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    • We also showed that higher ReHo in

    2018-11-01

    We also showed that higher ReHo in left middle frontal gyrus was associated with poorer cognitive control ability. Children who showed increased homogeneity in left middle frontal gyrus during rest took longer to switch from a rule they learned previously. Lesions to the prefrontal BV6 selectively impair reversal-learning (Dias et al., 1996), and animal studies show deficits in reversal-learning is associated with ELS (Pryce et al., 2005). These prefrontal disruptions may presage the developmental pathway from ELS to later behavioral disinhibition and externalizing spectrum disorders (Clark et al., 2015; Lupien et al., 2009; Zucker et al., 2011). ELS might influence underlying neural systems that underlie behavioral disinhibition at a level not yet detectable by task-based measures, as ELS itself was not related to reversal-learning. The neural differences we observed during rest, in the absence of behavioral differences, add to a growing body of literature highlighting the importance of examining resting-state fMRI in children with atypical developmental pathways (Sonuga-Barke, 2014). ReHo analyses were complemented with rs-FC analyses. rs-FC analyses revealed that the right middle frontal area, which was significantly related to stress, was positively connected to neighboring bilateral middle frontal areas and negatively connected to right middle temporal/parahippocampal areas. Middle temporal/parahippocampal areas are a central hub of the default-mode network, which shows coherent activity during rest and is suppressed during cognitive tasks (Raichle et al., 2001). Our results are consistent with a rich body of literature showing negative coupling between the default mode network and components of the task positive network, such as the prefrontal regions (Fox et al., 2005). Moreover, our findings revealed that stronger negative coupling was related to worse reversal-learning, suggesting that suppression of the default network during rest is associated with poorer cognitive control ability. Our results suggest that exposure to chronic psychosocial stress might lead to increased neural reactivity to daily experiences, which in turn might be associated with the development of psychopathology (Blair and Raver, 2012; Ganzel et al., 2013). In the presence of increased levels of stress, children might show increased vigilance and reactivity to daily life events. These experiences and reactions might alter prefrontal regions, which subserve executive function and cognitive control. Our findings suggest that individuals with higher early stress exposure may engage the task positive network to a greater degree that results in suppression of the resting default network during rest. Although we show that these effects are related to reversal-learning measured outside the scanner, future studies should use functional tasks during scanning to examine relations between ELS and cognitive control and link these to clinical patterns. Relation of ELS to increased ReHo in the middle frontal gyrus was independent of other stressors such as exposure to violence, acute life events or poverty. We measured ELS in terms of maternal perceptions of distress. ELS is a broad construct referring to multiple types of negative experiences in childhood. Our results suggest that different dimensions of ELS might differentially influence underlying neural systems (Sheridan and McLaughlin, 2014). Early psychosocial life stress might differentially influence prefrontal systems. Inequalities-related stressors might more strongly relate to differences in the neural basis of verbal processing involving inferior frontal and middle temporal gyri (Demir et al., 2015; Hackman and Farah, 2009). More extreme, adverse childhood experiences, such as maltreatment or abuse might differentially affect neural basis of emotional processing, such as amygdala (Sheridan and McLaughlin, 2014). Future studies should get a more nuanced understanding of different dimensions of ELS by using comprehensive models of stressors. Maternal stress perceptions may be particularly important for detecting patterns at the neural level, because these assessments tap into individual differences in stress appraisal and embodiment (e.g. individuals may evaluate the same stressor as differentially stressful). Our results highlight the importance of differentiating different types of ELS when examining its relation to neurocognitive development. We showed these associations in a community sample of young children even when controlling for individual difference factors, such as IQ and Temper Loss.