**1. Introduction**

The right and left nucleus accumbens (NAcc) are subcortical brain structures, located within the ventral striatum, that serve as a key limbic-motor interface, and have an important role in Pavlovian learning [1, 2]. This means that the right and left NAcc contribute to the regulation of emotional and motivation processing [3], incentive salience [4], pleasure, reward, and reinforcement [5]. In addition, neural reactivity to food- and/or drug-related reward cues evokes robust dopamine responses in the right and left NAcc [1]. This suggests that as parts of the brain reward system, the right and left NAcc function reflects how individuals respond to cues that signal a potential reward [1]. The right and left NAcc have also been implicated in obesity [2, 6], food addiction [7], tobacco, alcohol, and drug-seeking behaviors [8–10], obsessive-compulsive disorder [11, 12], depression [13], and anxiety [12].

To fulfill their functions, the right and left NAcc communicate with a number of large-scale brain networks such as the frontoparietal network (FPN) [14–16]. Neuroimaging studies have revealed some alterations of the connectivity between the NAcc and FPN as an indicator of altered NAcc function [15]. The FPN, also known as the central executive network (CEN), is a large-scale brain network that works with the NAcc, striatum, and basal ganglia [17]. FPN is implicated in the cognitive control [18], attention [19], problem-solving [19], and working memory [19]. Altered FPN function is linked to attention-deficit/hyperactivity disorder (ADHD) [18, 20], cocaine addiction [21], and several mental disorders [22] in children and adolescents. Disruption in the FPN during cognitive control tasks is a common element of schizophrenia, bipolar disorder, unipolar depression, anxiety, and substance use disorders [23].

Functional magnetic resonance imaging (fMRI) techniques have expanded what we know about functional connectivity across brain regions and networks. Restingstate functional connectivity (rsFC) investigates the temporal correlation of the spatially distributed brain regions' activity at the resting state (i.e., when the participant has not engaged in an explicit task yet) [24]. rsFC allows us to identify spontaneous brain activity patterns, which can provide insight into neural activity patterns [25]. One advantage of rsFC is that it can explore networks not easily assessed during tasks and activities. Finally, rsFC tends to be free from bias in task selection and allows relatively easy data collection [25].

The frontoparietal-accumbal connectivity has a role in motivated behavior, food seeking, emotion regulation, food preference, obesity, eating disorders, and dopaminergic and reward systems of the brain [14, 15, 26, 27]. Decreased functional connectivity between the NAcc and the FPN is seen in depression [28]. An increase in the functional connectivity between the FPN and the NAcc is seen following mindfulness training [29]. Connectivity between the right NAcc and the FPN is also associated with substance use and cognitive control [30].

In comparison to peers with high parental education, children from low parental education have worse brain development [31]. The effects of parental education are well described on brain reward system, inhibitory control, cognitive development [32], language [33], executive function [33], and school achievement [32]. Low parental education is a risk factor for several mental, physical, and behavioral problems [32] including anxiety [34], depression [34], substance use problems [35–37], early initiation of sexual behavior [38], delinquency [39], obesity [40], and high blood pressure [41]. Parental education reduces children's antisocial behaviors [42], externalizing problems [43], anxiety and depression [34], behavioral problems [44], psychiatric disorders [44], mental health problems [45], tobacco dependence and aggression [46], and school problems [47] *Parental Education, Ethnicity, and Functional Connectivity between Nucleus Accumbens… DOI: http://dx.doi.org/10.5772/intechopen.101335*

in children and adolescents. High parental education is linked to the size and function of the NAcc [48], thalamus [49], hippocampus [50], amygdala [34], and cerebral cortex.

According to the Minorities' Diminished Returns (MDRs) framework, parental education produces unequal outcomes for subpopulations [51, 52]. Additionally, based on the MDRs, ethnic minority children are less likely to have equal opportunities to gain from their parents' education to ensure health outcomes [53, 54]. Stratification, racism, segregation, and marginalization are shown to decrease parental education's effects on developmental outcomes for ethnic minorities [55, 56]. However, most of the MDRs' literature is on Black, rather than Latino, children [49, 57, 58]. While we know about the poor attention [59], low school performance [60], high reward dependence [61], impulsivity [62], suicide [63], aggression [64], depression [65], and problem behaviors [66] of Black children with highly educated parents, very limited knowledge exists on Latino children.

According to Harrist and Criss, influences of parental conditions such as parental education are not additive to the effects of other social and behavioral determinants. There are complex moderated mediational influences of parental conditions that are beyond additive effects and may be sub-additive, synergistic, or multiplicative. These effects also vary across diverse groups of families with different socioeconomic and demographic backgrounds [67]. For example, parental education may have diminished influences on children brain development of Black than White families, in part because structural racism may reduce what parental education can do for a Black child [68]. Thus, there is an interest to test heterogeneity of the effects of parental conditions and to investigate the multiplicative and nonadditive effects of parental resources and other factors that impact child development [67]. While these differential effects of parental education are shown for structure and function of some brain regions such as amygdala [69], thalamus [70], hippocampus [71], and cerebral cortex [68, 72, 73], less is known about heterogeneity of the effects of parental education on NAcc.

Previous neuroimaging studies have shown the association between parental education and children's brain function and structure [56, 65]. Different from other socioeconomic status (SES) indicators such as income and poverty, parental education tends to represent an aspect of SES that is not represented by the presence of financial or material resources in the family [74]. Still, there continues to be a lack of studies on the effects of parental education on brain functional connectivity of the NAcc and FPN in group differences at the resting state. Likewise, it is necessary to examine the connectivity between the right and left NAcc and FPN that may reflect reward salience, reward process, cognitive control [75–77], and various cognition, emotions, and psychological problems [75, 76].

#### **1.1 Aims**

Using a sample of 9/10-year-old preadolescents from the Adolescent Brain Cognitive Development research (ABCD) study [75, 78], the present study had two aims: first, to investigate the correlation between parental education and rsFC between the right and left Nacc and FPN; and second, to examine ethnic heterogeneity in this correlation. We hypothesized that parental education would be positively associated with the functional connectivity of the right and left NAcc and FPN, and that there would be a weaker effect of parental education on the right and left NAcc functional connectivity with FPN for Latino than non-Latino preadolescents.
