The provided code snippet is part of a computational neuroscience study that seeks to analyze and characterize specific features of brain activity during sleep. The two main features of interest being modeled are K-complexes and slow wave activity, both of which are important components of N2 sleep, a stage of non-rapid eye movement (NREM) sleep. ### Biological Basis of the Code 1. **K-Complexes:** - **Biological Role:** K-complexes are large, isolated waveforms that can be observed in the EEG during stage N2 sleep. They are the largest events in healthy human EEG and are thought to play a role in memory consolidation and synaptic plasticity, as well as in protecting sleep by differentiating between relevant and irrelevant stimuli. - **Wave Characteristics:** K-complexes appear as sharp, high-amplitude waves lasting about one second, reflecting a coordination of thalamocortical and cortical activity. 2. **Slow Wave Activity (SWA):** - **Biological Role:** SWA is characterized by slow oscillations (generally in the frequency range of ~1 Hz) in the EEG, representing a synchronized state of neural activity across large brain regions during NREM sleep. It is crucial for sleep homeostasis and has been implicated in restorative functions. - **Wave Characteristics:** These waves display a rhythmic pattern of high amplitude and low frequency. ### Computational Context - **Data Used:** - The code uses EEG data (`Data_N2`) representing biological signals recorded during stage N2 sleep and simulated data (`Ve_N2`) from a neural mass model that attempts to replicate these signals. - **Z-scoring** of the simulation data (`Ve_N2`) is employed for normalization purposes, allowing for better comparison with the biological EEG recordings. - **Time Axis and Visualization:** - The simulation spans a 30-second window divided into 3000 samples, indicating that the data is sampled at 100 Hz, which is a typical temporal resolution for EEG analyses. - **Figure Representation:** - The code plots the EEG data and simulation outputs, offset to facilitate visual comparison. This allows the researchers to visually assess how well the model replicates the biological features of K-complexes and SWA. This code provides a visualization tool used within a broader study to determine how closely the neural mass model can emulate the specific EEG features representative of stage N2 sleep, thereby shedding light on the potential underlying mechanisms of these phenomena in the human brain during sleep.