How can impedance in an EEG context be best described?

In the context of EEG, impedance is best described as the resistance to alternating current. EEG measures electrical activity in the brain, which involves alternating currents generated by the electrical signals of neurons. Impedance reflects both the resistance and the reactance (which accounts for the capacitance) of the electrode-skin interface and the conductive properties of the surrounding medium.

When measuring brain wave activity, it's essential to maintain low impedance to ensure that the signals picked up by the electrodes accurately represent brain activity without significant loss or distortion. High impedance can mean that signals will be weaker and noisier, which can negatively impact the quality of the EEG recording.

Understanding impedance as the resistance to alternating current emphasizes its role in the efficiency of signal capture in EEG. This is why selecting the correct electrodes and preparing the skin properly to minimize impedance is crucial in clinical EEG applications.