Shapeshifting for memory

Abstract

One of the biggest remaining mysteries of science is inside our heads: how does nature wire up a high-performance computer with­out having a detailed blueprint specifying the location and strength of every connection? It is assumed that local connectivity in our cor­tex is at first random, and during develop­ment undergoes refinement until only the ‘right’ connections are left over. But how can the brain tell ‘right’ from ‘wrong’ connections? The majority of excitatory connections are formed on dendritic spines, tiny excrescenc­es that cover almost the entire dendritic sur­face of most neurons. Since their discovery by Ramón y Cajal in 1896, neuroscientists have been fascinated by these structures, which ultimately determine which neurons in the brain become connected and form function­al networks. Here we review the many im­portant functions of spines and explain why electrical and biochemical processes in these tiny structures are thought to be crucial for the plasticity of the brain.