Neuroplasticity and Post-Synaptic Rebound-Induced Spiking at Purkinje Cell-Deep Cerebellar Nuclei Synapses

Abstract

Background: Within the cerebellum white matter are located four pairs of nuclei, collectively known as the deep cerebellar nuclei (DCN) (1). In the cerebellum, signal integration from pre-cerebellar structures via excitatory parallel fibers and climbing fibers in the cerebellar cortex occurs in GABAergic Purkinje cells (PC) (2). The main target of these PC cells is the DCN (2) and approximately 85% of GABAergic input on the DCN is from PCs (3). Furthermore, PCs outnumber DCN neurons (26:1) (2). Therefore, despite receiving substantial inhibition from Purkinje cells, DCN neurons are still active at rest showing regular spiking or spontaneous bursts (4). DCN neurons fire spontaneously at approximately 10-50 Hz (5). Given this unique anatomy of PC-DCN synapses, characterization of this synaptic circuit is important in understanding the overall role of the DCN in the brain.

Methods: The findings of 28 studies, including a few reviews, are reported in this paper. Studies selected focused principally on characterization of DCN circuitry properties and the role these properties have in the functioning of the DCN. Most studies employed in vivo and/or in vitro cellular recordings in rodents, among other models. Studies ranged from 1984 to 2013.

Summary: This review outlines current findings on the forms of plasticity found in the DCN, the function of the DCN and the connections between the DCN and other brain regions. In short, neurons in the DCN demonstrate both synaptic and non-synaptic plasticity. Cerebellar involvement in motor activity has been extensively studied therefore, not surprisingly; DCN neurons form connections with the motor cortex but also the prefrontal cortex. PC input on the DCN influences spike rate and timing through fluctuations in PC synchrony, and rebound depolarization.