Corticocortical and Thalamocortical Changes in Functional Connectivity and White Matter Structural Integrity after Reward-Guided Learning of Visuospatial Discriminations in Rhesus Monkeys.

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.SIGNIFICANCE STATEMENT Frontal neural networks and the temporal lobes contribute to reward-guided learning in mammals. Here, we provide novel insight by showing that specific corticocortical and thalamocortical functional connectivity is altered after rhesus monkeys received extensive training to learn novel visuospatial discriminations. Contiguous white matter fiber pathways linking these gray matter structures, namely, the uncinate fasciculus, fornix, and ventral prefrontal tract, showed structural changes after completing training in the visuospatial task. Additionally, different patterns of functional and structural connectivity are reported after removal of subcortical connections within the extended hippocampal system, via fornix transection. These results highlight the importance of both corticocortical and thalamocortical interactions in reward-guided learning in the normal brain and identify brain structures important for memory capabilities after injury.

Macaque parvocellular mediodorsal thalamus: dissociable contributions to learning and adaptive decision-making.

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.

An Update on Male Canine Infertility.

Infertility in the dog is a common reason for presentation of stud dogs for assessment with veterinarians. This article aims to discuss and outline some of the tests that can be done to try to ascertain the underlying cause of abnormalities found in a semen assessment. Topics discussed are semen alkaline phosphatase measurement, retrograde ejaculation assessment, ultrasound of the male reproductive tract, semen culture, human chorionic gonadotropin response testing, dietary assessment for phytoestrogens, environmental impacts on spermatogenesis, testicular biopsy, supplements to improve semen quality and quantity, and when to expect an improvement in semen quality after starting treatment.

Protective cranial implant caps for macaques.

BACKGROUND: Neuroscience studies with macaque monkeys may require cranial implants to stabilize the head or gain access to the brain for scientific purposes. Wound management that promotes healing after the cranial implant surgery in non-human primates can be difficult as it is not necessarily possible to cover the wound margins. NEW METHOD: Here, we developed an easily modifiable head cap that protects the sutured skin margins after cranial implant surgery and contributes to wound healing. The protective head cap was developed in response to monkeys picking at sutured skin margins around an implant, complicating healing. The user-friendly protective cap, made from Klarity- R™ Sheet (3.2 mm thick with 36 % or 42 % perforation) is affixed to the implant post-surgically. Once secured and while the monkey is still anesthetized, the plastic sheeting is molded around the implant. The protective head cap restricts the monkey's finger access to its' wound margins while allowing air to circulate to promote wound healing. RESULTS AND COMPARISON WITH EXISTING METHODS: Across two UK primate facilities, the protective head cap promoted wound healing. In monkeys that did not wear the head cap, re-suturing was necessary in ∼30 % of cases. In contrast, none of the monkeys that wore the head cap required re-suturing. The monkeys wearing the head cap also had reduced numbers of days of prescribed antibiotics and analgesia. CONCLUSION: This bespoken, easily adaptable, protective head cap supports postoperative wound healing, and enhances the welfare of monkeys involved in neuroscience research.

Effective chair training methods for neuroscience research involving rhesus macaques (Macaca mulatta).

BACKGROUND: Neuroscience research using macaques remains fundamental in our endeavours to understand how the human brain functions. Applying the refinement principle of the 3Rs is essential to optimise the monkeys' welfare and still produces high quality science. NEW METHOD: Here we document refinements in our training methods for acclimation to transport devices (i.e. primate chair or transport box) while working with 46 male rhesus macaques. Our training methods always used positive reinforcement training (PRT). However, PRT was sometimes combined with negative reinforcement training (NRT), but not pole and collar techniques, to successfully transfer each monkey from its home enclosure to its transport device. RESULTS AND COMPARISON WITH EXISTING METHODS: Training monkeys in pairs or groups, and starting their PRT training upon arrival within the unit reduced the days required to acclimate them. While the use of PRT is essential to establish a positive relationship with monkeys, NRT techniques are sometimes necessary, and are most effective when withdrawn immediately once the monkey makes the desired response, to reduce the days of acclimation. Once acclimatised to their chair, monkeys succeeded within 10 days to present their head voluntarily for neck-plating using PRT. Space reducers inside the chairs also facilitated head presentations for some monkeys. CONCLUSIONS: Acclimating (shaping) the monkeys to transport devices can be a stressful experience for monkeys and trainers. The adaptations to our training substantially reduced the days spent on this stage. We view this reduction in days as an effective implementation of the 3Rs (refinement) in monkey neuroscience research.

Current Review of Artificial Insemination in Dogs.

Artificial insemination is the collection of semen from the male and the subsequent insertion of the collected semen into the female. Artificial insemination may be requested for several reasons, including inability to achieve a mating or due to the use of fresh chilled or frozen semen. A good understanding of the cycle of the bitch is imperative for maximizing pregnancy rates, as poor timing of insemination is the most common cause of subfertility in the bitch. Insemination techniques commonly undertaken in the bitch include vaginal insemination, surgical intrauterine insemination, and transcervical insemination.