Experimental Brain Research最新文献

Rhythmic auditory cueing (RAC) improves spatiotemporal gait parameters in older adults, often using isochronous rhythmic cues (i.e., with constant inter-beat-intervals). However, healthy gait contains fractal-like variability, (i.e., with persistent long-range correlations; LRC) which is disturbed when walking to isochronous cues. Embedding auditory cues with a fractal structure increases LRC in gait among young and older adults, though middle-aged adults are under researched. Walking requires greater cognitive resources with increased age, though how different cue-types interact with attentional load during RAC is under researched. This may depend on beat perception, as those with better beat perception benefit more from RAC. The aim of this study was to investigate the optimal parameters for RAC across the adult lifespan. We predicted that 1) walking to fractal cues would increase LRC in gait across the adult lifespan; 2) increasing attentional load would decrease LRC in gait, particularly for older adults. Moderating effects of beat perception on the impact of cue-type on LRC were also explored. Young, middle-aged, and older adults (n = 62) walked around an elliptical track in silence and in three cued walking conditions of increasing attentional load. Tones were presented in isochronous and fractal rhythms. Fractal cues increased LRC in gait, with qualitatively greater increase among middle-aged adults. Attentional load had no effect on LRC in gait. Isochronous cues resulted in decreased LRC in gait, particularly for those with better beat perception. The optimal parameters of RAC therefore depend on age, beat perception, and the target gait parameter.

The dual visuomotor channel (DVC) theory proposes that reaching with a hand for an object is mediated by a reach channel that directs the hand in relation to spatial cues and a grasp channel that shapes the hand and fingers in relation to object cues. The theory derives from kinematic measures of reach and grasp movements that are used for obtaining static targets and targets rolling across a surface. Here we asked whether the theory extends to the movements used for catching. Measures from electromagnetic sensors, 3D video, and frame-by-frame video analyses were used to compare the hand movements of catching four balls (2.5 to 9 cm) to the hand movements of picking them up when static and intercepting them when they rolled across a surface. The results show that for catching, the reach features an open hand that is used to target and stop the flight of a ball. In turn, the grasp features apertures proportional to ball size, suggesting a relation to forthcoming grip organization, but not ball size per se. Grip analysis showed that a variety of finger synergies resulted in precision grips on larger balls and power grips on smaller balls. Once documented for catching, similar roles for the reach and the grasp are recognizable in the tasks of picking up static balls and intercepting balls rolling on a surface. The results are discussed with respect to their support for the DVC prediction of separate roles for visual reach and grasp channels and their integration with reach and grasp somatosensory channels.

Unconjugated bilirubin (UCB) induces neurotoxicity in newborns, yet effective interventions remain limited. This study explores the neuroprotective role and mechanisms of parthenolide (PRT) using both in vivo and in vitro models. Primary rat neuronal cells exposed to UCB were evaluated through CCK-8, flow cytometry, Western blot, and immunofluorescence assays. Additionally, a rat model of bilirubin encephalopathy was established via bilirubin injection to verify PRT's effects in vivo. The results indicated that UCB significantly suppressed autophagy, increased LDH release and apoptosis, and reduced cell viability. PRT treatment effectively attenuated UCB-induced neuronal injury by enhancing autophagic activity. Mechanistically, PRT mediated these protective effects through inhibition of the AKT/mTOR pathway. These findings demonstrate that PRT exerts notable neuroprotective properties and may serve as a promising therapeutic candidate for bilirubin encephalopathy.

We have shown that single-pulse transcranial magnetic stimulation (TMS) of the dorsolateral prefrontal cortex (dlPFC) inhibits muscle sympathetic nerve activity. However, this was likely due to arousal caused by the TMS pulses themselves, rather than altering the underlying neuronal circuitry. In extension, we have aimed to explore the effects of single-pulse TMS on skin sympathetic nerve activity (SSNA), which is more sensitive to arousal. It was hypothesised that TMS-evoked arousal would increase SSNA but would not generate de novo bursts from the dlPFC. Microneurographic recordings were taken from the right common peroneal nerve in 10 participants. TMS pulses were then delivered to the ipsilateral dlPFC at resting motor threshold (MT) of the finger, at stimulator output intensities 20% and 10% below MT, and at 110% and 120% of MT. The MT and 110% of MT intensities were also used in stimulating the right motor cortex and shoulder. Reductions in SSNA from baseline were seen at almost all intensities, and these mostly did not differ between intensities or sites despite the appearance of SSNA bursts after each pulse. This suggests that TMS is simply generating an arousal response, leading to initial excitation of SSNA followed by a period of sympathoinhibition.

A transient increase in cerebral blood flow (CBF) via exercise or hypercapnia has-in part-been linked to an executive function (EF) benefit. It is, however, unclear whether a transient reduction in CBF negatively impacts EF. In the present study, healthy young adults (n = 24) completed separate 3-h interventions involving - 12° head-down tilt (HDT) and a control (0°) supine posture. The HDT protocol was used because it induces a cephalad fluid shift that safely and reliably decreases CBF. To estimate CBF, transcranial Doppler ultrasound measured middle cerebral artery velocity (MCAv) at discrete timepoints (i.e., baseline, concurrent with the intervention and recovery) and the Stroop colour-naming task completed at baseline, 30-min intervals throughout the intervention and a recovery timepoint, assessed inhibitory control-based changes in EF. As expected, a time-dependent decrease in MCAv (8%) was observed in the HDT but not the control intervention; however, frequentist and Bayesian statistics demonstrated that Stroop performance metrics were not associated with the MCAv change (ps > 0.12). Instead, time-dependent deficits in Stroop task performance were associated with increased ratings of mental fatigue-a result observed across HDT and control interventions. Accordingly, a reduction in MCAv during a 3-h HDT intervention did not impact an inhibitory control measure of EF and our findings demonstrates neurocognitive resilience during a short-term reduction in CBF.

The sense of agency (SoA)-the experience of being in control of one's own actions and outcomes-is a fundamental aspect of daily life. Prior research shows that SoA can be disturbed when actions are externally instructed rather than voluntarily initiated; however, the role of the instructing agent specifically in shaping this effect remains underexplored. As artificial agents (e.g., online chatbots, virtual avatars) become increasingly embedded in everyday interactions, their potential to influence human action raises important questions about the experience of agency. Across three studies, we investigate how action instructions delivered by a human or an artificial agent (in the form of an on-screen embodied chatbot) influence both implicit (temporal binding) and explicit (self-reported control) measures of agency. The results of Study 1 (implicit) showed that binding was strongest in the free choice condition wherein participants' actions were of their own volition compared to actions conducted under external instruction. Notably, binding was significantly reduced when actions were directed by a chatbot compared to the free choice condition. Similarly, the results of Study 2 (explicit) showed that self-reported control ratings were the highest in the free choice condition and decreased significantly when comparing the free choice condition with both instruction conditions. After conducting a third follow-up study that integrates both implicit and explicit methods, we were able to replicate the findings of Study 1 and 2. These results highlight a distinction in the experience of agency when responding to human- versus technology-driven instructions.

Lifting everyday objects destabilizes the body and requires generation of anticipatory (APAs) and compensatory (CPAs) postural adjustments to maintain balance. Aging is associated with reduced efficiency of APA generation and greater reliance on CPAs. The role of Mild Cognitive Impairment (MCI) in postural control during lifting remains unclear. We investigated how age and MCI influence postural adjustments during a standing bimanual lifting task. 13 healthy older adults (OAH), 15 older adults with MCI (OAMCI), and 12 young adults (YAH) performed 35 trials of bimanual lifting of light and heavy loads in standing. Surface electromyography was collected bilaterally from trunk and lower limb muscles, and EMG integrals were calculated during the APA and CPA phases. Center of pressure (COP) displacements were derived from force platform data. YAH generated significantly greater APAs in muscle activity and exhibited larger anticipatory COP responses than both older groups during the heavy-to-light transition (p < .05). They also produced larger compensatory COP responses across transitions. OAMCI showed reduced TA activation during the light-to-heavy transition but demonstrated exaggerated APAs in posterior and lateral muscles during the heavy-to-light transition compared with OAH (p < .05). Change-point analysis indicated faster adaptation to load changes in YAH than in both older groups. Aging and MCI differentially affect the ability to regulate APAs and CPAs during lifting. Young adults demonstrated efficient scaling and rapid adaptation of postural control, whereas older adults showed reduced anticipatory efficiency and slower adjustment. Individuals with MCI exhibited exaggerated yet less targeted APA patterns, suggesting impaired strategy selection.

Avian pecking behavior in birds, analogous to reach-to-grasp in primates, is accompanied by unstable vision due to the co-location of the eyes and bills on the head. Fixation in birds, a brief pause during pecking, enables them to stabilize their visual input to plan their further movements. Several bird species have two high-acuity retinal regions, the area dorsalis and the fovea centralis, which receive input from frontal and lateral visual fields, respectively. However, the contributions of these regions to natural pecking during fixation, especially temporal dynamics and head posture involved in accommodation, remain poorly understood. We assessed the effects of visual-field-specific occlusion on the fixation behavior of pigeons, provided with three types of eye caps: frontal occlusion, lateral occlusion, and a no-occlusion control. Using video tracking methods, we analyzed the visual distance toward the target, fixation duration, head depression angle, and the covariation between visual distance and duration. Frontal occlusion markedly prolonged fixation duration and increased the head depression angle, whereas visual distance remained unaffected across conditions. Furthermore, the covariation between visual distance and fixation duration under control condition was abolished under frontal occlusion. These results suggest that the role of frontal vision involves the area dorsalis in temporal and postural compensation for accommodation during fixation of pecking.