Biological Sciences 300/301, Smith College | Neurophysiology

  MacRETINA SIMULATION

This is a self-paced assignment to be brought to class on the date specified in this year's Schedule of Topics and Assignments. To complete the assignment, work on the Macintosh computers in our lab. The program is in the folder Bio301 OS9 Applications/ MacRetina on the Macintosh HD. Double-click the yellow icon to start the program.

You are welcome to work in pairs and turn in maps of any 6 ganglion cell receptive fields, or work in a team of three and map all 10 cells. Make sure that everyone takes turns mapping their share of the cells, so everyone gets a feel for how it works. Put everyone's names on the pages you turn in.

 

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 dark or light spot 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 find the excitatory and inhibitory regions of a ganglion cell's receptive field, and to determine whether the ganglion cell's response is sustained or transient.

Map at least six cells

Your assignment is to map any six of the ten cells that MacRetina simulates (all ten if you work as a team of three). 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 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 and print the cell maps

After you have mapped at least six cells (and "Remembered" each map), examine the locations and overlap of the receptive fields by selecting "Show Maps" from the Maps menu. Click on a number to see that cell's map. Since Mac OS X 10.4 does not support printing from Mac Classic applications (like MacRetina), "Print Maps" will not work. Instead, capture a screenshot of each individual map using "Show Maps," and combine the screenshots in an Appleworks document. See the instructions on Computer Screenshots for a reminder on how to do this. Two special hints:

• capture only the gray map area, not the control panel or the oscilloscope trace (the trace is from the currently active cell, not the mapped cell)
• in Appleworks, select "Word Processing" (not "Drawing"). Two maps will fit on a word processing page, and the page breaks will take care of themselves.

When you have finished, select "Quit" from MacRetina's File menu.