Experience leaves a lasting structural trace in cortical circuits

Learning from experience It is common knowledge that early experience improves the brain's ability to adapt to similar events in the future, but it is not clear how the original experience is represented in neuronal circuits, or how it contributes to re-learning. The model of the temporary closure of one eye in mice provides a system in which such questions can be tackled. The new experience — monocular vision — induces growth of dendritic spines from nerve cells in the visual cortex. By alternating periods of monocular and binocular vision and following the morphology of the nerve cells for several days, Hofer et al. were able to record the experience-induced structural changes and to discover if they outlast the experience itself. They find that long-lived dendritic spine density increases in response to monocular deprivation and persists beyond the duration of the experience. Subsequent deprivation fails to induce further spine density increases, suggesting initial experience may provide a structural experience 'trace' that can be utilized in response to further functional shifts.