All Publications


  • Neural Correlates of Smartphone Dependence in Adolescents FRONTIERS IN HUMAN NEUROSCIENCE Tymofiyeva, O., Yuan, J. P., Kidambi, R., Huang, C., Henje, E., Rubinstein, M. L., Jariwala, N., Max, J. E., Yang, T. T., Xu, D. 2020; 14: 564629

    Abstract

    Increases in depressive and suicide-related symptoms among United States adolescents have been recently linked to increased use of smartphones. Understanding of the brain mechanisms that underlie the potential smartphone dependence may help develop interventions to address this important problem. In this exploratory study, we investigated the neural mechanisms underlying potential smartphone dependence in a sample of 19 adolescent volunteers who completed self-assessments of their smartphone dependence, depressive symptoms, and sleep problems. All 19 adolescents underwent diffusion MRI that allowed for assessment of white matter structural connectivity within the framework of connectomics. Based on previous literature on the neurobiology of addiction, we hypothesized a disruption of network centrality of three nodes in the mesolimbic network: Nucleus Accumbens, anterior cingulate cortex, and amygdala. Our results showed positive correlations between the node centrality of the right amygdala and self-reported smartphone dependence, between smartphone dependence and sleep problems, and between sleep problems and depressive symptoms. A higher phone dependence was observed in females compared to males. Supported by these results, we propose a model of how smartphone dependence can be linked to aberrations in brain networks, sex, sleep disturbances, and depression in adolescents.

    View details for DOI 10.3389/fnhum.2020.564629

    View details for Web of Science ID 000580387000001

    View details for PubMedID 33132878

    View details for PubMedCentralID PMC7577047

  • Gray Matter Changes in Adolescents Participating in a Meditation Training. Frontiers in human neuroscience Yuan, J. P., Connolly, C. G., Henje, E., Sugrue, L. P., Yang, T. T., Xu, D., Tymofiyeva, O. 2020; 14: 319

    Abstract

    Meditation has shown to benefit a wide range of conditions and symptoms, but the neural mechanisms underlying the practice remain unclear. Magnetic resonance imaging (MRI) studies have investigated the structural brain changes due to the practice by examining volume, density, or cortical thickness changes. However, these studies have focused on adults; meditation's structural effects on the adolescent brain remain understudied. In this study, we investigated how meditation training affects the structure of the adolescent brain by scanning a group of 38 adolescents (16.48 ± 1.29 years) before and after participating in a 12-week meditation training. Subjects underwent Training for Awareness, Resilience, and Action (TARA), a program that mainly incorporates elements from mindfulness meditation and yoga-based practices. A subset of the adolescents also received an additional control scan 12 weeks before TARA. We conducted voxel-based morphometry (VBM) to assess gray matter volume changes pre- to post-training and during the control period. Subjects showed significant gray matter (GM) volume decreases in the left posterior insula and to a lesser extent in the left thalamus and left putamen after meditation training. There were no significant changes during the control period. Our results support previous findings that meditation affects regions associated with physical and emotional awareness. However, our results are different from previous morphometric studies in which meditation was associated with structural increases. We posit that this discrepancy may be due to the differences between the adolescent brain and the adult brain.

    View details for DOI 10.3389/fnhum.2020.00319

    View details for PubMedID 32922278

  • Test-Retest Reliability of Graph Theoretic Metrics in Adolescent Brains BRAIN CONNECTIVITY Yuan, J. P., Blom, E., Flynn, T., Chen, Y., Ho, T. C., Connolly, C. G., Walter, R., Yang, T. T., Xu, D., Tymofiyeva, O. 2019; 9 (2): 144–54
  • High levels of mitochondrial DNA are associated with adolescent brain structural hypoconnectivity and increased anxiety but not depression JOURNAL OF AFFECTIVE DISORDERS Tymofiyeva, O., Blom, E., Ho, T. C., Connolly, C. G., Lindqvist, D., Wolkowitz, O. M., Lin, J., LeWinn, K. Z., Sacchet, M. D., Han, L. M., Yuan, J. P., Bhandari, S. P., Xu, D., Yang, T. T. 2018; 232: 283–90

    Abstract

    Adolescent anxiety and depression are highly prevalent psychiatric disorders that are associated with altered molecular and neurocircuit profiles. Recently, increased mitochondrial DNA copy number (mtDNA-cn) has been found to be associated with several psychopathologies in adults, especially anxiety and depression. The associations between mtDNA-cn and anxiety and depression have not, however, been investigated in adolescents. Moreover, to date there have been no studies examining associations between mtDNA-cn and brain network alterations in mood disorders in any age group.The first aim of this study was to compare salivary mtDNA-cn between 49 depressed and/or anxious adolescents and 35 well-matched healthy controls. The second aim of this study was to identify neural correlates of mtDNA-cn derived from diffusion tensor imaging (DTI) and tractography, in the full sample of adolescents.There were no diagnosis-specific alterations in mtDNA-cn. However, there was a positive correlation between mtDNA-cn and levels of anxiety, but not depression, in the full sample of adolescents. A subnetwork of connections largely corresponding to the left fronto-occipital fasciculus had significantly lower fractional anisotropy (FA) values in adolescents with higher than median mtDNA-cn.Undifferentiated analysis of free and intracellular mtDNA and use of DTI-based tractography represent this study's limitations.The results of this study help elucidate the relationships between clinical symptoms, molecular changes, and neurocircuitry alterations in adolescents with and without anxiety and depression, and they suggest that increased mtDNA-cn is associated both with increased anxiety symptoms and with decreased fronto-occipital structural connectivity in this population.

    View details for PubMedID 29500956

    View details for PubMedCentralID PMC5864120