Receptive fields
In this simulation you will "record" the neural activity from Aβ nerve fibers with skin receptors on the hand.
In the Receptive fields tab, you will explore the receptive field locations and sizes for three different nerve fibers. Click on the hand to simulate touching the hand at that location for one second. The oscilloscopes show the amplified voltage trace recorded extra-cellularly from an electrode close to each of the nerve fibers. Each of the near-vertical lines represents an action potential from that nerve. If your speakers are on, you will also be able to hear the neural activity from the nerve fiber of your choice (use the radio buttons next to each neurons' name to choose). If a click falls within the receptive field for any of the nerves, a coloured dot will appear at that spot.
Once you've found the receptive fields, make sure to explore their borders so that you can measure their size by dragging the ruler on the bottom left of the hand.
In the Sensitivity tab you will further explore the sensitivity profile for one of the receptive fields. Not all the areas of the receptive field produce the same neural response. You will map the response curve for three cross-sections of the receptive field by clicking on different points of three coloured bands. If you click several times on the exact same spot, will you get the same number of spikes? Why?
Once you've mapped enough of the three response curves (i.e. there are no large intervals in between dots on the coloured bands), check out the real world examples on the following tab.
The Examples tab shows some real world examples of receptive fields, redrawn from: Johansson, R. S. (1978). Tactile sensibility in the human hand: receptive field characteristics of mechanoreceptive units in the glabrous skin area. The Journal of physiology, 281, 101.
Receptive field locations
Find the receptive field for each of three neurons by clicking on different points of the hand. The neural responses for each click will appear on the oscilloscopes, and you can choose which neuron's response you would like to listen to at any point in time.
Once you've found the location on the hand that triggers a response for a particular neuron, measure the diameter of the receptive field by dragging the ruler in the lower left corner of the hand on top of the receptive field. Please enter the appropriate size for each neuron's receptive field on the table below. What relationship do you observe between the location of the receptive fields on the hand and their size?
Once you've measured the three diameters, access the next tab to learn about sensitivity.
Tip: If you can't find a response, and it's starting to get frustrating, click on the buttons above each oscilloscope to see a hint for the location of that neuron's receptive field. If you're happy to keep exploring on your own though, please do so!
| Neuron | Diameter (cm) |
|---|---|
| 1 | |
| 2 | |
| 3 |
Sensitivity profile
This shows the receptive field on the palm of the hand from the previous tab, zoomed in. The previous tab simplified the receptive fields by making it a binary response: the neuron responded equally when touched inside its receptive field and did not respond otherwise. In reality the response varies within the receptive field, and we will explore how it can vary in this tab.
Please map the response curve for each of the horizontal coloured bands in the receptive field, to discover changes in the rate of the neuron's response. Once you've mapped the three curves, a visual representation of the sensitivity profile will appear. You can then access the real world examples in the next tab.
Real world examples of receptive fields
In reality, the sensitivity profiles of tactile nerve fibers are a bit more complex than just concentric circles. These are some examples of human hand receptive fields:
