Distinct cerebellar engrams in short-term and long-term motor learning
Wen Wang1, Kazuhiko Nakadate, Miwako Masugi-Tokita
1Division of Cerebral Structure, National Institute for Physiological Sciences, Okazaki 444-8787, Japan.
Summary
Cerebellar motor learning involves changes in parallel fiber-Purkinje cell (PF-PC) synapses. Short-term learning decreases AMPA-type glutamate receptors (AMPARs), while long-term learning eliminates synapses, contributing to memory consolidation.
Area of Science:
- Neuroscience
- Synaptic Plasticity
- Motor Learning
Background:
- Cerebellar motor learning is linked to synaptic plasticity, specifically at parallel fiber-Purkinje cell (PF-PC) synapses.
- The role of changes in AMPA-type glutamate receptors (AMPARs) in PF-PC synapses during physiological motor learning and long-term memory remains unclear.
Purpose of the Study:
- To investigate the changes in AMPARs and PF-PC synapses during short-term adaptation (STA) and long-term adaptation (LTA) of the horizontal optokinetic response (HOKR) in mice.
- To determine if these synaptic changes serve as in vivo engrams for motor learning and memory consolidation.
Main Methods:
- Quantitative SDS-digested freeze-fracture replica labeling to measure AMPARs.
- Physical dissector electron microscopy to quantify PF-PC synapses and Purkinje cell (PC) spines.
- Utilized the HOKR adaptation model in mice.
Main Results:
- STA was associated with a transient 28% decrease in PF-PC synaptic AMPARs, correlating with adaptation levels and recovering within 24 hours.
- LTA, following daily HOKR training, did not alter AMPAR numbers but induced a 45% elimination of PF-PC synapses and PC spine loss.
- Recovery from LTA correlated with the restoration of PF-PC synapse numbers.
Conclusions:
- A decrease in PF-PC synaptic AMPARs represents an in vivo engram for short-term motor learning.
- Elimination of PF-PC synapses serves as an in vivo engram for long-term motor learning.
- These findings reveal unique synaptic plasticity mechanisms contributing to motor memory consolidation.
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