This introductory simulation demonstrates how electrodes may produce different EEG data in response to the same source of neural activity. This first simulation represents the hypothetical and idealized situation of activity from a single neuron in isolation. Here, an excitatory post-synaptic potential is induced in the dendrites and soma of a pyramidal neuron. The changes in ion concentrations surrounding the cell creates a dipole with a negative valence surrounding the dendrites and soma, and a positive valence surrounding the axon terminal branches. This signal propagates to the scalp, where it is measured by scalp electrodes.
Post-synaptic activity creates a difference in charge in the extracellular liquid, resulting in a dipole that can be measured by electrodes placed on the scalp. The strength and polarity (direction) of the signal recorded at each electrode will depend on the electrode location with respect to the source of the neural activity contributing to the dipole. The remaining videos in this series investigate the impact of dipole distance, orientation, and their combination on the EEG signal.
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Maggie Smith (art)
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Using the buttons below the computer image, you can play, pause, and adjust the speed of the simulation. You can proceed to the conclusion or return to the instruction screens.
You can turn electrodes on or off in any combination to examine how the EEG waveform is influenced by electrode location. Note that you must use the RESET button each time you wish to make a change to the electrodes.
In this simulation, three electrodes are placed at different orientations with respect to the neural dipole, and their signal is displayed on the left of the screen.