# The retrieval of previously learned motor memories is facilitated by the reinstatement of default mode network manifold structures

## TL;DR

The brain retrieves motor skills by reactivating past neural patterns in the default mode network, which helps in faster relearning.

## Contribution

The study identifies the default mode network's role in reinstating neural patterns for motor memory retrieval.

## Key findings

- Savings in motor relearning are linked to the reinstatement of cortical manifold structures from initial learning.
- The default mode network shows specific activity dynamics tied to learning and relearning differences between individuals.
- This neural mechanism aligns with reinstatement principles in other memory domains and computational models.

## Abstract

Motor learning induces alterations in neural activity that can persist long after the effects of such learning have faded. These persistent neural alterations are thought to manifest behaviorally as “savings,” or faster relearning, via access to a latent motor memory. How the human brain forms and retrieves these latent memories, and the specific neural systems involved, remains unresolved. Here, using human functional MRI and a two-day sensorimotor adaptation paradigm, we show that savings are associated with the reinstatement of a large-scale cortical manifold structure formed during initial learning. Notably, this neural reinstatement effect was not observed across sensorimotor systems but was localized to regions of the default mode network (DMN). Moreover, the specific dynamics of DMN activity were linked to inter-subject differences in patterns of learning and relearning across days. These results suggest that motor savings arises from the re-expression of DMN activity patterns associated with initial learning, establishing a key role for this network in motor memory formation and retrieval. This finding, paralleling reinstatement principles from other memory domains (episodic memory, fear conditioning) and anticipated by recent computational models of motor learning, suggests a common mechanism for the flexible recall and reuse of stored memories across diverse behavioral contexts.

How does the brain retrieve motor skills? This study shows that the default mode network actively reinstates past connectivity patterns to accelerate relearning, revealing a neural mechanism for preserving skills over time.