Motor Response Variations: Peripheral and Central Sources of Error

The purpose of this research was to test the hypothesis that the relative involvement of peripheral versus central nervous system activity during response variations determines the locus of error production in a subsequent criterion response. The hypothesis was tested by comparing ipsilateral and contralateral transfer of a criterion response following response variations that emphasized proportionately different involvement of the peripheral and central systems. When subjects were provided with knowledge of results (KR) to maintain a 30% maximum voluntary contraction (MVC), ipsilateral but not contralateral bias errors occurred on a subsequent dynamic response. When subjects maintained a 30% MVC without KR, however, subsequent ipsilateral bias errors were greater than contralateral bias errors. Finally, when subjects imaged a 30% MVC, subsequent bias errors were equivalent across limbs. These results are interpreted as support for the hypothesis.     

Freely Chosen Index Finger Tapping Frequency Is Increased in Repeated Bouts of Tapping

Healthy individuals (n = 40) performed index finger tapping at freely chosen frequency during repeated bouts and before and after near-maximal muscle action consisting of 3 intense flexions of the index finger metacarpal phalangeal joint. One experiment showed, unexpectedly, that a bout of tapping increased the tapping frequency in the subsequent bout. Thus, a cumulating increase of 8.2 ± 5.4% (p < .001) occurred across 4 bouts, which were all separated by 10 min rest periods. Follow-up experiments revealed that tapping frequency was still increased in consecutive bouts when rest periods were extended to 20 min. Besides, near-maximal muscle activation, followed by 5 min rest, did not affect the tapping frequency. In conclusion, freely chosen tapping frequency was increased in repeated bouts of tapping, which were separated by 10–20 min rest periods. The observed phenomenon is suggested to be termed repeated bout rate enhancement.     

Difference in Cortical Relay Time Between Intrinsic Muscles of Dominant and Nondominant Hands

The authors aimed to calculate and compare cortical relay time (CRT) between intrinsic hand muscles and between homonymous muscles of dominant and nondominant hands. The participants comprised 22 healthy volunteers. The CRT for long-latency reflexes (LLRs) was calculated by subtracting the peak latency of somatosensory evoked potentials of component N20 and the onset latency of motor evoked potentials from the onset latency of LLRs. CRT was significantly shorter for the first dorsal interosseous muscle than for the abductor pollicis brevis muscle, regardless of hand dominance. CRT for the abductor pollicis brevis muscle was significantly shorter in the dominant hand than in the nondominant hand. Evaluation of CRT for intrinsic muscles might be beneficial in the understanding of individuated finger functions.     

自体血清对腰背肌损伤修复作用的动物实验研究

研究自体血清局部注射对腰背肌损伤的治疗效果。建立动物模型,分组对照研究。共将实验动物分为四组,通过手术造成小鼠腰背部肌肉损伤。之后,在损伤的局部注射生理盐水,或原浓度的自体血清、二倍浓缩的自体血清、四倍浓缩的自体血清。在术后第2、4、7日分别测得各组小鼠腰背肌肌力,求四组小鼠腰背肌肌力的平均值及标准差,比较组内及组间的差异。最后,对实验结果进行了综合分析和讨论。自体血清局部注射处理的小鼠,肌力恢复更加明显,愈合后肌力明显增强,术后第7日各组肌力平均值具有显著性差异,以生理盐水注射组为对照组,原浓度血清组、二倍浓缩组、四倍浓缩组平均腰背肌力均高于对照组。动物模型验证了自体血清局部注射疗法在腰背肌损伤的动物模型中是有效的,可以促进腰背肌损伤的修复和愈合。     

Effects of scapular retraction/protraction position and scapular elevation on shoulder girdle muscle activity during glenohumeral abduction

According to scapulohumeral rhythm, shoulder abduction is followed through scapular upward rotation to ensure joint mobility and stability. Of interest, the shoulder abduction can be performed holding the scapula in different positions and in association with scapular elevation, with possible effects on shoulder muscle activity. Therefore, the aim of the study was to analyze the activity of relevant shoulder muscles and the activity ratios between the scapulothoracic muscles, during shoulder abduction performed in different combinations of scapular position (neutral, retracted, protracted) and scapular elevation.The electromyographic activity of middle deltoid, serratus anterior, upper, middle and lower fibers of trapezius was recorded during shoulder abduction movements executed holding the scapula in neutral, retracted and protracted position, and subsequently a shoulder elevation movement. The activation of each muscle and the scapulothoracic muscles activity ratios were determined every 15 degrees, from 15° to 120° of abduction.Scapular retraction led to higher activation of the entire trapezius muscle, whereas protraction induced higher upper trapezius, middle deltoid and serratus anterior activity, along with lower activity of middle and lower trapezius. Shoulder elevation led to higher activity of the upper trapezius and middle deltoid. Moreover, it induced lower activation of the serratus anterior and middle and lower trapezius, thus leading to high ratios between the upper trapezius and the other scapulothoracic muscles, especially between 15 and 75 degrees of abduction.This study highlights that shoulder abduction performed with scapular protraction and in combination with scapular elevation leads to increased activity of the middle deltoid and upper trapezius, resulting in imbalances between the scapulothoracic muscles that could hamper the optimal scapulohumeral rhythm. The abduction performed in the aforementioned scapular conditions also induce potential reciprocal inhibition effects between the movers and stabilizers muscles of scapula, suggesting different motor control strategies of integrating a common shoulder movement with various modification of the scapular position.     

Posture,muscular tone and visual attention in 5 month‐old infants

The present paper aims at studying the relationships between posture, muscle tone and visual attention in 5 month‐old infants. To this end, a specially designed seating arrangement made it possible to vary posture while keeping constant the spatial relationship between eyes and stimuli. Five month‐olds were placed in the reclining position (30°) or in a more erect position (60°). The more erect the posture, the more difficult it should be for the infant to maintain a straight body axis. Muscle tone was evaluated, and infants distinguished in terms of whether they were hypertonic or hypotonic. It was hypothesised that in a more erect position hypotonic children, who experience more difficulties in maintaining posture, should organise their visual exploration in ways different from those considered to be hypertonic. To test it, pairs of three‐dimensional stimuli were presented in the distal visual field for one group (N=48) and in the proximal visual field in another group (N=32) for 2 min in each posture. The dynamical organisation of attention was evaluated through the number and duration of fixations on each target, the number of shifts from one target to the other (alternations) and the number of repetitions (back to the previous target). Results showed that visual behaviour was significantly affected by the distance at which stimuli were presented. Infants spent more time in visual exploration when the object was within reach than when it was out of reach. Although posture was shown to play a role in the organisation of visual exploration, no link with muscle tone was found, a surprising result which is discussed. Copyright © 2002 John Wiley & Sons, Ltd.     

Impaired long-term potentiation and enhanced neuronal excitability in the amygdala of CaV1.3 knockout mice

Previously, we demonstrated that mice in which the gene for the L-type voltage-gated calcium channel Ca_V1.3 is deleted (Ca_V1.3 knockout mice) exhibit an impaired ability to consolidate contextually-conditioned fear. Given that this form of Pavlovian fear conditioning is critically dependent on the basolateral complex of the amygdala (BLA), we were interested in the mechanisms by which Ca_V1.3 contributes to BLA neurophysiology. In the present study, we used in vitro amygdala slices prepared from Ca_V1.3 knockout mice and wild-type littermates to explore the role of Ca_V1.3 in long-term potentiation (LTP) and intrinsic neuronal excitability in the BLA. We found that LTP in the lateral nucleus (LA) of the BLA, induced by high-frequency stimulation of the external capsule, was significantly reduced in Ca_V1.3 knockout mice. Additionally, we found that BLA principal neurons from Ca_V1.3 knockout mice were hyperexcitable, exhibiting significant increases in firing rates and decreased interspike intervals in response to prolonged somatic depolarization. This aberrant increase in neuronal excitability appears to be at least in part due to a concomitant reduction in the slow component of the post-burst afterhyperpolarization. Together, these results demonstrate altered neuronal function in the BLA of Ca_V1.3 knockout mice which may account for the impaired ability of these mice to consolidate contextually-conditioned fear.     

Effects of Posttraining Intrahippocampal Injections of Platelet-Activating Factor and PAF Antagonists on Memory

The present experiments examined the effects of posttraining intrahippocampal injections of the degradative enzyme-resistant methylcarbamyl analog of the bioactive phospholipid platelet-activating factor (mc-PAF) and the platelet-activating factor (PAF) receptor antagonists BN52021 and BN 50730 on memory in male Long-Evans rats trained in a hidden platform version of the Morris water maze. Following an eight-trial training session, rats received a unilateral intrahippocampal injection of mc-PAF (0.5, 1.0, or 2.0 μg/0.5 μl), lyso-PAF (1.0 μg/0.5 μl), the cell surface PAF receptor antagonist BN 52021 (0.25, 0.5, or 1.0 μg/0.5 μl), the intracellular PAF receptor antagonist BN 50730 (2.0, 5.0, or 10.0 μg/0.5 μl), or vehicle (50% DMSO in 0.9% saline; 0.5 μl). On a retention test conducted 24 h after training, the escape latencies of rats administered mc-PAF (1.0 or 2.0 μg) were significantly lower than those of the vehicle-injected controls, demonstrating a memory-enhancing effect of mc-PAF. Injections of lyso-PAF, a structurally similar metabolite of PAF, had no influence on memory, indicating that the memory-enhancing effect of mc-PAF is not caused by membrane perturbation by the phospholipid. The retention test escape latencies of rats administered BN 52021 (0.5 μg) and BN 50730 (5.0 or 10 μg) were significantly higher than those of the controls, indicating a memory impairing effect of both PAF antagonists. When mc-PAF, BN 52021, or BN 50730 was administered 2 h posttraining, no effect on retention was observed, indicating a time-dependent effect of the neuroactive substances on memory storage. The findings suggest a role for endogenous PAF in hippocampal-dependent memory processes.     

“面部反馈假设”的检验研究

该研究让被试做人为表现的面部表情并填写情绪分化量表,对“面部反馈假设”进行检验。结果表明:(1)愤怒表情显著地增强了被试怒体验的强度;(2)面部表情的反馈具有两重性:即既有分化性的反馈效果,它能增强与其相应的情绪体验的强度,而且又有加强或减弱“愉快—不愉快”维度上相反极的情绪体验;(3)面部表情反馈的发生无需以“自我知觉”作为中介。