Figure 1: Barnes maze training and delayed recall.
(Top) Rat during performance of the Barnes maze. For the brain mapping, the animal carries a subcutaneously implanted minipump that allows bolus infusion of the cerebral perfusion tracer [14C]-iodoantipyrine by remote-activation using a ceiling mounted infrared light [4, 95]. The pump consists of (a) an intravenous catheter connected to (b) a silicone-embedded solenoid valve powered by a lithium battery rechargeable by wireless power transfer and gated by a frequency-sensitive photodetector, (c) an ejection chamber containing the radiotracer, and (d) a silastic reservoir containing a euthanasia solution. (Bottom) Depicted is the group average latency (±SD, n=11) to find the target ‘safe-box’ over 19 days of daily training. The arrow indicates the day of retrieval testing and functional brain mapping. Also shown is a top-down view of the Barnes maze. Rats are released in this example at either the ‘1’ or ‘2’ position, and have to find the ‘escape box’ located below a single one of the available 18 holes (bottom position). The left maze image shows the pathlength of an animal before (A) and after (B) training.