We want to examine how hippocampal dependent spatial learning is altered with aging. We then examine how interventions such as physical exercise alter these cognitive outcomes. This behavioral paradigm allows us to readily examine these in the same cohort of mice.
Multiple cognitive tests are available to test spatial learning in mice, most of which have been established for decades. These include the Morris Water Maze, the Y Maze, and the Barnes Maze. Each of these have limitations, especially in relation to longitudinal testing.
The main experimental challenge is to test animals in a longitudinal manner, making it difficult to accurately determine the effect of exercise interventions. Most spatial learning tests are either easily learned or are very stressful or inappropriate for diseased models. By altering some key components of the active place avoidance, such as the rotational direction of the arena or the location of the shock zone.
This test is able to be used multiple times. By changing the color of the arena floor, we are able to test mice with different colors such as C57 black 6 or Swiss mice. To begin position the active place avoidance or APA apparatus within the camera frame mounted on the ceiling.
Open the animal tracking software to track the mouse. From the experiment tab, set the trial duration to 10 minutes, then specify the shock duration to 500 milliseconds and maintain the shock zone at 270 degrees from the target's edit tab. Place four neutral colored visual cues on different walls of the room at the same height as the rotating platform and 30 to 50 centimeters away from their arena.
Adjust the light intensity of the room between 30 to 70 lux. Open the tracking tab from the tracking software, then click the from calibrator tab and set the mouse size and area ranges accordingly to ensure the mouse is recognized when in the arena. While in the from calibrator tab, adjust the contrast threshold by moving the red line and the threshold pane to ensure accurate tracking of the animals.
Finally start the arena and ensure that as it rotates, it remains within the mask. Next, within the devices tab, select the current source and set the current mode to track dependent to modify how or when the foot shocks are delivered, set the shock level to 0.5 milliampers. Habituate the mouse in the room for 30 minutes.
Initiate the tracker software. Create an output directory using the file output tab to save the trial data. Then create an experiment specific folder, and depending on the experimental model, create separate folders for each day or trial.
Save the experiment data within the output folder. Before starting a trial, click the save button and in the newly opened window, add a unique mouse ID.Next, using a glove covered hand carefully lift the mouse from the base of its tail from the home cage. Place the mouse on the rotating arena of the APA apparatus for habitation without delivering shocks.
Retreat behind the curtain and on the tracker software, start the experimental trial. After five minutes, remove the mouse from the APA apparatus and return it to its home cage. Collect all waste and thoroughly clean the grid using 80%ethanol.
Next, from the experiment tab, set the trial duration to 10 minutes. Then specify the shock duration to 500 milliseconds and maintain the shock zone at 270 degrees from the target's edit tab, place the mouse on the arena of the APA apparatus as demonstrated previously. Retreat behind the curtain.
Click play to start the trial and monitor the mouse's activity. After the trial, remove the mouse from the APA arena and return it to its home cage. To analyze the mouse's APA task data, open the track analysis program.
And from the dropdown menu, select avoidance. Click on add task to upload the saved data files. Then in group name, create a group to analyze the data.
Click the output directory to select the location to save the analyzed data. Next, click add files and select the files for analysis from the local drive. Click set time and specify the analysis period between zero to 600 seconds.
After adding all tracks, click on the analysis tab and select run analysis. Open the data saved in the TBL files folder in a spreadsheet. Finally, save the spreadsheet for statistical analysis.
The mice with intact spatial learning ability exhibit a decrease in the number of shocks during successive acquisition trials. Additionally, these mice show an increase in the maximum time spent avoiding the shock zone. Trace maps showed that mice with intact spatial learning ability received only two shocks and predominantly spent time on the opposite side of the shock zone.
In contrast, the mice with learning disabilities received more shocks, and the trace map reveals a disordered pattern.
