Radial arm maze

The question

Picture the set-up for a second. How do we tell working memory from reference memory in one test? You're watching Morris Water Maze Software Guide, over at morriswatermazesoftware.com.

Meet the radial arm maze

The radial arm maze has a central hub with usually eight arms radiating out, some or all baited with a small food reward. Animals learn which arms to visit and must remember which they've already emptied. A radial arm water maze uses the same layout in a pool, with escape as the motivation instead of food.

How it runs

Let me walk you through it. First, habituate the animals to the maze and the reward, usually with mild food restriction for the dry version. Next, bait a fixed subset of arms (reference memory) or all arms (working memory). Then, place the animal in the hub and let it choose arms until all rewards are found or time runs out. Finally, record each arm entry, its order and its timing.

Strengths and limits

So what's in it for you? It separates working memory errors (re-entering an emptied arm) from reference memory errors (entering a never-baited arm). Errors are discrete and easy to count. The water version avoids food restriction. Where does it bite? Food restriction in the dry version adds a motivational variable. Animals can adopt a fixed sequence, such as always turning to the next arm, which solves the task without spatial memory. Arm-entry rules must be defined clearly or scoring varies.

What to measure

Let's open up the analysis. Working and reference memory errors: counted from the sequence of arm entries. Arm entries and choice sequence: to spot chaining-like fixed patterns, the maze version of circling. Latency per choice and total time: for motivation and motor checks. Time in arms versus hub: for hesitancy and exploration. A rat that always turns right into the next arm can score few errors. A sequence analysis shows it isn't remembering places; it's following a rule.

The takeaway

Short version: arm entries and choice sequence and its neighbours tell you how the task was done, not just how fast. The full transcript is on this page, with sources.