Horizontal intracortical projections for agonist and antagonist muscles exist in the primary motor cortex (M1), and reward may induce a reinforcement of transmission efficiency of intracortical circuits. We investigated reward-induced change in M1 excitability for agonist and antagonist muscles. Participants were 8 healthy volunteers. Probabilistic reward tasks comprised 3 conditions of 30 trials each: 30 trials contained 10% reward, 30 trials contained 50% reward, and 30 trials contained 90% reward. Each trial began with a cue (red fixation cross), followed by blue circle for 1 s. The subjects were instructed to perform wrist flexion and press a button with the dorsal aspect of middle finger phalanx as quickly as possible in response to disappearance of the blue circle without looking at their hand or the button. Two seconds after the button press, reward/non-reward stimulus was randomly presented for 2-s duration. The reward stimulus was a picture of Japanese 10-yen coin, and each subject received monetary reward at the end of experiment. Subjects were not informed of the reward probabilities. We delivered transcranial magnetic stimulation of the left M1 at the midpoint between center of gravities of agonist flexor carpi radialis (FCR) and antagonist extensor carpi radialis (ECR) muscles at 2 s after the red fixation cross and 1 s after the reward/non-reward stimuli. Relative motor evoked potential (MEP) amplitudes at 2 s after the red fixation cross were significantly higher for 10% reward probability than for 90% reward probability, whereas relative MEP amplitudes at 1 s after reward/non-reward stimuli were significantly higher for 90% reward probability than for 10% and 50% reward probabilities. These results implied that reward could affect the horizontal intracortical projections in M1 for agonist and antagonist muscles, and M1 excitability including the reward-related circuit before and after reward stimulus could be differently altered by reward probability.

This study aimed to investigate the relationship between knee extension strength and gait performance with walking aids and the threshold level of strength to predict gait performance with walking aids in patients with dementia using ordinal logistic modeling. This cross-sectional, observational correlation study was conducted in 56 hospital inpatients with dementia. Knee extensor strength was measured using a hand-held dynamometer. Gait performance was assessed by determining the walking aid that enables the subject to walk 10 m independently as well as without a walking aid. Ordinal logistic modeling showed that the strength of the knee extensor muscles was a significant gait predictor with walking aids (P = .028). Knee extension strength of 0.17, 0.43, and 0.57 N m/kg could reach 80% independence probability for gait with walker, with cane, and without walking aid, respectively. Knee extension strength was significantly related to gait performance with walking aid in people with dementia. Moreover, there are threshold levels of strength that could predict gait with particular walking aid in people with dementia. With regard to resistance training and prescription of walking aids, the probability of independence evaluated from ordinal logistic modeling contributes to efficient rehabilitation intervention.

The short-term effects of botulinum toxin type A (BoNT-A) treatment in stroke patients with upper extremity are well established. This study examined the association between the recovery of motor function of the upper extremity with subjective physical symptoms in outpatients receiving long-term BoNT-A and occupational therapy following stroke. We also investigated the expectations of patients who elected to continue treatment. Forty-seven patients (23 men and 24 women) aged 61 years received BoNT-A treatment more than 20 times. The subjective physical status was analyzed by using the visual analogue scale score through an eight-item questionnaire. Recovery of motor function in the upper extremity was detected by calculating the change (delta) in Fugl–Mayer Assessment (FMA), and ordinal logistic modeling analysis was used to determine the association between the delta-FMA score and the subjective level of agreement for each item. When the ordinal logistic modeling fit was statistically significant, results were interpreted as having logistic probability. The logistic curves discriminating one point (strongly disagree) from five points (strongly agree) were fit in a stepwise fashion. This study suggests that patients receiving long-term BoNT-A treatment and occupational therapy experienced an increased upper extremity mitigation and decreased insomnia after injection, regardless of the recovery of motor function.

To investigate the relationships between grip strengths and self-care activities in stroke patients using a non-linear support vector machine (SVM). Overall, 177 inpatients with poststroke hemiparesis were enrolled. Their grip strengths were measured using the Jamar dynamometer on the first day of rehabilitation training. Self-care activities were assessed by therapists using Functional Independence Measure (FIM), including items for eating, grooming, dressing the upper body, dressing the lower body, and bathing at the time of discharge. When each FIM item score was ≥6 points, the subject was considered independent. One thousand bootstrap grip strength datasets for each independence and dependence in self-care activities were generated from the actual grip strength. Thereafter, we randomly assigned the total bootstrap datasets to 90% training and 10% testing datasets and inputted the bootstrap training data into a non-linear SVM. After training, we used the SVM algorithm to predict a testing dataset for cross-validation. This validation procedure was repeated 10 times. The SVM with grip strengths more accurately predicted independence or dependence in self-care activities than the chance level (mean ± standard deviation of accuracy rate: eating, 0.71 ± 0.04, P < .0001; grooming, 0.77 ± 0.03, P < .0001; upper-body dressing, 0.75 ± 0.03, P < .0001; lower-body dressing, 0.72 ± 0.05, P < .0001; bathing, 0.68 ± 0.03, P < .0001). Non-linear SVM based on grip strengths can prospectively predict self-care activities.

Objective: The difference between positive and negative outcomes is important in trial‐and‐error decision‐making processes and affects corticospinal excitability. This study investigated corticospinal excitability during the performance of trial‐and‐error decision‐making tasks with varying competing behavioral outcomes.Methods: Each trial began with one of five colored circles presented as a cue. Each color represented a different reward probability, ranging from 10% to 90%. The subjects were instructed to decide whether to perform wrist flexion in response to the cue. Two seconds after the presentation of the cue, a reward stimulus (picture of a coin) or penalty stimulus (mauve circle) was randomly presented to the subject. If the picture of a coin appeared, the subjects received the coin after the experiment if they had performed wrist flexion, but not if they had not performed wrist flexion. If a mauve circle appeared, a coin was deducted from the total reward if the subjects had performed wrist flexion, but not if they had not performed wrist flexion. One second after the reward or penalty stimulus, transcranial magnetic stimulation was delivered to the primary motor cortex at the midpoint between the centers of gravity of the flexor carpi radialis (agonist) and extensor carpi radialis (antagonist) muscles.Results: Cumulative wrist flexions were positively correlated with reward probabilities. Motor evoked potential (MEP) amplitudes in agonist muscles were significantly higher when wrist flexion incurred a penalty than when it incurred a reward, but there was no difference in the MEP amplitudes of antagonist muscles.Conclusion: Positive and negative behavioral outcomes differentially altered behavior and corticospinal excitability, and unexpected penalties had a stronger effect on corticospinal excitability for agonist muscles.