Brown Institute for Brain Science

Novel Object Identity

  1. novel_object_id_1
  2. novel_object_id_2

Rationale of Test

This task is similar to the human delayed non-match to sample task, and uses the novelty preference to assess an animals ability to detect when an object in their environment is new. This task is typically used to assess short-term and long-term memory (working or prefrontal memory function).

Apparatus

The novel object placement apparatus consists of an open field made with a white Plexiglas arena (40 X 40 X 49 cm). The arena is digitally divided into 12 equal quadrants. The corners nearest the center of the northeast, northwest, southeast, and southwest corners serves as placement locations for the objects, which are toy trees made out of LEGO blocks (4.8 cm X 4.8 cm X 7 cm), cylindrical pencil sharpeners, or saki cups. Large stickers of differing shape and color are placed on the walls of the arena to provide spatial orienting cues. The arena is set up under an overhead digital camera connected to a computer with digitizer card and automated tracking software.

Procedure

On Day 1 (habituation) of the novel object placement task, a single mouse is placed in the center of the open field and behavior is recorded for 10 min and analyzed to confirm that there is no differences in anxiety-related behavior (as measured by avoidance of the center quadrants) or preference for one region of the arena over another. The arena is cleaned with a 70% ethanol solution and dried in between each subject so as to eliminate any potential odor cues left by previous subjects. On Day 2 of the task, the two identical objects are placed at adjacent northern locations of the arena and a single mouse is placed into the center of the arena. Behavior is recorded for 5 min and the time spent investigating each of the objects is measured. After the 5-min exploration period, (Trial 1 or T1), subjects are removed from the area and placed singly into a holding cage while both the arena and objects are cleaned and dried with 70% ethanol. One object is returned immediately to its former location, while a new object is placed in the place of the previously placed object. Placement of the objects is counterbalanced across both trials and subjects. After a predefined period of time, the same mouse is returned to the arena and time spent exploring each object is recorded and analyzed for the second trial, (Trial 2 or T2). A T2 Fraction is calculated by dividing the amount of time spent exploring the novel object divided by the amount of time spent exploring both objects (T2 = ((Time Novel)/(Time Old + Time Novel)) X 100), such that mice were successful at the task if they spent significantly more time than chance (50%) exploring the novel object. On Day 3, the task can be repeated with a different interval in between T1 and T2 and possibly different stimulus objects.

Interpretation

Successful performance at the task is assessed by relative exploration of the novel object relative to total exploration for both objects. Impairments in either novelty preference or memory are indicated if there is no preference for the novel object.

Relevant Controls

Care should be taken to insure no differences in anxiety-like behavior between groups or alterations in locomotor activity.

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