A systematic investigation reveals dissociable effects of ageing on implicit and explicit components of sensorimotor learning.

Deterioration in motor control is a hallmark of ageing, significantly contributing to a decline in quality of life. More controversial is the question of whether and how ageing impacts sensorimotor learning. We hypothesized that the inconsistent picture observed in current literature can be attributed to at least two factors. First, ageing studies tend to be underpowered. Second, the learning assays used in these experiments tend to reflect, to varying degrees, the operation of multiple learning processes, making it difficult to make inferences across studies. Here we took a two-pronged approach to address these issues. We first performed a systematic review and meta-analysis of sensorimotor adaptation literature focusing on outcome measures that provide estimates of explicit and implicit components of adaptation. We then conducted four well-powered experiments, two of which were preregistered, to systematically examine the effect of ageing on sensorimotor adaptation, using behavioural tasks designed to isolate explicit and implicit processes. Convergently, both approaches revealed a striking dissociation: Older adults showed a pronounced deficit in discovering new explicit strategies yet a marked enhancement in implicit recalibration. Follow-up studies revealed that the explicit re-aiming deficit stems from impaired caching of stimulus-response mappings rather than from failures to implement parametric algorithms. The enhancement in implicit recalibration is linked to age-related changes in the multisensory integration of proprioceptive and visual information. Together, these systematic, meta-analytic and empirical findings advance our understanding of how ageing differentially impacts the mechanisms underlying sensorimotor learning.