Electron Microscopy of Synaptic Contacts on Dendrite Spines of the Cerebral Cortex

WHEN stained by the Golgi or methylene-blue method for light microscopy, certain dendrites of the cerebral cortex and elsewhere appear to have numerous spinous projections1. The nature of these spines has long been disputed. For example, it has been suggested that they are simply ‘nutritive’ expansions, or pre-synaptic end-feet, or post-synaptic processes of the dendrite—the pre-synaptic component remaining unstained1–3. Electron microscopy shows that the spines are in fact sites of synaptic contact.