Developed as a variant between the Radial arm, Dry Morris Water, and Cheeseboard mazes, the rowed Cheeseboard uses food rewards to investigate both spatial reference memory and spatial working memory tasks in rodents.
This apparatus has been used to investigate neurological processes associated with memory retention (Gilbert et al., 1998; Dupret et al., 2010; Shimbo et al., 2018).
First developed by Gilbert et al., 1998, the Rowed Cheeseboard Maze is a cross between a Radial arm maze, Dry Morris Water Maze and Cheeseboard maze, and a dry Morris water maze. The purpose of the Rowed Cheeseboard was to assess the function of distal cues and therefore pattern separation on short-term memory and spatial location information which is processed in the Hippocampus.
The maze is composed of a white circular board elevated above the ground with 177 food wells drilled into the board in evenly spaced parallel rows. A black start box is centred perpendicular to the food wells. The start box has a hinged lid to place rodents into and a guillotine door on the side.
Rodent location can be tracked using a video tracking software package such as Noldus EthoVision, ANY-Maze, or BehaviorCloud.
Pre-training
Allow subjects to familiarize themselves with the apparatus for 30 minutes during 3 days. Over 3-4 days, each rodent was placed in the start box and given successive trails with visible food pellets spread out on the surface of the apparatus. The door was temporarily opened and the rodent was allowed to exit the box and retrieve all the food rewards while an additional food reward was placed in the start-box. Once all the rewards had been collected, the door was re-opened and the rodent was coaxed into the start box to consume the food rewards in the start box.
The procedure was repeated until the rodent consistently collects thefgood rewards from the apparatus and returns to the start box on its own.
A similar procedure to the “learning” session was employed. Over 2-3 days, three food rewards were hidden randomly selected food wells in within three baited locations within the apparatus.
pre-training cued conditions
Several rodents were also trained to retrieve food rewards from visually marked locations using 3 identical objects next to food locations.
The start box was periodically moved around the board between rest and probe sessions.
Testing
Sessions using the Rowed Cheeseboard were performed in the order of pre-probe, pre-rest, learning, post-rest, and post-probe.
Pre-probe/Post-probe
Two probe tests lasting 25 minutes each were not rewarded with food.
Pre-rest
After pre-probe and learning sessions, rodents were placed in the start box for rest sessions of 25 minutes,
Learning
Rodents were given 40 successive trials to find 3 hidden rewards, randomly placed in foo wells. Baited locations were altered day-to-day.
The following parameters can be observed using the Rowed Cheeseboard:
Memory for Spatial Location: Role of the Hippocampus in Mediating Spatial Pattern Separation
Gilbert et al investigated the role of the hippocampus in spatial pattern separation during memory for spatial location. Seven rats were trained to retrieve hidden rewards in a cheeseboard maze. The study found that before undergoing surgery to receive hippocampal or cortical control lesions, all animals reached a criterion of 75% successful food retrieval and maintained this performance for 80 trials. There was no significant difference in the number of trials needed to reach criterion of food retrieval rates between the control group and the to-be hippocampus-lesioned group. However, after the operation, the hippocampus-lesioned group was significantly impaired in spatial memory tasks across all spatial separations, except for the largest separation. Both groups tended to quickly exit the start box, scan the row of food wells and objects, and make a direct trajectory toward one of the objects. The straight trajectory was likely facilitated by intramaze landmarks in conjunction with extra maze cues to guide navigation.
The study found that the hippocampus plays a critical role in spatial pattern separation, with place cells showing a higher degree of separation between similar spatial locations than non-place cells. The results suggest that the hippocampus is essential for accurate memory for spatial location, and its dysfunction may underlie spatial memory deficits in various neurological disorders.
The reorganization and reactivation of hippocampal maps predict spatial memory performance
Dupret et al showed that remembering new goal locations requires the stabilization and enhanced reactivation of goal-related hippocampal assemblies through NMDA receptors.
During spatial learning, the CA1 region reorganizes place-related firing patterns to represent new goal locations, and this reorganization is necessary for memory retention. The study also examined whether the acquisition, stabilization, and/or reinstatement of goal-related firing patterns could be observed under memory impairment conditions. The results showed that NMDAR-dependent mechanisms are essential for the stabilization of hippocampal goal-related firing patterns and the recall of associated memories. Moreover, eSWR network responses were found to predict memory performance and were associated with on-line memory trace formation
Assembly patterns associated with sharp wave/ripple network oscillations predict memory performance, suggesting that hippocampal firing patterns represent the formation and expression of new spatial memory traces.
Overall, these results suggest that the reorganization and reactivation of assembly firing patterns in the hippocampus represent the formation and expression of new spatial memory traces.
Mice lacking hippocampal left-right asymmetry show non-spatial learning deficits
Shimbo et al demonstrated that left-right molecular asymmetry in the hippocampal CA3-CA1 circuit, with the distribution of NMDA receptor NR2B subunits being different depending on the input from the left or right CA3 pyramidal neurons. Using β2-microglobulin knock-out (β2m KO) mice, which lack hippocampal asymmetry, during the cheeseboard task, both groups acquired the spatial reference-memory task at similar rates. In the probe trial, both groups showed equally accurate spatial memory and spent more time in the North East quadrant of the arena than would be expected by chance.
The study concludes that the mice with the gene knockout displayed intact spatial reference memory. These results suggest that hippocampal asymmetry plays a role in certain aspects of non-spatial learning.
Strengths
The task performance is carried out in the absence of aversive cues such as high light intensity, loud noise, wind, or water. Therefore, it imposes minimum stress to the subjects. Compared to the Dry Morris Water Maze, the Cheeseboard Maze exhibits a dry environment that minimizes the stress in subjects.
Limitations
The number of potential reward sites, as well as their comparative spatial distribution, may increase task difficulty in the Cheeseboard Maze. The food deprivation may cause stress to the subjects. The Cheeseboard Maze has a single starting point compared to the Morris Maze with multiple starting points. However, the issue is resolved by using the random head direction of the subject by confining it in the center of the maze with the help of the beaker.
Dupret D, O’Neill J, Pleydell-Bouverie B, Csicsvari J. The reorganization and reactivation of hippocampal maps predict spatial memory performance. Nat Neurosci. 2010 Aug;13(8):995-1002. doi: 10.1038/nn.2599. Epub 2010 Jul 18. PMID: 20639874; PMCID: PMC2923061.
Gilbert PE, Kesner RP, DeCoteau WE. Memory for spatial location: role of the hippocampus in mediating spatial pattern separation. J Neurosci. 1998 Jan 15;18(2):804-10. doi: 10.1523/JNEUROSCI.18-02-00804.1998. PMID: 9425021; PMCID: PMC6792543.
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