The provided code is designed to conduct a computational analysis of neuronal excitability using various computational models. It focuses on the physiological responses of neurons to electrical stimulation, particularly in terms of the action potential generation and propagation. Here’s an overview of the biological context: ### Biological Background - **Pulse Width (PW):** The code examines responses to different pulse widths, which refer to the duration of an applied electrical stimulus. This is important because the duration of a stimulus can affect the likelihood of action potential initiation in neurons. Short and long stimulus durations can have different biophysical effects on neural membranes. - **Axonal Diameter (D):** The inclusion of different axonal diameters (0.5 µm and 1.5 µm) reflects the impact that physical size of neurons has on conduction velocity and excitability. Larger diameters typically allow for faster conduction velocities due to reduced electrical resistance. - **Inter-Pulse Interval (IPI):** This parameter refers to the time interval between successive pulses. In biological terms, it is relevant for studying phenomena like paired-pulse facilitation, which is a form of synaptic plasticity. This involves how neurons respond to subsequent stimuli that follow an initial stimulus. - **Model Types:** The code refers to multiple neuron models (Sundt, Tigerholm, Rattay, Schild97, Schild94). Each of these models simulates the electrical characteristics of neurons based on different sets of assumptions about ion channel dynamics and membrane properties. These models capture variations in ion channel distributions and gating kinetics, which are crucial for understanding how nerve impulses are generated and propagated. ### Key Biological Processes 1. **Action Potential Generation and Propagation:** By manipulating pulse width, axonal diameter, and inter-pulse interval, the code explores conditions under which neurons may become more or less excitable. These conditions relate to how action potentials are generated, either through direct electrical stimulation or synaptic input. 2. **Voltage Trace Analysis:** Collecting data related to "VoltageTrace" suggests the code tracks changes in membrane potential over time, capturing the dynamics of depolarization and repolarization that characterize action potential propagation. 3. **Calculating SD, CV, and PP:** - **SD (Strength-Duration Curve):** Used to relate the intensity and duration of a stimulus required to elicit an action potential. This is a fundamental relationship in neurophysiology describing neuronal thresholds. - **CV (Conduction Velocity):** Measures speed of action potential propagation, typically influenced by axonal diameter and myelination. - **PP (Paired-Pulse Response):** Analyzes neuronal responsiveness to paired stimuli, relevant for studying synaptic dynamics and plasticity. Overall, the code is simulating how neurons behave under electrical stimulation using different biophysically-inspired models to extract meaningful parameters such as conduction velocity, strength-duration relationship, and paired-pulse plasticity. These analyses are vital for understanding the functional properties of neurons and their responses to synaptic inputs and artificial stimuli.