Filopodia, spines, and the generation of synaptic diversity.

Abstract

The above studies appear to be generally consistent with the idea that dendrite dynamics and, consequently, patterns of neural connectivity are modulated by electrical activity. Given these facts, it still remains to be determined what this dynamism means to the organism. How large of a role do filopodia play in synaptogenesis in the developing brain? Is the refinement of topographic maps dependent on active dendritic filopodia? How are synapses stabilized? What are the interactions between axonal and dendritic arbors? What are the cellular and molecular differences responsible for generating a spine versus a filopodium? What are the specific functional and behavioral consequences of these cellular and molecular differences? The fundamental issue here, as elsewhere, is: What goes on in an organism when nobody is watching? Which small scale processes are important for a given large scale process and which are merely happening at the same time in a causally unrelated way? As is beginning to occur (11xJontes, J.D, Buchanan, J, and Smith, S.J. Nat. Neurosci. 2000; 3: 231–237Crossref | PubMed | Scopus (143)See all References, 13xLendvai, B, Stern, E.A, Chen, B, and Svoboda, K. Nature. 2000; 404: 876–881Crossref | PubMed | Scopus (491)See all References), such issues can be addressed by using minimally invasive techniques to watch cellular and molecular dynamics during the normal development and functioning of intact organisms.*To whom correspondence should be addressed (e-mail: sjsmith@leland.stanford.edu).