Figure 1.

"Open field" evaluation using the activity chamber. In the graphic, infrared beams are rendered as red, and these four beams for each axis are equidistant (20 cm) apart around the perimeter of the chamber (though in the drawing only two are shown in each axis for simplicity). The box is 100 × 100 × 20 cm. The beams are 4.5 cm high relative to the bottom of the chamber. The rat is placed in the middle of the chamber at the beginning of the test and usually allowed to explore the area for 30 minutes. Food was placed over the center of the box on top of a grid screen (not shown). A totalizer/counter registered the number of beams broken during the period of study. A computer with laboratory designed software (see Koob and Cirillo, 2006 for details and procurement) registered which individual beam was broken to determine where the rat was in space and time.