When examining the workings of the brain, it is all too easy to focus on neurons and glia, and to disregard the surrounding extracellular matrix (ECM). However, far from being the featureless void that some histological images might imply, the brain ECM is a highly complex structure that bustles with activity. Its roles in neural development and repair are already quite well established, and in a review on page 456 of this issue, Dityatev and Schachner turn their attention to the regulation of synaptic plasticity by ECM molecules — a process that is generating considerable interest but is rather less well understood at present.
The authors present the available evidence for the involvement of various ECM molecules, including laminin, reelin and the tenascins, in controlling the efficacy of synaptic transmission. Many of these molecules are found in the vicinity of the synapse, although Schachner and Dityatev point out that this is not an essential prerequisite, and that some ECM molecules might act over a longer range. In addition, the composition of the ECM might influence the rate of diffusion of other non-ECM molecules that regulate synaptic plasticity.
