Figure 1.

Recording procedures used with the cylinder and dual-chamber apparatus. A, The animal was removed from the cylinder and placed in an opaque holding chamber following the first recording session. The floor paper was then changed, the cue card removed, and the animal was disoriented prior to the second session. At the end of the second session, the animal received an IP injection of saline or atropine sulfate, and placed into the holding chamber for 15 min. The animal was then replaced in the cylinder without disorientation. Following session 3, the cue card was inserted while the animal continued to navigate within the cylinder. For all subsequent sessions, the animal was removed and placed into the holding chamber, the floor paper was changed, and the animal was disoriented before the next session.