Neuroscience
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Repetitive mild traumatic brain injury (RmTBI) is a prevalent and costly head injury particularly among adolescents. These injuries may result in long-term consequences, especially during this critical period of development. Insomnia and sleeping difficulties are frequently reported following RmTBI and greatly impair recovery. ⋯ Finally, although both MSG and RmTBI alone produced attenuated circadian amplitudes of activity and body temperature, exacerbated deficits were not identified in animals that received MSG and RmTBI. In sum, both MSG and RmTBI can alter behavior, circadian rhythm amplitude, SCN morphology, and gene expression independently, but the effects do not appear to be additive. Specific damage in the hypothalamus and SCN should be considered when patients experience sleeping problems following RmTBI, as this may improve therapeutic strategies.
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Decision-making in the mammalian brain typically involves multiple brain structures within the midbrain, thalamus, striatum, limbic system, and cortex. Although task specific contributions of each brain region have been identified, neurons responding to reinforcement have been found throughout these structures. We sought to determine if any brain area, or cluster of areas, are the source of information, and if the fidelity of information varies among the areas. ⋯ Analysis of FPs prior to reward revealed most regions reflected the prior probability of reward. Lastly, analyses of information flow suggested reinforcement information does not originate within a single structure of the network, within the resolution afforded by FP recordings. These data suggest reward delivery information is rapidly distributed non-uniformly across the network, and there is no canonical flow of information about reward events in the recorded structures.
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The thalamic dorsal lateral geniculate nucleus (dLGN) serves as a gating station for the transfer of light information en route to the primary visual cortex (V1). Although the modulatory input arising from the V1 and several brainstem nuclei to the dLGN is well characterised in higher mammals, little is known about its influence on dLGN activity in rodents. Using simultaneous recordings of electrocorticogram (ECoG) and single unit neuronal activity under urethane anesthesia in Long Evans rats, we managed to show that cyclic changes in the general brain state strongly affect spontaneous activity and light encoding properties of dLGN neurons. ⋯ Cells responding to light in a sustained manner encoded light intensity more accurately during the cortical activation phase of urethane anesthesia. On the other hand, isoflurane anesthesia does not induce such rhythmic changes in ECoG and shuts down the spontaneous neuronal activity in the dLGN. Together, these data suggest a greater modulation of spontaneous activity and dLGN neurons function, than it was previously reported for the rodent dLGN and highlight the role of anesthesia in interpretations of findings from ongoing acute experiments.
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Randomized Controlled Trial
Effects of Transcranial Static Magnetic Stimulation on Motor Cortex Evaluated by Different TMS Waveforms and Current Directions.
Transcranial static magnetic stimulation (tSMS) modulates cortical excitability probably by interacting with the GABA-glutamate intracortical balance. Different transcranial magnetic stimulation (TMS) waveforms probe distinct GABA-mediated cortical inhibition networks. The goal of the present work is to further characterize tSMS-induced changes in motor cortex reactivity and inhibition-excitation (I/E) balance. ⋯ MEP amplitude increased compared to sham with monoAP TMS, with no clear changes in general intracortical I/E balance. Biphasic TMS was not able to capture any effects of tSMS. The results show that the effects of tSMS on cortical excitability and inhibition involve specific interneuron circuits that are selectively activated by monoPA TMS.