Age-related EMG variables during maximum voluntary contraction

We studied the neuromuscular adaptation that occurs with aging by comparing changes in surface electromyography (EMG) variables from the tibialis anterior muscle in 12 young (21.4 +/- 1.7 yr. old) and 13 older subjects (70.8 +/- 3.1 yr. old). EMG variables such as the muscle fiber conduction velocity, median frequency, and averaged rectified value were calculated during maximum voluntary contraction for 5-sec. isometric contractions. The dorsiflexion force, muscle fiber conduction velocity, median frequency, and average rectified value during maximum voluntary contraction were significantly smaller in the older than in the younger group (p < .05). These results suggested that the neuromuscular system in older subjects is affected by the selective atrophy of fast twitch fibers and differences in motor unit firing statistics. Our results suggest the utility of applying the EMG observed during maximum voluntary contraction to the noninvasive evaluation of neuromuscular function in elderly persons.     

Effects of increasing expenditure of energy during exercise on psychological well-being in older adults

The purpose of present study was to examine the effects on psychological well-being of energy expended as a result of the exercise intervention. 33 older adults (M age=68.6 yr., SD=4.7) participated in three supervised water-based exercise sessions per week for 12 wk. Based on the relative changes in daily energy expenditure as measured by questionnaire between pre- and posttraining, the subjects were split into three groups. This classified each subject as either having experienced a relatively low change (n=11), moderate change (n= 11), or high change (n= 11) in daily energy expenditure. Our data showed that the group with the greater increase in energy expenditure as a result of exercise, when compared pre- and posttraining, improved only on Depression-Dejection on the Profile of Mood States more than did the group with low change. Consequently, we concluded that the amount of energy expended was partially related to improvement in psychological well-being.     

How Do Creative Experts Practice New Skills? Exploratory Practice in Breakdancers

How do expert performers practice as they develop creatively? This study investigated the processes involved in the practice of new skills by expert breakdancers. A great deal of evidence supports the theory of “deliberate practice” (Ericsson, Krampe, & Tesch‐Römer, 1993, Psychological Review, 100, 363) in skill acquisition; however, expert creative performers may emphasize other forms of practice for skill development. Four case studies collected through fieldwork and laboratory observation were analyzed to evaluate expert dancers’ practice processes as they developed proficiency in new, specific skills. We focused on three aspects of learning: the degree of skill acquisition, the content of skills included in practice, and dancers’ stated purposes for practicing. The results showed that dancers’ practice improved skills (as suggested by deliberate practice) and engaged the exploration of new, original skills, along with coordinating skills within performance. In their practice, these dance experts went beyond deliberative practice to highly exploratory processes for skill development.     

Right hemispheric dominance in gaze-triggered reflexive shift of attention in humans

Recent findings suggest a right hemispheric dominance in gaze-triggered shifts of attention. The aim of this study was to clarify the dominant hemisphere in the gaze processing that mediates attentional shift. A target localization task, with preceding non-predicative gaze cues presented to each visual field, was undertaken by 44 healthy subjects, measuring reaction time (RT). A face identification task was also given to determine hemispheric dominance in face processing for each subject. RT differences between valid and invalid cues were larger when presented in the left rather than the right visual field. This held true regardless of individual hemispheric dominance in face processing. Together, these results indicate right hemispheric dominance in gaze-triggered reflexive shifts of attention in normal healthy subjects.     

Dissimilar effects of task‐relevant and interpersonal threat on independent–interdependent self‐construal in individuals with high self‐esteem

Previous research has indicated that individuals with high trait self‐esteem (HSEs) become more independent and less interdependent after experiencing a task‐relevant threat. However, these studies have not investigated other sources of ego threats, such as interpersonal threats. Therefore, the moderating effects of the degree of trait self‐esteem on task‐relevant and interpersonal ego threats were investigated in relation to independent, or interdependent self‐construal. It was predicted that in HSEs, the level of task‐relevant stress would be positively–negatively related to their independence–interdependence, whereas the level of interpersonal stress would be negatively–positively related to their independence–interdependence. In individuals with low trait self‐esteem (LSEs), the two types of stresses and independent–interdependent self‐construal may not have a significant relationship. We conducted a questionnaire survey with undergraduates. Correlational analysis of the results indicated that in HSEs, greater task‐relevant stress was related to heightened independence, whereas greater interpersonal stress had the opposite effect, indicating lower independence and heightened interdependence. However, these stresses were not related to the self‐construal of LSEs. These findings suggest that task‐relevant and interpersonal threat could have differential effects on independent and interdependent self‐construal for HSEs, but not in LSEs.     

How does higher in‐group social value lead to positive mental health? An integrated model of in‐group identification and support

Previous research has indicated that the effects of in‐group social value on mental health are mediated by the extent to which individuals identify with their in‐group. Other research has shown that in‐group identification leads to positive mental health because it provides in‐group members with a psychological basis for social support. We examine how the individual's perception of the social value of the in‐group leads to positive mental health, integrating the effects of identification with and support from the in‐group. As predicted, the relationship between higher social value and decreased mental health (e.g. depression, perceived stressful events) is mediated by higher in‐group identification, which in turn leads the members to expect support from the in‐group but not the out‐group. An integrated model of the effects of perceived in‐group social value, identification, and support on mental health is proposed, and the implications are discussed.     

Bilateral capacity for speech sound processing in auditory comprehension: evidence from Wada procedures

Data from lesion studies suggest that the ability to perceive speech sounds, as measured by auditory comprehension tasks, is supported by temporal lobe systems in both the left and right hemisphere. For example, patients with left temporal lobe damage and auditory comprehension deficits (i.e., Wernicke's aphasics), nonetheless comprehend isolated words better than one would expect if their speech perception system had been largely destroyed (70-80% accuracy). Further, when comprehension fails in such patients their errors are more often semantically-based, than-phonemically based. The question addressed by the present study is whether this ability of the right hemisphere to process speech sounds is a result of plastic reorganization following chronic left hemisphere damage, or whether the ability exists in undamaged language systems. We sought to test these possibilities by studying auditory comprehension in acute left versus right hemisphere deactivation during Wada procedures. A series of 20 patients undergoing clinically indicated Wada procedures were asked to listen to an auditorily presented stimulus word, and then point to its matching picture on a card that contained the target picture, a semantic foil, a phonemic foil, and an unrelated foil. This task was performed under three conditions, baseline, during left carotid injection of sodium amytal, and during right carotid injection of sodium amytal. Overall, left hemisphere injection led to a significantly higher error rate than right hemisphere injection. However, consistent with lesion work, the majority (75%) of these errors were semantic in nature. These findings suggest that auditory comprehension deficits are predominantly semantic in nature, even following acute left hemisphere disruption. This, in turn, supports the hypothesis that the right hemisphere is capable of speech sound processing in the intact brain.     

Prefrontal cortex and hippocampus subserve different components of working memory in rats

Both the medial prefrontal cortex (mPFC) and hippocampus are implicated in working memory tasks in rodents. Specifically, it has been hypothesized that the mPFC is primarily engaged in the temporary storage and processing of information lasting from a subsecond to several seconds, while the hippocampal function becomes more critical as the working memory demand extends into longer temporal scales. Although these structures may be engaged in a temporally separable manner, the extent of their contributions in the "informational content" of working memory remains unclear. To investigate this issue, the mPFC and dorsal hippocampus (dHPC) were temporarily inactivated via targeted infusions of the GABA(A) receptor agonist muscimol in rats prior to their performance on a delayed alternation task (DAT), employing an automated figure-eight maze that required the animals to make alternating arm choice responses after 3-, 30-, and 60-sec delays for water reward. We report that inactivation of either the mPFC or dHPC significantly reduced DAT at all delay intervals tested. However, there were key qualitative differences in the behavioral effects. Specifically, mPFC inactivation selectively impaired working memory (i.e., arm choice accuracy) without altering reference memory (i.e., the maze task rule) and arm choice response latencies. In contrast, dHPC inactivation increased both reference memory errors and arm choice response latencies. Moreover, dHPC, but not mPFC, inactivation increased the incidence of successive working memory errors. These results suggest that while both the mPFC and hippocampus are necessarily involved in DAT, they seem to process different informational components associated with the memory task.