research in neurological diseases and injuries shed further light on the nature and importance of spine turnover. after stroke, a marked increase in structural plasticity occurs near the trauma site, and a five- to eightfold increase from control rates in spine turnover has been observed. dendrites disintegrate and reassemble rapidly during ischemia—as with stroke, survivors showed an increase in dendritic spine turnover. while a net loss of spines is observed in alzheimer's disease and cases of intellectual disability, cocaine and amphetamine use have been linked to increases in dendritic branching and spine density in the prefrontal cortex and the nucleus accumbens. because significant changes in spine density occur in various brain diseases, this suggests a balanced state of spine dynamics in normal circumstances, which may be susceptible to disequilibrium under varying pathological conditions.