Marble burying is used as an assay to infer compulsive, anxiety-like behavior and is widely used as a model of obsessive-compulsive disorder (Broekkamp et al., 1986; Njung'e and Handley, 1991a, b). In this test, a mouse is placed into a clean cage filled with a level layer of bedding, covered with glass marbles. The marbles are disturbed and become covered as the mouse digs into the bedding. Thus, the number of marbles buried correlates with the frequency of digging bouts (Deacon, 2006; Thomas et al., 2009). As with other models of anxiety, marble burying is decreased by traditional anxiolytics, such as benzodiazepines (Broekkamp et al., 1986; Njung'e and Handley, 1991b). Marble burying offers advantages over exploratory models in that it measures a repetitive, possibly goal-directed form of anxiety, such as obsessive-compulsive disorder. Importantly, mice do not readily habituate to the assay (Thomas et al., 2009), making within-subjects designs possible and thereby reducing overall animal numbers.
