Multi-unit spike-triggered averaging: a method for probing the physiology of central synapses

Area of Science:

• Neuroscience
• Computational Neuroscience
• Electrophysiology

Background:

• Identifying unitary synaptic connections is crucial for understanding neural circuit function.
• Traditional methods for probing synaptic connections are often low-throughput and labor-intensive.
• The central nervous system presents challenges for in vivo electrophysiological recordings.

Purpose of the Study:

• To develop and validate a high-throughput method for screening neuronal pairs for synaptic connections.
• To enable rapid characterization of synaptic properties using combined extracellular and intracellular recordings.
• To provide a feasible approach for studying synaptic connectivity in the intact brain.

Main Methods:

• Development of multi-unit spike-triggered averaging (multi-unit STA) combining extracellular and intracellular recordings.
• Utilizing multiple extracellular electrodes and online automated analysis for high-throughput screening.
• Averaging intracellular recordings triggered by extracellularly recorded action potentials from multiple units.

Main Results:

• Screened dozens of candidate neuronal pairs per hour, significantly increasing throughput.
• Identified that 1-2% of screened pairs were synaptically connected.
• Successfully quantified synaptic properties including latency, conductance, kinetics, and transmission failure rate for connected pairs.

Conclusions:

• Multi-unit STA is an efficient method for rapidly screening neuronal pairs for synaptic connections.
• The technique allows for accurate quantification of synaptic properties with a single intracellular recording.
• Multi-unit STA offers a promising approach for studying synaptic connectivity in vivo, overcoming limitations of multiple intracellular recordings.