Shu Morioka

The relationship between gait characteristics and clinical ataxia severity, after accounting for walking speed, remains insufficiently characterized following cerebellar stroke. We examined direction-specific trunk acceleration and lower-limb kinematics during comfortable walking. This multicenter cross-sectional study included 55 patients with subacute cerebellar stroke and 56 healthy controls. Inertial measurements quantified lower-limb kinematics, trunk acceleration root mean square (RMS; without speed normalization), and sample entropy (SampEn). Analyses included group-by-speed models, speed-matched one-dimensional statistical parametric mapping, and exploratory patient-only, speed-adjusted regressions and partial Spearman correlations with the Scale for the Assessment and Rating of Ataxia (SARA). Patients walked more slowly, with lower anteroposterior and mediolateral RMS but higher anteroposterior and vertical SampEn. After speed adjustment, each five-point higher SARA score was associated with smaller peak limb flexion (− 1.01°; 95% confidence interval, − 1.99 to − 0.02) and less-negative extension (+ 1.21°; 0.08 to 2.34), both with Benjamini–Hochberg-adjusted P = 0.045. None of the six full-cohort group-by-speed interactions met the adjusted significance criterion. In speed-matched comparisons (11 per group), significant waveform differences were confined to limb angles near the beginning and end of the gait cycle. In speed-adjusted rank analyses, vertical RMS correlated with SARA (partial ρ = 0.471) and limb angles, but the original-scale linear SARA coefficient remained uncertain. Vertical SampEn showed no clear association with SARA or limb kinematics. Higher ataxia severity was associated with smaller whole-limb excursions in speed-adjusted models. These exploratory findings support interpreting trunk acceleration magnitude and regularity alongside whole-limb movement and clinical severity.

Stroke rehabilitation cannot be fully explained by impairment severity alone and presents three dissociations: patients who can move a paretic limb but do not use it (learned nonuse); patients with mild motor paresis who nevertheless walk slowly; and patients with unilateral spatial neglect whose recovery plateaus despite preserved compensatory capacity. We hypothesize that these dissociations reflect a shared problem in cross-layer updating. We model the self as three hierarchically coupled comparators operating over distinct temporal scales: a sensorimotor comparator (the meter), which integrates predicted and actual sensory feedback within a millisecond-scale window and provides evidence for the feeling of agency; an intention–outcome comparator (the judge), which integrates action–outcome evidence over seconds and supports judgment of agency; and a narrative-self comparator (the author), which represents a months-to-years biographical horizon. Precision-weighted prediction error provides a common currency across layers, with social input operating at each layer, from joint action to social support. The model proposes that error-based adaptation occurs within layers, whereas recovery-supporting cross-layer revision is gated by self-attribution and personal meaning. Accordingly, revision of the generative models that support recovery requires success to be attributed to the self at the intention–outcome level and integrated as meaningful at the narrative level. This update rule frames learned nonuse as hypothesized under-crediting of self-generated success, slow walking despite mild paresis as hypothesized precision misallocation, and the neglect plateau as a hypothesis-generating extension involving narrative-level updating. We derive layer-specific rehabilitation principles, including perceptual learning, agency-amplifying technology, and narrative goal-setting mapped onto the International Classification of Functioning, Disability and Health (ICF), and state falsifiable predictions. The model complements the philosophical framework of narrative embodiment by specifying computational processes that link embodied and narrative selves and may become dissociated after stroke.

Background: Post‐stroke pain (PSP) presents with diverse pain qualities. However, the structural brain correlates underlying these distinct pain qualities remains poorly understood. Methods: We analysed PSP patients using clinical assessments, clustering based on pain qualities assessed using the Neuropathic Pain Symptom Inventory, longitudinal pain intensity evaluation and brain lesion/disconnection mapping (computed tomography/magnetic resonance imaging and Bayesian lesion‐deficit inference). Pain quality–based clusters and their corresponding lesion sites and white matter tracts were identified. Results: We analysed 114 PSP patients. Cluster analysis using pain qualities classified patients into four distinct subgroups: CL1 (cold‐evoked/tingling), CL2 (deep squeezing/pressure), CL3 (tingling) and CL4 (pressure‐evoked). CL1 and CL3 patients predominantly exhibited features of central post‐stroke pain, characterised by sensory disturbances such as allodynia and numbness. Lesion mapping revealed involvement of the thalamus, putamen and posterior insula. Disconnection analysis identified the superior thalamic radiation (Bayes factor > 70) as a common white matter tract. In contrast, CL2 and CL4 were characterised by musculoskeletal‐type pain associated with joint pain, restricted range of motion and higher motor impairment. Lesions in these groups were mainly localised to the frontal lobe, with disconnection of the corticospinal and fronto‐aslant tracts (Bayes factor > 50). Longitudinal analysis demonstrated pain intensity decreased over time across all clusters, with a trend towards slower improvement in Cluster 3. Conclusions: Pain quality reflects distinct pathological mechanisms of PSP and may be associated with specific patterns of brain lesions and white matter disconnections and rehabilitation prognosis. Identifying pain‐quality subtypes may help inform outcomes and guide personalised rehabilitation. Significance Statement: By linking distinct pain qualities with lesion and disconnection profiles, this study clarifies the neural mechanisms underlying post‐stroke pain. Identifying these pain‐quality subtypes provides insights into prognosis and supports the development of personalized rehabilitation strategies tailored to specific pain mechanisms.

Purpose: The prognosis of post-stroke ataxia remains controversial. It is unclear whether the proportional recovery rule (PRR) established for hemiparesis applies to ataxia, given that cerebellar plasticity suggests trajectories may not depend solely on initial severity. This study was conducted to quantitatively decompose longitudinal ataxia recovery trajectories into proportional recovery coefficient (r) and time constant (τ) using a Bayesian nonlinear mixed-effects model, and elucidate their independent determinants and associations with functional walking independence. Methods: We analyzed longitudinal SARA scores of 80 subacute patients with stroke to estimate individual initial severity (α), r, and τ. Recovery patterns were clustered based on these parameters. We analyzed the attainment of independent walking using the Kaplan–Meier method and identified predictors via hierarchical multiple regression analysis. Results: Three distinct clusters were identified. The moderate group (younger, preserved attention) achieved rapid improvement and early walking independence. In contrast, the severe group showed a significantly prolonged time constant (τ) but maintained a high proportional recovery coefficient (r), ultimately achieving walking independence in over 90% of cases. Regression analysis revealed a dissociation: biological age constrained the recovery ceiling (r), while attentional function independently regulated recovery speed (τ). Conclusions: Recovery from post-stroke ataxia bifurcates into rapid neurological restoration and a delayed process driven by compensatory learning. Especially in severe cases, long-term learning using attentional resources is crucial. These findings challenge prognosis prediction based solely on initial severity, supporting stratified rehabilitation strategies tailored to individual recovery ceilings and learning speeds.

Illusions have historically been used in experimental psychology to reveal information about perceptual processes. A recent study reported that participants felt a sense of body heaviness when given slightly delayed (incongruent) visual feedback compared with the predicted somatosensory feedback. In this study, we reported a novel illusion of feeling a sense of body lightness while walking. There is consensus that an important factor in a body’s perceptual process is congruency between the senses. When our 30 participants experienced “subjectively preceding feedback” while walking on a treadmill, nine of them felt a sense of body lightness. In this report, we discussed how we were able to generate the subjectively preceding feedback, the mechanism that induces the illusion of a sense of body lightness, and the potential applications of this illusion. Although this study was just a preliminary and exploratory research, this new illusion has the potential to contribute not only to the medical and rehabilitation fields but also to extended reality technology and other interdisciplinary fields.

Introduction: Improved walking ability is a common rehabilitation goal for individuals following a stroke. However, the reasons why hospitalized individuals with stroke consider walking to be important are not yet fully understood. This study aimed to elucidate the perceived importance of walking among hospitalized patients with stroke. Methods: This qualitative study employed thematic analysis. Hospitalized individuals with stroke undergoing gait rehabilitation were purposively sampled to capture variation in sex, age, and walking ability. The participants underwent in-person semi-structured interviews regarding the importance of walking, which were audio-recorded, transcribed verbatim, and systematically coded to generate themes. Results: A total of 19 patients participated in the study. Thematic analysis revealed six major themes. (1) Resumption of daily life: walking was perceived as essential for returning to pre-stroke activities and routines. (2) Health promotion and prevention of functional decline: participants viewed walking as important for maintaining health and preventing deterioration. (3) Uncomfortable walking: participants described physical and environmental challenges associated with walking. (4) Relationships with others: concerns were expressed about how walking difficulties might affect relationships with family and others. (5) Labeling of decreased walking ability: participants were conscious of how their walking was perceived by others. (6) Social environment: walking was linked to broader social factors such as work and transportation. Conclusion: The importance of walking for hospitalized patients with stroke ranges from impersonal and generalizable reasons to highly individualized and diverse factors, with implications for individualized walking rehabilitation.

Background: Pain, fear, and motor function are interrelated. This study aimed to clarify their causal relationships by examining longitudinal changes from the preoperative to the acute postoperative period after total knee arthroplasty (TKA). Methods: This exploratory prospective observational study included 27 inpatients (mean age, 74.1 years [SD = 9.9]; 40 knees). Pain, fear and motor function were assessed preoperatively and 1 and 2 weeks postoperatively. At each time point, rest pain, motion pain, fear of motion, and kinematic parameters of knee movement (velocity, angle, surplus null and spectral entropy) were measured. The cross‐lagged panel model was used to estimate causal relationships. Results: Longitudinal analysis revealed that reduced movement at 1 week predicted greater rest pain at 2 weeks, and higher rest pain at 1 week predicted more excessive movement irregularity at 2 weeks. Models including preoperative factors did not meet the goodness‐of‐fit criteria and were therefore excluded. Conclusions: Pain and motor function predicted each other through distinct factors and pathways during the acute postoperative recovery period after TKA. These interactions may contribute to persistent pain and functional limitations, highlighting the need for targeted early interventions. Significance: Understanding the temporal relationships between acute postoperative pain and knee kinematics may provide insights into the mechanisms underlying prolonged recovery. Significance Statement: Excessive behavioural avoidance in the acute postoperative period may be involved in prolonged pain and motor dysfunction after total knee arthroplasty. In this study, longitudinal analysis of pain, fear, and motor impairment (behaviour) was conducted using a cross lagged panel model. Decreased range of motion in the acute phase predicted delayed pain recovery, whereas pain intensity predicted awkward movement. These results may indicate specific problems that should be addressed in the early postoperative period.

The ability to detect small errors between sensory prediction in the brain and actual sensory feedback is important in rehabilitation after brain injury, where motor function needs to be restored. To date in the recent study, a delayed visual error detection task during upper limb movement was used to measure this ability for healthy participants or patients. However, this ability during walking, which is the most sought-after in brain-injured patients, was unclear. The main purpose of this study was to investigate the effects of walking parameters, the sense of body heaviness, and delayed error detection rate in a visual feedback delay experiment during treadmill walking for healthy participants. It was also unclear how sagittal or frontal feedback during walking, which is commonly used clinically, affects the error detection task. Therefore, another purpose of the study was to investigate whether each outcome was modulated by different observation viewpoints. We found that walking parameters (step time and stride time), sense of body heaviness, and incongruence detection rate were increasing with delay time and that these data did not depend on the observation viewpoints. In the future, this study will provide an important cue to develop the methods that assess the sensory-motor integration function of patients during walking.