The provided code is focused on modeling two types of neuronal cells: **cortical pyramidal cells** and **thalamocortical relay cells**. Each of these cell types plays crucial roles in the nervous system, particularly in processing and transmitting information across different regions of the brain. ### Pyramidal Cells **Pyramidal Cells** are the principal excitatory neurons in the cerebral cortex. Characterized by their pyramid-shaped cell bodies, these neurons are instrumental in integrating and transmitting signals across the cortical layers and to other regions of the brain. The biological features captured in the code involve: - **Reversal Potentials**: The sodium (Na⁺) and potassium (K⁺) ions have specified reversal potentials (50 mV for sodium and -100 mV for potassium), reflecting the gradients that drive their movement across the cell membrane. - **Hodgkin-Huxley Dynamics**: The `hh2` mechanism is employed to simulate the classical Hodgkin-Huxley model of action potential generation, crucial for understanding how neurons fire. - **Leak Currents**: The passive (`pas`) channel represents leak currents that exist in real neurons, contributing to their resting membrane potential. - **M Current**: The `im` channel relates to the M-type potassium current, attributed to regulating neuronal excitability and contributing to slow repolarization. - **Geometry and Basic Properties**: Parameters such as axial resistance (`Ra`), membrane capacitance (`cm`), and diameter (`diam`) reflect the specific geometry and biophysical properties of pyramidal cells. ### Thalamocortical Relay Cells **Relay Cells** in the thalamus convey sensory information to the cortex. They are involved in filtering and gating sensory inputs, a pivotal function in selective attention and consciousness. The relay cell model has the following biological aspects: - **Different Diameter and Length**: Reflects the structural variations between Relay and Pyramidal cells. - **Passive Properties**: Like pyramidal cells, relay cells have a leak current (`pas`) that simulates resting membrane properties. - **Ca²⁺ Dynamics**: The model includes the `itGHK` mechanism which relates to the low-threshold calcium currents critical for burst firing in thalamic relay neurons. The inclusion of calcium channels and dynamics suggests a focus on replicating the calcium-dependent bursting activity characteristic of these cells. - **Internal Calcium Handling**: The `cad` mechanism simulates intracellular calcium concentration dynamics, which is vital for processes such as neurotransmitter release and various calcium-dependent signaling pathways within neurons. These models aim to simulate action potential generation and transmission via crucial ionic channels and currents, capturing essential physiological features of pyramidal and relay neurons' excitability and synaptic integration.