Anterograde interference refers to the negative impact of prior learning on the propensity for future learning. There is currently no consensus on whether this phenomenon is transient or long lasting, with studies pointing to an effect in the time scale of hours to days. These inconsistencies might be caused by the method employed to quantify performance, which often confounds changes in learning rate and retention. Here, we aimed to unveil the time course of anterograde interference by tracking its impact on visuomotor adaptation at different intervals throughout a 24-h period. Our empirical and model-based approaches allowed us to measure the capacity for new learning separately from the influence of a previous memory. In agreement with previous reports, we found that prior learning persistently impaired the initial level of performance upon revisiting the task. However, despite this strong initial bias, learning capacity was impaired only when conflicting information was learned up to 1 h apart, recovering thereafter with passage of time. These findings suggest that when adapting to conflicting perturbations, impairments in performance are driven by two distinct mechanisms: a long-lasting bias that acts as a prior and hinders initial performance and a short-lasting anterograde interference that originates from a reduction in error sensitivity.

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2Anterograde interference refers to the negative impact of prior learning on the propensity 3 for future learning. Previous work has shown that subsequent adaptation to two 4 perturbations of opposing sign, A and B, impairs performance in B. Here, we aimed to 5 unveil the mechanism at the basis of anterograde interference by tracking its impact as a 6 function of time through a 24h period. We found that the memory of A biased performance 7 in B for all time intervals. Conversely, learning from error was hindered up to 1h following 8 acquisition of A, with release from interference occurring at 6h. These findings suggest 9 that poor performance induced by prior learning is driven by two distinct mechanisms: a 10 long-lasting bias that acts as a prior and hinders the initial level of performance, and a 11 short-lasting learning impairment that originates from a reduction in error-sensitivity. Our 12 work provides insight into the timeline of memory stabilization in visuomotor adaptation. 13 14 15 16 We gain robustness through adaptation: in the face of environmental and/or internal 18 perturbations, adaptation maintains the precise control of elementary movements like 19 reaching and saccades. Like other types of learning, adaptation may lead to interference 20 or facilitation depending on the level of congruency of sequentially learned materials. 21Facilitation of learning is commonly referred to as savings, a process by which subsequent 22 exposure to the same perturbation results in faster learning (Krakauer, 2009). In contrast, 23 successive adaptation to opposing perturbations (e.g., rotation A followed by rotation B) 24 may lead to a deficit in the learning of B. This phenomenon, known as anterograde 25 interference, has been reported in visuomotor and force-field adaptation paradigms when 26 successively adapting to conflicting perturbations within the same reaching task (Brashers-