Experimental Brain Research最新文献

Anticipatory postural adjustments (APAs) are generally understood to be cortically driven, however there is some evidence to suggest subcortical regulation and contribution. We tested the hypothesis that subcortical pathways, if contributing, would be evidenced in increased late portions of the motor evoked potential (MEP) elicited by transcranial magnetic stimulation during different time intervals before and during the APA. Recordings from both the tibialis anterior and soleus muscles showed little evidence for this throughout the course of the APA, pointing instead to a generally cortical source for the APA. Despite this, the brainstem did not appear inactive, with MEPs elicited during voluntary contraction of the soleus being significantly smaller than those elicited prior to executing an APA- specifically during the later portion of the MEP, thought reflective of subcortical contribution. Further work to isolate specific brainstem upregulation and contribution is needed.

Mental rotation can be performed more efficiently for objects that resemble the human body than for abstract objects. This human-body advantage is thought to reflect the involvement of body representations and motor processes. The present study investigated whether this advantage is reduced in older adults with knee osteoarthritis (OA), a condition associated with motor degeneration and altered body representation. Fifty-nine women with knee OA and thirty-six age-matched healthy controls completed a chronometric mental rotation task involving cube-shaped stimuli with or without a face. Results showed a significant human-body advantage in the control group but not in the knee OA group. This group difference remained even after controlling for body mass index and functional mobility, suggesting that the reduced advantage in the knee OA group may be associated with OA-related impairments such as disruptions in body schema or motor imagery. An exploratory analysis found no significant associations between the magnitude of the human-body advantage and clinical measures of knee OA severity (radiographic grade, symptom scores, gait-related self-efficacy, and functional mobility). These findings suggest that intact body representations may play a role in supporting the human-body advantage in mental rotation. They may also inform assessment of body representation in OA.

The ability to flexibly disengage and shift attention allows us to successfully interact with our environment and develops across infancy, childhood and adolescence. The aim of the present study was to investigate how attentional disengagement abilities develop. We leveraged a robust longitudinal dataset of the Gap-Overlap task of the YOUth cohort with over 3500 children tested at one or more timepoints to track the maturation of attentional control across infancy, childhood and adolescence (5 months, 10 months, 3 years, 6 years, 9 years, 12 years). While we replicated established group-level developmental patterns showing progressive improvement in saccadic reaction times, the time between the appearance of the target and the initiation of the saccade, our findings revealed individual variation in developmental trajectories of the gap effect that cannot be reliably predicted from performance at earlier timepoints. Although we found no associations between Gap-Overlap performance and (parent-reported) attention-related behaviors (n = 99-734 depending on age and measures), this may reflect the difficulty of identifying early markers in highly heterogeneous neurodevelopmental disorders and could be limited by examining subclinical traits rather than diagnosed conditions. The increased understanding of individual developmental patterns established here is a prerequisite for the identification of atypical patterns in clinical assessment. Future studies could build on this work by investigating atypical attention profiles across development and their relationship to Gap-Overlap task performance, particularly in clinical populations where attentional differences may be more pronounced.

Estimates of sound source distance are well described by a compressive function relating judged to actual distance; distance is systematically underestimated at larger distances. The current experiment investigated whether such compression is a general tendency of auditory distance judgments, by measuring the judged distance of silent objects based on a novel skill, using self-produced echolocation mouth clicks. The accuracy and precision of distance estimates were measured for aluminum or foam objects (the latter being less reflective than the former) positioned 30, 60, or 90 cm away from 11 blindfolded, normally sighted participants. The distance estimates were well characterized by compressive power functions. Distances were significantly more underestimated and consistency was significantly worse for the two closest object distances for foam than for aluminum objects. Systematic errors were similar for the two materials. The results are consistent with the idea that compression may be a general tendency of auditory distance judgments, both for sound-producing objects as observed in the literature and for silent objects whose distance is judged using a novel echolocation skill.

Ludic design in mental chronometry seeks to enhance engagement through socio-interactive elements. The present study examined whether a co-actor duel context influences both performance and subjective experience. Participants completed speeded arithmetic at two difficulty levels (easy, hard) under two context conditions (alone, duel) in a mixed within-subject design. Self-reports of engagement, distress, and worry were obtained before and after tasks. In the duel context, participants completed problems more quickly, accompanied by a small rise in errors, which however, remained far below the 10% margin allowed by duel rules, indicating that the increase was not a deliberate sacrifice of accuracy for speed. We interpret the speed-up as improved efficiency with preserved engagement, where the modest error rise reflects the probabilistic cost of reduced checking time rather than relaxed accuracy criteria. Such minor differences are unlikely to be consciously detected and therefore are not introspectable as a performance decline.

Offset analgesia (OA) is a disproportionate reduction in pain perception following a small decrease in noxious stimulation. However, the underlying mechanisms remain a matter of debate. At the peripheral level, specific contributions of A-δ nociceptors have been proposed, although some studies have reported conflicting results. This study aimed to investigate (A-δ vs. C-fiber) fiber contributions to OA by psychophysical assessment of first and second pain sensations in healthy individuals. Thirty-two pain-free participants underwent a randomized within-subject study with two distinct goals: (1) testing the concept of first and second pain to brief heat pulses; (2) investigating brief heat pulses applied during the analgesic phase of OA. Response times (RT), the perception of double sensations and fiber-specific pain descriptors were assessed to detect alterations suggesting predominant A-δ or C-fiber involvement. No significant differences were found between offset and control (constant) trials for the first or second pain reporting or the fiber-specific pain descriptors (p > 0.05). Nevertheless, a significant main effect of trial type and stimulus timing on RTs was observed (p = 0.03, η²_p​ = 0.02). Response times to noxious stimuli was delayed following prolonged stimulation in both offset and control trials (p < 0.05). The findings suggest that A-δ and C-fiber response characteristics were unaffected during the OA paradigm; however, higher stimulation intensities or prolonged pain induced a notably longer RT. This may indicate that specific peripheral nerve fibers play a negligible role in OA, however future studies should complement psychophysical assessment with more objective procedures to conclusively rule out peripheral contributions.

Non-invasive brain stimulation such as transcranial direct current stimulation over the primary motor cortex (M1) and supplementary motor area (SMA) during gait can positively affect gait ability in patients after stroke; however, the frequency-specific modulatory effects of rhythmic brain stimulation over the M1 and SMA on the oscillatory neural drives during gait remain unclear. Therefore, we investigated the effects of the alpha and beta to low-gamma oscillatory transcranial direct current stimulation (otDCS) over the M1 and SMA on the oscillatory neural drives to lower limb muscles during gait, using coherence analysis of paired surface electromyography, in 32 healthy young adults. Experiments involved treadmill gait measurements, comprising pre-stimulation gait, gait with otDCS in three stimulation conditions (10-Hz otDCS, 30-Hz otDCS, and sham stimulation) over the M1 and SMA, and post-stimulation gait. Although the 10-Hz otDCS and sham stimulation induced no effects, the 30-Hz otDCS over the M1 and SMA significantly increased the average values of the tibialis anterior intramuscular coherence and vastus medialis and lateralis intermuscular coherence, respectively, in the 20-40 Hz (beta to low-gamma) frequency bands during post-stimulation gait compared to the pre-stimulation gait. Therefore, beta to low-gamma otDCS over the M1 and SMA during gait selectively increased the oscillatory neural drives to distal and proximal lower limb muscles, respectively. This study provides novel evidence that beta to low-gamma rhythmic brain stimulation could be an effective rehabilitation strategy for improving gait ability in patients with central nervous system disorders, with specific deficits in the M1 or SMA.

Humans control their body movements by exploiting gravity to minimise muscle effort while achieving task goals. Most of these findings have been observed in physical environments, although some have also been confirmed in virtual environments. However, research using virtual environments to explore gravity-related motor control mechanisms has yet to directly compare motor performance between virtual and physical environments. Therefore, the present study aimed to examine in detail the potential differences in upper-limb pointing movements between virtual and physical environments. To this end, participants performed pointing tasks in four directions (upward, downward, leftward, and rightward, from an allocentric perspective) in both upright and lying postures, under both virtual and physical conditions. Our results showed that relative duration to peak velocity-a well-established kinematic indicator of gravity utilisation-was consistently shorter for upward than for downward movements across both environments and both postures. However, no differences were observed between the two environments when posture and movement direction were held constant. Furthermore, no differences were observed between the environments in terms of whole velocity and acceleration profiles, as well as in movement duration, peak velocity, peak acceleration, peak deceleration, and the relative durations to peak acceleration and peak deceleration. The similarity in relative duration to peak velocity between virtual and physical environments suggests that the effects of gravity on pointing movements can be reliably assessed in virtual environments as in physical ones. This supports the use of virtual environments as valid tools for studying pointing movements.

Mind wandering in the workplace often causes work errors and may trigger accidents, but there is a lack of clarity about the effects of working memory capacity on the neural mechanisms of mind wandering in drilling crews. Therefore, to determine the effects of different working memory capacities on mind wandering and to explore the neural mechanisms behind these effects, the present study was conducted with drilling crews from an actual drilling site. Participants were grouped based on their performance on the N-back task, and EEG data were collected during the SART task. The behavioral results showed that there were no significant differences in response time and accuracy between groups with different working memory capacities. The EEG results showed that the P3 amplitude during mind wandering was significantly larger in the group with high working memory capacity than in the group with low working memory capacity. Furthermore, there were significant differences in δ, θ, and α-band oscillatory power between the groups with high and low working memory capacities, suggesting the effects of attentional allocation of resources and executive control functions on mind wandering. These results highlight the influence of different working memory capacities on the neural mechanisms of mind wandering. The findings of this study offer novel evidence regarding the role of working memory capacity in the neural mechanisms underlying mind wandering and are expected to inform the development of vocational training programs and cognitive intervention strategies in the future.