Cortical gamma rhythms modulate NMDAR-mediated spike timing dependent plasticity in a biophysical model

Area of Science:

• Neuroscience
• Computational Neuroscience
• Systems Neuroscience

Background:

• Spike-timing-dependent plasticity (STDP) is a key mechanism for synaptic modification in neural networks.
• The influence of network rhythms on the precise timing of STDP remains incompletely understood.

Purpose of the Study:

• To investigate the effect of network rhythms, specifically pyramidal interneuronal gamma (PING) rhythms, on STDP at excitatory synapses.
• To characterize how input frequency and timing, modulated by network oscillations, influence synaptic potentiation and depression.

Main Methods:

• Utilized a simplified biophysical model of a cortical network generating PING rhythms.
• Simulated STDP at excitatory pyramidal cell synapses receiving gamma-frequency input.
• Analyzed the impact of distinct network and input frequencies, N-methyl-D-aspartate receptor (NMDAR) current decay, and input pauses on plasticity.

Main Results:

• Identified frequency regimes of potentiation and depression based on network and input frequencies.
• Demonstrated that the decay time of NMDAR currents regulates the optimal duration and amplitude of plasticity.
• Found that pauses in input, timed with NMDAR decay, enhance potentiation and may relate to theta rhythm function.

Conclusions:

• STDP in this model provides a frequency-dependent mechanism for synaptic potentiation and depression.
• The slow NMDAR current decay plays a crucial role in regulating plasticity.
• Input pausing, potentially orchestrated by theta rhythms, may represent a novel mechanism for modulating plasticity in corticothalamic circuits.