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Research Goals

• Advancing our understanding of how fear is inhibited in the adolescent brain

Research in Detail

My body of work primarily examines the behavioural, pharmacological, and neural mechanisms of fear extinction in adolescence. Within this research program, my work falls into three main areas:

�� �� 1. Neural mechanisms of fear extinction in adolescence

Despite stunning advances in recent decades in the knowledge of how the adult brain acquires and inhibits fear, significantly less is known about whether the adolescent brain uses the same mechanisms. This is a major gap in knowledge because adolescence is an important time when individuals learn to manage emotions. Many teens struggle with this, as evidenced by anxiety often emerging in this developmental stage. The process of extinction, which involves repeatedly exposing the individual to the feared stimulus/situation in the absence of any danger, is an important component of exposure-based therapies for anxiety disorders. Rats provide an excellent model to investigate the influence of brain maturation on fear extinction.

My empirical studies and reviews have made significant contributions towards understanding the neural mechanisms of fear inhibition in adolescence. For example, my work has shown that even when adolescents exhibit similar behavioural expressions of fear inhibition as younger animals, their brain mechanisms (e.g., recruitment of prefrontal and amygdala regions) can be completely different (Baker & Richardson, 2015).��

�� �� 2. Behavioural and pharmacological approaches to enhance extinction in adolescence

Youth often experience a relapse of anxiety after successful treatment. This has motivated my research to not only examine underlying reasons for why adolescents have difficulties in regulating fear but also novel, effective approaches to help reduce fear. Towards this goal, one stream of my research has focused on behavioural and pharmacological treatments that enhance fear reduction in adolescent rats. For instance, I have demonstrated the effectiveness of a simple behavioural manipulation for improving fear inhibition in adolescent rats (Baker, McNally, & Richardson, 2013 Learning & Memory), a procedure subsequently reported to eliminate fear in human adolescents only two years later (Johnson & Casey, 2015, Science Reports).��

Another promising approach to improving exposure therapy is with pharmacological adjuncts (i.e., medications given in combination with behavioural therapies) to enhance the acquisition or consolidation of extinction learning. Rodent studies on fear extinction are extremely useful in testing the safety and efficacy of a wide range of potential adjuncts before clinical trials. Our work has contributed to knowledge on the neural mechanisms underpinning effective adjuncts (e.g, D-cycloserine: Baker, McNally, & Richardson, 2018) and has identified others that are less effective in reducing fear in adolescence than in adulthood (e.g., those targeting the endocannabinoid system or opioid systems; Bisby, Richardson, & Baker, 2020; Bisby, Baker, & Richardson, 2020).

�� �� 3. Stress hormone and diet-induced dysregulation of brain function and fear memories

An exciting ongoing stream of my research is examining how circumstances like diet and stress exposure alter the mechanisms underlying fear regulation in adolescence. Although this work is fundamental basic research in nature, it aims to investigate factors that people experience in everyday life which profoundly alter brain function and hence behaviour. For example, one of my students found that chronic stress hormone exposure dramatically interferes with two approaches that improve fear regulation in adolescent male rats (Stylianakis et al., 2019). I have also demonstrated that rats fed a high-fat/high-sugar diet in adolescence exhibit��impaired fear extinction in adulthood and increased anxiety-like behaviour as well as altered prefrontal brain function (Baker & Reichelt, 2016).��

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