Specifying the timescale of early life unpredictability helps explain the development of internalising and externalising behaviours.

Early life unpredictability is associated with both physical and mental health outcomes throughout the life course. Here, we classified adverse experiences based on the timescale on which they are likely to introduce variability in children's environments: variations unfolding over short time scales (e.g., hours, days, weeks) and labelled Stochasticity vs variations unfolding over longer time scales (e.g., months, years) and labelled Volatility and explored how they contribute to the development of problem behaviours. Results indicate that externalising behaviours at age 9 and 15 and internalising behaviours at age 15 were better accounted for by models that separated Stochasticity and Volatility measured at ages 3 to 5. Both externalising and internalising behaviours were specifically associated with Volatility, with larger effects for externalising behaviours. These findings are interpreted in light of evolutionary-developmental models of psychopathology and reinforcement learning models of learning under uncertainty.

Early life adversity jointly regulates body-mass index and working memory development.

Previous work has proposed that balancing energy expenditure towards body and brain development in an optimal fashion results in a negative relationship between somatic and neurocognitive growth during development. An important issue, largely overlooked so far, is the extent to which this energetic trade-off is influenced by early life environmental factors. In this study, we estimated the association between neurocognitive (measured by working memory ability) and somatic (measured by body-mass index) developmental trajectories, while taking into account multiple dimensions of early life adversity. Results of our initial growth curve model were consistent with this brain-body trade-off in both girls and boys. In a subsequent model, we showed that early life adversity had positive associations with somatic and negative associations with neurocognitive growth trajectories, although the direct negative coupling between them remained consistent. Finally, a multidimensional adversity model, separating the effects of deprivation, threat and unpredictability, revealed that the dimension of deprivation-reflecting lack of access to resources and cognitive stimulation-contributed the most to both somatic and neurocognitive growth patterns. These results suggest that the way individuals balance energy between these two biological constructs during development is partly linked to environmental influences through phenotypic plasticity.

Dissociation between two aspects of procedural learning in Tourette syndrome: Enhanced statistical and impaired sequence learning.

Tourette syndrome (TS) is a childhood-onset neurodevelopmental disorder that primarily affects the cortico-basal ganglia-thalamo-cortical (CBGTC) circuitry and is characterized by motor and vocal tics. Previous studies have found enhancement in procedural memory, which depends on the CBGTC circuitry and plays an important role in the learning and processing of numerous motor, social, and cognitive skills and habits. Based on these studies, procedural hyperfunctioning in TS has been proposed. However, the neurocognitive mechanism underlying such hyperfunctioning is poorly understood. Here, we investigated how two aspects of procedural learning, namely 1) frequency-based statistical learning and 2) order-based sequence learning, are affected in TS. Twenty-one children with TS between the ages of ten and fifteen as well as 21 typically developing controls were tested on a probabilistic sequence learning task that enables the parallel assessment of these two aspects. We found that children with TS showed enhanced sensitivity to statistical information but impaired sequence learning compared to typically developing children. The deconstruction of procedural memory suggests that procedural hyperfunctioning in TS may be supported by enhanced sensitivity to statistical information. These results can provide a potential path for improving therapy methods and skill-oriented educational programs for TS.