Bio 300, Smith College | Neurophysiology


When you finish your experiment in lab this week, map the receptive fields of at least three retinal ganglion cells using the MacRetina simulation, which is available on our lab computers.

About MacRetina

MacRetina simulates an experiment to map the receptive fields of retinal ganglion cells. The program assumes that you know something about retinal ganglion cells, and that you are ready to conduct a simulated laboratory experiment. (A tutorial is available on start-up, and the tutorial and some supplementary text files are available under the program's "Help" menu, if you need a review.) With the mouse, you will be able to flash or drag a spot of light around a small region of a simulated retina, while you record with an extracellular electrode from one of ten retinal ganglion cells. Your goal is to map the excitatory and inhibitory regions of at least three of these cells. If several different lab groups use the same computer, we can accumulate maps of all ten receptive fields to compare.

How to start MacRetina

The program is in the "0S 9 Applications folder." Double-click the MacRetina icon (yellow eyeball). If someone else has left MacRetina running, you can select "New" from MacRetina's File menu to start over. MacRetina will launch the Mac Classic operating system (OS 9.2).

Map at least three cells

Your assignment is to map any three of the ten cells that MacRetina simulates. Since several maps were generated in class, it will be more interesting to choose from cells 4 to 10. To select a new cell, choose "Move electrode..." (in the Electrode menu), click one of the buttons in the electrode dialog box, and click "OK." The electrode will move instantly to the new retinal ganglion cell. (This is an extremely UNrealistic aspect of the simulation, since placing the electrode next to a cell is actually a delicate procedure.) Move the white or black spot around the screen, holding down the mouse button to activate the spot. If your cell makes a spike, a white or black dot will be placed at the center of the spot's location to mark the stimulus location. (Note that this will occur even if the response is only due to spontaneous activity.) By judicious movement of the spot, you can "paint in" the cell's receptive field. When you are satisfied with the detail in the map, "Remember" the map (Maps menu) and select another cell to record from.

Examine the cell maps

After you have mapped at least three cells (and "Remembered" each map), examine the locations and overlap of the receptive fields by selecting "Show Maps" from the Maps menu. Click on any of the cells to see its map. Mapping more cells makes a comparison of their receptive fields more interesting. Do any overlap? Keep a list of the cells and their characteristics (X or Y? on-center or off-center?), and bring your list to class on Thursday so we can compare results.