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Barnes maze strategy analysis

Introduction

The Barnes maze strategy analysis performed by ANY-maze is primarily based on the techniques described in the 2018 review paper Assessment of spatial learning and memory in the Barnes maze task in rodents — methodological consideration by Gawel et al. Here the animal's strategy is classified as either Direct, Serial or Mixed. Quoting from Table 1 of the paper:

Direct (spatial)

Moving directly to the target hole or to 1–2 adjacent hole(s) before visiting the target.

Serial

The first visit to the target hole preceded by visiting at least two adjacent holes (but not adjacent to target hole) in serial manner, in clockwise or counter-clockwise direction.

Mixed (random)

Hole searches separated by crossing through the center of the maze or unorganized search.

The exact criteria used by ANY-maze

ANY-maze allows you to tailor the criteria, for example, how many holes either side of the target hole should be considered 'adjacent' when scoring the Direct strategy. Also, ANY-maze adopts the names Direct, Serial and Random. The specifics of the scoring in ANY-maze are as follows:

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The Direct strategy occurs when the animal goes directly to the target hole, or to a hole within the 'target region' (being holes within a set distance of the target hole, for example, one or two holes either side) and then to the target hole, without visiting any holes outside the target region or re-visiting the centre (where it started the test).

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The Serial strategy occurs when the animal visits a series of consecutive holes, for example, it might need to visit three holes in sequence, such as hole 1, 2 and 3. In fact the animal can optional skip one or more holes, so visits to holes 1, 3 and 4 might still be considered a serial strategy. Any number of reversals during a serial strategy are allowed, so visits to holes, 1, 2, 3, 2, 1 would be still be considered serial, as would 1, 2, 3, 2, 3, 2, 3, 4. Entering the centre always 'breaks' a serial strategy, so moves 1, 2, 3, Centre, 4, 5 would not be considered a serial strategy.

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The Random strategy occurs when the animal isn't using a Direct or Serial strategy. For example, visits to holes 2, 16, 6 would be Random. An animal which never finds the target hole will be scored as using a Random strategy.

We appreciate that there are different ways of analysing strategy in the Barnes maze, so if you have a different method in mind, please do contact ANY-maze Support and we'll be happy to discuss it with you.

ANY-maze scores both Total and Primary strategies

ANY-maze scores both an 'overall' (total) strategy and a 'primary' strategy. The former is the strategy derived from all the movements of the animal throughout the entire test (i.e. up to the moment the animal enters the escape chamber, at which point the test should end). The latter is the strategy derived from the movements up to the first visit to the target hole. To understand the difference consider a test in which the target hole is hole 4 and the animal starts by visiting holes 1, 2, 3, 4. However, despite finding the escape hole it doesn't enter the escape chamber, but instead continues exploring the maze, visiting holes 6, 7, Centre, 4, at which point it does enter the escape chamber.

In this example, the primary strategy was Serial, because the animal simply went from holes 1 to 2 to 3 and then to 4 (the target hole), but the overall strategy was Random because the animal then went to holes 6, 7 and then to the centre (which always 'breaks' a serial strategy).

Note that for the strategies to be score correctly you should ensure that your protocol includes a procedure that will end the test when the animal enters the escape chamber - which should be set up as a hidden zone.

Additional measures scored when using the Barnes maze strategy analysis

As well as the actual strategy ANY-maze will also assess various other measures when using the Barnes maze strategy analysis. Again, these are based on the paper cited above and are defined there as:

Total Escape latency

Time needed to find and enter the escape chamber with whole body [which will cause the test to end].

Total Reference errors

[Count of the number of times] the animal makes a nose and head deflection [visit] into a non-escape hole.

Total Working errors

[Count of the number of times] the animal makes a nose and head deflection [visit] into a non-escape hole already visited during the same trial.

Total Perseverative errors

[Count of the number of times] the animal searches [visits] the same hole without searching another hole in between.

Total Path length

Animal's path length to reach the target hole with its whole body [i.e. to enter the escape chamber]. [This Barnes maze specific measure is not explicitly included in ANY-maze, but is the same as the standard Total distance travelled measure.]

Primary Escape latency

Time needed to find and enter the escape chamber with head alone [what ANY-maze calls a visit].

Primary Reference errors

[Count of the number of times] the animal makes a nose and head deflection [visit] into a non-escape hole [in the period up to the first visit to the escape hole].

Primary Working errors

[Count of the number of times] the animal makes a nose and head deflection [visit] into a non-escape hole already visited during the same trial [in the period up to the first visit to the escape hole].

Primary Perseverative errors

[Count of the number of times] the animal searches [visits] the same hole without searching another hole in between [in the period up to the first visit to the escape hole].

Primary Path length

Animal's path length to reach the target hole with its head [i.e. up to first visit to the target hole].

Hole deviation score

The number of holes between the first hole visited and the escape box.

Running speed

The average speed of an animal during the trial. [This Barnes maze specific measure is not explicitly included in ANY-maze, but is the same as the standard Average speed measure.]

Setting up Barnes maze strategy analysis

The various settings required to setup strategy analysis in the Barnes maze are described in detail here.

Changing analysis post test

As is usual in ANY-maze, should you change something relating to the strategy analysis, perhaps altering where the target hole was located in the test, then ANY-maze will automatically reanalyse the strategies used in the affected tests and all the results will update - this typically takes just a few seconds.