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Protocol for Radial-Arm Maze Training for Unit Recording

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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 recording!!!   Congrats.

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