Brown Institute for Brain Science

Marble Burying

Rationale of Test

The marble burying task can be used both as an indicator of obsessive compulsive-like (OCD) behavior and/or anxiety-like behavior. When mice are placed in a novel cage, a common response is to show increased digging behavior. Mice with OCD-like symptoms tend to engage in a high degree of repetitive behaviors (including digging). Mice with a high degree of anxiety tend to engage in a high degree of digging in novel contexts (potentially as a means to attempt to escape the new cage).

Apparatus

Testing is carried out in a standard shoebox cage (26 x 16 x 14mm) filled to about a 5cm depth with wood chip or corn cob bedding and covered with a bonnet top. Wire mesh cage top should not be used during testing to eliminate the possibility of climbing during the test. Prior to placing the mouse in the testing cage, twenty opaque (black or blue) glass marbles (14mm diameter) are evenly spaced on top of the bedding material.

Procedure

The procedure is adapted with minor modifications from that described by Deacon 2006. Briefly, mice are placed individually in the shoebox cage and left in the cage with marbles for a 30-min period. The mouse is then carefully removed from the cage to terminate the test. An overhead photograph is taken of the cage, converted to grayscale in Photoshop and imported into imageJ. The dimension of an uncovered marble are measured using the particle analyze function. Using the uncovered marble as a baseline, the image of the interior of the cage is thresholded and the particle analyze function is used to count the number of marbles in which greater than 33% of the area are covered with bedding.

Interpretation

Mice that engage that are more OCD-like or high anxiety, tend to dig in the bedding more, and end up covering a greater percentage of the marbles. Thus, the greater number of marbles covered is used as an indicator of heightened OCD or anxiety-like behavior.

Relevant Controls

Care should be taken to insure no gross motor differences between groups.

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