Back to basics: A methodological perspective on marble-burying behavior as a screening test for psychiatric illness

A critical inquiry into marble-burying as a preclinical screening paradigm of relevance for anxiety and obsessive–compulsive disorder: Mapping the way forward

“…Since marble-burying behavior may partly be driven by an inherent need for investigation, the novelty of burying substrates may trigger natural exploratory activity, in the form of digging and burrowing, and may therefore influence the number of marbles being covered (Gyertyán, 1995;Thomas et al, 2009). Although bolstered burying activity under novel circumstances has been demonstrated previously (Schultz, 1972), an influence of novelty-induced anxiety with respect to unfamiliar bedding or marbles has also largely been excluded (Gyertyán, 1995;Thomas et al, 2009), providing further support that marbles are often covered as a coincidental effect of normal exploratory behaviors (de Brouwer & Wolmarans, 2018;Gyertyán, 1995;Njung'e & Handley, 1991b;Thomas et al, 2009). However, to exclude the possible effects of novel cage exploration on burying outcomes, it is important to consider adequate habituation with the burying substrates before the onset of behavioral analysis.…”

“…Although burying behavior, as an intentional outcome of digging, may bear face resemblance to digging or burrowing, burying refers to the concerted effort to either cover a particular object with substrate (De Almeida, De Carvalho, Silva, De Sousa, & De Freitas, 2014;De Boer & Koolhaas, 2003;Kinsey, O'Neal, Long, Cravatt, & Lichtman, 2011;Pinel & Treit, 1978;Poling et al, 1981) or displace an object beneath any available substrate by means of digging in proximity to it (de Brouwer & Wolmarans, 2018;Gyertyán, 1995). Rodents have been shown to bury a number of objects, including food (Jenkins & Breck, 1998), marbles (Taylor et al, 2017), live scorpions (Londei, Valentini, & Leone, 1998), rodent chow (either contaminated or uncontaminated; Poling et al, 1981), electrified probes (Treit, 1990), mouse traps (Linfoot et al, 2009), flashing cubes, and air-blasting tubes (Terlecki, Pinel, & Treit, 1979).…”

“…However, investigations into phenotypic differences between the burying behaviors elicited by nonaversive and aversive objects have yielded inconsistent results (Londei et al, 1998;Poling et al, 1981;Terlecki et al, 1979). Collectively, the findings demonstrate that although rodents may initially express increased burying behavior toward potentially harmful, as compared to nonharmful, objects (De Boer & Koolhaas, 2003;Londei et al, 1998;Poling et al, 1981), burying behavior in general is primarily triggered by an investigative drive that is subject to habituation (Broekkamp et al, 1986;de Brouwer & Wolmarans, 2018;Poling et al, 1981;Thomas et al, 2009). It can therefore be concluded that the burying activity engaged in by rodents is a robust, naturally occurring behavior that, although initially modifiable by the nature of the stimulus, is displayed by all animals and is not dependent on a contextual trigger.…”

“…2b; weighed and calculated at 1.65 g/cm 3 ; de Brouwer & Wolmarans, 2018)are generally more resistant to the effects of normal exploration, and therefore may be better suited as appropriate substrates in which to carry out the MBT ( Supplementary Fig. 3a vs. 3b; Angoa-Pérez et al, 2013;de Brouwer & Wolmarans, 2018;Jimenez-Gomez et al, 2011).…”

“…Furthermore, as opposed to 1Z setups, the behaviors in a 2Z paradigm more appropriately reflect goal-directed interaction while also being reflective of definite avoidance behavior. Interestingly, with few exceptions (see, e.g., Schneider & Popik, 2007), most 2Z investigations have failed to demonstrate passive avoidance of marbles (Broekkamp et al, 1986;de Brouwer & Wolmarans, 2018;Kaehler, Singewald, Sinner, & Philippu, 1999;Nicolas et al, 2006;Njung'e & Handley, 1991b;Thomas et al, 2009). That said, these findings also do not indicate active neutralizing interaction with marbles, in that animals often spend equal time in both zones of the arena, regardless of the duration of the experiment, even if the two zones are separated by a divider (Nicolas et al, 2006;Njung'e & Handley, 1991b;Savy et al, 2015;Thomas et al, 2009;Torres-Lista et al, 2015).…”