The code provided models a current clamp, specifically a triggered current clamp (TriggeredIClamp). This model is designed to simulate a biophysical event where an artificial current pulse is injected directly into a neuron in response to an external trigger. Here's a breakdown of its biological basis:
Electrophysiological Technique: The model emulates a standard laboratory technique used in electrophysiology known as a current clamp. In biological experiments, current clamps are used to inject a defined amount of current into a neuron or neuron-like cell to study its response. This is crucial for measuring the electrical properties of cells, such as membrane resistance and current-voltage relationships.
Generated Current Pulse: The pulse of current generated by this model is characterized by an amplitude (amp) and a duration (dur). This simulates how neurons can be depolarized artificially through electrode current injection. Unlike naturally occurring transmembrane currents, this current is injected directly inside the cell, mimicking an experimental setup with the electrode.
Point Process and Event-driven: This is implemented as a point process in the NEURON simulation environment. The process is event-driven, meaning it is activated by an external event, similar to how a real experimental setup might involve triggering current injections in response to stimuli, such as synaptic inputs or controlled lab stimuli.
Impact on Cell Polarization: Positive values for the current (i) in this model depolarize the cell. Depolarization is a critical process in neuronal activity, where the normally negative resting membrane potential of a neuron becomes more positive, transmitting electrical signals down the axon or preparing neurons for action potential firing.
Extracellular Effects: The model mentions changes in vext when the extracellular mechanism is present due to i. In a biological setting, this refers to how injected current can affect both the intracellular and extracellular environments, potentially influencing local field potentials or even neighboring cells when considering network effects in a larger simulation framework.
The TriggeredIClamp module captures the essential features of artificial current injection into neurons for investigatory purposes. By mimicking the protocols used in experimental electrophysiology, this model helps researchers understand how neurons respond to controlled electrical stimulation, a procedure crucial for discerning the physiological properties of neuronal membranes and synaptic connectivity.