Spatial object recognition

The question

Today's maze is all about choices. How do we test whether an animal remembers where an object was, not just what it looked like? You're watching Morris Water Maze Software Guide, over at morriswatermazesoftware.com.

Meet the spatial object recognition

Spatial object recognition, also called object location memory, uses the same curiosity as novel object recognition, but what changes is place, not identity. After the animal explores two or more objects, one object is moved to a new location. More time at the moved object means the animal remembers where things were. That spatial judgement leans more on the hippocampus than a simple new-versus-old object test.

How it runs

The recipe is short. First, habituate the animal to the empty arena, with clear room cues. Next, run a sample phase with two or more identical objects in fixed places. Then, after a set delay, move one object to a new location, leaving the others where they were. Finally, score exploration of the moved and unmoved objects, usually when the nose is close to and pointing at an object.

Strengths and limits

Why do labs keep coming back to it? No food restriction or punishment. It tests memory for place with a short, gentle session. The delay can be set to probe short or longer-term memory. And the catch? Objects must be equally easy to explore and impossible to climb or move. Weak exploration makes the preference score unreliable.

What to measure

Now for the numbers, my favourite bit. Discrimination index: time at the moved object minus time at the unmoved one, divided by the total. Total exploration time: a check on motivation. Time at the moved location versus the old empty location: whether the animal notices the change. Time slices: preference often fades as the new arrangement becomes familiar. A mouse spends most of the test licking both objects equally. That looks like forgotten locations. But total exploration is only a few seconds, so the score is noise, not a memory result.

The takeaway

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