Biology subjects

Bacmeister, C. M.

Publications and source records attributed to Bacmeister, C. M..

3 recordsLinked to original sources

bioRxiv2026

Multiphasic myelination and dendritic growth modulate qMRI signals in human visual cortex.

How does myelin develop in human visual cortex? By combining immunohistochemistry with in vivo and postmortem magnetic resonance imaging of longitudinal relaxation rate (R1), which increases with myelin content, we find that myelin and R1 increase across development but follow distinct trajectories. Immunohistochemistry reveals two phases of myelination: an infant phase of limited oligodendrogenesis, with myelin restricted to deep cortical layers, followed by widespread myelination across all layers during childhood. Cortical R1 also increases across development and correlates with myelin by childhood. However, in infancy, R1 increases outpace myelin growth and instead tracks dendritic arborization, indicating that the microstructural drivers of R1 change across development. We hypothesize that deep layer myelination in infancy contributes to early visual function whereas later myelination of superficial layers enables prolonged cortical plasticity and learning of complex visual behaviors.

neuroscience↗

bioRxiv2021

Motor Learning Drives Dynamic Patterns of Intermittent Myelination onBehaviorally-Activated Axons

Myelin plasticity occurs when newly-formed and pre-existing oligodendrocytes remodel existing patterns of myelination. Recent studies show these processes occur in response to changes in neuronal activity and are required for learning and memory. However, the link between behaviorally-relevant neuronal activity and circuit-specific changes in myelination remains unknown. Using longitudinal, in vivo two-photon imaging and targeted labeling of learning-activated neurons, we explore how the pattern of intermittent myelination is altered on individual cortical axons during learning of a dexterous reach task. We show that behavior-induced plasticity is targeted to learning-activated axons and occurs in a staged response across cortical layers in primary motor cortex. During learning, myelin sheaths retract, lengthening nodes of Ranvier. Following learning, addition of new sheaths increases the number of continuous stretches of myelination. Computational modeling suggests these changes initially slow and subsequently increase conduction speed. Finally, we show that both the magnitude and timing of nodal and myelin dynamics correlate with behavioral improvement during learning. Thus, learning-activated, circuit-specific changes to myelination may fundamentally alter how information is transferred in neural circuits during learning.

neuroscience↗

bioRxiv2020

Motor Learning Promotes Remyelination via New and Surviving Oligodendrocytes

Oligodendrocyte loss in neurological disease leaves axons vulnerable to damage and degeneration, and activity-dependent myelination may represent an endogenous mechanism to improve remyelination following injury. Here, we report that while learning a forelimb reach task transiently suppresses oligodendrogenesis, it subsequently increases OPC differentiation, oligodendrocyte generation, and retraction of pre-existing myelin sheaths in the forelimb region of motor cortex. Immediately following demyelination, motor cortex neurons exhibit hyperexcitability, motor learning is impaired, and behavioral intervention provides no long-term benefit to remyelination. However, partial remyelination restores neuronal and behavioral function. Motor learning following partial remyelination increases oligodendrogenesis and enhances the ability of mature oligodendrocytes to generate new myelin sheaths, resulting in almost double the remyelination of denuded axons relative to untrained controls. Together, our findings demonstrate that the correct timing of behaviorally-induced neuronal circuit activation improves recovery from demyelinating injury via enhanced remyelination from new and surviving oligodendrocytes.

neuroscience↗