What is the source of the EEG?

Area of Science:

• Neuroscience
• Electrophysiology

Background:

• The human cortex processes information via electrical signals, enabling electroencephalogram (EEG) recordings.
• Large pyramidal neurons in deep cortical layers, with dendrites perpendicular to the surface, are key to EEG generation.

Purpose of the Study:

• To elucidate the role of deep cortical pyramidal neurons in generating EEG signals.
• To explain how synaptic inputs on apical dendrites influence EEG polarity.

Main Methods:

• Analysis of electrotonic spread and capacitive currents along apical dendrites.
• Modeling of postsynaptic potentials generated by excitatory and inhibitory neurotransmitters.

Main Results:

• Pyramidal neurons act as electrical dipoles due to postsynaptic potentials.
• Superficial excitatory or deep inhibitory inputs cause negative EEG deflections.
• Deep excitatory or superficial inhibitory inputs cause positive EEG deflections.

Conclusions:

• The orientation and connectivity of deep cortical pyramidal neurons are critical for EEG signal generation.
• The location of synaptic inputs on apical dendrites dictates the polarity of EEG deflections, providing insights into cortical processing.