Perineuronal nets in the auditory system

Perineuronal nets (PNs) are a unique and complex meshwork of specific extracellular matrix molecules that ensheath a subset of neurons in many regions of the central nervous system (CNS). PNs appear late in development and are supposed to restrict synaptic plasticity and to stabilize functional neuronal connections. PNs were further hypothesized to create a charged milieu around the neurons and thus, might directly modulate synaptic activity. Although PNs were first described more than 120 years ago, their exact functions still remain elusive. The purpose of the present review is to propose the nuclei of the auditory system, which are highly enriched in PN-wearing neurons, as particularly suitable structures to study the functional significance of PNs. We provide a detailed description of the distribution of PNs from the cochlear nucleus to the auditory cortex considering distinct markers for detection of PNs. We further point to the suitability of specific auditory neurons to serve as promising model systems to study in detail the contribution of PNs to synaptic physiology and also more generally to the functionality of the brain.