Synaptic plasticity rules driving representational shifting in the hippocampus.

Area of Science:

• Neuroscience
• Computational Neuroscience
• Systems Neuroscience

Background:

• Synaptic plasticity is crucial for memory storage.
• The specific rules governing in vivo synaptic changes remain largely unknown.
• Hippocampal place field dynamics offer a window into ongoing plasticity during memory tasks.

Purpose of the Study:

• To identify the plasticity rules that best explain observed place field dynamics in the hippocampus.
• To compare the explanatory power of behavioral timescale synaptic plasticity (BTSP) and spike-timing-dependent plasticity (STDP).
• To elucidate the role of synaptic plasticity in shaping neuronal representations during learning and familiarization.

Main Methods:

• Computational modeling of spiking place cells implementing various plasticity rules.
• Experimental measurement of hippocampal place fields in mice navigating familiar and novel environments.
• Comparative analysis of model predictions against experimental data to determine the best-fit plasticity rule.

Main Results:

• Behavioral timescale synaptic plasticity (BTSP) provided a superior explanation for place field shifting dynamics compared to STDP.
• BTSP events, though rare, are more frequent in novel environments and dynamically influence representational drift.
• BTSP was observed in the CA3 region, with distinct characteristics compared to CA1.

Conclusions:

• BTSP is a key mechanism driving representational drift and shaping neuronal ensembles during memory formation and familiarization.
• The study provides a novel framework for understanding how synaptic plasticity dynamically influences neural representations.
• Findings highlight the differential roles and characteristics of BTSP in hippocampal subregions (CA3 vs. CA1).