Shopping cart

Hit Enter for Search
Grade 9+ Grade 9+
Invertebrates Invertebrates

Experiment: Rate Coding of Touch Sensation

How does the brain differentiate between a light touch and a firm one? By exploring a cockroach leg, we can investigate how neurons encode touch intensity through rate coding.

What Will You Discover?

  • How touch intensity influences the rate of neural activity.
  • The mechanics behind rate coding in sensory neurons.
  • How tactile neurons encode information for the brain to process.

Background

The sensation of touch is critical for survival in both humans and cockroaches. For this experiment, we focus on the mechanics of rate coding, which explains how the frequency of neural spikes conveys information about the intensity of a stimulus.

When you press harder on a touch-sensitive hair of the cockroach, the neuron responds not by increasing the size of spikes but by increasing their frequency. This increase in spike rate provides the brain with critical information about the level of force being applied.

Procedure

To begin the experiment, prepare your cockroach leg setup using the SpikerBox, ensuring that the pins are securely placed for stable recordings.

For this setup you want to place the 2 pins close together:

Next, identify a touch-sensitive hair on the leg that generates neural spikes when gently pressed with a toothpick.

Once you’ve found a responsive hair, practice applying pressure in three distinct levels: light, medium, and firm.

Each press should be brief, lasting approximately half a second. As you apply these varying levels of pressure, use the SpikeRecorder app to observe the neural activity produced. Carefully record your observations for each level of pressure to analyze how the neural responses differ.

Analyzing Results

Count the number of spikes in the first half-second of each pressure level. Plot these results to visualize the relationship between pressure intensity and spike frequency. Observe how the neuron encodes information based on the rate of spikes, not their size.