The content-dependent effect of the N-back task on dual-task performance.

Impaired task accuracy under dual-task conditions leads to issues such as falls and traffic accidents. Specific cognitive tasks (e.g., the N-back task) potentially improves dual-task performance. This study aims to establish an effective cognitive-task methodology for clinical practice and identify dual-task combinations in which the N-back task is likely to improve performance. Twenty-one young, healthy adults performed an intervention task (either N-back or control), followed by single- and dual tasks in the disappearing or dexterity condition, to assess its effect on different days. The participants performed force-control and calculation tasks in both disappearing and dexterity conditions. In the disappearing force-control task, target waveforms disappeared after a few practice trials, and the participants recalled them and adjusted their knee extension torque. The dexterity force-control task involved presenting complex waveforms. The participants carefully observed the waveforms, and adjusted their knee extension torque. We measured changes in the excitability of the dorsolateral prefrontal cortex (DLPFC) using near-infrared spectroscopy to determine whether the N-back-task-induced changes contributed to improving dual-task performance. For dual-task performance in the disappearing condition, the N-back task improved the performance of the disappearing force-control task, but the control task did not. The other results were the same regardless of the type of intervention task. The N-back task enhanced a portion of the DLPFC excitability. However, no correlation was observed between changes in dual-task performance and in DLPFC excitability. Our findings may contribute to establishing an effective method for improving dual-task performance using cognitive tasks.

Clinical performance of a new intact FGF23 immunoassay in healthy individuals and patients with chronic hypophosphatemia.

While the positive association between automated intact fibroblast growth factor (FGF) 23 measurement kit (Determinar CL FGF23 [CL]) and the former assay (Kainos [KI]), and clinical utility of CL was well established, the clinical performance of Medfrontier FGF23 (MED), which was the manual intact FGF23 measurement kit with same antibody set as CL, has not yet been validated. Therefore, this study aims to compare MED FGF23 levels to KI FGF23 levels. A total of 380 samples were collected from healthy individuals, and 200 samples were collected from 20 patients with chronic hypophosphatemia. The intact FGF23 level of each sample was measured by KI and MED. Among the healthy individuals, the reference range of MED FGF23 levels was 18.6-59.8 pg/mL when calculated as the average ± 2 standard deviations. When compared with KI FGF23 levels, MED FGF23 levels were lower than KI levels both among samples from healthy individuals (KI FGF23, 40.9 [interquartile (IQR), 31.1-50.6]; MED FGF23, 38.0 [IQR, 31.5-45.7]; p value = 0.02) and among samples from patients with chronic hypophosphatemia (KI FGF23, 172.5 [IQR, 115.8-290.7]; MED FGF23, 130.2 [IQR, 93.6-247.0]; p value = 0.003). The linear regression analysis showed that the correlation between KI FGF23 and MED FGF23 was interpreted as a slope of 0.83 with a y-intercept of 0.53, revealing good linearity (R2 = 0.99). This study showed that the discrepancy between KI and MED was very similar to the previously reported data between KI and CL.

Does a Cognitive Task Promote Implicit or Explicit Motor Learning?

This study examined whether use of an N-back task could promote implicit and explicit motor learning. In Experiment 1, 30 healthy adults were assigned to an N-back task group (NTG) or a control task group (CG). All participants performed the serial reaction time task (SRTT) and generation task after either the N-back or control tasks. The results did not reveal whether the N-back task promoted implicit or explicit motor learning because participants in the NTG noticed a hidden loop in the SRTT and this "awareness" made it difficult to interpret the results in Experiment 1. In Experiment 2, we examined whether the N-back task promoted explicit motor learning only using a modified SRTT. Thirty healthy adults were assigned to the NTG or the CG. On day 1, all participants performed the modified SRTT after either the N-back or control tasks. On day 7, all participants repeated the modified SRTT. As a result, the performance on the modified SRTT was faster in the NTG than in the CG on days 1 and 7. In summary, although the N-back task might promote explicit motor learning, the present study could not clearly conclude whether the N-back task promoted implicit and explicit motor learning.

Clinical performance of a novel chemiluminescent enzyme immunoassay for FGF23.

INTRODUCTION: Measurement of fibroblast growth factor 23 (FGF23) has been reported to be clinically useful for the differential diagnosis of chronic hypophosphatemia. However, assays for research use only are available in Japan. Thus, the objective of this study was to examine the clinical utility of a novel and automated chemiluminescent enzyme immunoassay for the measurement of FGF23. MATERIALS AND METHODS: Participants were recruited from July 2015 to January 2017 at six facilities in Japan. Thirty-eight patients with X-linked hypophosphatemic rickets (XLH 15 males, 23 females, age 0-66 years), five patients with tumour-induced osteomalacia (TIO 3 males, 2 females, age 60-73 years), and twenty-two patients with hypophosphatemia (11 males, 11 females, age 1-75 years) caused due to other factors participated in this study. RESULTS: With the clinical cut-off value of FGF23 at 30.0 pg/mL indicated in the Diagnostic Guideline of Rickets/Osteomalacia in Japan, the sensitivity and specificity of FGF23-related hypophosphatemic rickets/osteomalacia without vitamin D deficiency (disease group-1) were 100% and 81.8%, respectively, which distinguished it from non-FGF23-related hypophosphatemia (disease group-2). Furthermore, the diagnostic sensitivity of FGF23-related hypophosphatemia with vitamin D deficiency remained at 100%. Among the four patients with FGF23 levels ≥ 30.0 pg/mL in disease group-2, two patients with relatively higher FGF23 values were suspected to have genuine FGF23-related hypophosphatemia, due to the ectopic production of FGF23 in pulmonary and prostate small cell carcinomas. CONCLUSION: The novel FGF23 assay tested in this study is useful for the differential diagnosis of hypophosphatemic rickets/osteomalacia in a clinical setting.

Enhancement of prefrontal area excitability induced by a cognitive task: Impact on subsequence visuomotor task performance.

Cognitive tasks may have the potential to improve visuomotor task performance; however, the reason for this is unclear. If this can be clarified, it may be possible to develop clinically valuable outcomes, such as promotion of motor learning though cognitive tasks. The present study aimed to investigate whether changes in prefrontal area excitability induced by cognitive tasks, especially within the dorsolateral prefrontal cortex (DLPFC), influenced the speed of improvement during visuomotor task performance. Twenty young healthy adults were recruited. The serial reaction time task (SRTT) was used to assess visuomotor task performance. Cognitive tasks included an adjusted N-back task, a non-adjusted N-back task, and a control task, which were evaluated on different days. Additionally, we measured cerebral hemodynamic activity using near-infrared spectroscopy while each cognitive task was being performed. We observed that the adjusted N-back task significantly enhanced the speed of improvement during the SRTT performance compared to the control task. However, there was no relationship between the speed of improvement during the SRTT performance and changes in prefrontal area excitability induced by the cognitive tasks. Our findings contribute towards developing an effective method that uses cognitive tasks to promote visuomotor learning.

The Effects of Transcranial Direct Current Stimulation on Dual-Task Interference Depend on the Dual-Task Content.

Recently, some studies revealed that transcranial direct current stimulation (tDCS) reduces dual-task interference. Since there are countless combinations of dual-tasks, it remains unclear whether stable effects by tDCS can be observed on dual-task interference. An aim of the present study was to investigate whether the effects of tDCS on dual-task interference change depend on the dual-task content. We adopted two combinations of dual-tasks, i.e., a word task while performing a tandem task (word-tandem dual-task) and a classic Stroop task while performing a tandem task (Stroop-tandem dual-task). We expected that the Stroop task would recruit the dorsolateral prefrontal cortex (DLPFC) and require involvement of executive function to greater extent than the word task. Subsequently, we hypothesized that anodal tDCS over the DLPFC would improve executive function and result in more effective reduction of dual-task interference in the Stroop-tandem dual-task than in the word-tandem dual-task. Anodal or cathodal tDCS was applied over the DLPFC or the supplementary motor area using a constant current of 2.0 mA for 20 min. According to our results, dual-task interference and the task performances of each task under the single-task condition were not changed after applying any settings of tDCS. However, anodal tDCS over the left DLPFC significantly improved the word task performance immediately after tDCS under the dual-task condition. Our findings suggested that the effect of anodal tDCS over the left DLPFC varies on the task performance under the dual-task condition was changed depending on the dual-task content.

Motor adaptation is promoted by an incongruent Stroop task, but not by a congruent Stroop task.

Motor adaptation plays an important role in the acquisition of new motor skills. It has been reported that cognitive tasks can promote motor adaptation; however, which cognitive tasks effectively promote motor adaptation remains unknown. This study aimed to examine what factors of cognitive tasks contribute to promoting motor adaptation. Forty-two healthy young adults were randomly assigned to one of three groups: incongruent Stroop task group (iSTG), congruent Stroop task group (cSTG), and control group (CG). All participants underwent 20 blocks of a mouse-tracking task on the 1st and 2nd days. Before the mouse tracking task on the 1st day, the iSTG and cSTG completed the incongruent and congruent Stroop tasks, respectively. Participants in the CG did not perform any cognitive tasks. On the 28th day, all participants underwent 3 blocks of the mouse tracking task to evaluate their retention of motor adaptation. As a result, on the 1st day, the mouse tracking task performance improved equally for both groups. However, on the 2nd and 28th days, the mouse tracking task performance in the iSTG showed greater improvements for all blocks compared to those in the CG. These results suggest that the incongruent Stroop task promotes motor adaptation, but the congruent Stroop task does not. In addition, it is suggested that factors, which are primarily involved in the incongruent Stroop task, might promote motor adaptation.

Changes in brain activity induced by the N-back task are related to improved dual-task performance.

Dual-task performance often influences athletic competition results. Previous studies have suggested that cognitive tasks might improve dual-task performance. However, the factors that contribute to the manner in which cognitive tasks improve dual-task performance remain unknown. This study aimed to examine whether changes in brain activity induced by cognitive tasks are associated with improvement in dual-task performance. Nineteen young healthy adults performed an N-back and a reaction task on different days. A dual-task was constructed by combining a force-control and a calculation task. In the force-control task, participants adjusted their knee extension force according to target waves. In the calculation task, participants were required to subtract and respond to auditory stimuli delivered via earphones. We evaluated dual-task performance before and after performing each cognitive task. Additionally, we measured cerebral hemodynamic activity using near-infrared spectroscopy during the performance of each cognitive task. As a result, performing the N-back task improved performance in the force-control task under the dual-task setup. Furthermore, increase in oxyhemoglobin in a part of the right dorsolateral prefrontal cortex during the N-back task was positively correlated with improved force control during the subsequent dual-task. Cognitive tasks can be easily performed in a clinical field. Thus, cognitive tasks could be incorporated in traditional physical training. Future research should investigate whether the present findings can translate to improving performance in athletic competitions.

Feasibility Case Study for Treating a Patient with Sensory Ataxia Following a Stroke with Kinesthetic Illusion Induced by Visual Stimulation.

BACKGROUND: Sensory ataxia is a disorder of movement coordination caused by sensory deficits, especially in kinesthetic perception. Visual stimulus-induced kinesthetic illusion (KINVIS) is a method used to provide vivid kinesthetic perception without peripheral sensory input by using a video showing pre-recorded limb movements while the actual limb remains stationary. We examined the effects of KINVIS intervention in a patient with sensory ataxia. CASE: The patient was a 59-year-old man with a severe proprioceptive deficit caused by left thalamic hemorrhage. During KINVIS intervention, a computer screen displayed a pre-recorded mirror image video of the patient's unaffected hand performing flexion-extension movements as if it were attached to the patient's affected forearm. Kinematics during the flexion-extension movements of the paretic hand were recorded before and after 20-min interventions. Transcranial magnetic stimulation was applied to the affected and non-affected hemispheres. The amplitude of the motor-evoked potential (MEP) at rest was recorded for the muscles of both hands. After the intervention, the total trajectory length and the rectangular area bounding the trajectory of the index fingertip decreased. The MEP amplitude of the paretic hand increased, whereas the MEP amplitude of the non-paretic hand was unchanged. DISCUSSION: The changes in kinematics after the intervention suggested that KINVIS therapy may be a useful new intervention for sensory ataxia, a condition for which few effective treatments are currently available. Studies in larger numbers of patients are needed to clarify the mechanisms underlying this therapeutic effect.

Effect of Auditory or Visual Working Memory Training on Dual-Task Interference.

Dual-task interference causes many accidents. Working memory (WM) training has the potential to reduce dual-task interference. However, an effective method of WM training for reducing dual-task interference has not been established. This study aimed to examine whether WM training using auditory stimuli (auditory WM training) or visual stimuli (visual WM training) would more effectively reduce dual-task interference. Twenty-two young adults performed an N-back task with auditory or visual stimuli for auditory or visual WM training, for 2 weeks. The authors assessed dual-task interference before and after each training. The authors used a hierarchic multilevel model for these assessment parameters. As a result, visual WM training might be more effective for reducing dual-task interference than auditory WM training.

Repetition of a cognitive task promotes motor learning.

Motor learning plays an important role in the acquisition of new motor skills. In this study, we investigated whether repetition of a cognitive task promoted motor learning. Fifty-one young adults were assigned to either the early, late, or control groups. All participants completed a mouse tracking task in which they manipulated a mouse to track a moving target on a screen. The cursor was rotated 165° in the counterclockwise direction from the actual mouse position, requiring participants to learn how to use a new tool. To determine the task performance, we calculated the distance between the cursor and target position. In addition, to assess the effects of a cognitive task on the progress of motor learning, curve fitting of the learning curves was performed for the total distance. Experiments were conducted as per the following schedule: learning day 1 (L1), learning day 2 (L2: the day after learning day 1), retention day 1 (R1: 2 weeks after learning day 1), and retention day 2 (R2: 4 weeks after learning day 1). Participants underwent mouse tracking for 20 min on L1 and L2 and for 3 min on R1 and R2. As a cognitive task, we adopted the N-back task. The early or late group performed the N-back task for 20 min before performing motor tracking task on L1 or L2, respectively. The control group did not perform the N-back task. Based on curve fitting analysis, it was observed that the rate of change for motor learning in the early group was higher than that in the control group. The retention of motor learning did not differ between all groups. Our results indicate that the repetition of a cognitive task enhanced in the early phase of motor learning of the mouse tracking task.

Creation of haemoglobin A1c direct oxidase from fructosyl peptide oxidase by combined structure-based site specific mutagenesis and random mutagenesis.

The currently available haemoglobin A1c (HbA1c) enzymatic assay consists of two specific steps: proteolysis of HbA1c and oxidation of the liberated fructosyl peptide by fructosyl peptide oxidase (FPOX). To develop a more convenient and high throughput assay, we devised novel protease-free assay system employing modified FPOX with HbA1c oxidation activity, namely HbA1c direct oxidase (HbA1cOX). AnFPOX-15, a modified FPOX from Aspergillus nidulans, was selected for conversion to HbA1cOX. As deduced from the crystal structure of AnFPOX-15, R61 was expected to obstruct the entrance of bulky substrates. An R61G mutant was thus constructed to open the gate at the active site. The prepared mutant exhibited significant reactivity for fructosyl hexapeptide (F-6P, N-terminal amino acids of HbA1c), and its crystal structure revealed a wider gate observed for AnFPOX-15. To improve the reactivity for F-6P, several mutagenesis approaches were performed. The ultimately generated AnFPOX-47 exhibited the highest F-6P reactivity and possessed HbA1c oxidation activity. HbA1c levels in blood samples as measured using the direct assay system using AnFPOX-47 were highly correlated with the levels measured using the conventional HPLC method. In this study, FPOX was successfully converted to HbA1cOX, which could represent a novel in vitro diagnostic modality for diabetes mellitus.

Neuromuscular electrical stimulation increases serum brain-derived neurotrophic factor in humans.

Brain-derived neurotrophic factor (BDNF) plays several important roles in nervous system function including neuronal growth and plasticity. The purpose of the present study was to clarify whether neuromuscular electrical stimulation (NMES) and voluntary exercise to the same integrated force as by the NMES-induced exercise would enhance serum BDNF. Eleven healthy male subjects completed three interventions (NMES, voluntary exercise, and resting interventions) for 20 min on different days. In the NMES intervention, NMES was applied to the quadriceps femoris muscles. The stimulus intensity of NMES was progressively increased to the highest tolerated intensity during the experiment. In the voluntary exercise intervention, subjects performed an isometric knee-extension task; in this intervention, the target torque was calculated in accordance with the integrated force of knee extension obtained during the NMES intervention. In the resting intervention, subjects relaxed in a sitting posture. We measured serum BDNF, blood lactate, heart rate, oxygen uptake, respiratory ratio, and blood pressure. Serum BDNF was increased in the NMES (p = 0.003) and voluntary exercise interventions (p = 0.004) after each intervention. At the post-timepoint, serum BDNF in the NMES intervention was highest among all interventions (p = 0.038) and significantly higher than in the voluntary exercise (p = 0.036) and resting (p = 0.037) interventions. Our results showed that NMES was more effective for enhancing serum BDNF than voluntary exercise at least when employing the same method and integrated force.

Working Memory Training Improves Dual-Task Performance on Motor Tasks.

The authors investigated whether working memory training improves motor-motor dual-task performance consisted of upper and lower limb tasks. The upper limb task was a simple reaction task and the lower limb task was an isometric knee extension task. 45 participants (age = 21.8 ± 1.6 years) were classified into a working memory training group (WM-TRG), dual-task training group, or control group. The training duration was 2 weeks (15 min, 4 times/week). Our results indicated that working memory capacity increased significantly only in the WM-TRG. Dual-task performance improved in the WM-TRG and dual-task training group. Our study provides the novel insight that working memory training improves dual-task performance without specific training on the target motor task.

An enzyme combination assay for serum sphingomyelin: Improved specificity through avoiding the interference with lysophosphatidylcholine.

Serum sphingomyelin (SM) has predictive value in the development of atherosclerosis. Furthermore, SM plays important roles in cell membrane structure, signal transduction pathways, and lipid raft formation. A convenient enzymatic method for SM is available for routine laboratory practice, but the enzyme specificity is not sufficient because of nonspecific reactions with lysophosphatidylcholine (LPC). Based on the differential specificity of selected enzymes toward choline-containing phospholipids, a two-step assay for measuring SM was constructed and its performance was evaluated using sera from healthy individuals on a Hitachi 7170 autoanalyzer. Results from this assay were highly correlated with theoretical serum SM concentrations estimated by subtracting phosphatidylcholine (PC) and LPC concentrations from that of total phospholipids determined using previously established methods. There was a good correlation between the results of SM assayed by the proposed method and the existing enzymatic method in sera from healthy individuals. Moreover, the proposed method was superior to the existing method in preventing nonspecific reactions with LPC present in sera. The proposed method does not require any pretreatment, uses 2.5 µl of serum samples, and requires only 10 min on an autoanalyzer. This high-throughput method can measure serum SM with sufficient specificity for clinical purposes and is applicable in routine laboratory practice.

Effect of blood volume in resting muscle on heart rate upward drift during moderately prolonged exercise.

The aim of this study was to determine whether the increase in blood volume in resting muscle during moderately prolonged exercise is related to heart rate (HR) upward drift. Eight healthy men completed both arm-cranking moderately prolonged exercise (APE) and leg-pedaling moderately prolonged exercise (LPE) for 30 min. Exercise intensity was 120 bpm of HR that was determined by ramp incremental exercise. During both APE and LPE, HR significantly increased from 3 to 30 min (from 108±9.3 to 119±12 bpm and from 112±8.9 to 122±11 bpm, respectively). However, there was no significant difference between HR in APE and that in LPE. Oxygen uptake was maintained throughout the two exercises. Skin blood flow, deep temperature, and total Hb (blood volume) in resting muscle continuously increased for 30 min of exercise during both APE and LPE. During both APE and LPE, there was a significant positive correlation between total Hb and deep temperature in all subjects. Moreover, there was a significant positive correlation between HR and total Hb (in seven out of eight subjects) during LPE. However, during APE, there was no positive correlation between HR and total Hb (r=0.391). These findings suggest that an increase of blood pooling in resting muscle could be proposed as one of the mechanisms underlying HR upward drift during moderately prolonged exercise.

Evaluation of partial body composition using bioelectrical impedance in Japanese children.

To clarify the growth pattern of body composition by body part for the management of childhood obesity, we measured body fat and muscle using BIA (bioelectrical impedance analysis) in 685 Japanese elementary schoolchildren (aged 6-11 years). The growth patterns of percentage body fat (%BF), fat mass (FM), and muscle mass (MM) were examined throughout the whole body and in various body parts. The %BF of the whole body was greater in females than in males, and this difference widened with age. The %BF, FM, and MM in each body part showed similar growth patterns and gender differences to those of the whole body. The mean %BF of the left limbs was higher than that of the right limbs at all age groups. BMI was strongly correlated with %BF in both sexes. In conclusion, the compositions of all body parts change similarly with age, and gender differences are also similar in childhood. The effect of one's dominant arm on body composition is seen at a young age. The accumulation of body composition data according to body part is indispensable for understanding childhood body composition and managing obesity.

Examination of oxygen uptake kinetics in decremental load exercise by a numerical computation model.

The purpose of this study was to establish a numerical computation model for estimation of oxygen uptake (V(.)O2) kinetics in decremental load exercise (DLE) starting from a work rate (WR) above the ventilatory threshold (>VT). In the model, WR in DLE were separated into several steps (constant load exercise, CLE) of which the durations increased step by step. V(.)O2 kinetics in each step was estimated using an exponential equation, and the sum of VO2 values from all steps at a given time was regarded as simulated V(.)O2 in DLE. In the model, the time constants were set symmetrically in a step VT at onset and offset (tau(off)) of exercise. As a result, simulated V(.)O2 qualitatively, but not quantitatively, approximated measured V(.)O2. Consequently, we incorporated a new model in which a step >VT was subdivided into several parts. Although there was a slight difference quantitatively, the interval of subdivision of 3.0 min and tau(off) of 2.8 min allowed for qualitative approximation. The numerical computation model adopted in this study is useful for estimation of V(.)O2 kinetics during DLE starting from high intensity (>VT).

Predicting obesity in early adulthood in Japanese women.

AIM: We analysed the body measurements of Japanese women to determine which factors may forecast adult obesity and also performed a comparative study of the utility of body mass index (BMI), which is used widely in Western Europe, and percentage of overweight, which is used in Japan. METHODS: Subjects included 244 Japanese women who were born between 1983 and 1986. Using a questionnaire, we investigated anthropometric values from birth to present and parents' present anthropometric data, and analysed factors that correlate with current BMI data. RESULTS: (i) BMI after 10 years of age and BMI increase between ages 7 and 8 years correlated with BMI in adulthood. The carrying over rate of overweight increased with age. Meanwhile, percentage of overweight after 13 years onwards correlated with BMI in adulthood. (ii) Adult BMI positively correlated to both parents' BMI. CONCLUSIONS: (i) For a Japanese woman, BMI in childhood is a good indicator of young adult BMI, and has the possibility of becoming an important parameter to monitor obesity progression. (ii) Therefore, attempts to control obesity in elementary school girls are necessary. (iii) Parents' weights may potentially influence obesity in adulthood; however, further examination of other confounding factors is necessary.

Effect of oral administration of sodium bicarbonate on surface EMG activity during repeated cycling sprints.

The purpose of this study was to determine the effect of oral administration of sodium bicarbonate (NaHCO3) on surface electromyogram (SEMG) activity from the vastus lateralis (VL) during repeated cycling sprints (RCS). Subjects performed two RCS tests (ten 10-s sprints) interspersed with both 30-s and 360-s recovery periods 1 h after oral administration of either NaHCO3 (RCSAlk) or CaCO3 (RCSPla) in a random counterbalanced order. Recovery periods of 360 s were set before the 5th and 9th sprints. The rate of decrease in plasma HCO3- concentration during RCS was significantly greater in RCSAlk than in RCSPla, but the rates of decline in blood pH during the two RCS tests were similar. There was no difference between change in plasma lactate concentration in RCSAlk and that in RCSPla. Performance during RCSAlk was similar to that during RCSPla. There were no differences in oxygen uptake immediately before each cycling sprint (preVO2) and in SEMG activity between RCSAlk and RCSPla. In conclusion, oral administration of NaHCO3 did not affect SEMG activity from the VL. This suggests that the muscle recruitment strategy during RCS is not determined by only intramuscular pH.