Behavioural brain research
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Randomized Controlled Trial
Effects of 10 Hz and 20 Hz transcranial alternating current stimulation (tACS) on motor functions and motor cortical excitability.
Synchronized oscillatory activity at alpha (8-12 Hz) and beta (13-30 Hz) frequencies plays a key role in motor control. Nevertheless, its exact functional significance has yet to be solved. Transcranial alternating current stimulation (tACS) allows the frequency-specific modulation of ongoing oscillatory activity. ⋯ While 10 Hz effects developed over 30 min after stimulation, 20 Hz tACS effects were found immediately after stimulation. Following 10 Hz tACS these effects were significantly correlated with CSP duration, indicating interference with inhibitory pathways. The present findings suggest differential effects of stimulation frequency on motor behaviour and M1 excitability.
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Traumatic brain injuries (TBIs) affect millions of people each year. Research investigating repeated or serial damage in the form of lesions indicates that behavioral deficits are reduced in animals given sequential lesions separated by a sufficient period of recovery. In the lesion literature, this phenomenon is known as the serial lesion effect (SLE). ⋯ A serial lesion effect was demonstrated across a majority of the behavioral tasks. However, histological analyses did not suggest a clear mechanistic link to the behavioral phenomena. This is the first study to demonstrate the SLE in a model of TBI, suggesting that behavioral deficits may actually be reduced in repeated head injuries, given an adequate time window between injuries.
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The aim of this study was to investigate the neural mechanisms underlying the changes in the ipsilateral primary motor cortex (ipsi-M1) excitability induced during the unilateral rhythmic muscle contraction of the first dorsal interosseous (FDI) (rhythmic contraction) muscle with three different frequencies of auditory cues (1, 2, and 3 Hz). The effect of different frequencies of unilateral rhythmic contraction on changes in the ipsi-M1 excitability was assessed using a single-pulse transcranial magnetic stimulation (TMS) technique when subjects were performing the unilateral rhythmic contractions according to each auditory cue frequency. After that, the changes in short intracortical inhibition (SICI)/facilitation (ICF), long intracortical inhibition (LICI) within the ipsi-M1, and interhemispheric inhibition (IHI), as well as dorsal premotor cortex to M1 (PMd-M1), and dorsolateral prefrontal cortex to M1 (DLPFC-M1) connectivity from the contralateral hemisphere to the ipsi-M1 were assessed using paired-pulse TMS techniques. ⋯ Furthermore, PMd-M1 connectivity and LICI were significantly modulated depending on the frequency of the unilateral rhythmic contraction. In contrast, the changes in the SICI, ICF, IHI, and DLPFC-M1 were not directly associated with the rhythm frequency. These results suggest that PMd-M1 connectivity and LICI within the ipsi-M1 are likely to preferentially operate to modulate ipsi-M1 excitability during the performance of unilateral rhythmic contraction with different frequencies.
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Age-related changes in brain function are complex. Although ageing is associated with a reduction in cerebral blood flow and neuronal activity, task-related processing is often correlated with an enlargement of the corresponding and additionally recruited brain areas. This supplemental employment is considered an attempt to compensate for deficits in the ageing brain. ⋯ Our study revealed dramatic age-related differences in the processing of a simple tactile stimulus in the somatosensory network. Specifically, we detected enhanced activation in the contralateral SI and ipsilateral motor cortex assumingly caused by deficient inhibition and decreased activation in later stages of somatosensory processing (SII, cingulate cortex) in elderly subjects. These results indicate that, in addition to over-activation to compensate for impaired brain functions, there are complex mechanisms of modified inhibition and excitability involved in somatosensory processing in the ageing brain.
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The present study focused on investigating the antidepressant potential of tetrandrine and its possible mechanisms of action. Forced swimming test (FST) and tail suspension test (TST) were used to reveal the antidepressant-like effect of tetrandrine. Potential mechanisms were explored applying reserpine-induced ptosis and hypothermia in mice, as well as using the chronic unpredictable mild stress (CUMS) induced depression model in rats. ⋯ However, these changes could be significantly reversed by tetrandrine application. Furthermore, the levels of the brain-derived neurotrophic factor (BDNF) in hippocampi increased in the tetrandrine-treated rats exposed to CUMS. In summary, our findings suggest that the antidepressant-like effect of tetrandrine is involved in the regulation of the central monoaminergic neurotransmitter system and the levels of BDNF.