Distinct Functions of the Primate Putamen Direct and Indirect Pathways in Adaptive Outcome-Based Action Selection

Cortico-basal ganglia circuits are critical regulators of reward-based decision making. Reinforcement learning models posit that action reward value is encoded by the firing activity of striatal medium spiny neurons (MSNs) and updated upon changing reinforcement contingencies by dopamine (DA) signaling to these neurons. However, it remains unclear how the anatomically distinct direct and indirect pathways through the basal ganglia are involved in updating action reward value under changing contingencies. MSNs of the direct pathway predominantly express DA D1 receptors and those of the indirect pathway predominantly D2 receptors, so we tested for distinct functions in behavioral adaptation by injecting D1 and D2 receptor antagonists into the putamen of two macaque monkeys performing a free choice task for probabilistic reward. In this task, monkeys turned a handle toward either a left or right target depending on an asymmetrically assigned probability of large reward. Reward probabilities of left and right targets changed after 30-150 trials, so the monkeys were required to learn the higher-value target choice based on action-outcome history. In the control condition, the monkeys showed stable selection of the higher-value target (that more likely to yield large reward) and kept choosing the higher-value target regardless of less frequent small reward outcomes. The monkeys also made flexible changes of selection away from the high-value target when two or three small reward outcomes occurred randomly in succession. DA D1 antagonist injection significantly increased the probability of the monkey switching to the alternate target in response to successive small reward outcomes. Conversely, D2 antagonist injection significantly decreased the switching probability. These results suggest distinct functions of D1 and D2 receptor-mediated signaling processes in action selection based on action-outcome history, with D1 receptor-mediated signaling promoting the stable choice of higher-value targets and D2 receptor-mediated signaling promoting a switch in action away from small reward outcomes. Therefore, direct and indirect pathways appear to have complementary functions in maintaining optimal goal-directed action selection and updating action value, which are dependent on D1 and D2 DA receptor signaling

Layered double hydroxide supported cobalt nanocluster: size control and the effect in catalytic hydrogen generation

Synthesizing metal nanoclusters with diameters smaller than 5nm is challenging, but desirable because of the high ratio of surface area to interior atom. However, in this report it was achieved by utilizing magnesium-aluminium layered double hydroxide (Mg/Al-LDH) as a host for cobalt citrate anion precursor, which was later reduced into cobalt nanoclusters (Co-NC). Size of the Co-NC was controlled by changing the concentration of cobalt-citrate (Co-citrate) precursor during anion exchange. XRD and FTIR showed that Co-citrate precursor was successfully intercalated on the LDH while nitrogen adsorption/desorption isotherms confirmed that mesopores in the sample were formed after chemical reduction. Furthermore, TEM/STEM observations confirmed the formation of Co-NC. It was also verified that reducing the concentration of Co-citrate from 4mM to 0.5mM resulted in a reduction in the size of Co-NC from 4.4 to 1.3 nm. However, catalytic hydrogen generation from sodium borohydride (NaBH4) hydrolysis experiment indicated that catalytic activity decreased as the size of Co-NC decreases. This is mainly attributed to the limitation in mass transport within the interlamellar space of the smaller cluster LDH compared to the bigger one. Overall, Co-NC-LDH is a promising catalyst for NaBH4 hydrolysis. However, an optimum Co-NC size is critical for enhanced catalytic activity

Activation on Ammonia Absorbing Reaction for Magnesium Chloride

Hexa-ammine complex (Mg­(NH₃)₆Cl₂) is directly formed at room temperature by the reaction between magnesium chloride (MgCl₂) and ammonia (NH₃) without formation of mono- and diammine complexes (Mg­(NH₃)­Cl₂ and Mg­(NH₃)₂Cl₂) even though these are more stable phases. The high kinetic barrier exists for the formation of low coordinated ammine complexes. The activation by using heat treatment and ball milling is carried out, and then the NH₃ absorption properties are investigated to understand kinetic properties of the ammine complexes formation of MgCl₂. At 373 K, the formation of Mg­(NH₃)₂Cl₂ is realized. Furthermore, it is found that a higher temperature than 573 K is required to form Mg­(NH₃)­Cl₂. Interestingly, the ball milled MgCl₂ can transform into low coordinated ammine complexes even at room temperature, indicating that the structural disorder state generated by the ball milling induces the formation of the above phases with low activation energy. Therefore, it is expected that the kinetic barrier to form ammine complexes of MgCl₂ is strongly related to the process on the structural change

Prolonged bioluminescence monitoring in mouse ex vivo bone culture revealed persistent circadian rhythms in articular cartilages and growth plates.

The bone is a metabolically active organ which undergoes repeated remodeling cycles of bone resorption and formation. In this study, we revealed a robust and extremely long-lasting circadian rhythm in ex vivo culture maintained for over six months from the femoral bone of a PERIOD2(Luciferase) mouse. Furthermore, we also identified robust circadian clocks in flat bones. High- or low-magnification real-time bioluminescence microscopic imaging revealed that the robust circadian rhythms emanated from the articular cartilage and the epiphyseal cartilage within the growth plate of juvenile animals. Stimulation by forskolin or dexamethasone treatment caused type 0 phase resetting, indicating canonical entraining properties of the bone clock. Together, our findings from long-term ex vivo culture revealed that "tissue-autonomous" circadian rhythm in the articular cartilage and the growth plate of femoral bone functions for several months even in an organ culture condition, and provided a useful in vitro assay system investigating the role of the biological clock in bone formation or development