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Week 08: Electroencephalography (EEG)

Electroencephalography provides millisecond-level temporal resolution of macroscopic neural dynamics directly from scalp electrodes. This week examines the biophysical origin of scalp potentials in aligned cortical pyramidal cells, classical frequency bands, Event-Related Potentials (ERPs), and artifact decontamination.

Interactive Demos & Activities

• EEG Simulator: From Dipoles to ERPs

  Full Recording Simulator · Volume Conduction, Artifacts, ICA, ERP Averaging & Dipole Fitting

  Describe a recording in a small language (cap, reference, sampling rate, filters and a stimulus timeline with trials and conditions), record it from dipole sources in a four-shell head, and switch blinks, eye movements, muscle, cardiac, line noise, drift, pops and a bad channel on and off. Then re-reference, filter with the distortions visible, remove ICA components checked against the ground truth, watch an ERP emerge as SNR grows with $\sqrt{N}$, and fit a dipole to see how noise, electrode count and depth make the inverse ambiguous.

• EEG Forward Model & Scalp Potential Mapper

  Electrophysiological Biophysics · 3-Shell Concentric Spheres

  Interact with a current dipole in a 3-shell concentric head model (brain, skull $\sigma_{ratio} \approx 1:80$, scalp). Observe how volume conduction and skull resistivity smear potentials across the scalp, and visualize isopotential voltage contours and 10-20 electrode readouts in real time.

• EEG Inverse Problem & Source Localization Studio

  Source Localization · Underdetermined Inverses, MNE, Depth Weighting & LCMV Beamformers

  Reconstruct cortical current dipoles from 16-channel scalp electric potentials. Compare unregularized pseudoinverse noise explosion against Tikhonov Minimum Norm Estimation (MNE), depth-weighted wMNE, and spatial LCMV beamforming.

• Interactive Multi-Channel EEG & Artifact Simulator

  Live Waveform Generator · Brainwaves & Artifacts

  Switch between canonical brainwave bands (Delta, Theta, Alpha, Beta, Gamma) across Frontal (Fp1), Central (Cz), and Occipital (O1) channels. Test realistic artifact injection buttons for Eye Blinks (EOG) and Jaw Clenching (EMG).

• Local Field Potential (LFP) Population Simulator

  Summed Extracellular Field Simulation

  Explore how 150 individual pyramidal neurons summate: asynchronous firing causes phase cancellation, while rhythmic synchrony generates high-amplitude oscillations and seizure hypersynchrony.

• Hodgkin-Huxley Action Potential Simulator

  Membrane Biophysics · Ion Conductance

  Investigate the voltage-gated $Na^+$ and $K^+$ channel dynamics that govern neuronal excitability and establish the membrane potentials measured by electrophysiological tools.

• EEG Modality Card Game

  Educational Card Game · Electrodes & Brain Waves

  Match electrode types, the alpha, beta, theta and delta bands, the acquisition-to-artifact-removal pipeline, and clinical and BCI applications.

Topics Covered

• Biophysical Origin of Scalp Potentials: Open-field geometry of layer V cortical pyramidal neurons, dipolar postsynaptic potentials (PSPs) vs. quadrupolar action potentials.
• The Volume Conduction Problem: Signal blurring through cerebrospinal fluid, the high electrical resistivity of the skull, and spatial resolution limits.
• ERP Analysis & Frequency Decomposition: Time-locked trial averaging (P300, N400), Fast Fourier Transforms (FFT), time-frequency wavelets, and independent component analysis (ICA) for artifact removal.