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1.  The development of spatial behaviour and the hippocampal neural representation of space 
The role of the hippocampal formation in spatial cognition is thought to be supported by distinct classes of neurons whose firing is tuned to an organism's position and orientation in space. In this article, we review recent research focused on how and when this neural representation of space emerges during development: each class of spatially tuned neurons appears at a different age, and matures at a different rate, but all the main spatial responses tested so far are present by three weeks of age in the rat. We also summarize the development of spatial behaviour in the rat, describing how active exploration of space emerges during the third week of life, the first evidence of learning in formal tests of hippocampus-dependent spatial cognition is observed in the fourth week, whereas fully adult-like spatial cognitive abilities require another few weeks to be achieved. We argue that the development of spatially tuned neurons needs to be considered within the context of the development of spatial behaviour in order to achieve an integrated understanding of the emergence of hippocampal function and spatial cognition.
doi:10.1098/rstb.2013.0409
PMCID: PMC3866458  PMID: 24366148
development; hippocampus; navigation; spatial; place cell; grid cell
2.  Boundary coding in the rat subiculum 
The spatial mapping function of the hippocampal formation is likely derived from two sets of information: one based on the external environment and the other based on self-motion. Here, we further characterize ‘boundary vector cells’ (BVCs) in the rat subiculum, which code space relative to one type of cue in the external environment: boundaries. We find that the majority of cells with fields near the perimeter of a walled environment exhibit an additional firing field when an upright barrier is inserted into the walled environment in a manner predicted by the BVC model. We use this property of field repetition as a heuristic measure to define BVCs, and characterize their spatial and temporal properties. In further tests, we find that subicular BVCs typically treat drop edges similarly to walls, including exhibiting field repetition when additional drop-type boundaries are added to the testing environment. In other words, BVCs treat both kinds of edge as environmental boundaries, despite their dissimilar sensory properties. Finally, we also report the existence of ‘boundary-off cells’, a new class of boundary-coding cells. These cells fire everywhere except where a given BVC might fire.
doi:10.1098/rstb.2012.0514
PMCID: PMC3866438  PMID: 24366128
boundary vector cell; border cell; boundary-off cell; subicular; wall; edge
3.  Effects of Perceived Racial Discrimination on Health Status and Health Behavior: A Differential Mediation Hypothesis 
Objective
Prospective data tested a “differential mediation” hypothesis: The relations (found in previous research) between perceived racial discrimination and physical health status versus health-impairing behavior (problematic substance use) are mediated by two different types of affective reactions, internalizing and externalizing.
Methods
The sample included 680 African American women from the Family and Community Health Study (M age = 37 at Time 1; 45 at Time 4). Four waves of data were analyzed. Perceived discrimination was assessed, along with anxiety and depression (internalizing) and hostility / anger (externalizing) as mediators, and physical health status and problematic substance use (drinking) as outcomes.
Results
Structural equation modeling indicated that discrimination predicted increases in both externalizing and internalizing reactions. These affective responses, in turn, predicted subsequent problematic substance use and physical health status, respectively, also controlling for earlier reports. In each case, the indirect effects from discrimination through the affective mediator to the specific health outcome were significant and consistent with the differential mediation hypothesis.
Conclusion
Perceived racial discrimination is associated with increases in internalizing and externalizing reactions among Black women, but these reactions are related to different health outcomes. Changes in internalizing are associated with self-reported changes in physical health status, whereas changes in externalizing are associated with changes in substance use problems. Discussion focuses on the processes whereby discrimination affects health behavior and physical health status.
doi:10.1037/a0033857
PMCID: PMC3893709  PMID: 24417690
Discrimination; Physical Health; Substance Use
4.  Good Self-Control Moderates the Effect of Mass Media on Adolescent Tobacco and Alcohol Use: Tests With Studies of Children and Adolescents 
Objective
To investigate whether self-control moderates the effect of media influences on tobacco and alcohol use among youth and if so how this effect occurs.
Design
In Study 1, a regional sample of 10-year olds (N = 290) was interviewed in households; attention to tobacco/alcohol advertising was assessed. In Study 2, a national sample of youth ages 10–14 years (N = 6,522) was surveyed by telephone; exposure to tobacco/alcohol use in movies was assessed. Good self-control was measured in both studies.
Main Outcome Measures
Willingness to use substances and affiliation with peer substance users (Study 1); involvement in smoking or drinking (Study 2).
Results
In Study 1, the effect of tobacco/alcohol advertising on predisposition for substance use was lower among persons scoring higher on good self-control. In Study 2, the effect of movie smoking/alcohol exposure on adolescent tobacco/alcohol use was lower, concurrently and prospectively, among persons scoring higher on good self-control. Moderation occurred primarily through reducing the effect of movie exposure on positive smoking/alcohol expectancies and the effect of expectancies on adolescent use; some evidence for moderation of social processes was also noted. Covariates in the analyses included demographics, sensation seeking, and IQ.
Conclusion
Good self-control reduces the effect of adverse media influences on adolescent tobacco and alcohol use. Findings on the processes underlying this effect may be useful for media literacy and primary prevention programs.
doi:10.1037/a0020818
PMCID: PMC3719172  PMID: 20836609
adolescent smoking/alcohol use; moderation; self-control; movies; advertising
5.  The Erosive Effects of Racism: Reduced Self-control Mediates the Relation between Perceived Racial Discrimination and Substance Use in African American Adolescents 
Perceived racial discrimination, self-control, anger, and either substance use or use cognitions were assessed in two studies conducted with samples of African American adolescents. The primary goal was to examine the relation between discrimination and self-control over time; a second goal was to determine if that relation mediates the link between discrimination and substance use found in previous research. Study 1, which included a latent growth curve analysis with three waves of data, indicated that experience with discrimination (from age 10 to age 18) was associated with reduced self-control, which then predicted increased substance use. Additional analyses indicated anger was also a mediator of this discrimination to use relation. Study 2, which was experimental, showed that envisioning an experience involving discrimination was associated with an increase in substance-related responses to double entendre words (e.g., “pot,” “roach”) in a word association task, especially for participants who were low in dispositional self-control. The effect was again mediated by reports of anger. Thus, the “double mediation” pattern was: discrimination → more anger and reduced self-control → increased substance use and/or substance cognitions. Results are discussed in terms of the long-term impact of discrimination on self-control and health behavior. Implications for interventions aimed at ameliorating the negative effects of discrimination and low self-control on health are also discussed.
doi:10.1037/a0027404
PMCID: PMC3341491  PMID: 22390225
6.  Behavioral Self-Regulation and Weight-Related Behaviors in Inner-City Adolescents: A Model of Direct and Indirect Effects 
Childhood obesity (Print)  2011;7(4):306-315.
Background
This study examined the association of two distinct self-regulation constructs, effortful control and dysregulation, with weight-related behaviors in adolescents and tested whether these effects were mediated by self-efficacy variables.
Methods
A school-based survey was conducted with 1771 adolescents from 11 public schools in the Bronx, New York. Self-regulation was assessed by multiple indicators and defined as two latent constructs. Dependent variables included fruit/vegetable intake, intake of snack/junk food, frequency of physical activity, and time spent in sedentary behaviors. Structural equation modeling examined the relation of effortful control and dysregulation to lifestyle behaviors, with self-efficacy variables as possible mediators.
Results
Study results showed that effortful control had a positive indirect effect on fruit and vegetable intake, mediated by self-efficacy, as well as a direct effect. Effortful control also had a positive indirect effect on physical activity, mediated by self-efficacy. Dysregulation had direct effects on intake of junk food/snacks and time spent in sedentary behaviors.
Conclusions
These findings indicate that self-regulation characteristics are related to diet and physical activity and that some of these effects are mediated by self-efficacy. Different effects were noted for the two domains of self-regulation. Prevention researchers should consider including self-regulation processes in programs to improve health behaviors in adolescents.
PMCID: PMC3522174  PMID: 23243551
7.  Behavioral and Emotional Regulation and Adolescent Substance Use Problems: A Test of Moderation Effects in a Dual-Process Model 
In a structural model, we tested how relations of predictors to level of adolescent substance use (tobacco, alcohol, marijuana), and to substance-related impaired-control and behavior problems, are moderated by good self-control and poor regulation in behavioral and emotional domains. The participants were a sample of 1,116 public high-school students. In a multiple-group analysis for good self-control, the paths from negative life events to substance use level and from level to behavior problems were lower among persons scoring higher on good behavioral self-control. In a multiple-group analysis for poor regulation, the paths from negative life events to level and from peer substance use to level were greater among persons scoring higher on poor behavioral (but not emotional) regulation; an inverse path from academic competence to level was greater among persons scoring higher on both aspects of poor regulation. Paths from level to impaired-control and behavior problems were greater among persons scoring higher on both poor behavioral and poor emotional regulation. Theoretical implications for the basis of moderation effects are discussed.
doi:10.1037/a0022870
PMCID: PMC3130053  PMID: 21443302
substance use; adolescents; self-regulation; substance use problems; moderation
8.  Comparing media and family predictors of alcohol use: a cohort study of US adolescents 
BMJ Open  2012;2(1):e000543.
Objective
To compare media/marketing exposures and family factors in predicting adolescent alcohol use.
Design
Cohort study.
Setting
Confidential telephone survey of adolescents in their homes.
Participants
Representative sample of 6522 US adolescents, aged 10–14 years at baseline and surveyed four times over 2 years.
Primary outcome measure
Time to alcohol onset and progression to binge drinking were assessed with two survival models. Predictors were movie alcohol exposure (MAE), ownership of alcohol-branded merchandise and characteristics of the family (parental alcohol use, home availability of alcohol and parenting). Covariates included sociodemographics, peer drinking and personality factors.
Results
Over the study period, the prevalence of adolescent ever use and binge drinking increased from 11% to 25% and from 4% to 13%, respectively. At baseline, the median estimated MAE from a population of 532 movies was 4.5 h and 11% owned alcohol-branded merchandise at time 2. Parental alcohol use (greater than or equal to weekly) was reported by 23% and 29% of adolescents could obtain alcohol from home. Peer drinking, MAE, alcohol-branded merchandise, age and rebelliousness were associated with both alcohol onset and progression to binge drinking. The adjusted hazard ratios for alcohol onset and binge drinking transition for high versus low MAE exposure were 2.13 (95% CI 1.76 to 2.57) and 1.63 (1.20 to 2.21), respectively, and MAE accounted for 28% and 20% of these transitions, respectively. Characteristics of the family were associated with alcohol onset but not with progression.
Conclusion
The results suggest that family focused interventions would have a larger impact on alcohol onset while limiting media and marketing exposure could help prevent both onset and progression.
Article summary
Article focus
Predictors of drinking during adolescence.
Particular focus on predicting onset versus binge drinking and media/marketing exposures versus family risk factors.
Key messages
Somewhat different risk factors exist for alcohol onset versus binge drinking.
Movie alcohol, alcohol marketing, friend drinking and sensation seeking predicted both outcomes.
Parent drinking, availability of alcohol at home and parenting predicted alcohol onset, not binge drinking.
Strengths and limitations
Strengths include longitudinal design, large sample size and analysis that accounted for attrition.
Limitations include inability to generalise beyond US adolescents or beyond this age bracket.
doi:10.1136/bmjopen-2011-000543
PMCID: PMC3289988  PMID: 22349939
9.  The abrupt development of adult-like grid cell firing in the medial entorhinal cortex 
Understanding the development of the neural circuits subserving specific cognitive functions such as navigation remains a central problem in neuroscience. Here, we characterize the development of grid cells in the medial entorhinal cortex, which, by nature of their regularly spaced firing fields, are thought to provide a distance metric to the hippocampal neural representation of space. Grid cells emerge at the time of weaning in the rat, at around 3 weeks of age. We investigated whether grid cells in young rats are functionally equivalent to those observed in the adult as soon as they appear, or if instead they follow a gradual developmental trajectory. We find that, from the very youngest ages at which reproducible grid firing is observed (postnatal day 19): grid cells display adult-like firing fields that tessellate to form a coherent map of the local environment; that this map is universal, maintaining its internal structure across different environments; and that grid cells in young rats, as in adults, also encode a representation of direction and speed. To further investigate the developmental processes leading up to the appearance of grid cells, we present data from individual medial entorhinal cortex cells recorded across more than 1 day, spanning the period before and after the grid firing pattern emerged. We find that increasing spatial stability of firing was correlated with increasing gridness.
doi:10.3389/fncir.2012.00021
PMCID: PMC3338009  PMID: 22557949
development; grid cell; entorhinal cortex; hippocampus
10.  Media as Social Influence: Racial Differences in the Effects of Peers and Media on Adolescent Alcohol Cognitions and Consumption 
Racial differences in the effects of peer and media influence on adolescents’ alcohol cognitions and consumption were examined in a large-scale panel study. With regard to peer influence, results from cross-lagged panel analyses indicated that the relation between perceived peer drinking and own drinking was significant for both Black and White adolescents, but it was stronger for the White adolescents. With regard to media influence, structural modeling analyses indicated that exposure to drinking in movies was associated with more alcohol consumption 8 months and 16 months later. These effects were mediated by increases in: the favorability of the adolescents’ drinker prototypes, their willingness to drink, and their tendency to affiliate with friends who were drinking. Multiple group analyses indicated that, once again, the effects (both direct and indirect) were much stronger for White adolescents than for Black adolescents. The results suggest media influence works in a similar manner to social influence, and that Whites may be more susceptible to both types of influence.
doi:10.1037/a0020768
PMCID: PMC3058338  PMID: 21198226
media influence; adolescent drinking; prototype-willingness
11.  Environmental novelty elicits a later theta phase of firing in CA1 but not subiculum 
Hippocampus  2010;20(2):229-234.
The mechanism supporting the role of the hippocampal formation in novelty detection remains controversial. A comparator function has been variously ascribed to CA1 or subiculum, while the theta rhythm has been suggested to separate neural firing into encoding and retrieval phases. We investigated theta phase of firing in principal cells in subiculum and CA1 as rats foraged in familiar and novel environments. We found that the preferred theta phase of firing in CA1, but not subiculum, was shifted to a later phase of the theta cycle during environmental novelty. Furthermore, the amount of phase shift elicited by environmental change correlated with the extent of place cell remapping in CA1. Our results support a relationship between theta phase and novelty-induced plasticity in CA1.
doi:10.1002/hipo.20671
PMCID: PMC3173854  PMID: 19623610
Hippocampus; novelty; theta; rhythmic slow activity; encoding; retrieval
12.  Effect of Visual Media Use on School Performance: A Prospective Study1 
Purpose
To identify mechanisms for the impact of visual media use on adolescents' school performance.
Methods
We conducted a 24-month, four-wave longitudinal telephone study of a national sample of 6,486 youth aged 10-14 years. Exposure Measures: Latent construct for screen exposure time (weekday time spent viewing television/playing videogames, presence of television in bedroom) and variables for movie content (proportion of PG13 and R movies viewed). Outcome Measure: Self and parent reports of grades in school. Effects of media exposures on change in school performance between baseline and 24 months were assessed using structural equation modeling. Information about hypothesized mediators (substance use, sensation-seeking, and school problem behavior) was obtained at baseline and at the16-month follow-up.
Results
Adjusted for baseline school performance, baseline levels of mediators, and a range of covariates, both screen exposure time and media content had adverse effects on change in school performance. Screen exposure had an indirect effect on poor school performance through increased sensation-seeking. Viewing more PG-13 and R-rated movies had indirect effects on poor school performance mediated through increases in substance use and sensation-seeking. R-rated viewing also had an indirect effect on poor school performance through increased school behavior problems. The effect sizes of exposure time and content on the intermediate variables and ultimately on school performance were similar to those for previously recognized determinants of these mediators – including household income, parenting style, and adolescents' self-control.
Conclusions
These aspects of visual media use adversely affect school performance by increasing sensation-seeking, substance use and school problem behavior.
doi:10.1016/j.jadohealth.2009.05.012
PMCID: PMC2818002  PMID: 20123258
visual media; sensation-seeking; school performance; mediation; screen time; screen exposure; media content
13.  Alcohol Abuse and Dependence Symptoms: A Multidimensional Model of Common and Specific Etiology 
This study tested a theoretical model hypothesizing differential pathways from five predictors to alcohol abuse and dependence symptoms. The participants were college students (N= 2,270) surveyed on two occasions in a 6-month prospective design. Social norms, perceived utility of alcohol use, and family history of alcohol problems were indirectly associated with Time 2 (T2) abuse and dependence symptoms through influencing level of alcohol consumption. Poor behavioral control had a direct effect on alcohol abuse but not dependence symptoms at T2, whereas affective lability exhibited a direct prospective effect on alcohol dependence but not abuse symptoms. A multigroup analysis showed that high levels of poor control increased the strength of paths from both consumption level and affective lability to abuse symptoms. Implications for prevention of alcohol problems among college students are discussed.
doi:10.1037/a0016003
PMCID: PMC2800947  PMID: 19769426
Alcohol abuse and dependence; self-control; affect regulation; etiology
14.  Watching and drinking: Expectancies, prototypes, and peer affiliations mediate the effect of exposure to alcohol use in movies on adolescent drinking 
Objective
To investigate the psychological processes that underlie the relation between exposure to alcohol use in media with adolescent alcohol use.
Design
Structural equation modeling analysis of data from four waves of a longitudinal, nationally-representative, random-digit dial telephone survey of adolescents in the United States.
Main Outcome Measures
Adolescent alcohol consumption and willingness to use alcohol. Tested mediators were alcohol-related norms, prototypes, expectancies, and friends' use.
Results
Alcohol prototypes, expectancies, willingness, and friends' use of alcohol (but not perceived prevalence of alcohol use among peers) were significant mediators of the relation between movie alcohol exposure and alcohol consumption, even after controlling for demographic, child, and family factors associated with both movie exposure and alcohol consumption.
Conclusion
Established psychological and interpersonal predictors of alcohol use mediate the effects of exposure to alcohol use in movies on adolescent alcohol consumption. The findings suggest that exposure movie portrayals may operate through similar processes as other social influences, highlighting the importance of considering these exposures in research on adolescent risk behavior.
doi:10.1037/a0014777
PMCID: PMC2746653  PMID: 19594272
alcohol drinking patterns; social influences; alcohol attitudes; adolescent development; films
15.  Movie Exposure to Alcohol Cues and Adolescent Alcohol Problems: A Longitudinal Analysis in a National Sample 
The authors tested a theoretical model of how exposure to alcohol cues in movies predicts level of alcohol use (ever use plus ever and recent binge drinking) and alcohol-related problems. A national sample of younger adolescents was interviewed by telephone with 4 repeated assessments spaced at 8-month intervals. A structural equation modeling analysis performed for ever-drinkers at Time 3 (N = 961) indicated that, controlling for a number of covariates, movie alcohol exposure at Time 1 was related to increases in peer alcohol use and adolescent alcohol use at Time 2. Movie exposure had indirect effects to alcohol use and problems at Times 3 and 4 through these pathways, with direct effects to problems from Time 1 rebelliousness and Time 2 movie exposure also found. Prospective risk-promoting effects were also found for alcohol expectancies, peer alcohol use, and availability of alcohol in the home; protective effects were found for mother’s responsiveness and for adolescent’s school performance and self-control. Theoretical and practical implications are discussed.
doi:10.1037/a0014137
PMCID: PMC2805125  PMID: 19290687
alcohol use; alcohol problems; adolescents; movies; structural modeling
16.  Good Self-Control as a Buffering Agent for Adolescent Substance Use 
We tested the prediction that self-control will have buffering effects for adolescent substance use (tobacco, alcohol, and marijuana) with regard to three risk factors: family life events, adolescent life events, and peer substance use. Participants were a sample of public school students (N = 1,767) who were surveyed at four yearly intervals between 6th grade and 9th grade. Good self-control was assessed with multiple indicators including planning and problem solving. Results showed that the impact of all three risk factors on substance use was reduced among persons with higher scores on good self-control. Buffering was found in cross-sectional analyses with multiple regression and in longitudinal analyses in a latent growth model with time-varying covariates. Implications for addressing self-control in prevention programs are discussed.
doi:10.1037/a0012965
PMCID: PMC2674381  PMID: 19071971
self-control; substance use; adolescents; buffering effect; growth modeling
17.  Movie Smoking Exposure and Smoking Onset: A Longitudinal Study of Mediation Processes in a Representative Sample of U.S. Adolescents 
The authors tested 2 mechanisms for the relation of movie smoking exposure with onset of cigarette smoking in adolescence. Longitudinal data with 8-month follow-up were obtained from a representative sample of 6,522 U.S. adolescents, ages 10–14 years. Structural modeling analysis based on initial nonsmokers, which controlled for 10 covariates associated with movie exposure, showed that viewing more smoking in movies was related to increases in positive expectancies about smoking and increases in affiliation with smoking peers, and these variables were both related to smoking onset. A direct effect of movie exposure on smoking onset was also noted. Mediation findings were replicated across cross-sectional and longitudinal analyses. Tests for gender differences indicated that girls showed larger effects of movie exposure for some variables. Implications for policy and prevention research are discussed.
doi:10.1037/0893-164X.22.2.269
PMCID: PMC2746493  PMID: 18540724
smoking; adolescents; movies; expectancies; peers
18.  Theta-modulated place-by-direction cells in the hippocampal formation in the rat 
We report the spatial and temporal properties of a class of cells termed theta-modulated place-by-direction cells (TPD) recorded from the pre- and parasubicular cortices of the rat. The firing characteristics of TPD cells in open field enclosures were compared to those of two other well-characterised cell classes in the hippocampal formation: place and head-direction cells. Unlike place cells, which code only for the animal's location, or head direction cells which code only for the animal's directional heading, TPD cells code for both the location and the head direction of the animal. Their firing is also strongly modulated, firing primarily at the negative-to-positive phase of the locally recorded theta wave. TPD theta modulation is significantly stronger than that of place cells. By contrast, the firing of head direction cells is not modulated by theta at all.
In repeated exposures to the same environment, the locational and directional signals of TPD cells are stable. When recorded in different environments, TPD locational and directional fields can uncouple, with the locational field shifting unpredictably (“remapping”), while its directional preference remains similar across environments.
doi:10.1523/JNEUROSCI.2635-04.2004
PMCID: PMC2683733  PMID: 15385610
19.  Experience-dependent increase in CA1 place cell spatial information, but not spatial reproducibility, is dependent on the autophosphorylation of alphaCaMKII 
Place cells in hippocampal area CA1 are essential for spatial learning and memory. Here we examine whether daily exposure to a previously unexplored environment can alter place cell properties. We demonstrate two previously unreported slowly developing plasticities in mouse place fields: both the spatial tuning and the trial-to-trial reproducibility of CA1 place fields improve over days. We asked whether these two components of improved spatial coding rely on alphaCaMKII autophosphorylation, an effector mechanism of NMDA receptor-dependent long-term potentiation and an essential molecular process for spatial memory formation. We show that, in mice with deficient autophosphorylation of alphaCaMKII, the spatial tuning of place fields is initially similar to that of wild-type mice, but completely fails to show the experience-dependent increase over days. In contrast, place field reproducibility in the mutants, although impaired, does show the experience-dependent increase over days. Consequently, the progressive improvement in spatial coding in new hippocampal place cell maps depends on the existence of two molecularly-dissociable, experience-dependent processes.
doi:10.1523/JNEUROSCI.1704-07.2007
PMCID: PMC2680063  PMID: 17634379
hippocampus; place cell; alphaCaMKII; plasticity
20.  Self-Control Constructs Related to Measures of Dietary Intake and Physical Activity in Adolescents 
Purpose
To test self-regulation concepts in relation to dietary intake and physical activity patterns in adolescence, which we predicted to be influenced by components of a self-control model.
Methods
A survey was conducted with a multiethnic sample of 9th grade public school students in a metropolitan area (N = 539). Confirmatory analysis tested the measurement structure of self-control. Structural equation modeling tested the association of self-control constructs with measures of fruit and vegetable intake, saturated-fat intake, physical activity, and sedentary behavior.
Results
Confirmatory analysis of 14 indicators of self-control showed best fit for a two-factor structure, with latent constructs of good self-control (planfulness) and poor self-control (impulsiveness). Good self-control was related to more fruit and vegetable intake, more participation in sports, and less sedentary behavior. Poor self-control was related to more saturated-fat intake and less vigorous exercise. These effects were independent of gender, ethnicity, and parental education, which themselves had relations to diet and exercise measures. Multiple-group modeling indicated that effects of self-control were comparable across gender and ethnicity subgroups.
Conclusions
Self-control concepts are relevant for patterns of dietary intake and physical activity among adolescents. Attention to self-control processes may be warranted for prevention programs to improve health behaviors in childhood and adolescence.
doi:10.1016/j.jadohealth.2007.06.013
PMCID: PMC2190087  PMID: 18023783
self-control; diet; exercise; adolescents; gender; ethnicity

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