Competitive interactions between motor and episodic memory systems during interleaved learning

Abstract

Distinct motor and episodic memory systems are widely thought to compete during memory consolidation and retrieval, yet the nature of their interactions during learning is less clear. Motor learning is thought to depend on contributions from both systems, with the episodic system supporting rapid updating and the motor system supporting gradual tuning of responses by feedback. However, this competition has been identified when both systems are engaged in learning the same material (motor information), and so competition might be emphasized. We tested whether such competition also occurs when learning involved separate episodic-memory and motor information presented distinctly but yet in close temporal proximity. We measured behavioral and brain-activity correlates of motor-episodic competition during learning using a novel task with interleaved motor-adaptation and episodic-learning demands. Despite unrelated motor versus episodic information and temporal segregation, motor learning interfered with episodic learning and episodic learning interfered with motor learning. This reciprocal competition was tightly coupled to corresponding reductions of fMRI activity in motor versus episodic learning systems. These findings suggest that distinct motor and episodic learning systems compete even when they are engaged by system-specific demands in close temporal proximity during memory formation.