Role of perineuronal nets in the cerebellar nuclei: Insights from histology and behavior

Abstract

Perineuronal nets are structures in the extracellular matrix that previous work implicates in either inhibiting synaptic plasticity or protecting neurons from oxidative damage. We use histological techniques to explore the distribution of perineuronal nets in different areas of the central nervous system. We find that perineuronal nets do not necessarily surround high activity cells with large oxidative loads. We do find that they are somewhat more prevalent in motor areas, and are most prevalent in the cerebellar nuclei. The cerebellum is important for motor control and learning. We study the role of perineuronal nets in the cerebellar nuclei using a long term saccade adaptation task. Long term saccade adaptation changes the size of eye movements. It mimics recovery from damage to the motor areas of the nervous system or muscles, that make movements too small. We find that dissolving perineuronal nets in the cerebellar nuclei, where they are extremely abundant, does not change the speed, magnitude or persistence of long term adaptation. This indicates that in the saccade-related part of the cerebellar nuclei, perineuronal nets are not important for inhibiting plasticity and thereby do not maintain saccade gain. Therefore, we cannot summarize role of PNNs as exclusively either neuroprotection or inhibition of plasticity. Perineuronal nets could be important for both or either, depending on the region. This work will enable future investigation of perineuronal net function.