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Electrophysiological implants enable exploration of the relationship between neuronal activity and behavior. These technologies evolve rapidly, with multiple iterations of recording systems developed and utilized. Chronic implants must address a litany of complications, including retention of high signal-to-noise ratio in probes and the ability to withstand excess force over the experimental period. To overcome these issues, we designed a chronic implant for rats. Our comprehensive protocol optimizes the entire implant process, from assembling and testing the probes (Neuropixels) to implantation. In addition to addressing the complications previously mentioned, our implant can vertically adjust probes with micron precision and is con- structed using modular components, allowing it to be easily modified for various research contexts, electro- physiological recording systems, headstages, and probe types. 

Abstract Optimal decision-making requires consideration of internal and external contexts. Biased decision-making is a transdiagnostic symptom of neuropsychiatric disorders. We created a computational model demonstrating how the striosome compartment of the striatum constructs a context-dependent mathematical space for decision-making computations, and how the matrix compartment uses this space to define action value. The model explains multiple experimental results and unifies other theories like reward prediction error, roles of the direct versus indirect pathways, and roles of the striosome versus matrix, under one framework. We also found, through new analyses, that striosome and matrix neurons increase their synchrony during difficult tasks, caused by a necessary increase in dimensionality of the space. The model makes testable predictions about individual differences in disorder susceptibility, decision-making symptoms shared among neuropsychiatric disorders, and differences in neuropsychiatric disorder symptom presentation. The model provides evidence for the central role that striosomes play in neuroeconomic and disorder-affected decision-making. 

Our internal and external environments are not stable; these ever-changing contexts produce stress on bodily systems. In response, the body recruits numerous peripheral hormones to bring those systems back within a desired homeostatic range. When our environments change in extreme ways and for prolonged periods of time, a different set of hormonal stress responses are recruited. These chronic stress responses produce adaptive changes but can also drive maladaptation. This chapter begins by reviewing the peripheral hormones that are recruited as part of the acute stress response and describing their adaptive impact on brain and peripheral function. We then examine new research describing the role of ghrelin, a hormone produced by the gut, in chronic stress. We review the role of ghrelin in hunger and consider how energy deficiency, a state shared by both hunger and stress, might explain why ghrelin is elevated by both. We consider how the unique recruitment of ghre- lin during chronic stress mediates responses in the brain that can help an organism respond to future stressors, but also how chronic eleva- tion of ghrelin can produce additional adapta- tions that contribute to stress-sensitive psychiatric disorders. Lastly, we identify important future areas for research on the biol- ogy of ghrelin. 

Optimal decision-making requires consideration of internal and external contexts. Biased decision-making is a transdiagnostic symptom of neu- ropsychiatric disorders. We created a computational model demonstrating how the striosome compartment of the striatum constructs a context- dependent mathematical space for decision-making computations, and how the matrix compartment uses this space to define action value. The model explains multiple experimental results and unifies other theories like reward prediction error, roles of the direct versus indirect pathways, and roles of the striosome versus matrix, under one framework. We also found, through new analyses, that striosome and matrix neurons increase their synchrony during difficult tasks, caused by a necessary increase in dimensionality of the space. The model makes testable predictions about individual differences in disorder susceptibility, decision-making symptoms shared among neuropsychiatric disorders, and differences in neuropsychiatric disorder symptom presenta- tion. The model provides evidence for the central role that striosomes play in neuroeconomic and disorder-affected decision-making. 

Abstract AimsWe sought to explore how acute alcohol exposure alters decision-making in rats performing an approach-avoid decision-making task. Increasing concentrations of alcohol were mixed with decreasing concentrations of sucrose to mimic mixed/sweetened alcoholic beverages. MethodsRats were trained on an apparatus in which different concentrations of sucrose were available in four different corners of the arena. During daily sessions, a tone signaled each trial start, followed by illumination (15 lux, blue LEDs) of a single corner port, indicating the potential availability of sucrose at that location. The rat (one rat per arena, both females and males) then chose to approach the lit corner to have the solution dispensed or avoid it, with no solution being dispensed. We examined how the decisions to pursue sucrose rewards shifted with the addition and subsequent removal of ethanol from the sucrose ports. ResultsMales were greatly affected by the introduction of alcohol into the task environment, shifting their approach preference to solutions containing higher alcohol concentrations rather than maintaining the prior preference for high-sucrose-concentration solutions. In contrast, females’ choice patterns and task performance remained largely unchanged. We also explore a method for identifying changes in decision-making tendencies during and after alcohol consumption within individual subjects. ConclusionsThis research explores the introduction of alcohol in varying concentrations with sucrose solutions during an approach-avoid task, with male decision-making and behavioral patterns significantly impacted. We also explore a novel approach for identifying individual adaptations of decision-making behavior when alcohol becomes available, which could be expanded upon in future research.