Use of horizontal and vertical climbing structures by captive common marmosets (Callithrix jacchus)

Differential Ageing of the Brain Hemispheres: Evidence from a Longitudinal Study of Hand Preferences in Common Marmosets

This paper is concerned with decreasing asymmetry of motor control in ageing. It discusses age-related changes in humans and reports a longitudinal study of hand preferences in common marmosets. An annual assessment of hand preference for holding food was recorded throughout the lifespan of 19 marmosets that lived for at least 9 years, and half of those lived for at least 11 years. Those with a left-hand preference showed a gradual reduction in the strength of their hand preference throughout adult life. No significant change in the strength of hand preference was found in right-handed marmosets. Hence, ageing has a specific effect on motor control by the right hemisphere.

Spectral Power in Marmoset Frontal Motor Cortex during Natural Locomotor Behavior

During primate arboreal locomotion, substrate orientation modifies body axis orientation and biomechanical contribution of fore- and hindlimbs. To characterize the role of cortical oscillations in integrating these locomotor demands, we recorded electrocorticographic activity from left dorsal premotor, primary motor, and supplementary motor cortices of three common marmosets moving across a branch-like small-diameter pole, fixed horizontally or vertically. Animals displayed behavioral adjustments to the task, namely, the horizontal condition mainly induced quadrupedal walk with pronated/neutral forelimb postures, whereas the vertical condition induced walk and bound gaits with supinated/neutral postures. Examination of cortical activity suggests that β (16–35 Hz) and γ (75–100 Hz) oscillations could reflect different processes in locomotor adjustments. During task, modulation of γ ERS by substrate orientation (horizontal/vertical) and epoch (preparation/execution) suggests close tuning to movement dynamics and biomechanical demands. β ERD was essentially modulated by gait (walk/bound), which could illustrate contribution to movement sequence and coordination. At rest, modulation of β power by substrate orientation underlines its role in sensorimotor processes for postural maintenance.

Head-cocking as a form of exploration in the common marmoset and its development

Head-cocking of 15 infant marmosets (Callithrix jacchus) was scored from Day 1 to 60 of postnatal life, the growth period with overproduction of interneuronal synapses. Head-cocking was scored during four 30 min intervals daily, including angle of head-cocking and objects being fixated. Mean age of onset of head-cocking was Day 13 (+/-1.3) and frequency increased to a fixed rate by Day 24-29, at the time of maturation of the foveal representation in layer 6 of the visual cortex, thus lending further support to the importance of head-cocking to visual processing. The most common distance of objects fixated during head-cocking was up to .5 m. Angle of head-cocking increased with age, and some asymmetry of direction was noted. Fewer head-cocking events occurred in the morning than in the afternoon. We also scored anogenital licking of offspring. Head-cocking occurred at higher levels in marmosets receiving more anogenital licking. As this was associated positively with increased exploration, head-cocking may be regarded as an exploratory behavior.