Protocol for Radial-Arm Maze Training for Unit Recording

Description

From the lab of Lucien T. "Tres" Thompson, Ph.D. The University of Texas at Dallas

Protocol for Radial-Arm Maze Training for Unit Recording

By Tim Goble


Introduction: Radial-arm training will differ for place-cell recording versus other behavioral paradigms. The emphasis for place-cell recording is on fast, reliable recording sessions where the rat transverses to each arm at least once. Other behavioral paradigms may emphasize number of visits, the order of arms transversed, and/or remembered previous sessions. This training protocol is sufficient for place-cell unit recording sessions. You may need to adapt this protocol for things of specific importance in other paradigms.



I. Food Depriving Rats



Items Needed: Rat

Rat Cage

Rat Weight Scale

Food Pellets

Chart

Calculator



Purpose: In order to get your rat to move on a maze you need to encourage them. They will not just wander around if they don’t have a reason too. Food depriving them to 85% of their original body weight and baiting the end of each arm with a food reward is a safe and effective way to encourage the rat to transverse in its environment.



· Weigh rat on scale

· Write down the ‘original weight’ amount on chart

· Calculate 85% of original weight

· Write ‘food deprived’ weight on chart for a reference of desired weight of rat

· Daily, weigh your animal and manually feed your rat by giving him 2-3 food pellets

· Within 4-6 days, your rat should be around ‘food deprived’ weight

· Adjust the amount of food daily to maintain the ‘food deprived’ weight through out maze training and experiments



II. Setting up the Maze Environment



Items Needed: 8-Arm Radial-Arm Maze

Prepared Sucrose Dispensing Cups (8)

Micro Spray Cleaner

Paper Towels





Purpose: For unit recording training, the maze environment for behavioral training purposes only is not terribly crucial. The goal is to get the rat used to transversing to the end of all 8 arms for its sucrose reward. The maze environment is crucial for unit recording. Training can be done on any radial arm maze, if the others are set up, but it is usually done on the maze used for recording sessions. Therefore, there has been much care taken in setting up the maze environment for unit recording. Please find out what care you need to take if you are training an animal on the unit recording radial arm maze.



· Make sure there are prepared sucrose dispensing cups on the end of all arms and make sure that they are clean

· Spray the Micro cleaner onto paper towels and wipe off the arms

· Make sure the arms are secure on the maze are will not wobble as the rat transverses them



III. Making the 30% Sucrose Solution



Items Needed: Sugar (15g)

Distilled Water (60mL)

Large Weigh Boat

Stir Plate

Stir Bar

Balance

60cc Syringe

Blunted 18G Needle

Plastic Spoon (large Spatula)

100mL beaker

Refrigerator



Purpose: The end of each arm will be baited to encourage the rat to transverse to the ends of each arm. Sucrose solution works well in that it is easy to make, easy to store, easy to dispense, and does not create artifact in neural signals seen with food pellets.



· Prepare you work area around the balance

· Refer to the ‘Protocol for Use of Balance’ for proper use and clean-up of the balance

· Weigh out 15g of sugar on the balance

· Place 60mL of water in 100mL beaker

· Place stir bar in beaker and place on stir plate

· Turn on stir plate (Please refer to ‘Protocol for Use of Stir Plate’ if you do not know how to properly use and clean a stir plate)

· Place 15g of sugar into water and let it stir until solution is clear

· Stop stir plate

· Remove beaker from plate and place on work bench

· With a blunted 18G needle and 60cc syringe, fill the syringe with sucrose solution

· Store in refrigerator until needed

· Clean up balance, stir plate, and work area properly

· Wash stir bar and beaker

· Put all items away



IV. Initial Training of Rat on Radial-Arm Maze





Days of Training: First Few Days of Training



Items Needed: Prepared Sucrose Solution

Set-up Maze Environment

Rat

Rat Cage



Purpose: Your initial training will differ from latter training. Rats are not used to walking on radial arms (to them, it’s a 50 feet high plank!). They also have no idea that the ends of each arm baited with sucrose. You will have to convince them that the maze is safe and that the sucrose is good to drink! Not as easy as it sounds. This is how I would approach initial training



· Lower the amount of lights in the room (remember, your rat is nocturnal; it is most active in the dark)

· Place approximately 1mL of sucrose solution into each cup located on the ends of each arm

· Place rat in center of maze (Your rat will not move around very much. Typically, it’ll just sit there)

· After a few minutes of the rat idle in the center, pick up the rat by it’s tail and place him at the end of one of the arms (Your rat will run back to the center. You might see that the rat has a hard time walking. Your rat has to accommodate its wide limb positions to the diameter of the arms)

· After a few minutes of the rat idle in the center, repeat to the other arms on the maze

· Take the rat off and place him into his cage

· Give the rat a 15min break

· Place the rat back on the center of the maze and observe (if your rat is still just sitting in the center of the maze and not moving his body onto the arms, even if it’s just slightly, then repeat above)

· If your rat is exploring a little bit and moving around, let your rat explore for a few minutes and take him off

· Give him another 15min break

· Place the rat back on the center of the maze and attempt to the get rat to transverse to the end of an arm to where the baited cup is

· If he will not move on his own all the way down the arm, pinch the base of his tail slightly and or nudge him along to the end

· When he is at the end, dip your finger in the sucrose and touch your sucrose finger to the rats nose (Make sure that the distance between the rat and the cup is minimal. The idea to make the rat aware that there is sucrose at the end of the arm, not that your finger will taste good. Be careful, the rat may try to bite you)

· Continue this once or twice and observe to see if the rat explores the baited cup

· If he does, observe if he drinks any of the sucrose

· Let the rat turn and walk back to the center

· Observe if he walks on his own down any of the other arms

· If he does not, pinch the base of his tail or nudge him down other arms

· Repeat above for all eight arms

· Take rat off and place him into his cage

· Feed him his 2-3 food pellets after you are done with the daily training

· Do the above for a few days until he appears to get the point that the arms are baited with sucrose



Your rat will not run the maze very well if he isn’t hungry. That’s why you should monitor his weight and feed him daily after your done training.



V. Daily Training After Initial Training



Days of Training: After Initial Training for 7-10 days



Items Needed: Same as above



Purpose: Now that your rat knows that he won’t fall off of the maze and that there’s a reward at the end of the arms, he needs to get used to running to all eight arms, taken off of the maze, given, a 15 min break, and the repeated 4-5 more times.



· Place rat in center of the maze and move back (out of the room if possible) to where you can observe the rat but out of the way

· Mentally (if possible for you) monitor the rat as he transverses down each of the eight arms

· After he has gone to the end of each arm once (if he goes down the same arm twice, that’s okay… he’ll realize that there’s only sucrose the first time down) take him off and place him into his cage

· Refill the sucrose cups

· Wait 15min between sessions and repeat the above 5 times
The goal is to get him to complete a session (defined as transversing to the end of all 8 arms) in about 4-6min. If it is taking him 10-15min to complete a session, make sure that he is drinking the sucrose solution at the ends of each arm. He may be going to the end of each arm and not drinking the solution. If so, your rat won’t really care to move quickly to each arm to get his reward. Repeat some of the ‘initial training’ for the rat. When your rat can complete 5 sessions, 15min apart, drinking the sucrose, in 4-6min per session, then you have successfully trained a rat on a radial arm maze for purposes of unit