Neuroscience
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Theories of emotion suggest a close relation of interoception and emotion. However, knowledge of underlying neuronal networks is still sparse. Repetitive transcranial magnetic stimulation (rTMS) is one neurostimulation method allowing causal conclusions between functions and brain regions via stimulation or inhibition of underlying brain structures. ⋯ Moreover, cardiac and respiratory IAc were positively associated with P3 amplitudes and negatively related to positive valence ratings. Positive associations of decreases of cardiac/respiratory IAc with decreases of arousal ratings and decreases of P3 amplitudes for negative stimuli after inhibition of the frontotemporal insular network and after inhibition of somatosensory cortices allow the conclusion of a causal relationship between reduced activity in interoceptive network structures and blunted emotional processing of visual stimuli. Our results suggest that both arousal, and valence aspects of emotional processing are disturbed after inhibition of interoceptive network structures, confirming core assumptions of peripheral theories of emotions and models of interoceptive predictive coding.
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Repeatedly pairing a brief train of vagus nerve stimulation (VNS) with an auditory stimulus drives reorganization of primary auditory cortex (A1), and the magnitude of this VNS-dependent plasticity is dependent on the stimulation parameters, including intensity and pulse rate. However, there is currently little data to guide the selection of VNS train durations, an easily adjusted parameter that could influence the effect of VNS-based therapies. Here, we tested the effect of varying the duration of the VNS train on the extent of VNS-dependent cortical plasticity. ⋯ Trains lasting 0.125 or 2.0 s failed to alter A1 responses, indicating that both shorter and longer stimulation durations are less effective at enhancing plasticity. A second set of experiments evaluating the effect of delivering 4 or 64 pulses in a fixed 0.5 s VNS train duration paired with tone presentation reveal that both slower and faster stimulation rates are less effective at enhancing plasticity. We incorporated these results with previous findings describing the effect of stimulation parameters on VNS-dependent plasticity and activation of neuromodulatory networks to generate a model of synaptic activation by VNS.
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Persistent demyelination has been implicated in axon damage and functional deficits underlying neurodegenerative diseases such as multiple sclerosis. The cuprizone diet model of demyelination allows for the investigation of mechanisms underlying timed and reproducible demyelination and remyelination. However, spontaneous oligodendrocyte (OL) progenitor (OPC) proliferation, OPC differentiation, and axon remyelination during cuprizone diet may convolute the understanding of remyelinating events. ⋯ There was minimal change in CAP amplitude between groups, however, a significant decrease in conduction velocity of the slower, non-myelinated CAP component was observed in the rapamycin group relative to the non-rapamycin group. During remyelination, rapamycin groups showed a significant decrease in OPC proliferation and mature OLs, suggesting a delay in OPC differentiation kinetics. In conclusion, we question the use of rapamycin to produce consistent demyelination as rapamycin increased inflammation and axonal damage, without affecting myelination.
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Our study aimed to determine the neural correlates of speech planning and execution in adults who stutter (AWS). Fifteen AWS and 15 controls (CON) completed two tasks that either manipulated speech planning or execution processing loads. Functional near-infrared spectroscopy (fNIRS) was used to measure changes in blood flow concentrations during each task, thus providing an indirect measure of neural activity. ⋯ Broadly, group level effects corroborate previous PET/fMRI findings including under-activation in left-hemisphere perisylvian speech-language networks and over-activation in right-hemisphere homologs. Increased planning load revealed atypical left-hemisphere activation in AWS, whereas increased execution load yielded atypical right fronto-temporo-parietal and bilateral motor activation in AWS. Our results add to the limited literature differentiating speech planning versus execution processes in AWS.
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The relationship between attention and incentive motivation has been mostly examined by administering Posner style cueing tasks in humans and varying monetary stakes. These studies found that higher incentives improved performance independently of spatial attention. However, the ability of the cueing task to measure actual attentional orienting has been debated by several groups that have highlighted the function of the motor system in affecting the behavioral features that are commonly attributed to spatial attention. ⋯ In Experiment 2, the task was modified to fit a paradigm of Go/NoGo target identification. We found that attention and motivation interacted exclusively in Experiment 2, wherein anticipated motor activation was discouraged and more demanding visual processing was imposed. Consequently, we suggest a protocol that provides novel insights into the study of the relationship between spatial attention and motivation and highlights the influence of the arm motor system in the estimation of the deployment of spatial attention.