Cell Assembly Signatures Defined by Short-Term Synaptic Plasticity in Cortical Networks

Area of Science:

• Neuroscience
• Computational Neuroscience
• Systems Neuroscience

Background:

• The cell assembly (CA) hypothesis posits that neuronal groups with synchronous activity form memories.
• Examining CA signatures is challenging due to the unknown identities and locations of assembly members.
• Understanding synaptic properties is key to elucidating CA formation and function.

Purpose of the Study:

• To investigate the synaptic properties that define cell assembly (CA) signatures.
• To explore the relationship between neuronal connectivity and activity patterns in memory formation.
• To identify the basic signatures of CAs in simple cortical networks.

Main Methods:

• Utilized optical and electrophysiological approaches to record identified neuron activity in mouse cortical cultures.
• Applied population analysis and graph theory to detect sequential activity patterns and network state transitions.
• Performed whole-cell pair recordings to analyze synaptic properties (short-term synaptic depression/facilitation) of connected neurons.

Main Results:

• Synchronous firing (concomitant firing) in CAs is associated with strong synaptic connectivity and short-term synaptic depression (STD).
• Sequential firing (alternation) is observed in neuronal groups with weaker synaptic connections exhibiting short-term synaptic facilitation (STF).
• Modulating synaptic weights directly influenced the generation of sequential activity and network state transitions.

Conclusions:

• Simple cortical networks exhibit fundamental cell assembly signatures related to perception and memory.
• Synaptic strength plays a critical role in determining network activity patterns (synchrony vs. sequential firing).
• The study provides insights into the synaptic mechanisms underlying memory formation at the network level.