8 arm retrieval practice behavioral protocol
General Notes:
The retrieval practice task is run on a 8 arm radial maze, where rats must collect the pellets located at the end of each arm.
Reference Memory vs Working Memory
The version of the radial ram maze that we use allows us to differentiate and check both reference memory and working memory. Reference memory is where one check previously learned information to guide current decision making. Working memory is ongoing memory processes. Because the task is separated into a study phase and test phase. Working memory can be judged in both the study and test phase, where as reference memory can be judged in the test phase. By judged I mean checking for the number of errors, a working memory error is when a rat reenters an arm they have already entered during that phase. A Reference memory error is where a rat re enters an arm during the test phase that they already entered during the test phase. In this study we will record all arm entries made in both study and test phase to look at both types of memory.
Hypothetical example:
During the study phase a rat enters arms 1 2 3 4 and 2 again, they have made one working memory error.
Next in the test phase the rat enters arms 5, 6, 3, 5, 7, 8 the rat made 1 reference memory error when he reentered arm 3 and working memory error when he re entered arm 5.
Habituation:
1. For 3 days rats will be each handled for 10 minutes, following handling each rat should be placed for 30 seconds in to the center of the radial arm maze with the doors up. In addition a handful ~15-20 of pellets should be placed into the ceramic dish which is placed into the rats’ cage and refilled/ cleaned out of bedding each day.
2. Rats should separated and placed on food restriction the first day and kept on food restriction unless otherwise instructed.
Preliminary Training:
1. For 3 days Pellets ~ 5 should be placed along each arm with two in the food wells, Rats are then individually placed in the center with the doors already down and allowed to forage for the pellets for 10 minutes or until all pellets are consumed whichever comes first.
2. After each rat is run the maze must be cleaned using chlorohexadine solution this applies to this and all following stages of training.
Initial Training:
1. For 10 days; 1 session each day 2 pellets should be placed into each of the food wells, rats should then be individually placed in the center hub and the lights turned off, then all the doors opened when doors open turn on the lights. Session should end when food was collected at each arm or when 15 mins has elapsed whichever comes first.
2. For each session the time the rat is kept in the center hub before the doors opened should be increased incrementally by 10 seconds until 1 minute is reached, from then on 1 minute delay after hub placement and before doors are opened is maintained through the rest of the stages.
3. The lights should be turned off right before placing the rat in the center and turned on when the doors open.
4. How many total pellets are left and in which arms are they left should be recorded.
Pre-task training:
1. Next “study” and “test” phases are introduced separated by an approximately 8 min retention interval. The arms are baited according to the pseudo-randomly assigned configuration. The rat is placed in the central hub for 1 minute the four (random) doors are opened and the rat collect each of the rewards. The rat is then removed after collecting the final reward and placed back into this cage with the top placed back on.
2. The 8 minute retention interval is then started and the maze is cleaned between the study and test using chlorohexidane this is done for all the stages of training that follow.
3. After the retention interval the test phase begins the rat is placed by in the hub for 1 minute followed by the all 8 doors opening. All arm entries and their specific order is to be recorded by the experimenter. Session ends when all rewards are collected or 15 minutes have elapsed.
4. Criterion for completing pre-task training is 4 days at 3 errors with each day the minimum number of arm entries for example 5 entries at 75 percent and 6 entries at 50 percent.
Task & Infusions:
Note: Infusions must be given in the manner spelled out in the intracranial infusion protocol.
1. Post surgery rats are retrained back up to the criterion for pre-task training, during this time each day after the study the rats should undergo a mock infusion to habituate them to the process.
2. Task and infusions begins post recovery from surgery after re-hitting criterion, infusions are given according the infusion schedule file found in the Newmanlab google drive > 8 arm maze > Infusion Schedule.
3. Infusions are given such that each infusion type is repeated twice pseudo randomly
4. Recording behavior is exactly the same as before.
5. Infusions are given immediately after the rat has collected the final pellet from the study phase, the rat should be placed in the experimenters lap and the infusion process started,
6. Then the rat should be placed back in the cage and the maze is cleaned as usual, the time the infusion takes counts against the 8 minute delay so, 8 minute delay = infusion time + time sitting in cage (as normal). Ex. if the infusion process takes 3 minutes for a rat there is five minutes left before the test phase begins.
References:
Supplemental Information: Practicing memory retrieval improves long-term retention in Rats. Jonathon D. Crystal, J. Aaron Ketzenberger, and Wesley T. Alford. 2013. Cell.
De Luca, S. N., Sominsky, L. and Spencer, S. J. (2016). Delayed Spatial Win-shift Test on Radial Arm Maze. Bio-protocol 6(23): e2053. DOI: 10.21769/BioProtoc.2053;