the maturation of the brain during adolescence as studied using imaging technologies, illustrate how plasticity shapes the structure of the brain using examples of pathological conditions such as Tourette's' syndrome and attention deficit hyperactivity disorder, and a review of the key molecular systems involved in this plasticity and how some commonly abused substances alter brain development. The role of stimulants used in the treatment of attention deficit hyperactivity disorder (ADHD) in the plasticity of the reward circuit is then described. Lastly, clinical data promoting an understanding of peer-influences on risky behavior in adolescents provides evidence for the complexity of the roles that peers play in decision making, a phenomenon different from that in the adult. Imaging studies have revealed that activation of the social network by the presence of peers at times of decision making is unique in the adolescent. Since normal brain development relies on experiences which alter the functional and structural connections between cells within circuits and networks to ultimately alter behavior, readers can be made aware of the myriad of ways normal developmental processes can be hijacked. The vulnerability of developing adolescent brain places the adolescent at risk for the development of a life time of abnormal behaviors and mental disorders.