Distributed brain networks govern adaptive decision-making, new learning and rapid updating of information. However, the functional contribution of the rhesus macaque monkey parvocellular nucleus of the mediodorsal thalamus (MDpc) in these key higher cognitive processes remains unknown. This study investigated the impact of MDpc damage in cognition. Preoperatively, animals were trained on an object-in-place scene discrimination task that assesses rapid learning of novel information within each session. Bilateral neurotoxic (NMDA and ibotenic acid) MDpc lesions did not impair new learning unless the monkey had also sustained damage to the magnocellular division of the MD (MDmc). Contralateral unilateral MDpc and MDmc damage also impaired new learning, while selective unilateral MDmc damage produced new learning deficits that eventually resolved with repeated testing. In contrast, during food reward (satiety) devaluation, monkeys with either bilateral MDpc damage or combined MDpc and MDmc damage showed attenuated food reward preferences compared to unoperated control monkeys; the selective unilateral MDmc damage left performance intact. Our preliminary results demonstrate selective dissociable roles for the two adjacent nuclei of the primate MD, namely, MDpc, as part of a frontal cortical network, and the MDmc, as part of a frontal-temporal cortical network, in learning, memory and the cognitive control of behavioural choices after changes in reward value. Moreover, the functional cognitive deficits produced after differing MD damage show that the different subdivisions of the MD thalamus support distributed neural networks to rapidly and fluidly incorporate task-relevant information, in order to optimise the animals' ability to receive rewards.

The frontal cortex and temporal lobes together regulate complex learning and memory capabilities. Here, we collected resting-state functional and diffusion-weighted MRI data before and after male rhesus macaque monkeys received extensive training to learn novel visuospatial discriminations (reward-guided learning). We found functional connectivity changes in orbitofrontal, ventromedial prefrontal, inferotemporal, entorhinal, retrosplenial, and anterior cingulate cortices, the subicular complex, and the dorsal, medial thalamus. These corticocortical and thalamocortical changes in functional connectivity were accompanied by related white matter structural alterations in the uncinate fasciculus, fornix, and ventral prefrontal tract: tracts that connect (sub)cortical networks and are implicated in learning and memory processes in monkeys and humans. After the well-trained monkeys received fornix transection, they were impaired in learning new visuospatial discriminations. In addition, the functional connectivity profile that was observed after the training was altered. These changes were accompanied by white matter changes in the ventral prefrontal tract, although the integrity of the uncinate fasciculus remained unchanged. Our experiments highlight the importance of different communication relayed among corticocortical and thalamocortical circuitry for the ability to learn new visuospatial associations (learning-to-learn) and to make reward-guided decisions.

Highlights Refining training for monkeys in neuroscience is essential to optimise their welfare. Refinements still produce high quality science. Pair- or group-training monkeys helps acclimate them quicker to transport devices. Commencing positive reinforcement training on arrival facilitates acclimation. Negative reinforcement techniques used effectively are also sometimes necessary.

Highlights A non-human primate protective head cap that promotes wound healing after cranial implants. Use of the head cap reduced wound dehiscence and the need to re-suture surgical wounds. The head cap is easily adjustable to cover most primate cranial implants. The head cap facilitates primate cranial implant wound management in neuroscience.

A prospective clinical trial was conducted to evaluate the efficacy of a collagen-alginate wound dressing in the postoperative management of chemical matricectomies. The study involved 20 patients and 23 separate procedures. The collagen-alginate-dressing treatment group had an average healing time of 24.4 days, compared with 35.8 days for the control group, which received treatment consisting of soaks and daily dressing changes (P < .05). The authors suggest that using a collagen-alginate wound dressing in the postoperative management of chemical matricectomies will shorten healing time, thus reducing infection rates and increasing patient compliance and satisfaction.