Neuroscience
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Randomized Controlled Trial
Short-term immobilization influences use-dependent cortical plasticity and fine motor performance.
Short-term immobilization that reduces muscle use for 8-10h is known to influence cortical excitability and motor performance. However, the mechanisms through which this is achieved, and whether these changes can be used to modify cortical plasticity and motor skill learning, are not known. The purpose of this study was to investigate the influence of short-term immobilization on use-dependent cortical plasticity, motor learning and retention. ⋯ Furthermore, training-related MEP facilitation was greater after, compared with before, immobilization. These results indicate that immobilization can modulate use-dependent plasticity and the retention of motor skills. They also suggest that changes in intracortical excitability are unlikely to contribute to the immobilization-induced modification of cortical excitability.
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The amygdala has been associated with a variety of functions linked to physiological, behavioral and endocrine responses during emotional situations. This brain region is comprised of multiple sub-nuclei. These sub-nuclei belong to the same structure, but may be involved in different functions, thereby making the study of each sub-nuclei important. ⋯ In contrast, the BMA chemical activation by the bilateral microinjection of bicuculline methiodide (BMI; GABAA antagonist), blocked the increases in MAP and HR observed when an intruder rat was suddenly introduced into the cage of a resident rat, and confined to the small cage for 15min. Additionally, the increase in HR and MAP induced by BMA inhibition were eliminated by DMH chemical inhibition. Thus, our data reveal that the BMA is under continuous GABAergic influence, and that its hyperactivation can reduce the physiological response induced by a social novelty condition, possibly by inhibiting DMH neurons.
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Anabolic-androgenic steroids decrease dendritic spine density in the nucleus accumbens of male rats.
Recent studies have demonstrated that anabolic-androgenic steroids (AAS) modify cognitive processes such as decision making and behavioral flexibility. However, the neural mechanisms underlying these AAS-induced cognitive changes remain poorly understood. The mesocorticolimbic dopamine (DA) system, particularly the nucleus accumbens (Acb), is important for reward, motivated behavior, and higher cognitive processes such as decision making. ⋯ Eightweeks of testosterone treatment significantly decreased spine density in AcbSh compared to brains of vehicle-treated rats (F1,14=5.455, p<0.05). Testosterone did not significantly affect total spine number, dendritic length, or arborization measured by Sholl analysis. These results show that AAS alter neuronal morphology in AcbSh by decreasing spine density throughout the dendritic tree, and provides a potential mechanism for AAS to modify cognition and decision-making behavior.
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The mammalian brain has evolved in close synchrony with the natural environment; consequently, trends toward disengagement from natural environments in today's industrialized societies may compromise adaptive neural responses and lead to psychiatric illness. Investigations of rodents housed in enriched environments indicate enhanced neurobiological complexity; yet, the origin of these stimuli, natural vs. manufactured, has not been sufficiently explored. In the current study, groups of rats were exposed to one of three environments: (1) a standard environment with only food and water, (2) an artificial-enriched environment with manufactured stimuli and (3) a natural-enriched environment with natural stimuli. ⋯ Both enriched groups exhibited less anxiety in response to a novel object but the natural-enriched rats exhibited less anxiety-typical behavior in response to a predator odor than the other groups. Less fos activation in the amygdala was observed in both enriched groups following a water escape task whereas an increase in fos activation in the nucleus accumbens was observed in the natural-enriched animals. Thus, the current findings indicate the potential importance of exposure to complex environments, especially natural-like habitats, in the maintenance of emotional health, perhaps providing a buffer against the emergence of anxiogenic responses.
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We have previously demonstrated that inferotemporal neurons respond to objects viewed from a range of angles, even without any prior experience in learning the associations among the views. Several models have been proposed to explain object recognition across disparate views. However, direct neuronal evidence is rare. ⋯ The time period over which the similarity was significant began and endured similarly for 60° separated views at 190-850ms. For 90° separated views, the time period over which the similarity was significant was shorter and started later, at 230-550ms. The results demonstrate the dynamics of cell population activity and suggest a possible explanation for object recognition across disparate views.