Neuroscience
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Randomized Controlled Trial
Failure to Improve Verbal Fluency with Transcranial Direct Current Stimulation.
Previous studies in healthy populations have provided equivocal evidence whether the application of anodal transcranial direct current stimulation (tDCS) over the left prefrontal cortex (PFC) can improve performance in verbal fluency tasks. In this double-blind, randomised within-participant study, we investigated whether anodal tDCS over the left PFC improves verbal fluency performance relative to sham tDCS. Forty eight healthy native German speakers performed two verbal fluency tasks after having received 20 min of anodal or sham tDCS over the left PFC. ⋯ Overall, the current study found no evidence that verbal fluency performance in healthy speakers could be improved by excitatory stimulation of the left PFC. We argue that previously observed positive effects could be false positives and should be interpreted with caution. The findings from the current study thus cast further doubt on the utility of tDCS in enhancing cognitive performance in the healthy (young) brain.
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The theory of communication through coherence (CTC) posits the synchronization of brain oscillations as a key mechanism for information sharing and perceptual binding. In a parallel literature, hippocampal theta activity (4-10 Hz) has been shown to modulate the appearance of neocortical fast gamma oscillations (100-150 Hz), a phenomenon known as cross-frequency coupling (CFC). Even though CFC has also been previously associated with information routing, it remains to be determined whether it directly relates to CTC. ⋯ To answer this question, we combined CFC (modulation index) and CTC (phase-locking value) metrics in order to detect the modulation of the cross-regional high-frequency synchronization by the phase of slower oscillations. Upon applying this method, we found that the inter-hemispheric synchronization of neocortical fast gamma during REM sleep depends on the instantaneous phase of the theta rhythm. These results show that CFC is likely to aid long-range information transfer by facilitating the synchronization of faster rhythms, thus consistent with classical CTC views.
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This is the first study to examine the influence of activity in one limb on corticospinal excitability to the contralateral limb during a locomotor output. Corticospinal and spinal excitability to the biceps brachii of the ipsilateral arm were assessed using transcranial magnetic stimulation (TMS) of the motor cortex and transmastoid electrical stimulation (TMES) of corticospinal axons, respectively. Responses were evoked during the mid-elbow extension position of arm cycling across three different cycling tasks: (1) bilateral arm cycling (BL), (2) unilateral, contralateral cycling with the ipsilateral arm moving passively (IP), and (3) unilateral, contralateral cycling with the ipsilateral arm at rest (IR). ⋯ TMES-evoked cervicomedullary MEP (CMEPs) amplitudes followed a similar pattern of task-dependent modulation, with BL having the smallest CMEPs and IR having the largest. In line with our previous findings, MEP amplitudes increased and CMEP amplitudes decreased as the cadence increased from 60 to 90 rpm. We suggest that the higher corticospinal excitability to the ipsilateral limb during the IP and IR conditions was predominantly due to disinhibition at both the cortical and spinal levels.
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Parthanatos is a modality of regulated cell death initiated by poly(ADP-ribose) polymerase 1 (PARP-1) hyperactivation and characterized by apoptosis inducing factor (AIF)-dependent and microphage migration inhibitory factor (MIF)-dependent DNA degradation. It is a caspase-independent, mitochondrial-linked paradigm of cell death and has been demonstrated to be related to the pathogenesis of various nervous system diseases. An in-depth understanding of the role that parthanatos plays in the pathological processes of these diseases can provide new targets for nervous system diseases treatments. In this review, on the basis of parthanatos mechanism, the involvement of parthanatos in the pathogenesis of nervous system diseases including neurodegenerative disorders, cerebrovascular diseases, spinal cord injury and glioma will be summarized in detail.
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Rats are a popular animal model for vision research and for investigating disorders of the visual system. The study aimed to quantify the spatiotemporal contrast sensitivity function (CSF) of healthy adult Brown-Norway rats under scotopic and photopic illumination. Animals were trained to jump onto the one of two adjacent platforms behind which was displayed a sinewave grating pattern. ⋯ CSFs were also measured via the visual head-tracking reflex. Photopic contrast sensitivity, spatial acuity, and temporal acuity were all markedly below that of the grating detection task and optomotor findings for other rat strains. The CSF data provide a comprehensive and quantitative description of rat spatial and temporal vision and a benchmark for evaluating effects of ocular diseases on their ability to see.