Myelin plasticity modulates neural circuitry required for learning and behavior.

Oligodendrocytes, which form the myelin sheaths that insulate axons, regulate conduction velocity. Myelinated axons make up the brain's white matter and contribute to the efficiency of information processing by regulating the timing of neural activity. Traditionally, it has been thought that myelin is a static, inactive insulator around the axon. However, recent studies in humans using magnetic resonance imaging have shown that structural changes in the white matter occur during learning and training, suggesting that 1) white matter change depends on neural activity and 2) activity-dependent changes in white matter are essential for learning and behavior. Furthermore, suppression of oligodendrocytes and their progenitor cells leads to deficits in motor learning and remote fear memory consolidation, suggesting a causal relationship between glial function and the learning process. However, for technical reasons, it remains unclear how myelin-generating glia modulate neural circuitry and what underlying mechanisms they employ to affect learning and behavior. Recent advances in optical and genetic techniques have helped elucidate this mechanism. In this review, we highlight evidence that neural activities regulated by myelin plasticity play a pivotal role in learning and behavior and provide further insight into possible therapeutic targets for treating diseases accompanied by myelin impairment.