Written by Travis M. Moore
Last edited 19-Jul-2020
Just like psychoacoustics challenged you to think in new ways, electrophysiology has its own unique perspectives that will require you to learn some background information. However, also like psychoacoustics, once you learn the basics, you will have an entire new field at your disposal for understanding and assessing the auditory system.
There are three main topics that we'll discuss before we begin talking about specific electrophysiological tests in detail. First, we will cover how and where electrical signals are generated in the auditory system. Second, we will learn how to measure those signals using non-invasive methods. Third, we will become familiar with interpreting test results.
By the end, you will have the knowledge to adapt to any electrophysiological test - even those outside the auditory system. (And yes, audiologists can and do work with tests of the facial nerve and various muscles.) Your new skill set will also help you remember the proper implementation, interpretation, and limitations of these tests.
Before you embark on your journey into neurophysiology, you should become familiar with the basic unit: the neuron. Figure 1 labels the major structures of a neuron.
Dendrites accept incoming signals from other neurons. The soma contains the organelles and machinery to maintain the cell. The axon sends signals out from the neuron to the dendrites of other neurons. We'll talk about the other structures later. The only other thing to know for now is that neurons are surrounded by fluid that has a different electrical charge relative to the inside of the neuron.
Electrophysiological tests measure the electrical activity of large groups of neurons. The voltage of firing neurons is recorded over time, and the result looks something like Figure 2. You see a series of peaks and valleys as the voltage (neuron firing) increases and decreases. That's the big picture view anyway. Read on to learn the specifics!