The code provided is part of a computational model that simulates the dynamics of neural activity during non-rapid eye movement (NREM) sleep, particularly focusing on the thalamocortical system. This system is a crucial component in the generation and modulation of electroencephalogram (EEG) signals during different sleep stages. ### Biological Basis #### Thalamocortical System - **Thalamic and Cortical Columns**: The code models interactions between the thalamus and cortex, represented as separate modules—`Cortical_Column` and `Thalamic_Column`. These modules simulate the neural mass models of the cortical and thalamic populations, respectively. The thalamus acts as a relay station and plays a pivotal role in sleep processes by modulating sensory information flow to the cortex. - **Cortical Module**: Represents the cortical neurons and circuits, which are involved in high-level processing and integration of sensory input. During NREM sleep, cortical activity is characterized by slow oscillations, sleep spindles, and K-complexes. - **Thalamic Module**: This module models thalamic neurons, which are involved in generating sleep spindles—a hallmark of NREM sleep. The thalamus is crucial in synchronizing cortical activity through these spindles, which are involved in memory consolidation. #### Neural Activity Simulation - **ODE Integration**: The code utilizes ordinary differential equations (ODE) to simulate the dynamics of the cortical and thalamic populations over time. ODEs are used to model the continuous changes in membrane potentials and ionic currents essential for generating action potentials. #### Stimulation Protocol - **Stimulation**: The `Stim` object in the code refers to a stimulation protocol that likely mimics auditory or other external stimuli. The aim is to observe the response of the thalamocortical network to such inputs, which can influence sleep architecture and cognitive processes. - **Data Markers**: These indicate moments of stimulation, allowing researchers to correlate modeled neural responses with stimuli, which is important for studying the effects of sensory input during sleep. ### Key Parameters - **Time Constants and Rates**: Fixed simulation settings such as `onset`, `res`, and `dt` set the scale for the biological time processes, allowing for accurate representation of neuronal firing rates and rhythms characteristic of NREM sleep. - **Connectivity**: The `Connections` parameter models the synaptic connectivity between the cortical and thalamic modules, reflecting the biological reality of neural circuitry that underlies EEG signal generation. The model's key focus is on how the thalamocortical network processes auditory stimuli during sleep and how this impacts EEG features associated with NREM sleep. This provides insights into larger questions about memory consolidation and sensory processing during sleep.