How synaptic strength, short-term plasticity, and input synchrony contribute to neuronal spike output

Area of Science:

• Neuroscience
• Computational Neuroscience

Background:

• Neurons integrate thousands of synapses with varying strengths.
• Strong synapses in mouse neocortex connect similarly tuned cells, potentially driving spiking output.
• The role of weak synapses, short-term plasticity, and temporal factors in spiking remains unclear.

Purpose of the Study:

• Investigate how synaptic properties and computational primitives shape neuronal spiking.
• Map excitatory postsynaptic potential (EPSP) amplitudes and paired-pulse ratios in L2/3 barrel cortex.
• Develop a computational model to understand synaptic information processing.

Main Methods:

• Paired recordings and extracellular stimulation in mouse neocortex.
• Mapping synaptic properties (EPSP amplitude, paired-pulse ratio) of L2/3 pyramidal neuron connections.
• Development and constraint of a computational model using experimental and in vivo data.

Main Results:

• Strong synaptic connections were exclusively depressing, with overall weak net short-term plasticity.
• No clustering of synaptic properties was observed on individual neurons.
• Strong synapses, despite depression during ongoing activity, amplified information transfer and responsiveness due to larger EPSP amplitudes and temporal synchrony.

Conclusions:

• Cortical neurons utilize a combination of temporal coding, synaptic properties, and noise for information processing.
• Strong synapses play a crucial role in amplifying information transfer and neuronal responsiveness.
• Findings provide a nuanced framework for understanding synaptic integration and spiking in the cortex.