This task is similar in logic to the Novel Object Recognition Task as it exploits the natural tendency of most mammals to pay greater attention to novelty than to familiarity. Instead of memory for object identity, however, this task assesses the memory for the location of objects.

In our lab, there are typically three phases in an object location recognition experiment – Habituation, Sampling, and Probe.

1. Habituation. We familiarize the rats four times to the open field, once per day for four consecutive days. There are no objects in the open field during Habituation.
2. Sampling. We typically use two identical copies of an object and place them into opposing corners during the Sampling trials. The location of the objects are constant. The number and the duration of the Sampling trials depends on the experimental question.
3. Probe. One of the objects is moved to a new place, the other one stays where it was during Sampling. Typically, we move the object from a corner to the middle of a wall, i.e., midway between two corners.

If the animal recognizes that the object moved to a new location, we expect it to explore it more than the object at the familiar location.

Similar to the novel object recognition task, many variables of this protocol can be modified, such as the number of trials in each phase and their dureation, memory retention interval, how many objects are in the open field, and how many of them are moved.

We record all phases on video with cameras mounted above the open field. There are never other animals or an experimenter in the room while a rat is in the open field during a trial. Trained observers score animal behaviour, i.e., the time they explore objects, from the recorded videos. The data are then used to calculate the novelty preference index DI=[(time exploring object at novel location)-(time exploring object at familiar location)]/(time exploring both). DI=0 indicates that both object locations were explored the same, i.e., the absence of preference or the behaviour that would be expected by chance alone. Di>0 indicates that the object moved to a novel location was explored more than the one that did not change its position, and DI<0 indicates the opposite. To determine whether DI is significantly different from what would be expected by chance alone, a one-sample t-test comparing DI against 0 can be used.

Our detailed protocols are available at the SOP section.