Fig. 4. Pathological changes in spine density. Common pathological alterations in dendritic spines are altered spine density and abnormal spine shapes.

A: Healthy neuronal dendrites contain spines with a typical variation of spine types. B: Reduced spine density is common in many cognitive and developmental disorders, such as Rett syndrome. C: Increased spine density with abnormally increased long and thin types of spines is commonly found in patients with fragile X syndrome.