Inter-individual variability in sensory weighting of a plantar pressure-based, tongue-placed tactile biofeedback for controlling posture

The purpose of the present experiment was to investigate whether the sensory weighting of a plantar pressure-based, tongue-placed tactile biofeedback for controlling posture could be subject to inter-individual variability. To achieve this goal, 60 young healthy adults were asked to stand as immobile as possible with their eyes closed in two conditions of No-biofeedback and Biofeedback. Centre of foot pressure (CoP) displacements were recorded using a force platform. Overall, results showed reduced CoP displacements in the Biofeedback relative to the No-biofeedback condition, evidencing the ability of the central nervous system to efficiently integrate an artificial plantar-based, tongue-placed tactile biofeedback for controlling posture during quiet standing. Results further showed a significant positive correlation between the CoP displacements measured in the No-biofeedback condition and the decrease in the CoP displacements induced by the use of the biofeedback. In other words, the degree of postural stabilization appeared to depend on each subject's balance control capabilities, the biofeedback yielding a greater stabilizing effect in subjects exhibiting the largest CoP displacements when standing in the No-biofeedback condition. On the whole, by evidencing a significant inter-individual variability in sensory weighting of an additional tactile information related to foot sole pressure distribution for controlling posture, the present findings underscore the need and the necessity to address the issue of inter-individual variability in the field of neuroscience.     

Behavioral impairments of the aging rat

Several disturbances occurring during aging of humans and rodents alike stem from changes in sensory and motor functions. Using a battery of behavioral tests we have studied alterations in performance with advancing age in female and male rats of some frequently used strains. In parallel, we collected survival and body weight data. The median survival age was similar for female and male Sprague-Dawley rats, inbred female Lewis and outbred male Wistar rats (29-30 months). In contrast, male Fisher 344 had a significantly shorter median life span. During aging there is a gradual decline in locomotor activity and explorative behavior while disturbances of coordination and balance first became evident at more advanced age. In old age, also weight carrying capacity, limb movement and temperature threshold were impaired. While whole body weight continues to increase over the better part of a rats' life span, the behavioral changes in old age associated with a decrease in both total body weight and muscle mass. Dietary restriction increases median life span expectancy; retards the pace of behavioral aging and impedes sarcopenia. Housing in enriched environment did not improve the scoring in the behavioral tests but tended to increase median life span. Finally, there was an agreement between behavioral data collected from longitudinal age-cohorts and those obtained from multiple age-cohorts.     

Touch sensitivity in Caenorhabditis elegans

The nematode Caenorhabditis elegans was the first organism for which touch insensitive mutants were obtained. The study of the genes defective in these mutants has led to the identification of components of a mechanosensory complex needed for specific cells to sense gentle touch to the body. Multiple approaches using genetics, cell biology, biochemistry, and electrophysiology have characterized a channel complex, containing two DEG/ENaC pore-forming subunits and several other proteins, that transduces the touch response. Other mechanical responses, sensed by other cells using a variety of other components, are less well understood in C. elegans. Many of these other senses may use TRP channels, although DEG/ENaC channels have also been implicated.     

The effect of target modality on visual and proprioceptive contributions to the control of movement distance

The goal of this study was to determine whether the sensory nature of a target influences the roles of vision and proprioception in the planning of movement distance. Two groups of subjects made rapid, elbow extension movements, either toward a visual target or toward the index fingertip of the unseen opposite hand. Visual feedback of the reaching index fingertip was only available before movement onset. Using a virtual reality display, we randomly introduced a discrepancy between actual and virtual (cursor) fingertip location. When subjects reached toward the visual target, movement distance varied with changes in visual information about initial hand position. For the proprioceptive target, movement distance varied mostly with changes in proprioceptive information about initial position. The effect of target modality was already present at the time of peak acceleration, indicating that this effect include feedforward processes. Our results suggest that the relative contributions of vision and proprioception to motor planning can change, depending on the modality in which task relevant information is represented.     

Imagery of different sensory modalities: hypnotizability and body sway

Postural control in subjects with high (Highs) and low (Lows) susceptibility to hypnosis is differentially affected by changes in visual and neck tactile/proprioceptive input. The aim of the present experiment was to investigate whether imagery of the visual and tactile sensory modalities also induces different modulation of postural control in Highs and Lows. Fourteen Highs and 16 Lows were included in the study; they were recorded while standing upright with eyes closed during visual and tactile imagery tasks and during mental computation. Their posture and movement were recorded with an Elite System and their experience was assessed after each task in a structured interview. Visual imagery was judged “easier” than tactile imagery by Lows, while Highs performed both tasks easily and judged the tactile imagery less effortful and more vivid than Lows. No difference was observed for the mental computation. The Highs’ body sway was not affected by the cognitive tasks, while Lows showed a task-related modulation of body sway. The results are in line with the hypothesis of lower vulnerability of Highs to the effects of tasks interfering with postural control and of different sensory-motor integration in Highs and Lows.     

Sensory versus motor information in the control of predictive saccade timing

Humans readily make predictive saccades to periodic alternating targets. This predictive behavior depends on internal monitoring of timing error of past saccades in order to determine the time of initiation of future saccades; our earlier studies have confirmed this by finding correlations between latencies of consecutive predictive saccades. It is natural to consider that timing error is determined by visual detection of the difference between the time the target appears and the time the eyes arrive at the target; this in turn implies that saccades must actually be produced in order for their timing errors to be determined and predictive saccade timing to be established. We tested this hypothesis by having subjects view alternating visual targets while fixating a central target in order to eliminate saccade production. After six alternating target presentations, subjects began tracking the alternating targets. Tracking performance was assessed with an error measure that compared saccade latency and inter-saccade interval with desired values (zero and inter-stimulus interval, respectively). Errors in this Prior Viewing paradigm were compared to those from a conventional De Novo paradigm in which saccades began as soon as the alternating targets were presented. Saccades under Prior Viewing reached a low-error steady predictive state more rapidly than under De Novo tracking. The initial saccade under Prior Viewing had a higher latency than the others, suggesting that this saccade was reactive even though the paradigm is predictable; other reasons for this higher latency include time to disengage from the fixation target and time required to pre-program the initial set of saccades. The results show that visual detection of timing error from an actual motor act (saccades) is not necessary to establish predictive saccadic pacing: sensory-only information from viewing the moving targets can help to establish this predictive state.     

Forces applied by anterior and posterior teeth and roles of periodontal afferents during hold-and-split tasks in human subjects

Hold-and-split tasks were performed by 20 subjects (12 females and 8 males) using the right central incisors, canines, 2nd premolars, and 1st molars, respectively. Half a peanut was positioned on a transducer-equipped plate and the subject was instructed to hold the plate with the peanut between two antagonistic teeth, and not using more force than necessary. After ca. 3 s the subject was instructed to split the peanut in a natural manner. Each session consisted of a series of three in which the subject performed the hold-and-split task five times for each tooth. Thus, in total, data were obtained from 60 trials for each subject. The magnitude of the forces and the force rates used to split the peanut increased distally along the dental arch. However, the duration of the split phase was similar for the various teeth examined. During anesthesia of the periodontal ligament (four subjects), no significant changes were seen in the split phase. The forces used to hold the peanut between the teeth also increased distally along the dental arch: 0.60 N for the incisor, 0.77 N for the canine, 1.15 N for the 2nd premolar, and 1.74 N for the 1st molar. The difference in hold forces for the various teeth can be explained by the different sensitivity characteristics of the periodontal afferents innervating anterior and posterior teeth. During periodontal anesthesia, the magnitude and variability of the hold forces increased for all types of teeth, thus supporting the suggestion that periodontal afferent information is used in the regulation of the level of forces used to hold and manipulate morsels between the teeth.     

感觉再训练及口服弥可保在周围神经损伤患者感觉功能恢复中的作用

目的探讨感觉再训练及口服弥可保片剂对周围神经修复术后患者感觉功能恢复的促进作用。方法共收集急诊腕部正中神经或尺神经切割离断伤患者92例，经神经修复术后将其随机分为4组，联合组给予感觉再训练及口服弥可保（甲基维生素B12）片剂治疗；训练组给予单纯感觉再训练治疗；弥可保组则给予单纯口服弥可保片剂治疗；对照组未给予感觉再训练及口服弥可保片剂治疗。以术后第1年及第2年随访得到的感觉功能分级及动态两点辨别觉作为疗效评测指标。结果术后第1年及第2年时，联合组、训练组及弥可保组上述各检测指标均优于对照组（P均〈0．05）；术后第1年时，联合组疗效优于弥可保组与训练组（P〈0．05），且弥可保组与训练组之间差异无统计学意义（P〉0．05）；术后第2年时，联合组与训练组疗效均优于弥可保组（P〈0．05），且联合组与训练组之间的差异无统计学意义（P〉0．05）。结论感觉再训练或口服弥可保片剂均能显著促进周围神经损伤患者感觉功能的恢复，如将两者早期联用则疗效更佳。     

正中神经损伤后手部感觉功能的康复训练

目的 观察正中神经损伤后早期康复训练对手部感觉功能恢复的影响。方法 将70例正中神经损伤患者随机分为康复组及对照组，康复组于术后2周开始康复治疗，并在康复治疗前及治疗过程中，参照国际标准分别评定手的感觉等级及两点辨别觉，对照组仅行一般处理。经过1个疗程(6—8周)治疗后，进行第2次评定，以后每1个疗程评定1次，共4-5次。结果 康复组患者手的感觉功能优良率达88％，有效率达97％。结论 感觉康复训练能够促进正中神经损伤患者手的感觉功能恢复。     

掌背动脉逆行岛状皮瓣修复手指掌侧软组织缺损的感觉功能随访研究

背景:目前临床对掌背动脉逆行岛状皮瓣的研究报道较多,随访着重在皮瓣的成活、外形质地、手指屈伸活动等方面,缺少对感觉恢复的系统测定。目的:观察掌背动脉逆行岛状皮瓣修复手指掌侧软组织缺损的感觉恢复情况。方法:回顾性分析2015年1月至2017年12月收治的采用掌背动脉逆行岛状皮瓣修复的手指掌侧软组织缺损患者22例,其中6例采用皮瓣内的掌背神经和指固有神经缝合。术后1、3、6、9、12、18、24个月随访患者深压痛觉、单丝触觉、两点辨别觉恢复情况。结果:所有患者均在止血带下顺利完成手术。术后20例皮瓣完全成活,2例皮瓣远端少部分坏死,经换药处理后愈合。随访时间24~30个月,平均(24.5±0.3)个月。术后1个月22例患者深压痛觉均恢复;末次随访感觉恢复评价达S3:3例,S2:18例,S1:1例,末次随访两点辨别觉测定均大于20mm。随访患者中最长一例随访30个月,末次随访感觉测定S3,两点辨别觉测定大于20mm。该例患者感觉恢复在术后18个月以后基本无变化。结论:掌背动脉逆行岛状皮瓣修复手指掌侧软组织缺损的深压痛觉在术后1个月就能恢复;感觉恢复能达到S3,达S3+困难;无法恢复两点辨别觉。对一些特殊行业、对指掌侧感觉要求较高的手指掌侧缺损患者慎重应用。