Human finger independence: limitations due to passive mechanical coupling versus active neuromuscular control

We studied the extent to which mechanical coupling and neuromuscular control limit finger independence by studying passive and active individuated finger movements in healthy adults. For passive movements, subjects relaxed while each finger was rotated into flexion and extension by a custom-built device. For active movements, subjects moved each finger into flexion and extension while attempting to keep the other, noninstructed fingers still. Active movements were performed through approximately the same joint excursions and at approximately the same speeds as the passive movements. We quantified how mechanical coupling limited finger independence from the passive movements, and quantified how neuromuscular control limited finger independence using an analysis that subtracted the indices obtained in the passive condition from those obtained in the active condition. Finger independence was generally similar during passive and active movements, but showed a trend toward less independence in the middle, ring, and little fingers during active, large-arc movements. Mechanical coupling limited the independence of the index, middle, and ring fingers to the greatest degree, followed by the little finger, and placed only negligible limitations on the independence of the thumb. In contrast, neuromuscular control primarily limited the independence of the ring, and little fingers during large-arc movements, and had minimal effects on the other fingers, especially during small-arc movements. For the movement conditions tested here, mechanical coupling between the fingers appears to be a major factor limiting the complete independence of finger movement.     

Reduced muscle selectivity during individuated finger movements in humans after damage to the motor cortex or corticospinal tract

We investigated how damage to the motor cortex or corticospinal tract affects the selective activation of finger muscles in humans. We hypothesized that damage relatively restricted to the motor cortex or corticospinal tract would result in unselective muscle activations during an individuated finger movement task. People with pure motor hemiparesis attributed to ischemic cerebrovascular accident were tested. Pure motor hemiparetic and control subjects were studied making flexion/extension and then abduction/adduction finger movements. During the abduction/adduction movements, we recorded muscle activity from 3 intrinsic finger muscles: the abductor pollicis brevis, the first dorsal interosseus, and the abductor digit quinti. Each of these muscles acts as an agonist for only one of the abduction/adduction movements and might therefore be expected to be active in a highly selective manner. Motor cortex or corticospinal tract damage in people with pure motor hemiparesis reduced the selectivity of finger muscle activation during individuated abduction/adduction finger movements, resulting in reduced independence of these movements. Abduction/adduction movements showed a nonsignificant trend toward being less independent than flexion/extension movements in the affected hands of hemiparetic subjects. These changes in the selectivity of muscle activation and the consequent decrease in individuation of movement were correlated with decreased hand function. Our findings imply that, in humans, spared cerebral motor areas and descending pathways that remain might activate finger muscles, but cannot fully compensate for the highly selective control provided by the primary motor cortex and the crossed corticospinal system.     

Inactivation of the ventral premotor cortex biases the laterality of motoric choices

The visual, tactile, and motor properties of neurons in the ventral premotor cortex (PMv) suggest that the PMv plays an important role in the interaction of the face and upper extremities with visual objects, a function that might be disrupted by inactivation of the PMv. The behavior of three rhesus monkeys was, therefore, examined while the PMv was reversibly inactivated by intracortical injection of muscimol. Unilateral PMv inactivation produced no overt deficit in a monkey's ability to reach out and grasp a food morsel with either hand, nor did the monkey have difficulty in extracting a food morsel from a narrow well or in performing a visually cued individuated finger movement task. Unilateral PMv inactivation did bias the laterality of the monkeys' motoric choices, however. When two equivalent food morsels were presented simultaneously to the monkey's right and left, the likelihood that the monkey would make motoric responses contralateral to the inactivated PMv was reduced. After PMv muscimol injections, a monkey was less likely to initially turn its head contralaterally to inspect food morsels, less likely to reach for the food morsel with its contralateral hand, and less likely to take the morsel on its contralateral side. Catch trials in which a food morsel was present only on one side showed that the monkey was aware of the contralateral food morsels and was able to turn its head contralaterally and to use its contralateral arm and hand promptly and accurately. These observations suggest that, when equivalent visual objects for behavioral interaction are present bilaterally, the PMv plays a role in choosing the side to which motoric responses will be directed and the body part that will be deployed as the response effector.     

Local administration of ramiprilat is less effective than oral ramipril in preventing restenosis after balloon angioplasty in an animal model

PURPOSE: To test the hypothesis that local administration of angiotensin converting enzyme (ACE) inhibitor via a microporous balloon catheter would be more effective than oral administration of ACE inhibitor in preventing neointima formation after balloon angioplasty. MATERIALS AND METHODS: Neointima formation was induced by balloon denudation followed by 0.5% cholesterol diet in 29 New Zealand White rabbits. Directly after denudation, local administration of 1.8 mg of ramiprilat (n = 7) or saline (n = 7) with a microporous balloon catheter at a pressure of 3 atm was performed. Both groups additionally received ramipril orally (1 mg/d). Seven animals were treated exclusively with oral ramipril. The control group was fed a 0.5% cholesterol diet and given no medication (n = 8). Six weeks after intervention, the animals were killed and morphometric and immunohistologic analyses were performed. RESULTS: Oral administration of ramipril resulted in a significant reduction of placque area (-66%, P < .05). Oral and local administration of the ACE inhibitor was followed by a nonsignificant reduction of the neointimal area (-17%). Local administration of saline combined with oral ramipril failed to prevent neointimal formation (reduction of 6%, NS). CONCLUSION: Oral administration of ramipril resulted in a significant reduction of neointimal proliferation in New Zealand White rabbits. The possible benefit of an additional administration of local ramiprilat was diminished by an excessive neointimal hyperplasia, which was most likely caused by the inherent vessel trauma with use of the microporous balloon catheter.     

Personality traits as vulnerability factors in body dysmorphic disorder

Cognitive behavioural models consider certain personality traits to be risk factors for the development of Body Dysmorphic Disorder (BDD). Research on personality traits in BDD is scarce, therefore this study examined perfectionism, aesthetic sensitivity and the behavioural inhibition system (BIS) in BDD. Furthermore, the association between these personality traits and the extent of dysmorphic concerns was investigated.     

Stage-based Variation in the Effect of Primary Tumor Side on All Stages of Colorectal Cancer Recurrence and Survival

Background

Multiple studies have defined the prognostic and potential predictive significance of the primary tumor side in metastatic colorectal cancer (CRC). However, the currently available data for early-stage disease are limited and inconsistent.

Case-mix differences between hospital-based and freestanding skilled nursing facilities. A review of the evidence

Many health care services are available in both hospital and freestanding settings. Hospital-based providers are usually much more expensive than freestanding providers. According to Medicare data, costs in hospital-based skilled nursing facilities (SNFs) are twice those of freestanding facilities. While critics charge that this is the result of inefficiency, hospitals counter that higher costs are caused by treatment of sicker patients and provision of higher-quality care. This paper analyzes the research on the case-mix differences between hospital-based and freestanding SNFs. On the basis of this analysis, it appears that hospital-based facilities tend to serve more severely ill patients (i.e., have a more difficult case mix) than do freestanding facilities. Case-mix differences, however, appear to explain less than half of the cost differential between the two types of facilities.     

Partial reconstruction of muscle activity from a pruned network of diverse motor cortex neurons

Primary motor cortex (M1) neurons traditionally have been viewed as "upper motor neurons" that directly drive spinal motoneuron pools, particularly during finger movements. We used spike-triggered averages (SpikeTAs) of electromyographic (EMG) activity to select M1 neurons whose spikes signaled the arrival of input in motoneuron pools, and examined the degree of similarity between the activity patterns of these M1 neurons and their target muscles during 12 individuated finger and wrist movements. Neuron-EMG similarity generally was low. Similarity was unrelated to the strength of the SpikeTA effect, to whether the effect was pure versus synchrony, or to the number of muscles influenced by the neuron. Nevertheless, the sum of M1 neuron activity patterns, each weighted by the sign and strength of its SpikeTA effect, could be more similar to the EMG than the average similarity of individual neurons. Significant correlations between the weighted sum of M1 neuron activity patterns and EMG were obtained in six of 17 muscles, but showed R(2) values ranging from only 0.26 to 0.42. These observations suggest that additional factors-including inputs from sources other than M1 and nonlinear summation of inputs to motoneuron pools-also contributed substantially to EMG activity patterns. Furthermore, although each of these M1 neurons produced SpikeTA effects with a significant peak or trough 6-16 ms after the triggering spike, shifting the weighted sum of neuron activity to lead the EMG by 40-60 ms increased their similarity, suggesting that the influence of M1 neurons that produce SpikeTA effects includes substantial synaptic integration that in part may reach the motoneuron pools over less-direct pathways.     

Mobile Technology Affinity in Renal Transplant Recipients

Background

Medication nonadherence is a common problem in renal transplant recipients (RTRs). Mobile health approaches to improve medication adherence are a current trend, and several medication adherence apps are available. However, it is unknown whether RTRs use these technologies and to what extent. In the present study, the mobile technology affinity of RTRs was analyzed. We hypothesized significant age differences in mobile technology affinity and that mobile technology affinity is associated with better cognitive functioning as well as higher educational level.