Journal of Neurophysiology

Motor sequence performance improves during and between brief practice bouts (micro-online and offline gains). We compared both metrics across two groups: one exposed to an implicit motor sequence, and one not. Micro-online gains drove sequence-specific learning and positively correlated with overall skill. However, micro-offline gains were comparable between groups and did not track sequence-specific learning. We conclude that implicit motor sequence learning is driven by micro-online rather than micro-offline gains.

The long-latency reflex (LLR), the fastest feedback response that recruits supraspinal pathways, is an important model for understanding how descending motor pathways shape rapid corrective responses in humans. While the corticospinal tracts contribution to the LLR has been well established, that of the reticulospinal tract, the other major descending motor pathway, remains purely speculative. To address this online contribution to the generation of the LLR, we used loud acoustic stimulation (LAS), which can strongly engage brainstem circuits including the pontomedullary reticular formation. By delivering LAS at nine timings (0-80 ms in 10-ms steps) relative to perturbation onset, we tested whether LAS selectively facilitates the LLR but not the short-latency reflex (SLR), and whether the facilitated epoch shifts systematically with LAS timing. In twelve healthy participants, elbow extension perturbations were applied to evoke stretch reflexes in the biceps brachii muscle. LAS produced significant supralinear facilitation in the LLR but not in the SLR. Moreover, at LAS timings of 50 ms or more after perturbation onset, LLR facilitation shifted progressively later with LAS, remaining at an approximately fixed delay of 30 ms after LAS onset. This fixed delay indicates that LAS-evoked descending input from the same origin facilitates the ongoing LLR. Together with the lack of significant SLR facilitation, this temporal pattern supports an online reticulospinal contribution to the human LLR, alongside the established corticospinal contribution. This approach provides a new, non-invasive means to investigate the physiological role of the reticulospinal tract in human motor control. Key PointsO_LIThe long-latency reflex is a rapid muscle response to sudden stretch. Unlike faster spinal reflexes, it is shaped by commands descending from the brain and adjusts to the task. C_LIO_LIThough the corticospinal tract is known to shape this reflex, whether the reticulospinal tract also contributes to the reflex has not been tested in humans. C_LIO_LIWe stretched the arm and, at various delays, played a loud sound that engages the brainstem origin of the reticulospinal tract. The sound significantly enhanced the long-latency reflex, whereas no significant enhancement was detected in the faster spinal reflex. C_LIO_LIWhen the sound came 50 milliseconds or more after the stretch, the enhancement followed the sound at a stable delay, indicating that sound-evoked descending signals interacted with the ongoing reflex response. C_LIO_LIThese findings support a real-time contribution of the reticulospinal tract to the human long-latency reflex and provide a non-invasive way to study this pathway. C_LI

Past studies using transcranial magnetic stimulation have shown larger motor-evoked potentials when people observe someone lifting a heavy object than when they observe someone lifting a light one. This means that observers may engage their own motor system in proportion to the perceived effort. However, the different responses during the observation of light and heavy objects may have been influenced by predictable trial sequences within blocked presentation, making it unclear whether corticospinal excitability reflects online processing of kinematics or is affected by top-down expectations. In this Registered Report, 57 right-handed participants passively observed videos of a precision grip and lift of heavy and light objects while receiving a single-pulse TMS to the left primary motor cortex during the lift phase of the movement. Motor-evoked potentials were recorded from the right first dorsal interosseous muscle. The study compared two main observation contexts: a predictable trial sequence in which repeated videos of the same lifts were presented in a blocked order, and an unpredictable one in which videos were presented semi-randomly and participants could rely only on kinematic cues to perceive the weight of the lifted object. In both conditions, the same videos of lifts of equivalent-looking heavy and light objects were used and only the order of presentation differed. Contrary to our predictions, in the blocked (predictable) condition, there was no significant difference in MEPs elicited by light and heavy lifts. In the unpredictable condition, participants showed greater corticospinal excitability during the observation of the light lifts compared to the heavy lifts. This suggests that in the absence of predictable information, the corticospinal system was sensitive to the observed kinematics, but contrary to previous findings, its excitability varied inversely with the object weight.

The sodium leak channel NALCN regulates resting membrane potential and spontaneous firing in neurons and can be modulated by G-protein coupled receptors (GPCRs). Whether metabotropic glutamate receptors (mGluRs) modulate NALCN is unknown and would represent a novel mechanism through which glutamate could affect neuronal excitability. Here we examine NALCN function and modulation by mGluRs in cerebellar unipolar brush cells (UBCs) in mouse brain slices. Activation of group II mGluRs inhibited the NALCN current through a G protein-dependent mechanism, as the effect was abolished by intracellular GDP-{beta}-S and by NALCN deletion. The OFF UBC subtype that is inhibited by glutamate had a larger NALCN current than the ON UBC subtype that is excited by glutamate. OFF UBCs also had a tonic NALCN current that was absent in ON UBCs. Genetic deletion of NALCN converted the regular spontaneous firing pattern of OFF UBCs, to an irregular pattern similar to that of ON UBCs, suggesting that a tonic NALCN current may be a general mechanism to promote regular firing. Additionally, we identify the presence of group III mGluRs in OFF UBCs and GABA-B receptors in ON UBCs and show that neither inhibit NALCN, demonstrating that different GPCRs engage distinct downstream ion channels. These findings identify a previously unrecognized form of glutamatergic synaptic inhibition that is selectively initiated by group II mGluRs, but not other Gi/o-coupled GPCRs, within the same neurons.

Emerging evidence suggests that cortical activity is organized in traveling waves that coordinate neural activity across space and time. How anesthesia alters these waves remains underexplored. We recently showed that cortical activity undergoes spontaneous state transitions at steady-state anesthetic concentrations including a paradoxical state exhibiting awake-like spectral properties during deep anesthesia. Here, we investigated traveling wave dynamics across spontaneous cortical states using hemispheric electrocorticography in rats anesthetized with desflurane at inhaled concentrations of 6, 4, 2, and 0%. Compared with the awake state, delta-band traveling waves in cortical states predominantly associated with 4-6% desflurane were more frequent and exhibited more stereotyped propagation patterns, characterized by a greater prevalence of planar waves and a corresponding reduction in source/sink wave patterns. The occurrence rate and pattern complexity of theta- and gamma-band waves remained largely unchanged, whereas the propagation direction of planar waves became more variable. Feedforward-feedback organization was also altered: compared with the awake state, the feedback-dominance of theta-band diminished, and the feed-forward dominance of gamma-band was attenuated. Despite occurring predominantly in deep anesthesia associated with behavioral unresponsiveness, traveling-wave dynamics of the paradoxical state exhibited partial, frequency-dependent shifts toward those observed in the awake state. These findings demonstrate that spontaneous cortical states under anesthesia are associated with frequency-dependent reorganization of cortical traveling waves and identify the paradoxical state as a distinct dynamical regime of deep anesthesia. Significance StatementAnesthesia is commonly thought to alter cortical dynamics progressively with increasing anesthetic depth, yet cortical activity can transition spontaneously between distinct states even at constant anesthetic concentrations. Here, we show that cortical states spectrally derived from the electrocorticogram of rats are associated with distinct frequency-specific organization of cortical traveling waves, revealing spatiotemporal dynamics beyond conventional spectral measures. Notably, a paradoxical state, occurred predominantly in deep anesthesia associated with behavioral unresponsiveness, exhibited traveling-wave dynamics that approached those observed during wakefulness. These findings demonstrate that cortical traveling-wave organization changes dynamically with brain state rather than anesthetic concentration alone. They suggest that structured cortical dynamics can emerge during deep anesthesia, providing new insights into large-scale cortical dynamics associated with anesthetic modulation of consciousness.

Head-eye coordination during ball interception depends on both task demands and motor experience. The purpose of this study is to determine how these factors influence head-eye contributions to gaze control. Twenty-five female university students (novices with no ball sport experience, n = 13; experienced softball players, n = 12) performed two tasks: visually tracking an approaching ball (tracking task) and, in addition, moving the hand to the ball's landing position (reaching task). Head, eye, and gaze velocities, cross-correlation coefficients between gaze and head velocity, and gaze-head lag time were analyzed using linear mixed models. The results showed that although gaze velocity remained unchanged regardless of tasks or groups, decomposing gaze into head and eye components revealed task-dependent contributions. Compared with the tracking task, the reaching task showed significantly larger head velocity and smaller eye velocity, indicating complementary adjustments that were not revealed by gaze movements alone. The cross-correlation between head and gaze was significantly higher in the reaching task than the tracking task, indicating stronger temporal coupling under greater task demand. Furthermore, the experienced group showed greater task-dependent modulation of eye velocity than the novice group, demonstrating greater flexibility in adjusting the magnitude of head-eye movements to task demands. In addition, the experienced group showed a consistently near-zero gaze-head lag regardless of task, whereas the novice group showed a prolonged gaze-leads-head interval. These findings suggest that ball sport experience shapes two distinct aspects of head-eye coordination: task-dependent flexibility in movement magnitude, and stable, temporally synchronized gaze-head control.

In the current experiment, we compared reported perceptual awareness of the visuomotor rotation to motor awareness of changes in reaches established using the process dissociation procedure and drawing task following visuomotor adaptation to a large (50 degrees; R50 group) or a small (30 degrees; R30 group) cursor rotation. Results revealed that perceptual and motor awareness did not differ in magnitude for the R50 group and were significantly correlated. In contrast, while the R30 group perceptually reported being aware of the visuomotor rotation, motor awareness was significantly less and responses were not significantly correlated across tasks. Overall, results suggest that perceptual and motor tasks assess different processes underlying visuomotor adaptation to a small cursor rotation, such that perceptual awareness of the visuomotor rotation is not reflected in reaching performance on tasks assessing motor awareness.

When in a stressful situation, making fast and accurate decisions is crucial. Previous work has shown that sensorimotor decisions can improve under threat. However, it is unclear if these improvements are achieved by improvements in perceptual or motor performance. Here, we present two hypotheses for how threat might influence motor preparation and use muscular stretch reflexes to test both. The task-unspecific hypothesis predicts that threat promotes motor preparation irrespective of the reach target, through tonic upregulation of the short latency stretch reflex. In contrast, the task-specific hypothesis predicts that threat increases sensory processing for a specific reach target, leading to direction-selective up- and down-regulation of the long latency stretch reflex. Participants were asked to reach to one of two targets that appeared shortly before a perturbation eliciting a stretch reflex, they performed this task either under threat of an electric shock or under safe circumstances. Skin conductance and heart rate results show that the threat manipulation significantly increased sympathetic activation, but not parasympathetic activation. Supporting the task-specific hypothesis, the EMG findings demonstrate a direction-selective modulation of the long-latency response of stretch reflexes, starting ~100 ms after perturbation onset. Our results suggest that stress affects action preparation through upregulation of cortical visuomotor circuits.

Persistent inward currents (PICs), which are facilitated by monoaminergic inputs such as serotonin (5-HT), amplify synaptic drive and strongly influence motoneuron excitability. Although rhythmic locomotor activity increases serotonergic drive in animal models, its effects on intrinsic motoneuron properties in humans remain unclear. We examined whether rhythmic arm cycling alters motoneuron excitability of the non-exercising tibialis anterior during submaximal contractions. Twelve healthy adults (8 males, 4 females) performed triangular isometric dorsiflexion contractions at 25% and 50% MVC under four conditions: resting arm (CONTROL), finger tapping (TAP), arm cycling at 50-60 RPM (LOW), and arm cycling at 80-90 RPM (HIGH). Motor unit activity was identified from high-density surface electromyography that was decomposed into spike trains. Recruitment thresholds of identified and tracked motor units were consistent across conditions, but {Delta}F (i.e., an estimate of the PIC-related contributions to motor unit discharge) decreased during high-cadence arm cycling at stronger contraction intensities, which may reflect either reduced neuromodulation and/or increased or altered patterns of inhibition. In contrast, ascending discharge rate modulation deviated from linearity to a greater extent (i.e., brace height was larger) during both low- and high-cadence cycling, indicating greater neuromodulatory influence on the ascending discharge rate pattern. Self-sustained discharge was also elevated during cycling tasks, reflecting prolonged motor unit discharge. Taken together, these findings suggest that rhythmic activity of the arms modulates the discharge characteristics of motoneuron pools in the legs via unique combinations of excitatory, neuromodulatory and inhibitory inputs, which advances our understanding on the mechanisms of interlimb neural coupling.

Tree shrews (Tupaia belangeri) are increasingly used in comparative neuroscience, yet their respiratory physiology remains poorly characterized. We quantified spontaneous breathing and respiratory rhythm variability in awake adult tree shrews (n = 10; 5 males, 5 females) using whole-body plethysmography. Respiratory frequency decreased by approximately 16% with acclimatization to the recording chamber, while respiratory timing, body-mass-normalized respiratory amplitude, inspiratory flow, and minute ventilation remained relatively stable. After acclimatization, mean respiratory parameters were similar between sexes, but short-term breath-to-breath variability (SD1) was greater in males than females, whereas SD2 was comparable. These findings establish baseline respiratory characteristics in awake tree shrews and identify sex-dependent differences in short-term respiratory rhythm stability.

Despite our best efforts to stay focused on a task, our arousal waxes and wanes over time. Lower levels of arousal are typically associated with drowsiness, whereas higher levels are often associated with stress. These changes in arousal move us away from ideal task performance and manifest as fluctuations in neural activity. We asked whether moment-by-moment neurofeedback could be used to counteract neural fluctuations and thereby regulate arousal levels. Here, we developed an intracortical brain-computer interface (BCI) in which animals used visual neurofeedback to maintain neural population activity in prefrontal cortex near a pre-specified activity target. We found animals used moment-to-moment neurofeedback to reduce neural fluctuations on timescales of seconds to hundreds of milliseconds, and that arousal-related regulation of neural activity was associated with BCI use. Our findings suggest that neurofeedback may enhance or restore regulation of neural activity, with potential clinical applications in conditions where such regulation is impaired.

Sex-related differences in force steadiness are often attributed to maximal strength and motor unit (MU) properties, but their independent contributions remain unclear. This study strength-matched females and males to remove the influence of maximal strength and determine whether MU properties are associated with sex-related differences in force steadiness. Twelve young adults (6 females) were matched for elbow flexion strength (females, 188.6{+/-}15.6 N; males, 199.7{+/-}24.8 N, p=0.4). Both groups performed submaximal isometric elbow flexion contractions at 2.5%, 5%, 10%, 15%, and 25% MVC. The MU recruitment thresholds (RT), discharge rates (MUDR), and coefficient of variation of interspike intervals (CVISI) were measured from intramuscular fine wire electromyography (EMG) electrodes. Force steadiness was quantified as the standard deviation (SD) and coefficient of variation (CV) of force. Across forces, SD and CV of force did not differ between females and males (p>0.05). Females had a higher recruitment threshold than males (p<0.05). Females had higher MUDR at 15% and 25% MVC (p<0.02), while males were higher at 5% MVC (p=0.02). The CVISI was greater in females (p<0.001) and positively correlated with SD of force (r=0.2) and negatively with CV of force (r=-0.2) in females and males. When strength was matched, sex-related differences in force steadiness were not evident. However, females exhibited higher MU recruitment thresholds, MUDR and CVISI. Despite greater CVISI in females, these differences did not translate into greater force fluctuations, suggesting that individual MU discharge variability is not a primary predictor of force steadiness when maximal strength is controlled. NEW & NOTEWORTHYO_LIStrength matching eliminated sex-related differences in elbow flexor force steadiness. C_LIO_LIFemales achieved similar force steadiness using higher MU recruitment thresholds and discharge rates, particularly in the short head of the biceps brachii. C_LIO_LIIn females, the greater variability in motor unit discharge was not associated with reduced force steadiness. C_LI

Abstract Background: Reward can influence both the selection and execution of goal-directed actions. Healthy ageing is associated with changes in reward processing, raising the possibility that reward effects on motor control may be reduced in older adults. Objective: This study examined how monetary reward affects action execution and action selection during reaching movements and whether these effects differ between younger and older adults. Methods: 28 younger adults and 28 older adults performed a reward-based reaching task. Behaviourally non-distracted trials were used to assess action execution, whereas distractor-containing trials were used to assess action selection. Outcomes included maximum velocity, movement time, endpoint error, reaction time, and selection accuracy. Results: Reward increased maximum velocity and reduced movement time in both age groups without increasing error. These reward-related changes in movement vigour were larger in younger adults. During action selection, reward shortened reaction time but reduced selection accuracy in both groups, indicating faster but less accurate responses. The reward-related changes in reaction time and selection accuracy did not differ significantly between age groups. Conclusion: Ageing did not produce a uniform reduction in reward responsiveness. Instead, ageing attenuated reward-driven movement invigoration, while reward-related changes in action-selection behaviour were similar across age groups. These findings may inform the design of reward-based interventions that promote movement vigour without encouraging speed at the expense of accurate action selection.

Unipolar brush cells (UBCs) are excitatory interneurons that have a characteristic dendritic brush that amplifies and extends incoming signals in the cerebellum. UBCs transform synaptic input through their ionotropic and metabotropic glutamate receptors. Differential regulation of receptor subunits is a critical developmental process, but how the expression of glutamatergic receptors changes in UBCs as they develop is unclear. NMDA-type glutamate receptors (NMDARs) are particularly important for development and plasticity. We examined the expression of NMDAR subunits during development and tested whether signaling through these receptors is necessary for the development of the elaborate dendritic structure and unusual synaptic function of UBCs. Whole-cell patch clamp recordings from UBCs in acute brain slices revealed tonic and synaptic NMDAR-mediated currents in early postnatal UBCs that decrease during development. RNAscope in situ hybridization revealed differential developmental regulation of GluN2C/D subunits. Cell-type specific constitutive NMDAR knockout had no apparent effect on dendritic brush development, but increased UBC number in adulthood, suggesting a role in programmed cell death. Both pharmacological blockade or genetic deletion of NMDARs produced a paradoxical increase in excitability, which was calcium dependent and was occluded by inhibition of calcium activated potassium channels. Thus, NMDA receptors are dispensable for migration and dendritic development but may be involved in cell death pathways. Their functional roles include synaptic signaling as well as providing a tonic calcium flux that dampens excitability in developing UBCs and may influence transformations of vestibular signals essential for smooth movements and balance.

Objectives: Transcranial magnetic stimulation (TMS) is widely used to probe corticospinal excitability by eliciting motor evoked potential (MEP)s in targeted muscles, with MEP characteristics such as magnitude and latency reflecting the physiological state of the pathways being stimulated. Although numerous studies have examined MEP reliability in upper extremity muscles, less is known about the reliability of this measurement across the lower extremity. We hypothesized that inter-session, test-retest reliability of MEPs recorded simultaneously from multiple lower-limb muscles, from a single TMS location, would differ by muscle, stimulation intensity, and quantification method. Materials and Methods: Ten healthy participants (5 males, 5 females) completed three TMS sessions separated by atleast one week. At each session, the stimulation hotspot was identified using a five-location virtual grid anchored at the vertex, with electromyography (EMG) recorded from all eight muscles of interest at each grid location; the grid location producing the largest and most consistent MEPs in the tibialis anterior (TA), the primary target muscle, was selected as the stimulation site and held constant across all three sessions. MEPs were then recorded bilaterally from the TA, soleus, rectus femoris, and biceps femoris muscles at two stimulation intensities (110% and 120% resting motor threshold (RMT)). MEP size was quantified using mean rectified magnitude and peak-to-peak amplitude, and inter-session reliability was assessed using intraclass correlation coefficients (ICC). Bland-Altman analysis was used to characterize the range of measurement variability across all eight muscles. Results: MEP size differed across sessions, and reliability varied by muscle, intensity, and quantification method. The highest reliability was observed in the right TA, the muscle used to establish the stimulation hotspot, using mean rectified magnitude at 120% RMT. Reliability was comparatively lower in the seven non-target muscles recorded from the same fixed stimulation site, indicating that MEP consistency was not uniform across the lower-limb musculature. Conclusions: MEP reliability in the lower extremity depends heavily on the muscle, stimulation intensity, and quantification method used, and is highest in the muscle for which the stimulation site was optimized. These findings support the interpretation that coil positioning targeted to a specific muscle yields more consistent responses in that muscle than in others recorded from the same fixed site, and underscore the importance of careful muscle selection and hotspot optimization when designing TMS protocols for longitudinal or clinical lower-limb research.

PurposeThe neural representation of pitch and timbre in complex sounds has previously been studied using synthetic, controlled stimuli to investigate underlying encoding mechanisms. These studies provide information about how single attributes of sound are represented in the inferior colliculus (IC), a critical hub of the auditory pathway where neurons are sensitive to stimulus periodicity and spectral shape, giving rise to representations of pitch and timbre, respectively. However, there is a gap in understanding how natural sounds with both pitch and timbre attributes, such as instrument sounds, are represented in the IC. MethodsIn this study, extracellular recordings were made in the IC of awake rabbits in response to natural instrument stimuli varying in fundamental frequency (F0) to determine how instrument identity (timbre) and F0 (pitch) are represented in IC neurons. ResultsUsing decoding models for instrument identification, we found that instrument identity was redundantly encoded in a population of neurons with diverse rate and timing characteristics. F0 identification using decoding models trained on single-neuron rate responses was poor, but the population of rate responses contained enough information to identify F0 reliably. F0 information was also encoded in single-neuron temporal responses up to 196 Hz. F0 identification from a population of temporal responses was accurate up to approximately 900 Hz, but accuracy decreased at high F0s. For the task in which F0 was identified based on responses to both oboe and bassoon stimuli that had overlapping F0s, performance decreased compared to F0 identification based on responses to a single instrument. ConclusionThis result supports the hypothesis that pitch and timbre information are encoded jointly in the IC.

Pacemaking neurons, often found in mammalian nervous systems, integrate their inputs differently than quiescent neurons. Rhythmic single-spike pacemaking that is robust to noise can be achieved with a slow process that enforces a "resting potential" at each point along a ramp-like interspike interval (ISI) coupled with a fast restorative component. To demonstrate this phenomenon, we modeled previously identified distinct subpopulations of midbrain dopamine neurons that differed in projection target and in the regularity of their pacemaking. In the model of the more regularly-firing subpopulation projecting to the dorsomedial striatum, KV4 current was recruited by a deep after-hyperpolarizing potential (AHP) mediated by the SK channel. In the model of the less regularly-firing subpopulation projecting to the medial shell of the nucleus accumbens, the AHP was too shallow to recruit the KV4 current. In the more regularly firing population, the trajectory in the phase space of membrane potential and slow inactivation of KV4 was confined to move slowly through a narrow channel during the ramp-like portion of the ISI. Noisy perturbations from this channel were quickly damped by fast activation of KV4. In contrast, the smaller AHP in the model of the subpopulation projecting to the medial shell of the nucleus accumbens failed to recruit Kv4-mediated current, therefore the narrow channel was never entered, greatly decreasing the regularity in the presence of noise. This mechanism may be broadly applicable to single-spike pacemakers and explains how slow pacemaking with small net currents can be robust to fluctuations in single channel openings. Author SummaryPacemaking cells spike at regular intervals without the need for external input. There are numerous examples of pacemaking cells in the nervous system. We show that a process with slow dynamics relative to the individual spikes can make regular pacemaking robust to the noise that is always present in biological systems.

Decisions are often modeled as a sequential process in which evidence accumulates until it reaches a threshold, triggering a response. Studies in freely moving animals raise questions about how ongoing behavior, not just stimulus properties, shapes this process. We trained rats of both sexes on a visual detection task with three luminance levels, each associated with the same reward outcome. Rats controlled cue duration through sustained head entries into a center port, yielding a measurable index of active sampling. Females consistently sampled longer than males. Sampling durations were shorter on error than correct trials, and reaction times were longer on error trials. We used drift diffusion models to relate these behaviors to the decision process. Luminance selectively affected the rate of evidence accumulation, with drift rate increasing monotonically across low, mid, and high luminance levels. Active sampling time was associated with the decision threshold, with longer sampling predicting higher thresholds in both sexes. The relationship between sampling time and drift rate differed by sex. Females showed a negative association between sampling duration and drift rate that was absent in males. These findings suggest that cue properties and active sampling make separable contributions to the decision process. These findings suggest that cue properties and active sampling make separable contributions to decision making, with a negative association between sampling duration and drift rate evident in females but not males.

Gut-brain communication has emerged as a rapidly expanding field of research, with recent electrophysiological studies revealing rhythmic gut-brain coupling between gastric activity and brain oscillations in humans. Gut motility is a key determinant of gastrointestinal function, but it remains unclear whether individual differences in gut motility reflected by weekly bowel movements (e.g., defecation frequency) are associated with differences in gut-brain coupling. Here, we address this question by examining women with self-reported daily bowel movements (N = 38) and women with less frequent bowel movements (N = 38). We recorded simultaneous electroencephalography (EEG) and electrogastrography (EGG) at fasting state, performed cognitive assessments, and analysed faecal short-chain fatty acids (SCFAs) as markers of colonic fermentation. In a subset of participants, EEG-EGG coupling was assessed twice over an interval of at least eight weeks to assess test-retest reliability. In this group, EEG-EGG coupling showed moderate test-retest reliability (Intraclass Correlation Coefficient (ICC) = 0.50). When comparing the two groups of women, the phase-amplitude coupling (PAC) analysis between EEG and EGG signals revealed a significantly stronger gut-brain coupling in women with daily bowel movements compared to women with less frequent bowel movements (p = 0.03). We additionally found that women with daily bowel movements made less errors in the cognitive tasks and had higher levels of faecal SCFAs. A path analysis suggested that bowel movements significantly affect gut-brain phase-amplitude coupling through faecal SCFAs. However, neither faecal SCFAs nor phase-amplitude coupling significantly predicted cognitive performance, suggesting the existence of alternative pathways for the association between bowel movements and cognitive performance. Together, our findings suggest that the strength of gut-brain coupling is associated with bowel movements and cognitive performance, making EEG-EGG coupling a promising marker of human gut-brain interactions.

This paper introduces a sensorimotor learning framework for a corticocerebellar network, grounded in the perspective of population dynamics. Using an optimal control theory approach, the cerebellum model enhances preparatory activity through premotor input, allowing the motor cortex to reach the desired initial conditions for movement more efficiently. Unlike traditional motor learning approaches that focus on acquiring new skills, this paradigm emphasizes automatization of already executable behaviors through repetition driven by intrinsic motivation. The proposed model is evaluated using a center-out reaching task, demonstrating that the role of the cerebellum is to shorten the preparatory period required for the successful execution of the movement. These findings suggest that corticocerebellar interactions play a crucial role in optimizing motor preparation, offering insight into the neural mechanisms underlying movement efficiency.