Touch and Pressure: How Your Body Feels Different Forces

How does the brain tell a light tap from a firm press? By examining a cockroach leg, we can see how sensory neurons encode touch intensity through a process called rate coding.

Devices and Accessories2

About the Experiment

What Will You Discover?

How touch intensity changes neural firing rate.
The mechanics of rate coding in sensory neurons.
How tactile neurons package information for the brain.

Background

The sense of touch is vital for both humans and cockroaches. When you press harder on a touch-sensitive hair, the neuron does not increase spike size; instead it fires spikes more rapidly. This higher frequency tells the brain that the force has increased.

Experiment

Rate-Coding With Three Levels of Pressure
Setup
1. Prepare a cockroach leg on cork and insert two recording pins very close together for a clear single-neuron signal.
2. Locate a touch-sensitive hair that spikes when probed with a toothpick.
Procedure
1. Using the toothpick, apply three brief presses—light, medium, firm—each lasting about 0.5 s.
2. Watch the spikes in SpikeRecorder and note the firing rate for each press.
3. Repeat several trials, recording the first half-second of activity each time.

Analyzing Results

Count the spikes in the first half-second of each pressure level and plot them. You should see firing rate rise with force, illustrating that neurons encode intensity in rate, not spike size.

NGSS alignment

Performance expectations

Firing rate transmits stimulus intensity to the brain.

MS-LS1-8 Gather and synthesize information that sensory receptors respond to stimuli by sending messages to the brain for immediate behavior or storage as memories.
HS-LS1-2 Develop and use a model to illustrate the hierarchical organization of interacting systems that provide specific functions within multicellular organisms.
4-LS1-2 Use a model to describe that animals receive different types of information through their senses, process the information in their brain, and respond to the information in different ways.

Light, medium and firm presses show an animal's touch sense sending different information to its brain.

Science and engineering practices

3 Planning and Carrying Out Investigations

Give one touch hair light, medium and firm presses, several trials each.
4 Analyzing and Interpreting Data

Note the firing rate for each press.
5 Using Mathematics and Computational Thinking

Count spikes in the first half-second of each press and plot them.

Crosscutting concepts

Cause and Effect

Pressure sets firing rate.

Disciplinary core ideas

LS1.D Information Processing

Sensory transmission.
LS1.A Structure and Function

Receptor structure and function.

Performance expectations, crosscutting concepts and core ideas from Hands-On Neuroscience Curriculum Overview, Unit 1, module 1.2, whose core lab this is. The practices are the ones this page asks students to do. 4-LS1-2 is a Backyard Brains addition for elementary classes (Greg, 2026-10-06); the book itself is written for older students.