Visual and Proprioceptive Adaptation of Arm Position in a Virtual Environment

The authors examined the resolution of a discrepancy between visual and proprioceptive estimates of arm position in 10 participants. The participants fixed their right shoulder at 0°, 30°, or 60° of transverse adduction while they viewed a video on a head-mounted display that showed their right arm extended in front of the trunk for 30 min. The perceived arm position more closely approached the seen arm position on the display as the difference between the actual and visually displayed arm positions increased. In the extreme case of a 90° discrepancy, the seen arm position on the display was very gradually perceived as approaching the actual arm position. The magnitude of changes in sensory estimates was larger for proprioception (20%) than for vision (< 10%).     

Load Perturbation Facilitates Interpersonal Error Compensation in a Dyadic Force Production Task

The present study tested the hypothesis that a load perturbation facilitates interpersonal compensation for force error. Ten groups performed both control and perturbation conditions. In the control condition, a target discrete peak force was the sum of 10% of the maximum voluntary contraction produced by two participants. In the perturbation condition, two cooperative participants a and b produced the same target force as the control condition, and the force produced by a non-cooperative participant c increased or decreased the total forces produced by participants a and b. The load perturbation facilitated interpersonal compensation for force error but negatively affected performance during joint action. The participants further learned to improve the error compensation over experimental blocks in the perturbation condition.     

Social Networks as a Factor in Volunteering Among Elderly Japanese with Lower Socioeconomic Status

We investigated the effect of social networks on volunteering, which is known to be beneficial for people and society, among elderly Japanese of lower socioeconomic status. Western studies have demonstrated that social networks boost volunteering among wealthy people because of the norm that they should help the less fortunate. However, wealthy East Asians do not share this norm. Therefore, socioeconomic variables and volunteering tend not to be significantly related in Japan. We hypothesized that social networks would be more important to volunteering among the Japanese elderly, especially among people of a lower socioeconomic status. A total of 768 respondents (319 men, 432 women, 17 sex unspecified; M_age = 73.99 years, SD = 7.40 years) completed the survey. The results indicated that social networks were positively related to volunteering only among people with lower financial status. This result suggests that social networks can increase opportunities and help less advantaged elderly people to reap the benefits of volunteering.     

Adolescents with Down syndrome exhibit greater force and delay in onset of tapping movements

This study examined the control of force and timing during finger tapping sequences of adolescents with Down syndrome. Participants performed both unimanual and bimanual tapping tasks with one self-paced test trial after three audible-synchronized practice trials with concurrent feedback of force output. All tasks consisted of a target force of 2N and a target intertap interval of 500 msec. Adolescents with Down syndrome exhibited a greater magnitude of positive constant error and variable error for peak force than typical adolescents. They also exhibited a greater magnitude of negative constant error and variable error for intertap interval than typical adolescents. Although normally developing comparison adolescents exhibited a linear relationship between peak force and press duration or time-to-peak force, the relationship was not familiar to adolescents with Down's syndrome. This may suggest differences in the manner of motor unit recruitment between the group with Down's syndrome and comparison adolescents.     

Chemical effects on periodicity and structure of decagonal phases in Al-Ni- and Al-Co-based alloys

Abstract

The structures of decagonal phases in binary Al-Ni and Al-Co systems and ternary Al₇₀Ni _x TM_1?x(TM = Co, Rh or Ir) alloys have been studied by electron diffraction. In the Al-Co system, the periodicity of the decagonal phase is 1.6 nm in Al₈₀Co₂₀, and 0.8 nm in Al₇₆.₅Co_23.5 and Al₇₂Co₂₈, suggesting that the stacking rule between Al and Co atoms is different along the c axis for the three alloys. In the ternary systems, diffuse streaks and periodicity systematically vary with the atom substitution of Co for Ni and Ir for Ni, indicating that Ni, Co and Ir atoms play different roles in the decagonal phase and exhibit various sorts of chemical order with Al atoms.     

A longitudinal study of the moderating effects of social capital on the relationships between changes in human capital and ikigai among Japanese older adults

Ikigai, one of the indices of well‐being, tends to decline with age because resources relating to ikigai decline. However, there are individual differences in this decline. This study tested for maintenance of ikigai among Japanese elderly, using a longitudinal study investigating the moderating role of social capital on the effects of changes in human capital on ikigai. We conducted a panel survey targeting 1,068 people (M age = 73.01 years) in 2013, and 686 people in 2017. The variables were ikigai, changes in human capital (self‐rated financial status, physical health) and social capital (social networks, trust in others), educational level, and control variables. Multiple regression analyses revealed the interaction effects of changes in physical health and changes in social networks (strong ties, weak ties) on follow‐up ikigai. Post hoc analyses indicated that declines in physical health predicted declines in ikigai among those whose social networks (strong ties and weak ties) had declined in the 4‐year study, but these relationships were not significant among those whose social networks had increased. The results suggest that older adults can weaken the adverse effect of a decline in human capital on ikigai by maintaining or increasing social networks.     

A Common Force-Sharing Pattern in Joint Action That Consists of Four People

The authors examined the force-sharing patterns in a joint action performed by a group of two, three, or four people compared with a solo action. In the joint actions, 28 participants produced periodic isometric forces such that the sum of forces they produced cycled between 5% and 10% maximum voluntary contraction with the right hand at 1 Hz. In both the three- and four-person tasks, the correlation between forces produced by two of the three or four participants was negative, and the remaining one or two participants produced intermediate forces. The errors of force and interval and force variabilities were smaller in four- and three-people groups than individuals. Four- and three-people groups thus performed better than individuals.     

Influence of motoric encoding on forgetting function of memory for action sentences in patients with Alzheimer's disease

This study assessed whether verbal encoding and motoric encoding have different effects on the forgetting function for action sentences of patients with Alzheimer's disease. Subjects were 13 healthy elderly adults and 10 patients diagnosed with Alzheimer's disease. Three tasks were used: verbal tasks, subject-performed tasks, observed tasks. On the verbal tasks, subjects only heard the action sentences as read to them. On the subject-performed tasks, subjects heard, then performed each action sentence. On the observed tasks, subjects heard the action sentences read while observing the object mentioned in each action sentence. After presentation of each task, subjects conducted immediate and 30-min. delayed recall tests, and then a recognition test. Analysis indicated recall performance for subject-performed tasks was significantly better than that for verbal tasks and observed tasks at both immediate and delayed recall in each group. On the recognition test, carrying out the action had no effect, but for both groups recognition was enhanced by observing the object. Elderly adults performed significantly better than patients on all tasks of recall and recognition. However, the results indicate that patients with Alzheimer's disease can use multimodal resources from motoric encoding even if time passes.     

A pilot study of change in cerebral activity during personality rating by questionnaire and personal computer

The purpose of this study was to examine cerebral blood flow in the frontal cortex area during personality self‐rating tasks. Our two hypotheses were (1) cerebral blood flow varies based on personality rating condition and (2) cerebral blood flow varies based on the personality traits. This experiment measured cerebral blood flow under 3 personal computer rating conditions and 2 questionnaire conditions. Comparing the rating conditions, the results of the t‐test indicated that cerebral blood flow was higher in the questionnaire condition than it was in the personal computer condition. With respect to the Big Five, the result of the correlation coefficient, that is, cerebral blood flow during a personality rating task, changed according to the trait for agreeableness. The results of the analysis of the 5‐cluster on individual differences indicated that certain personality traits were related to the factors that increased or decreased cerebral blood flow. An analysis of variance indicated that openness to experience and Behavioural Activation System‐drive was significant given that participants with high intellectual curiosity were motivated in this experiment, thus, their cerebral blood flow may have increased. The significance of this experiment was that by employing certain performance measures we could examine differences in physical changes based on personality traits.     

Practice effects on decreasing and increasing force-control during periodic isometric movements of the index finger

The present study examined whether improvement in control while decreasing force to achieve a lower force target would be facilitated by comparison of performance while increasing force to achieve a higher force target. Participants practiced control of isometric force and timing during a unimanual force production task cycling between 5 and 10% of maximum voluntary contraction with a target interval of 500 msec. Although errors and variability of both peak and valley forces and interval decreased during early practice, the valley force was still more inaccurate and variable than the peak force in the final practice. Variabilities of both forces did not decrease when the valley force was synchronized with an audible metronome pulse but did decrease when the peak force was synchronized with it.