The roles of perineuronal nets and the perinodal extracellular matrix in neuronal function

Perineuronal nets(PNNs) are extracellular matrix (ECM) chondroitin sulfate proteoglycan(CSPG)-containing structures that surround the somaand dendrites of various mammalian neuronal cell types. PNNs appear during development around the time that the critical periodsfor developmental plasticityend and are important for both their onset and closure. A similar structure — the perinodal ECM — surrounds the axonal nodesof Ranvierand appears as myelination is completed, acting as an ion- diffusion barrierthat affects axonal conduction speed. Recent work has revealed the importance of PNNs in controlling plasticity in the CNS. Digestion, blocking or removal of PNNs influences functional recovery after a variety of CNS lesions. PNNs have further been shown to be involved in the regulation of memory and have been implicated in a number of psychiatric disorders.