Silent regulators of trauma: the microRNA blueprint underlying post-traumatic stress disorder biology.

It has been long established that individuals demonstrate considerable variability in the ways they make decisions and process information pertaining to rewards (; ). However, the neurobiological basis of these differences is not currently well characterised. A plausible explanation may be that inter-individual differences in cortical microstructures are driving this behavioural variability (). Cortical microstructures such as myeloarchitecture play a vital role in the efficiency of neural signalling, by improving conduction velocity and reducing signal-to-noise ratio (; ). By investigating how individual-specific differences in the brain’s structural features relate to decision-making, we can gain insight into the latent causes of such wide-ranging behavioural differences. Through this approach, we may reveal why aberrant or suboptimal decision-making strategies are often observed in individuals suffering from mental health conditions such as ADHD or depression (; ). Inter-individual differences in learning and decision-making become apparent when examining decision-making dilemmas such as the exploration-exploitation trade-off. In such situations, one must choose either the option with the greatest known value (exploitation), or an alternative, lesser-known option which may potentially yield yet greater rewards but at the risk of disappointing outcomes (exploration). The methods by which agents select different decision-making strategies is highly idiosyncratic and context-specific, and individuals vary greatly in their preferred decision strategies (; ; ). Recent advances have led to the development of computational models that allow for the estimation of subject-specific parameters to describe key signatures of these exploration-exploitation behaviours (; ). Previous work has identified the employment of exploration strategies that consider all available choices to be equally likely by disregarding all existing knowledge of the decision space, including any uncertainty and expectation estimates, thus reducing computational complexity (; ). This strategy is referred to as . A recent study by Dubois et al. () found clear evidence that humans employ a combination of complex resource-heavy approaches and simpler heuristic exploration strategies such as value-free random exploration, as well as uncertainty-led exploration and novelty exploration, to estimate an optimal decision method (). Recent work has also highlighted the neurochemical basis for decision-making, demonstrating that noradrenergic and dopaminergic activity play crucial roles in modulating exploration-exploitation strategy selection (; ; ). However, these neuromodulatory influences are expressed through distributed cortical circuits, suggesting that variability in the structural properties of such circuits controls how neurochemical signals are integrated and translated into behaviour. These findings highlight the potential for individual-specific neurobiological foundations of decision-making, yet further research is necessary to confirm this link between biology and behaviour.