dendritic spines can develop directly from dendritic shafts or from dendritic filopodia. during synaptogenesis, dendrites rapidly sprout and retract filopodia, small membrane organelle-lacking membranous protrusions. recently, i-bar protein mim was found to contribute to the initiation process. during the first week of birth, the brain is predominated by filopodia, which eventually develop synapses. however, after this first week, filopodia are replaced by spiny dendrites but also small, stubby spines that protrude from spiny dendrites. in the development of certain filopodia into spines, filopodia recruit presynaptic contact to the dendrite, which encourages the production of spines to handle specialized postsynaptic contact with the presynaptic protrusions.