Y-maze

The question

Today's maze is all about choices. How does a three-armed maze reveal working memory in a few minutes? You're watching Morris Water Maze Software Guide, over at morriswatermazesoftware.com.

Meet the Y-maze

The Y-maze has three identical arms set at equal angles. Rodents tend to explore the arm they visited least recently, so a run of entries into three different arms in a row is called a spontaneous alternation. It relies on remembering recent choices, so it's a quick test of spatial working memory. A two-trial version blocks one arm first, then measures preference for the newly opened arm.

How it runs

The recipe is short. First, place the animal at the end of one arm and let it explore freely, often for about eight minutes. Next, record the sequence of arm entries, counting an entry when all four paws are inside the arm. Then, for the two-trial version, block one arm in the first trial, then open it after a delay. Finally, clean the maze between animals to remove odour cues.

Strengths and limits

Why do labs keep coming back to it? No training and no food restriction. Quick, and kind to the animals. Pairs well with other tests in a battery. And the catch? Low activity means few entries and noisy scores. Entry rules must be fixed, or scores vary between labs. Odour and room cues can guide choices.

What to measure

Now for the numbers, my favourite bit. Spontaneous alternation percentage: alternations divided by the total entries minus two, times one hundred. Total arm entries: a check on activity, because alternation needs enough entries. Novel arm time in the two-trial version: preference for the arm that was blocked. Arm sequence: to spot fixed turning habits that can fake alternation. Two mice both alternate 70 percent of the time. One made 30 entries; the other made 8. The second score rests on so few choices that it's barely worth reading.

The takeaway

One thing to take away: total arm entries and its neighbours tell you how the task was done, not just how fast. Scripts, chapters and sources live on this page.