Refractoriness Accounts for Variable Spike Burst Responses in Somatosensory Cortex

Area of Science:

• Neuroscience
• Computational Neuroscience
• Systems Neuroscience

Background:

• Neurons in the primary somatosensory cortex (S1) exhibit synchronized bursting in response to peripheral stimuli.
• These bursts synchronize with macroscopic 600-Hz electroencephalography (EEG) waves.
• The underlying mechanisms for burst generation and synchronization in S1 remain unclear.

Purpose of the Study:

• To investigate the biophysical mechanisms driving synchronized neuronal bursting in the primary somatosensory cortex.
• To model single-neuron responses and reproduce observed trial-to-trial variability and population activity correlations.
• To elucidate how neural systems encode information through spike patterns.

Main Methods:

• Developed computational models of single-neuron responses.
• Fitted models to unit recordings from macaque monkey S1.
• Incorporated correlated synaptic inputs, refractory mechanisms, noise, and global excitability fluctuations.
• Analyzed thalamic inputs, depressing synapses, and high-conductance states.

Main Results:

• Synchronized bursts result from correlated synaptic inputs and a refractory mechanism.
• Models with noise replicate trial-to-trial response variability and stereotypical temporal spike patterns.
• Global excitability fluctuations correlate single-neuron patterns with population activity.
• Thalamic inputs via depressing synapses in a high-conductance state underpin S1 responses.

Conclusions:

• Simple feedforward processing of peripheral inputs can generate complex temporal and population statistics in neuronal responses.
• Neural systems may utilize refractoriness to encode variable cortical states into stereotypical short-term spike patterns.
• These patterns are suitable for processing at millisecond timescales by downstream neurons.