Background: In this study, a cast brace was used to immobilize the knee, hip, and trunk, and relations between the event-related brain potential (ERP) and postural muscle activity were investigated while standing on an oscillating table.Methods: Twelve healthy young adults maintained a standing posture for 1 min per trial while oscillating in the anteroposterior direction at 0.5 Hz with a 2.5-cm amplitude. Trials were performed without and with the cast brace (no-fixation and fixation condition, respectively) until the subject had adapted to the floor oscillation. The ERP from the Cz electrode, postural muscle activity, and joint movement range were analyzed for the first and last two trials (before and after adaptation, respectively).Results: Movement range of the hip and knee was lower in the fixation condition than in the no-fixation condition, and postural control was achieved by pivoting at the ankle. Peak muscle activity was largest in the gastrocnemius (GcM) in both conditions. GcM activity significantly increased after fixation and then decreased with adaptation. The time of peak erector spinae (ES) activity in the fixation condition was significantly earlier than in the no-fixation condition and was not significantly different from the time of the anterior reversal and peak of triceps surae activity. The negative ERP peaked approximately 80 ms after the anterior reversal. Significant correlations between the time of the peak negative ERP and the peak GcM, soleus, and ES activity were observed only after the adaptation, and were greater in the fixation condition (r = 0.83, 0.84, and 0.83, respectively) than in the no-fixation condition (r = 0.62, 0.73, and 0.51, respectively).Conclusion: All joints of the leg and trunk except for the ankle were rigidly fixed by the cast brace, and the phase differences between body segments were very small in the fixation condition. High correlations between the time of the peak negative ERP and the peak GcM, soleus, and ES activity after adaptation in the fixation condition suggest that attention would be more focused on anticipatory processing of muscle sensory information from the triceps surae and/or ES, particularly GcM, which had the greatest activation.

The event-related potential (ERP) mainly reflecting activation of the frontal lobe was measured during periodic floor oscillation, and changes in postural preparation and attention to the postural disturbance according to this adaptation were investigated. The experiment consisted of two tasks with eyes closed: adaptation to floor oscillation and finger flexion coinciding with the anterior and posterior reversals of oscillation. Subjects were 20 healthy young adults. They maintained a standing posture for 1 min (1 trial) on the force platform which oscillated in the anteroposterior direction at 0.5 Hz and an amplitude of 2.5 cm. ERP from a Cz electrode, activity of postural muscles and the center of foot pressure in the anteroposterior direction (CoPy) were analyzed. In the adaptation task, the speeds of CoPy fluctuation gradually decreased and reached a plateau between 4th and 14th trials, with inter-subject differences. Posterior postural muscles were activated in response to the anterior reversal of oscillation according to adaptation and also in the finger flexion task, with the largest activation of the gastrocnemius (GcM). A negative ERP peak was observed to occur locally around the anterior reversal of oscillation after adaptation. The peak ERP time had the strongest positive correlation with the peak activation time of the GcM, and the amplitude of the negative peak decreased with adaptation. In the finger flexion task, a negative ERP peak was observed around each target point. This negative peak was related to the anticipatory attention directed to the reversal point and to motor preparation for finger flexion. It is conceivable that the increasing negative ERP in the adaptation task reflects the dynamics of motor preparation and attention mainly for the anterior reversal, where the negative ERP peak is closely related to anticipatory information processing of somatosensory stimuli arising around the time of the reversal.

Background: We investigated the effect of time constraint on activation timing of postural muscles during bilateral arm flexion in self-timing, oddball and simple-reaction tasks.Methods: Thirteen healthy adults flexed their arms from a suspended position with maximum speed and stopped at the shoulder level. For erector spinae-longissimus (ES), biceps femoris (BF), and gastrocnemius (GcM), onset timing of burst activation with respect to the anterior deltoid (AD), and the displacement of the center of pressure in the anteroposterior direction (CoPy) were analyzed.Results: AD reaction time was significantly shorter in the simple-reaction task than oddball task, suggesting that time constraint would be lower in the task order noted above and affected the state of postural preparation. The following properties were found in the onset timing of postural muscle: (1) the onset timing of BF and GcM were earlier in the task order noted above, and (2) the earliest activated distal muscle in the self-timing task was activated later in the simple-reaction task. CoPy displacement was smaller in the same task order as the onset timing.Conclusions: It appears that with sufficient postural preparation, the focus of postural control is on the reduction of postural disturbance and earlier lower leg muscle activation. (C) 2011 Elsevier Ltd. All rights reserved.

We investigated the effects of balance difficulty on contingent negative variation (CNV) and postural preparation against perturbation. Thirteen subjects were perturbed by a backward floor translation (S2) after an auditory warning stimulus. To alter balance difficulty, subjects maintained standing posture from four initial positions before perturbation. The position of the center of pressure in the anteroposterior direction (CoPy) was expressed as a percentage distance of foot length (%FL) from the heel: 10%FL anterior to extreme backward leaning; quiet standing (QS); and 20%FL and 10%FL posterior to extreme forward leaning. CNV, CoPy, and electromyography (EMG) of the lower leg muscles were analyzed. Balance difficulty was represented by the relative distance of the forward peak position of CoPy after S2 from the QS position. Balance difficulty was higher with a more anterior initial position. The late CNV peaked just before S2 (latency: -76 to -306 ms), then started becoming small. CNV peak was earlier and larger with increasing balance difficulty. CoPy backward shift and a continuous EMG increase were observed as the strategy for postural preparation, and were significantly earlier (61 ms and 42 ms, respectively) than the CNV peak. CNV peak time correlated closely with onset times of CoPy backward shift (r=0.78) and continuous EMG increase (r=0.71). These findings suggest that as balance difficulty increases, attentional allocation to sensory information and/or postural preparation starts earlier just before the perturbation.

The current work presents an integrated solution for task-centric proactive information delivery (PID) in agile knowledge working (AKW) environments. The approach exploits a lightweight incremental modeling of task relevant knowledge domains and process know-how using concept maps together with concept-based task tagging to improve the quality of PID results. The feasibility of the described approach was proved during the joint research project TaskNavigator conducted by Ricoh Co. Ltd and DFKI GmbH.

During the last decade, a plenty of approaches for intelligent user assistance in knowledge intensive working environments were developed. These solutions vary from a lightweight proactive information delivery (PID) based on a non-intrusive user observation to workflow-based assistance that requires formal modeling of processes, organizations, knowledge domains and task specific information needs. Whereas lightweight solutions have low precision and sometimes yet increase the user’s information overflow, approaches based on sophisticated modeling have severe problems with bootstrapping and maintenance. The work presented in the current paper aims to find an optimal integrated solution for user assistance in agile knowledge working environments that exploits a lightweight incremental modeling of task relevant knowledge and process know-how using concept maps and concept-based task tagging to improve the quality of PID results. The feasibility of the described approach was proved during the joint research project TaskNavigator conducted by Ricoh Co. Ltd and DFKI GmbH.

No previous study has investigated age-related changes in prefrontal hemodynamics during saccade tasks in a large number of elderly adults. The purpose of this study was to evaluate prefrontal activity related to the performance of anti-saccade in the elderly using near-infrared spectroscopy (NIRS). Ninety-six elderly adults and 22 young adults performed pro- and anti-saccade tasks. Measures included reaction times of both saccades, error rate during anti-saccade, and concentration of oxyhemoglobin (Deltaoxy-Hb) in the prefrontal cortex during both saccades. Saccade performance, especially error rate, was significantly poorer in the elderly than the young. In the elderly, error rates were widely distributed from 5% to 100%. In about half (48%) of the elderly, error rates were distributed under the mean+3 standard deviations (48%) for the young, and Deltaoxy-Hb did not differ significantly from that in the young. Elderly subjects whose anti-saccade reaction time was over the regression line (of reaction time in anti-saccade to that in pro-saccade in the young)+2 standard errors showed a strong positive correlation (r=0.79) between Deltaoxy-Hb and error rate, as did those whose error rate exceeded 48%. In the elderly subjects whose error rates exceeded 90%, Deltaoxy-Hb was extremely small and deviated greatly from the correlation between Deltaoxy-Hb and error rate. Based on these findings, we propose a method of evaluating inhibitory function and attention allocation in anti-saccade performance, which is mainly related to the prefrontal cortex, in the elderly, using NIRS.

The soleus, one of the triceps surae muscles, greatly contributes to standing and walking. Strength training focused on the soleus could be important to prevent age-related deterioration in these functions. We therefore investigated the effects of regular heel-raise training focused on the soleus for the elderly. Forty-nine healthy women aged 60 to 79 years trained for at least 40 days in a period of two months. Training consisted of a set of 100 repetitions per day of heel-raise with both legs in a standing position. The training effect was evaluated by changes in each muscle thickness of the soleus and gastrocnemius medialis, which was measured using an ultrasound scanner, as well as plantar flexor strength. The subjects' ability to perform the training and their subjective opinions of its effects were assessed by a questionnaire survey. Plantar flexor strength and thicknesses of the soleus and gastrocnemius medialis were increased significantly by the training. The percentage increase in thickness was significantly greater for the soleus than for the gastrocnemius medialis (12.7% vs. 6.6%). These improvements did not significantly correlate with age. The questionnaire results suggested that the elderly were able to safely and easily perform the heel-raise training at home. This study demonstrated that regular heel-raise training is an effective muscle training method for the elderly, focused on the soleus.

During the last decade, a plenty of approaches for intelligent user assistance in knowledge intensive working environments were developed. These solutions vary from a lightweight proactive information delivery (PID) based on a non-intrusive user observation to workflow-based assistance that requires formal modeling of processes, organizations, knowledge domains and task specific information needs. Whereas lightweight solutions have low precision and sometimes yet increase the user’s information overflow, approaches based on sophisticated modeling have severe problems with bootstrapping and maintenance. The work presented in the current paper aims to find an optimal integrated solution for user assistance in agile knowledge working environments that exploits a lightweight incremental modeling of task relevant knowledge and process knowhow using concept maps and concept-based task tagging to improve the quality of PID results. The results from our case study show that the task tagging is feasible and facilitates PID quality improvement.

We investigated the effects of neck flexion on contingent negative variation (CNV) and anticipatory postural control using an arm flexion task in standing. CNV was adopted to evaluate the state of activation of brain areas related to anticipatory postural control. Subjects were required to flex the arms in response to a sound stimulus preceded by a warning sound stimulus. Two different intervals (2.0 and 3.5s) between these two stimuli were used in neck position in quiet standing (neck resting) and neck position at 80% angle of maximal neck flexion. The mean amplitude of CNV 100-ms before the response stimulus, recorded from a Cz electrode, was calculated. Onset timing of activation of the postural muscles (lumbar paraspinal, biceps femoris and gastrocnemius) with respect to the anterior deltoid was analyzed. Reaction time at the anterior deltoid was significantly shorter in the 2.0s period than in the 3.5s period, and in the neck flexion than in the neck resting in both periods. In the 2.0s, but not in the 3.5s period, neck flexion resulted in an increased CNV amplitude and an increased duration of preceding activation of the postural muscles, and the correlation between these increases was significant.