This virtual lab explores how the nervous system encodes sensory information. A core concept, called the "labeled line" principle, is that each neuron has a specific identity and carries a specific type of information. For example, one neuron may carry touch information from the left big toe. When this neuron is active, the brain "knows" that something is touching the left big toe.

To demonstrate this concept, the lab simulates neurophysiological experiments with a leech, a classic model system for studying the touch or tactile sensory system. The lab consists of two modules.

In the first module, "Leech Dissection," you observe the procedure for leech ganglion preparation, which isolates part of the leech's nervous system for the experiments. This module shows how the dissected part of the leech used in the experiments relates to the whole animal. Note that some images in this module are actually slideshows. These images have horizontal bars near the bottom that automatically advance between slides. Clicking on each bar will reshow the corresponding slide.

In the second module, "Probe & Identify," you explore simulations of real neurophysiological experiments to learn more about the leech's nervous system. The experiments include:

• monitoring a neuron's electrical response while stimulating the leech's skin with different tools
• injecting the neuron with a fluorescent dye to observe the neuron's anatomy
• comparing these data with published results to identify the neuron's type

You can practice this process several times to identify multiple neurons.

You can navigate through each module by clicking on the forward and backward arrows on the right and left edges of the screen. After you have completed the modules, you can print a report of your virtual experiment.

Credits

Producer/Writer
Satoshi Amagai, PhD, HHMI

Design and Development
Bill Pietsch, A3MG
Davey Thomas, A3MG

Scientific Review and Special Thanks
Peter Brodfuehrer, PhD

Photographs
Bill Pietsch, A3MG

Additional Photo Credits
"Introduction" leech images supplied by iStock/Thinkstock

This virtual lab was originally published as part of the 1997 Holiday Lectures on Science, "Senses and Sensitivity: Neuronal Alliances of Sight and Sound." Original credits included Joseph Perpich, MD, JD as Executive Producer and Dennis W. C. Liu, PhD as Producer.

Version 2.0 Beta
Updated on 04/9/19