Youth is not wasted on the young: Commentary on a BBR themed issue on developmental regulation of memory in anxiety and addiction

Differential effects of adolescent and adult-initiated voluntary exercise on context and cued fear conditioning

Adolescence is a critical period for postnatal brain maturation and a time during which there is increased susceptibility to developing emotional and cognitive-related disorders. Exercise during adulthood has been shown to increase hippocampal plasticity and enhance cognition. However, the impact of exercise initiated in adolescence, on brain and behaviour in adulthood is not yet fully explored or understood. The aim of this study was to compare the impact of voluntary exercise that was initiated either during adolescence or early adulthood on cognitive performance in hippocampal and amygdala-dependent fear conditioning tasks in adulthood. Adult (eight weeks old) and adolescent (four weeks old) male Sprague Dawley rats had access to a running wheel (exercise) or were left undisturbed (sedentary control) for seven weeks. Adult-initiated exercise enhanced both contextual and cued fear conditioning, while conversely, exercise that began in adolescence did not affect performance in these tasks. These behaviours were accompanied by differential expression of plasticity-related genes in the hippocampus and amygdala in adulthood. Specifically, adolescent-initiated exercise increased the expression of an array of plasticity related genes in the hippocampus including BDNF, synaptophysin, Creb, PSD-95, Arc, TLX and DCX, while adult-initiated exercise did not affect hippocampal plasticity related genes. Together results show that exercise initiated during adolescence has a differential effect on hippocampal and amygdala-dependent behaviour and neuronal plasticity compared to when exercise was initiated in adulthood. These findings reinforce adolescence as a period during which environmental influences have a distinct impact on neuronal plasticity and cognition. This article is part of the Special Issue entitled "Neurobiology of Environmental Enrichment".

Reducing Fear During Childhood to Prevent Anxiety Disorders Later: Insights From Developmental Psychobiology

Anxiety disorders are neurodevelopmental with the median age of onset 10 to 11 years, but developmental processes underlying fear and anxiety are rarely investigated. In the last decade, however, developmental rodent studies have increased our understanding of how to treat and prevent the persistence of anxiety. Behavioral findings from rodent studies match the observations in anxious children, and the neural and molecular findings help explain why anxiety disorders are indeed neurodevelopmental. Extinction processes that are involved in cognitive-behavioral therapy appear particularly effective in children compared with older populations. Policy should mandate school psychologists and government subsidies for therapy sessions to increase children’s mental-health-service utilization. Funding bodies also should challenge anxiety studies exclusively targeting adults to include younger people to investigate why anxiety disorders are developmental disorders and focus more on preventing their persistence later in life.