Ebba Widegren: Development of the emotional brain: Investigating the neuroscience of fear conditioning and emotional functioning from childhood to adulthood

Abstract

Understanding the neural circuitry underlying cognitive, social, and emotional development is essential for understanding normative and atypical development. Adolescence represents a vulnerable period in the emergence of psychopathology, particularly depression and anxiety; disorders associated with emotion processing. This highlights the need to elucidate the neurodevelopmental mechanisms supporting emotion processing in adolescence in both typical and atypical development. This thesis aimed to advance the understanding of the adolescent brain and, more broadly, neurodevelopment of emotion processing from childhood to adulthood.

To address this aim, we explored different aspects of neurodevelopment using functional magnetic resonance imaging (fMRI), Magnetic Resonance Spectroscopy (MRS), psychophysiological measures, and self-report data. Studies I–III are based on a cross-sectional study, comprising 120 typically developing children, adolescents, and adults. Study I examined the role of the excitatory and inhibitory neurotransmitters glutamate and gamma-aminobutyric acid (GABA), in emotion regulation and reactivity in adolescents and adults. Study II investigated fear extinction retention across development using fMRI, psychophysiological measures, and self-report, with a specific focus on the proposed adolescent dip in fear extinction retention. Study III focused on the relationship between dACC glutamate and GABA and fear extinction retention, from childhood to adulthood. Study IV used neuroimaging data from the English and Romanian Adoptees Brain Imaging Study (ERABIS) to examine the long-term consequences of severe childhood deprivation on brain activity and connectivity in socioemotional processing.

Our results from paper I and III indicate that both dACC glutamate and GABA+ are involved in emotion processing and fear conditioning, with developmental differences. Lower concentration of dACC glutamate was found to be related to better emotion regulation skills in adolescents in Paper I.  Notably, dACC GABA+ was found to be related to increased emotion reactivity, as well as increased fear responding at the fear retention test, in adults in papers I and III. Our results from paper II do not lend support for the idea of an extinction dip specific to the adolescent period. Further, our results from paper IV lend no support for the stress-acceleration hypothesis of altered connectivity between the amygdala and mPFC following deprivation. However, in paper IV, differences were observed between groups in connectivity, mainly involving face-processing regions. Critically, alterations in connectivity within the group of Romanian adoptees were associated with deprivation duration. Taken together, the results from this thesis add to the knowledge of the neuroscience underlying emotion processing and fear conditioning from childhood to adulthood. Further, it provides a contribution to understanding both typical and atypical neurodevelopment.