Rats use their whiskers to gain sensory information about the world around them. The whiskers are arranged in a characteristic patterns of rows and arcs on their faces and receive sensory input through whisking, a motion that occurs between 5 and 10 Hz. From these interactions, they are able to discern shapes and features of the surrounding environment. But what is still unknown is the resolution at which they are able to sense, and if whiskers alone are responsible for fine-grain distance discrimination. Krupa et. al. (2001) performed an experiment to determine the ratís accuracy using a behavioral apparatus, whose schematic is depicted in Figure 1. The gates are able to move back and forth and be set at specific distances to test what the rat is able to tell apart. The first step is to train the rat to first distinguish between very large and very small openings by using a food reward system. These opening sizes are changed as training progresses to be incrementally closer together, and less easily distinguishable. After weeks of training, rats in current studies have shown a discrimination ratio of between 5 and 9%. This translates to recognizing the difference between 62 mm and 65 or 68 mm openings. The measurements represent the distance between the two gates, with an equal distance between the center line and each gate. For this experiment, the sliding door at the back of the center discrimination chamber (shown below) will be closed in between trials to maintain quality of animal attention. There is a 30 second inter-trial period, in which we will have to move the doors to the prescribed locations. Professor Mitra Hartmann in the biomedical engineering department is our client for this project, and she would like to take this initial design and expand on it, as detailed in the goals section, for a new set of experiments.

Experimental Setup (Krupa et. al., 2001).

The focus of this project will be to create only the Center Discrimination Chamber, and computer controlled stepper motor doors.

DESIGN CRITERIA

1.   Dimensions: The Center Discrimination Chamber shown in Figure 1 should be 200 mm wide to not interfere with the rat's whiskers, and 300 mm long. Doors need to be 20-30 mm thick, and the height of all walls should be about 125 mm.

2.   Range of Motion: Our version of the Krupa design will be able to open between 10 and 150 mm, with an acceptable resolution of 0.5 mm (but a desired resolution of 0.1 mm). This means that each motor must be able to move through a range of 70 mm, with an individual resolution of 0.25 mm (but ideally 0.05 mm).

3.   Verification: The precision of these measurements are the main priority for the client, and must include some sort of verification, probably a continual monitoring and subsequent control to ensure correct distance between doors.

4.   Independent movement of doors: The doors must be able to move independently of one another, such that both symmetric and asymmetric distances from the midline can be used in experiments.

5.   Budget: There is a budget from the class of $150. Depending on the parts needed, our client may be able to supplement this to a limited degree.