Feeling Frequencies: How the Nervous System Detects Vibrations

Sensing vibration is core to our perception of the world. You experience vibrations when you take a pencil to paper, when you strum a guitar, and when you feel the roar of a jet engine.

Vibrations can help you identify dangers in the environment, such as an oncoming vehicle, and provide feedback to your nervous system during movement.

So, how do we actually detect vibrations?

Vibrations in the environment happen at different frequencies. There are several types of touch neurons that detect vibration, and each is sensitive to a certain frequency range. One of the most fascinating neurons is the Pacinian — because it's the only neuron that can detect high frequencies.

[Text on screen: Anatomy of the Pacinian]

The Pacinian neuron detects vibrations through an onion-like structure called the Pacinian corpuscle. Pacinian corpuscles are mostly located in the deep tissues of our hands and feet.

Vibration triggers an electrical signal that travels up the axon to its cell body in the dorsal root ganglion. The signal is then relayed through the axon to the spinal cord and brain stem. Here, it can be sent to other neurons to reach the brain, so that we perceive vibration.

All of this happens in only milliseconds.

We use mice to study Pacinian neurons. We can take beautiful images of the Pacinian corpuscle, allowing us to examine its cellular components.

The axon exists in the center of the corpuscle, surrounded by layers of supporting cells that form an inner and outer core. The corpuscle changes shape in response to vibration, triggering an electrical signal in the axon.

[Text on screen: Activity of the Pacinian]

In the lab, we use genetically modified mice to see the Pacinian cell bodies light up in response to vibration. This helps us find a Pacinian neuron so we can record its electrical activity using a technique called electrophysiology, which provides a detailed view of exactly how the Pacinian neuron responds to vibration and at what frequencies.

The electrical activity of the Pacinian neuron can be converted into a tone, so you can hear what a Pacinian neuron sounds like when it detects different frequencies.

The Pacinian response aligns directly with the vibration stimulus. This shows just how precise the nervous system is.

[Text on screen: Feeling the future]

Our perception of the world happens in large part through touch. As you feel the world around you, vibration-sensitive neurons in your body are activated.

Researchers are working to understand how the structure of the Pacinian neuron underlies its remarkable ability to detect high frequencies. This might ultimately help in designing prosthetics to reestablish the sense of touch, or in repairing touch pathways that have been damaged from injury.

As we discover more about the sensory system and vibration detection, we develop a deeper understanding of how we interface with the world.