Quantification of three-dimensional exploration in the cylinder test by the common marmoset (Callithrix jacchus).

The increasing trend in use of marmoset monkeys in behavioral studies has necessitated a greater understanding of their natural behavior, especially within confined spatial environments. One way to approach this issue is to examine locomotor and exploratory strategies using the cylinder test, as done recently for the rat by Gharbawie et al. [Gharbawie OA, Whishaw PA, Whishaw IQ. The topography of three-dimensional exploration: a new quantification of vertical and horizontal exploration, postural support, and exploratory bouts in the cylinder test. Behav Brain Res 2004;151:125-35]. We have used this paradigm in conjunction with Eshkol-Wachmann movement analysis in marmoset monkeys. We provide evidence that marmosets display systematic changes in both horizontal and vertical progressions during exploration. Quantitative analysis and comparison with the extant data in rats showed both similarities and differences. For example, both species display horizontal and vertical scanning movements, although the variability is considerably greater for the marmoset. The horizontal progressions consist of head scans, turning, and stepping. The amplitude of these progressions oscillates and decreases with trial duration. Vertical progressions, which consist of rears, head scans, and descent, also strongly oscillate but with constant mean amplitude during a trial. The difference between the two species is most evident in locomotor behavior. Rats use their forepaws primarily for postural support and follow forequarter movements while body weight shifts are generated by the hind limbs. Marmosets, however, can hold a vertical position without hand support and display more complex movement characteristics during exploration. The data from this study should be of use in designing experiments in which marmosets are engaged in free-roaming behavior within a confined space.