Behavioural brain research
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Emotional and cognitive dysregulation in major depressive disorder (MDD) have been consistently considered to be attributed to structural and functional abnormalities in affective network (AN) and cognitive control network (CCN). This study was to investigate the functional connectivity (FC) patterns and altered functional interactions between both networks in MDD. We investigated resting-state functional connectivity magnetic resonance imaging in the AN and the CCN in 25 MDD and 35 healthy controls (HC). ⋯ Interestingly, the altered FC between right ACC and left AMG was negatively correlated with depressive symptom score while the altered FC between right ACC and DLPFC was positively correlated the executive function in MDD. The right ACC not only supports the cognitive and emotional processes, but also is an altered functional interaction hub between AN and CCN in MDD. It further suggest multiple sources of dysregulation in AN and CCN implicate both top-down cognitive control and bottom-up emotional expression dysfunction in MDD.
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Comparative Study
Noradrenergic signaling in the medial prefrontal cortex and amygdala differentially regulates vicarious trial-and-error in a spatial decision-making task.
In uncertain choice situations, we deliberately search and evaluate possible options before taking an action. Once we form a preference regarding the current situation, we take an action more automatically and with less deliberation. In rats, the deliberation process can be seen in vicarious trial-and-error behavior (VTE), which is a head-orienting behavior toward options at a choice point. ⋯ Injection of clonidine into either region impaired selection of the advantageous choice in the task. Furthermore, clonidine injection into the mPFC suppressed occurrence of VTE in the early phase of the task, whereas injection into the AMY inhibited the decrease in VTE in the later phase and thus maintained a high level of VTE throughout the task. These results suggest that the mPFC and AMY play a role in the increase and decrease in VTE, respectively, and that noradrenergic mechanisms mediate the dynamic regulation of VTE over experiences.
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Comparative Study
The neural substrates for the rewarding and dopamine-releasing effects of medial forebrain bundle stimulation have partially discrepant frequency responses.
Midbrain dopamine neurons have long been implicated in the rewarding effect produced by electrical brain stimulation of the medial forebrain bundle (MFB). These neurons are excited trans-synaptically, but their precise role in intracranial self-stimulation (ICSS) has yet to be determined. This study assessed the hypothesis that midbrain dopamine neurons are in series with the directly stimulated substrate for self-stimulation of the MFB and either perform spatio-temporal integration of synaptic input from directly activated MFB fibers or relay the results of such integration to efferent stages of the reward circuitry. ⋯ Whereas the psychometric functions decline monotonically over a broad range of pulse frequencies and level off only at high frequencies, the chemometric functions obtained with the same rats and electrodes are either U-shaped or level off at lower pulse frequencies. This discrepancy was observed when the dopamine transients were recorded in either anesthetized or awake subjects. The lack of correspondence between the psychometric and chemometric functions is inconsistent with the hypothesis that dopamine neurons projecting to the NAc shell constitute an entire series stage of the neural circuit subserving self-stimulation of the MFB.
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The elevated plus maze (EPM) is used to assess anxiety in rodents. Beam-walking tasks are used to assess vestibulomotor function. Brain injury in rodents can disrupt performance on both of these tasks. ⋯ Further, these effects were dissociated from the effects of bTBI on motor function simultaneously measured on MBW. Over the course of 168h post-bTBI, rats gradually recovered on both EPM and MBW. The MBW apparatus succeeded at capturing and dissociating two separate facets of rat behavior, motor function and anxiety, simultaneously.
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Comparative Study
A behavioral and histological comparison of fluid percussion injury and controlled cortical impact injury to the rat sensorimotor cortex.
Our primary goal was to evaluate the behavioral and histological outcome of fluid percussion injury (FPI) and cortical contusion injury (CCI) to the sensorimotor cortex (SMC). The SMC has been used to evaluate neuroplasticity following CCI, but has not been extensively examined with FPI. In both the CCI and FPI models, a mechanical force of 4mm in diameter was applied over the SMC, allowing for a direct comparison to measure the relative rates of histology and recovery of function in these models. ⋯ The neuroplastic changes and ease at which damage to this area can be measured behaviorally make this an excellent location to assess traumatic brain injury (TBI) treatments. No injury model can completely mimic the full spectrum of human TBI and any potential treatments should be validated across both focal and diffuse injury models. Both of these injury models to the SMC produce severe and enduring behavioral deficits, which are ideal for evaluating treatment options.