Development of the prefrontal cortex and its relationship to self-regulatory abilities during adolescence

© 2014 Dr. Nandita VijayakumarPublications included in thesis:Vijayakumar, N., Whittle, S., Dennison, M., Yücel, M., Simmons, J., & Allen, N.B. (2014). Development of temperamental effortful control mediates the relationship between maturation of the prefrontal cortex and psychopathology during adolescence: a 4-year longitudinal study. Developmental Cognitive Neuroscience, 9, 30–43. DOI:10.1016/j.dcn.2013.12.002Vijayakumar, N., Whittle, S., Yücel, M., Dennison, M., Simmons, J., & Allen, N.B. (2014). Prefrontal structural correlates of cognitive control during adolescent development: a 4-year longitudinal study. Journal of Cognitive Neuroscience, 26(5), 1118-1130. DOI: 10.1162/jocn_a_00549Vijayakumar, N., Whittle, S., Yücel, M., Dennison, M., Simmons, J., & Allen, N.B. (2014). Thinning of the lateral prefrontal cortex during adolescence predicts emotion regulation in females. Social Cognitive and Affective Neuroscience. DOI: 10.1093/scan/nst183Adolescence is a period of significant brain maturational changes in regions associated with self-regulation. While normative patterns of cortical thinning are postulated to underlie adaptive functioning, aberrations of this process are thought to result in poor self-regulatory abilities. This study characterises the development of three regions known to underlie regulatory processes, the anterior cingulate cortex (ACC), dorsolateral prefrontal cortex (dlPFC) and ventrolateral prefrontal cortex (vlPFC), during adolescence. The study also examines the relationship between development of these cortical regions with three aspects of self-regulation: i. temperamental effortful control, ii. proactive and reactive forms of cognitive control, and iii. cognitive reappraisal, an adaptive emotion regulation strategy. Ninety-two adolescents (47 females) were examined longitudinally during early (mean age = 12.67), mid- (mean age = 16.42) and late adolescence (mean age = 18.78). Structural MRI scans were obtained at early and mid-adolescence, and cortical thickness of the regions of interest was measured using a semi-automated software (FreeSurfer). Effortful control (measured using the Early Adolescent Temperament Questionnaire-Revised), and proactive and reactive cognitive control (measured using a modified Stroop task), were also examined at early and mid-adolescence. Finally, cognitive reappraisal was measured at late adolescence using the Emotional Regulation Questionnaire. Linear mixed models were employed to analyse brain development between early and mid-adolescence, including sex and hemisphere effects. Subsequently, general linear and linear mixed models were employed to investigate the relationship between change in cortical thickness and change in effortful control/cognitive control over time. Finally, general linear models were employed to investigate the relationship between change in cortical thickness and use cognitive reappraisal strategies during late adolescence. Sex effects were included in all models. Findings revealed that the ACC, dlPFC and vlPFC exhibited significant reductions in cortical thickness between early and mid-adolescence across both hemispheres and sexes. Greater effortful control across time (i.e., averaged across early and mid-adolescence) was related to greater thinning of the left ACC, dlPFC and vlPFC over time, while greater proactive cognitive control across time was related to greater thinning of the right ACC. In addition, greater thinning of the left dlPFC and vlPFC was related to greater engagement in cognitive reappraisal during late adolescence in females. In relation to the development of self-regulation, greater relative increase in effortful control was related to greater thinning of the left dlPFC at trend level. However, greater relative increase in proactive control was related to less thinning of the right vlPFC, and greater relative increase in reactive control was related to less thinning of the left ACC (the latter in males alone). These findings highlight a complicated and dynamic relationship between cortical and self-regulatory development during adolescence, with different patterns of cortical maturation being advantageous for different forms of self-regulation. The importance of investigating sexual dimorphism in brain-behaviour relationships is also emphasised, as different associations were identified between cortical maturation and self-regulation in males and females. These findings suggest that early to mid-adolescence is a developmentally sensitive period for self-regulation, and provide a foundation for understanding abnormal patterns of brain development, and associated behavioural difficulties and psychopathology