Experimental Brain Research最新文献

A vexing characteristic of motor disability after stroke is that many individuals fail to use their affected arm effectively despite having the capacity to do so, a phenomenon termed arm nonuse. Based on the hypothesis that nonuse is influenced by the competing cognitive demands of many daily activities, we examined the effects of cognitive load on arm choice and motor performance in individuals with stroke using a novel virtual reality paradigm that mimics the demands of real-life visual search, object selection, and reaching to targets. Twenty individuals with single left or right hemispheric chronic stroke (11 left cerebrovascular accident; 9 right cerebrovascular accident) and 10 age-matched neurotypical participants completed the Virtual Reality Arm Choice task, in which they reached for target objects in an array under varied cognitive demand. To manipulate cognitive demand, we varied the semantic similarity of objects in the reaching space and the presence or absence of a secondary task. The results showed reduced use of the paretic arm under increased demand. Under cognitive load, participants with stroke also showed slower reach initiation, slower movements, increased reach curvature, and increased performance differences between the paretic and non-paretic arms. The arm choice of neurotypical individuals was also modulated under cognitive load. These data indicate that cognitive factors influence arm choice and motor performance in naturalistic reaching tasks in individuals with chronic stroke. Performance decrements under cognitive load may in turn influence reduced paretic arm use during daily activities.

Methamphetamine (METH) has well-documented long-term effects on the brain, including increased psychomotor activity and behavioral sensitization. However, its immediate effects on the brain's reward system following acute exposure, which may contribute to the development of addiction, are less understood. This study aimed to investigate the effects of acute METH on brain oscillations in the nucleus accumbens of C57BL/6 mice. Mice in the METH group received 5 mg/kg of METH for 5 days during the conditioning phase, followed by an 8-day abstinence period. Afterward, they underwent a 6-minute tail suspension test and were given a 1 mg/kg METH challenge. Local field potential (LFP) data were analyzed for percent total power, mean frequency indices, and phase-amplitude coupling (PAC) to assess the neural effects of METH exposure across these phases. A reduction in theta power was observed across the conditioning, abstinence, and challenge phases of METH exposure. The subsequent METH challenge enhanced gamma oscillations, and PAC analysis revealed a consistent theta-gamma coupling index during both the METH administration and challenge phases. It highlights the sensitivity of the reward system to intense, short-term drug exposure, providing new insights into how acute neural stimulation may contribute to the development of addictive behaviors, reinforcing the brain's vulnerability to drug-induced changes in neural circuitry.

Animal studies have shown that exposure of newborns to general anesthesia drugs can lead to neurodegenerative diseases and subsequent decline in learning and memory abilities. The neurotoxicity of general anesthesia drugs can also occur in the fetus. Therefore, in order to investigate the effect of the Long non-coding RNA(LncRNA)-LIN-microRNA(miRNA)-9-Dopamine receptor D2(DRD2) regulatory network on the development of the neuronal system after the inhalation of the anesthetic sevoflurane, RT-qPCR was used to detect the mRNA levels of LncRNA-LIN, miRNA-9, and DRD2. A dual-luciferase reporter system was used to detect the relationship between LncRNA-LIN and miRNA-9, and miRNA-9 and DRD2. Western blotting and immunofluorescence staining was employed to detect the protein levels of DRD2 and cleaved caspase-3. Flow cytometry was carried out to detect the number of apoptotic cells. The escape latency, swimming distance, and platform crossing times were analyzed using the Morris water maze. The results showed that, after treatment with sevoflurane, the mRNA levels of LncRNA-LIN and DRD2, the expression levels of the DRD2 protein, and the number of neuronal levels of DRD2 were significantly decreased, whereas the expression levels of miRNA-9 and the cleaved caspase-3 protein and neuronal apoptosis were significantly increased. miR-9 knockdown revealed that miRNA-9 regulated DRD2 expression and affected the function of mouse neuronal cells. In turn, LncRNA-LIN overexpression indicated that LncRNA-LIN regulated miR-9 and affected the function of mouse neuronal cells. The present results demonstrated that the LncRNA-LIN-miRNA-9-DRD2 regulatory network is involved in the effects of the inhalation anesthetic sevoflurane on neuronal system development.

We conducted an fMRI study to investigate the neural basis of bimanual coordination, which is fundamental to upper extremity control. Considering bimanual movement as a combination of bimanual chord formation and sequence control, we hypothesized that the areas with the learning effect of both chord formation and sequence learning are critical in bimanual coordination. We adopted the serial reaction time task (SRTT) to test this hypothesis. Thirty-five healthy right-handed volunteers practiced visually cued bimanual SRTT, including the "mirror" and more complex "parallel" modes of random movements or repeating fixed sequences to separately depict the neural substrates of bimanual posture control for chord formation and those of sequence. Random movements' reaction time (RT) continuously declined, indicating learning of bimanual chord formation. The RT in the sequential condition declined more rapidly than in the random condition, confirming sequence learning. The parallel random conditions evoked a more prominent learning-related decrease of task-related activation in the left M1 and cerebellar vermis than the less difficult mirror random conditions. The left M1 showed learning-related enhancement of functional connectivity with the anterior cingulate cortex during the parallel random conditions compared with the mirror random conditions. Thus, the left M1, anterior cingulate cortex, and cerebellar vermis are related to learning bimanual chord formation. The left M1 and cerebellar vermis also showed sequence-specific learning-related activity increments more prominent in the parallel mode than in the mirror mode. Thus, the left M1 and cerebellar vermis are critical in the bimanual motor learning network.

Recent studies highlight a persistent increase in subsequent injury risk following a sport-related concussion (SRC) despite clinical recovery. However, markers of persistent alterations in sensorimotor integration have yet to be identified. One possibility is that compensatory adaptation following SRC may only be unmasked during transient periods of high task complexity in specific sensorimotor circuits. The current study used short-latency afferent inhibition (SAI) to investigate the long-term sequelae of sport-related concussion (SRC) in different short-latency sensorimotor circuits converging in the motor cortex. Specific sensorimotor circuits sensitive to posterior-anterior current with a positive phase lasting 120µs (PA₁₂₀) and anterior-posterior current with a positive phase lasting 30µs (AP₃₀) were assessed using controllable pulse parameter transcranial magnetic stimulation (cTMS) while young adults with and without a history of SRC were at rest or responded to valid and invalid sensorimotor cues. SAI was quantified as the ratio of the motor-evoked potential (MEP) elicited by peripherally conditioned cTMS stimuli to the unconditioned MEP for each cTMS configuration. Individuals with a SRC history demonstrated persistent adaptation in AP₃₀ SAI, but only in response to invalid cues. Persistent adaptation in AP₃₀ SAI was not apparent at rest or during simple sensorimotor transformations in response to valid cues. PA₁₂₀ SAI demonstrated similar responses at rest and in response to both valid and invalid cues, regardless of SRC history. AP₃₀-sensitive sensorimotor circuits may mark the long-term SRC sequelae and the increased susceptibility to momentary breakdowns in sensorimotor integration during periods of high cognitive-motor demands.

The purpose of our study was to evaluate the accuracy with which classification algorithms could distinguish among standing postures based on center-of-pressure (CoP) trajectories. We performed a secondary analysis of published data from three studies: Study A) assessment of balance control on firm or foam surfaces with eyes-open or closed, Study B) quantification of postural sway in forward-backward and side-to-side directions during four standing-balance tasks that differed in difficulty, and Study C) an evaluation of the impact of two modes of transcutaneous electrical nerve stimulation on balance control in older adults. Three classification algorithms (decision tree, random forest, and k-nearest neighbor) were used to classify standing postures based on the extracted features from CoP trajectories in both the time and time-frequency domains. Such classifications enable the identification of differences and similarities in control strategy. Our results, especially those involving time-frequency features, demonstrated that distinct CoP trajectories could be identified from the extracted features in all conditions and postures in each study. Although the overall classification accuracy was similar using time-frequency features (~ 86%) for the three studies, there were substantial differences in accuracy across conditions and postures in Studies A and B but not in Study C. Nonetheless, the models were far superior to the published results with conventional metrics in distinguishing between the conditions and postures. Moreover, a Shapley Additive exPlanation analysis was able to identify the most important features that contributed to the classification performance of the models.

The aim of this study is to investigate the effect of induced excitation of the bottom-up pathways at the lateral elbow muscles on local muscle fatigue in the neck region in healthy participants. Eligible participants (n:55) were randomly allocated to an intervention group (n:28) or a control group (n:27). The fatigue of bilateral neck flexor(sternocleidomastoid) and extensor (upper trapezius) muscles was evaluated using surface electromyography, at baseline and immediately post-intervention during a neck flexor and extensor endurance test respectively. Excitation of the bottom-up pathways was performed at multiple lateral elbow muscles in the intervention group by using a temporal summation protocol of mechanical pain, and the pressure pain threshold was determined once in each of the multiple lateral elbow muscles in the control group. Linear mixed model analyses were performed for each outcome measure to evaluate changes over time and within- and between-group differences. No significant "group X time" interaction effects were detected for any of the outcome measures. Significant main effects for time was found for "amplitude over time" of the left upper trapezius (p:0.003) and right sternocleidomastoid muscle (p: 0.013), and for "amplitude changes" of the left upper trapezius muscle (p:0.021). Significant within-group changes were identified in some outcomes in the control group: increased "amplitude over time" of the right sternocleidomastoid muscle (p:0.024) and decreased "amplitude changes" of the left upper trapezius muscle (p:0.024), decreased "normalized median frequency slope over time" of the left UT (p: 0.013). There were no significant within-group changes in the intervention group. No significant between-group differences for any of the outcome measures were found. This study shows no effect of the induction of excitation of the bottom-up pathways at the lateral elbow muscles on the neck muscles' fatigue characteristics compared to a control intervention. Clinical Trial Number: NCT05146960. Date of Registration: December 7, 2021.

The possible cognitive effect of sense of agency (SoA) has attracted increasing attention. Previous findings suggest that SoA has an effect on action control, time perception, and memory. Here we investigated whether SoA can also influence decision-making. We conducted two experiments, in which we induced high or low predictability by manipulating the contingency between keypresses (action) and ball movements (effect), before assessing SoA and risk-taking (in Experiment 1); and induced both predictability and short or long time delay of action-effect, before assessing SoA, risk-taking, and intertemporal decision-making (in Experiment 2). Higher predictability increased SoA and promoted risk-taking, but did not impact intertemporal decision-making; Shorter delay increased SoA and promoted Larger-Later options, but did not impact risk-taking decision-making. While our findings suggest that some decision-making processes are affected by the same factors as SoA is, we did not find any evidence for any direct impact of SoA on decision-making.

Cochlear implants (CIs) are the most successful neural prostheses, enabling individuals with severe to profound hearing loss to access sounds and understand speech. While CI has demonstrated success, speech perception outcomes vary largely among CI listeners, with significantly reduced performance in noise. This review paper summarizes prior findings on speech-evoked cortical activities in adult CI listeners using functional near-infrared spectroscopy (fNIRS) to understand (a) speech-evoked cortical processing in CI listeners compared to normal-hearing (NH) individuals, (b) the relationship between these activities and behavioral speech recognition scores, (c) the extent to which current fNIRS-measured speech-evoked cortical activities in CI listeners account for their differences in speech perception, and (d) challenges in using fNIRS for CI research. Compared to NH listeners, CI listeners had diminished speech-evoked activation in the middle temporal gyrus (MTG) and in the superior temporal gyrus (STG), except one study reporting an opposite pattern for STG. NH listeners exhibited higher inferior frontal gyrus (IFG) activity when listening to CI-simulated speech compared to natural speech. Among CI listeners, higher speech recognition scores correlated with lower speech-evoked activation in the STG, higher activation in the left IFG and left fusiform gyrus, with mixed findings in the MTG. fNIRS shows promise for enhancing our understanding of cortical processing of speech in CI listeners, though findings are mixed. Challenges include test-retest reliability, managing noise, replicating natural conditions, optimizing montage design, and standardizing methods to establish a strong predictive relationship between fNIRS-based cortical activities and speech perception in CI listeners.