Motor skill training induces coordinated strengthening and weakening between neighboring synapses

Area of Science:

• Neuroscience
• Cell Biology
• Motor Learning

Background:

• Motor skill acquisition involves synaptic plasticity in the cerebellum.
• Purkinje cells are crucial for motor learning and receive input via parallel fibers.
• The precise synaptic changes underlying motor skill training at the Purkinje cell level remain incompletely understood.

Purpose of the Study:

• To investigate the structural basis of synaptic plasticity induced by motor skill training in the rat cerebellum.
• To determine the dendritic origin of multiple-synapse boutons (MSBs) contacting Purkinje cell dendrites after training.
• To elucidate how synaptic modifications contribute to information encoding during motor learning.

Main Methods:

• Three-dimensional electron microscopy reconstruction of synaptic connectivity.
• Analysis of Purkinje cell dendritic spine morphology and synapse formation.
• Comparison of synaptic structures between trained and untrained rats.

Main Results:

• Motor skill training selectively induced MSBs contacting two spines originating from the same Purkinje cell dendrite.
• This targeted synaptogenesis suggests a strengthening of local synaptic efficacy.
• Excitatory synapses adjacent to MSBs were smaller in trained animals, indicating compensatory synaptic depression.

Conclusions:

• Motor skill training induces specific structural plasticity at Purkinje cell synapses, involving both strengthening (MSBs) and weakening (neighboring synapses).
• This concerted synaptic modification may enhance synaptic weight differences for efficient information encoding.
• The observed plasticity contributes to maintaining stable overall activity levels within local dendritic segments during motor learning.