Abstract
Two-photon imaging in behaving animals has revealed neuronal activities related to behavioral and cognitive function at single-cell resolution. However, marmosets have posed a challenge due to limited success in training on motor tasks. Here we report the development of protocols to train head-fixed common marmosets to perform upper-limb movement tasks and simultaneously perform two-photon imaging. After 2–5 months of training sessions, head-fixed marmosets can control a manipulandum to move a cursor to a target on a screen. We conduct two-photon calcium imaging of layer 2/3 neurons in the motor cortex during this motor task performance, and detect task-relevant activity from multiple neurons at cellular and subcellular resolutions. In a two-target reaching task, some neurons show direction-selective activity over the training days. In a short-term force-field adaptation task, some neurons change their activity when the force field is on. Two-photon calcium imaging in behaving marmosets may become a fundamental technique for determining the spatial organization of the cortical dynamics underlying action and cognition.
Highlights
Two-photon imaging in behaving animals has revealed neuronal activities related to behavioral and cognitive function at single-cell resolution
When such imaging is combined with a genetically encoded calcium indicator (GECI), it allows the detection of long-term plasticity and stability in the activity of individual neurons during motor learning and sensory experience in rodents[1,2,3,4,5], and can do so in a layer- and cell type-specific manner
To ensure efficient learning of the association between the manipulandum position and the reward delivery[29], we introduced an L-shape spout pole, the bottom of which was attached to the X–Y slide table, and the top of which delivered a drop of juice (Fig. 5a)
Summary
Two-photon imaging in behaving animals has revealed neuronal activities related to behavioral and cognitive function at single-cell resolution. We previously established a two-photon calcium imaging technique for the neocortex of anesthetized head-fixed marmosets, and succeeded in detecting neuronal responses to upper-limb stimuli at cellular and subcellular resolutions[21]. It is less dexterous than the macaque, the marmoset possesses a large behavioral repertoire[20]. The only behavioral tasks that have previously been reported for the headfixed marmoset are saccade and licking tasks[25,26], and the teaching of upper-limb movement tasks to head-fixed marmosets is considered to be difficult[26] To address this issue, we developed a novel behavioral apparatus, which restrains the marmoset in a chair, and trained the animal to control a two-dimensional (2D) manipulandum to move a cursor on a monitor. We demonstrate that head-fixed marmosets can learn internally triggered and external stimulus-triggered reaching tasks, and that neuronal a
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