Fig. 1.

Changes in intrinsic excitability and other plasticity types in the cerebellar nuclei neurons during EBC. (A) Schematic representation of the main components of the olivocerebellar circuit involved in EBC, centered around the cerebellar nuclei (CN). Excitatory and inhibitory projections are indicated with (+) and (−) symbols, respectively. Transsynaptic neuronal tracer PRV-152 (orange) injected in the orbicularis oculi muscle led to retrograde labeling of projection neurons in the CN. (B) Learning-associated changes in intrinsic excitability in CN neurons manifested as 1, a reduced after-hyperpolarization (AHP) amplitude; 2, a reduced action potential (AP) latency after a depolarizing current step; and 3, a reduced threshold (indicated with arrows) and latency for rebound APs after release of a hyperpolarizing current step. Traces from our own recordings have been modified for illustrative purposes. (C) Earlier research suggests that EBC induces changes in different types of plasticity and dynamic mechanisms controlling plasticity. Synaptic plasticity may result in changes in postsynaptic potentials. Changes in structural plasticity may take place, including formation of new synaptic contacts. Dynamic changes in perineuronal nets may occur during learning, facilitating formation of new synaptic contacts, possibly through down-regulation of chemorepulsive molecules. EPSP, excitatory postsynaptic potential; UR, unconditioned response.