Gastrin and somatostatin levels in patients with gastric cancer

Gastrin and somatostatin-like immunoreactivity (SLI) levels were studied by means of radioimmunoassay in peripheral venous blood of healthy volunteers and patients suffering from gastric adenocarcinoma or duodenal and gastric ulcers. Gastrin and SLI levels were also evaluated in patients in blood drawn from gastric veins during surgery. The elevations of gastrin and SLI levels were found in patients with gastric cancer as compared with healthy people and patients suffering from ulcers. The impairment of the negative feedback between gastrin and somatostatin secretions in patients with gastric cancer was suggested.     

The Efficiency of the Brain-Computer Interfaces Based on Motor Imagery with Tactile and Visual Feedback

In this study we compared tactile and visual feedbacks for the motor imagery-based brain–computer interface (BCI) in five healthy subjects. A vertical green bar from the center of the fixing cross to the edge of the screen was used as visual feedback. Vibration motors that were placed on the forearms of the right and the left hands and on the back of the subject’s neck were used as tactile feedback. A vibration signal was used to confirm the correct classification of the EEG patterns of the motor imagery of right and left hand movements and the rest task. The accuracy of recognition in the classification of the three states (right hand movement, left hand movement, and rest) in the BCI without feedback exceeded the random level (33% for the three states) for all the subjects and was rather high (67.8% ± 13.4% (mean ± standard deviation)). Including the visual and tactile feedback in the BCI did not significantly change the mean accuracy of recognition of mental states for all the subjects (70.5% ± 14.8% for the visual feedback and 65.9% ± 12.4% for the tactile feedback). The analysis of the dynamics of the movement imagery skill in BCI users with the tactile and visual feedback showed no significant differences between these types of feedback. Thus, it has been found that the tactile feedback can be used in the motor imagery-based BCI instead of the commonly used visual feedback, which greatly expands the possibilities of the practical application of the BCI.     

Resistance of peripheral and sub-cortical somatosensory pathway to electrical noise

The somatosensory system is vulnerable to large amounts of noise distortion. But how does the central nervous system distinguish the peripheral inputs which carry information to the brain from that which does not possess information? To address this question we studied the effect of electrical stimulation of the median nerve on tactile spatial frequency perception in healthy subjects and Parkinson's disease (PD) patients. Subjects were categorized in two groups (healthy and PD patients) and were asked to report if a test tactile frequency pattern (TFP) was the same as the reference TFP given to the other hand. In each case stimulation was either present or absent on the median nerve of the hand holding the test pattern. We observed no impairment of tactile performance in the presence of electrical stimulation of the median nerve. This result together with previous work on direct stimulation of the somatosensory relay nucleus of the thalamus in which the same result of no impairment of the tactile discrimination task was observed suggest a high degree of noise tolerance exists in the somatosensory pathway.     

Tactile Gap Detection Deteriorates during Bimanual Symmetrical Movements under Mirror Visual Feedback

It has been suggested that incongruence between signals for motor intention and sensory input can cause pain and other sensory abnormalities. This claim is supported by reports that moving in an environment of induced sensorimotor conflict leads to elevated pain and sensory symptoms in those with certain painful conditions. Similar procedures can lead to reports of anomalous sensations in healthy volunteers too. In the present study, we used mirror visual feedback to investigate the effects of sensorimotor incongruence on responses to stimuli that arise from sources external to the body, in particular, touch. Incongruence between the sensory and motor signals for the right arm was manipulated by having the participants make symmetrical or asymmetrical movements while watching a reflection of their left arm in a parasagittal mirror, or the left hand surface of a similarly positioned opaque board. In contrast to our prediction, sensitivity to the presence of gaps in tactile stimulation of the right forearm was not reduced when participants made asymmetrical movements during mirror visual feedback, as compared to when they made symmetrical or asymmetrical movements with no visual feedback. Instead, sensitivity was reduced when participants made symmetrical movements during mirror visual feedback relative to the other three conditions. We suggest that small discrepancies between sensory and motor information, as they occur during mirror visual feedback with symmetrical movements, can impair tactile processing. In contrast, asymmetrical movements with mirror visual feedback may not impact tactile processing because the larger discrepancies between sensory and motor information may prevent the integration of these sources of information. These results contrast with previous reports of anomalous sensations during exposure to both low and high sensorimotor conflict, but are nevertheless in agreement with a forward model interpretation of perceptual modulations during goal directed movement.     

Resistance of peripheral and sub-cortical somatosensory pathway to electrical noise

The somatosensory system is vulnerable to large amounts of noise distortion. But how does the central nervous system distinguish the peripheral inputs which carry information to the brain from that which does not possess information? To address this question we studied the effect of electrical stimulation of the median nerve on tactile spatial frequency perception in healthy subjects and Parkinson's disease (PD) patients. Subjects were categorized in two groups (healthy and PD patients) and were asked to report if a test tactile frequency pattern (TFP) was the same as the reference TFP given to the other hand. In each case stimulation was either present or absent on the median nerve of the hand holding the test pattern. We observed no impairment of tactile performance in the presence of electrical stimulation of the median nerve. This result together with previous work on direct stimulation of the somatosensory relay nucleus of the thalamus (Abbassian et al., Stereotact Funct Neurosurg 76: 19–28, 2001) in which the same result of no impairment of the tactile discrimination task was observed suggest a high degree of noise tolerance exists in the somatosensory pathway.     

Interstitial fluid flow as a factor in decubitus ulcer formation

Decubitus ulcers form as a result of prolonged excessive external pressure on soft tissue. The mechanisms of ulcer formation are poorly understood. In this preliminary study, the effects of external pressure on interstitial fluid dynamics are analysed, using a simple mathematical model. Calculations revealed that an inverse relationship exists, between the intensity and duration of external pressure required for the interstitial fluid volume in the pressurized region to reach a given portion of its initial volume, which is similar to the experimentally observed relationship between the intensity and duration of external pressure required to produce threshold damage. The preliminary analysis suggests that interstitial fluid flow may play an important role in the ulcer formation.     

Real-time knee adduction moment feedback for gait retraining through visual and tactile displays

The external knee adduction moment (KAM) measured during gait is an indicator of tibiofemoral joint osteoarthritis progression and various strategies have been proposed to lower it. Gait retraining has been shown to be an effective, noninvasive approach for lowering the KAM. We present a new gait retraining approach in which the KAM is fed back to subjects in real-time during ambulation. A study was conducted in which 16 healthy subjects learned to alter gait patterns to lower the KAM through visual or tactile (vibration) feedback. Participants converged on a comfortable gait in just a few minutes by using the feedback to iterate on various kinematic modifications. All subjects adopted altered gait patterns with lower KAM compared with normal ambulation (average reduction of 20.7%). Tactile and visual feedbacks were equally effective for real-time training, although subjects using tactile feedback took longer to converge on an acceptable gait. This study shows that real-time feedback of the KAM can greatly increase the effectiveness and efficiency of subject-specific gait retraining compared with conventional methods.     

虚拟现实技术应用于运动障碍康复的研究

概述了近年来虚拟现实技术在运动障碍康复中的应用。介绍了该技术在运动障碍康复领域的四个重点研究方向：康复机器人、虚拟人、基于触觉反馈和力反馈的虚拟现实康复平台以及游戏机Wii的应用和新进展。最后总结了虚拟现实应用于运动障碍康复的优势及面临的主要挑战。     

Positive feedback in a brainstem tactile sensorimotor loop

The trigeminal loop in the brainstem comprises the innermost level of sensorimotor feedback in the rat vibrissa system. Anatomy suggests that this loop relays tactile information from the vibrissae to the motoneurons that control vibrissa movement. We demonstrate, using in vitro and in vivo recordings, that the trigeminal loop consists of excitatory pathways from vibrissa sensory inputs to vibrissa motoneurons in the facial nucleus. We further show that the trigeminal loop implements a rapidly depressing reflex that provides positive sensory feedback to the vibrissa musculature during simulated whisking and contact. On the basis of these findings, we propose that the trigeminal loop provides an enhancement of vibrissa muscle tone upon contact during active touch.     

Effects of carpal tunnel syndrome on adaptation of multi-digit forces to object weight for whole-hand manipulation

The delicate tuning of digit forces to object properties can be disrupted by a number of neurological and musculoskeletal diseases. One such condition is Carpal Tunnel Syndrome (CTS), a compression neuropathy of the median nerve that causes sensory and motor deficits in a subset of digits in the hand. Whereas the effects of CTS on median nerve physiology are well understood, the extent to which it affects whole-hand manipulation remains to be addressed. CTS affects only the lateral three and a half digits, which raises the question of how the central nervous system integrates sensory feedback from affected and unaffected digits to plan and execute whole-hand object manipulation. We addressed this question by asking CTS patients and healthy controls to grasp, lift, and hold a grip device (445, 545, or 745 g) for several consecutive trials. We found that CTS patients were able to successfully adapt grip force to object weight. However, multi-digit force coordination in patients was characterized by lower discrimination of force modulation to lighter object weights, higher across-trial digit force variability, the consistent use of excessively large digit forces across consecutive trials, and a lower ability to minimize net moments on the object. Importantly, the mechanical requirement of attaining equilibrium of forces and torques caused CTS patients to exert excessive forces at both CTS-affected digits and digits with intact sensorimotor capabilities. These findings suggest that CTS-induced deficits in tactile sensitivity interfere with the formation of accurate sensorimotor memories of previous manipulations. Consequently, CTS patients use compensatory strategies to maximize grasp stability at the expense of exerting consistently larger multi-digit forces than controls. These behavioral deficits might be particularly detrimental for tasks that require fine regulation of fingertip forces for manipulating light or fragile objects.     

Skin barrier homeostasis in atopic dermatitis: feedback regulation of kallikrein activity

Atopic dermatitis (AD) is a widely spread cutaneous chronic disease characterised by sensitive reactions (eg. eczema) to normally innocuous elements. Although relatively little is understood about its underlying mechanisms due to its complexity, skin barrier dysfunction has been recognised as a key factor in the development of AD. Skin barrier homeostasis requires tight control of the activity of proteases, called kallikreins (KLKs), whose activity is regulated by a complex network of protein interactions that remains poorly understood despite its pathological importance. Characteristic symptoms of AD include the outbreak of inflammation triggered by external (eg. mechanical and chemical) stimulus and the persistence and aggravation of inflammation even if the initial stimulus disappears. These characteristic symptoms, together with some experimental data, suggest the presence of positive feedback regulation for KLK activity by inflammatory signals. We developed simple mathematical models for the KLK activation system to study the effects of feedback loops and carried out bifurcation analysis to investigate the model behaviours corresponding to inflammation caused by external stimulus. The model analysis confirmed that the hypothesised core model mechanisms capture the essence of inflammation outbreak by a defective skin barrier. Our models predicted the outbreaks of inflammation at weaker stimulus and its longer persistence in AD patients compared to healthy control. We also proposed a novel quantitative indicator for inflammation level by applying principal component analysis to microarray data. The model analysis reproduced qualitative AD characteristics revealed by this indicator. Our results strongly implicate the presence and importance of feedback mechanisms in KLK activity regulation. We further proposed future experiments that may provide informative data to enhance the system-level understanding on the regulatory mechanisms of skin barrier in AD and healthy individuals.     

Design and technical construction of a tactile display for sensory feedback in a hand prosthesis system

Background  

The users of today's commercial prosthetic hands are not given any conscious sensory feedback. To overcome this deficiency in prosthetic hands we have recently proposed a sensory feedback system utilising a "tactile display" on the remaining amputation residual limb acting as man-machine interface. Our system uses the recorded pressure in a hand prosthesis and feeds back this pressure onto the forearm skin. Here we describe the design and technical solution of the sensory feedback system aimed at hand prostheses for trans-radial/humeral amputees. Critical parameters for the sensory feedback system were investigated.     

The Roles of Dopamine and Hypocretin in Reward: A Electroencephalographic Study

The proper functioning of the mesolimbic reward system is largely dependent on the neurotransmitter dopamine. Recent evidence suggests that the hypocretin system has significant projections to this reward system. We examined the distinct effects of reduced dopamine or reduced hypocretin levels on reward activity in patients with Parkinson’s disease, dopamine deficient, as well as patients with narcolepsy-cataplexy, hypocretin depleted, and healthy controls. Participants performed a simple game-like task while high-density electroencephalography was recorded. Topography and timing of event-related potentials for both reward cue, and reward feedback was examined across the entire dataset. While response to reward cue was similar in all groups, two distinct time points were found to distinguish patients and controls for reward feedback. Around 160ms both patient groups had reduced ERP amplitude compared to controls. Later at 250ms, both patient groups also showed a clear event-related potential (ERP), which was absent in controls. The initial differences show that both patient groups show a similar, blunted response to reward delivery. The second potential corresponds to the classic feedback-related negativity (FRN) potential which relies on dopamine activity and reflects reward prediction-error signaling. In particular the mismatch between predicted reward and reward subsequently received was significantly higher in PD compared to NC, independent of reward magnitude and valence. The intermediate FRN response in NC highlights the contribution of hypocretin in reward processing, yet also shows that this is not as detrimental to the reward system as in Parkinson’s. Furthermore, the inability to generate accurate predictions in NC may explain why hypocretin deficiency mediates cataplexy triggered by both positive and negative emotions.     

Respiratory system stability and abnormal carbon dioxide homeostasis.

We have tested the hypothesis that interactions among eight parameters of the respiratory and cardiovascular systems that determine the loop gain (LG) of the respiratory CO2 feedback control system might account for the degree of stability or instability of breathing patterns in healthy sleeping volunteers as well as in familial dysautonomia (FD) and congenital central hypoventilation syndrome (CCHS) patients. The predictability of cycle duration was tested as well. We measured the values of CO2 sensitivity, CO2 delivery capacity in the circulation, circulation delay, mean lung volume for CO2, and mixed venous PCO2 in 8 FD patients, 2 CCHS patients, and 19 healthy controls. The values of these parameters were used in a mathematical model to compute the LG of the respiratory control system during sleep for each epoch of respiration analyzed. The strength of the ventilatory oscillations (R) was quantified using power density spectra of the ventilation time series. All subjects were studied at inspiratory O2 concentrations (FIO2) of 0.21 and 0.15; CCHS patients and controls were also studied at 0.12 FIO2 to examine the effect of steady-state hypoxia on respiratory system stability. In 2 FD patients, LG was elevated at both levels of FIO2 and periodic breathing was observed; the values of R were elevated. Elevated mixed venous PCO2 and reduced CO2 delivery capacity were chiefly responsible for the abnormally high LG observed. In three healthy volunteers, high LG and unstable patterns were associated with high chemosensitivity. The CCHS patients, however, remained stable even at 0.12 FIO2 because LG remained equivalent to zero due to a lack of chemosensitivity.(ABSTRACT TRUNCATED AT 250 WORDS)     

A Tactile Automated Passive-Finger Stimulator (TAPS)

Although tactile spatial acuity tests are used in both neuroscience research and clinical assessment, few automated devices exist for delivering controlled spatially structured stimuli to the skin. Consequently, investigators often apply tactile stimuli manually. Manual stimulus application is time consuming, requires great care and concentration on the part of the investigator, and leaves many stimulus parameters uncontrolled. We describe here a computer-controlled tactile stimulus system, the Tactile Automated Passive-finger Stimulator (TAPS), that applies spatially structured stimuli to the skin, controlling for onset velocity, contact force, and contact duration. TAPS is a versatile, programmable system, capable of efficiently conducting a variety of psychophysical procedures. We describe the components of TAPS, and show how TAPS is used to administer a two-interval forced-choice tactile grating orientation test.Corresponding Author: Daniel Goldreich     

Relationship between somatosensory function and the spinothalamocortical pathway in chronic stroke patients

Abstract

Diffusion tensor tractography (DTT) allows for identification and evaluation of the spinothalamic tract and its thalamocortical pathway (STP). We attempted to investigate the relationship between tactile sensation and the STP in chronic stroke patients. We measured fractional anisotropy, mean diffusivity, and tract volume of the STP. The tactile sensation score of the affected side in patients with preserved STP integrity was higher compared with that of patients with an interrupted STP. The remaining volume and integrity of the STP in the affected hemisphere were important factors for tactile sensation of the affected side in chronic patients with intracerebral hemorrhage (ICH).     

Impaired Temporal Processing of Tactile and Proprioceptive Stimuli in Cerebellar Degeneration

Performance of timed motor sequences relies on the cerebellum and basal ganglia, which integrate proprioceptive information during the motor task and set internal timing mechanisms. Accordingly, these structures are also involved in other temporal processes, such as the discrimination of the different afferent information in the domain of time. In the present study we tested temporal processing of proprioceptive and tactile stimuli in 20 patients with neurodegenerative cerebellar ataxia and 20 age- and sex-matched healthy subjects. Tactile temporal discrimination threshold was defined as the value at which subjects recognized the two stimuli as asynchronous. Temporal discrimination movement threshold of the first dorsal interosseous and flexor carpi radialis was defined as the shortest interval between two paired electrical stimuli in which the subjects blindfolded perceived two separate index finger abductions and wrist flexions. Both tactile and movement temporal discrimination thresholds were higher in patients with cerebellar ataxia. No correlation was found with disease duration and severity. Our study demonstrates that temporal processing of tactile and proprioceptive stimuli is impaired in patients with cerebellar neurodegeneration and highlights the involvement of cerebellum in temporal processing of somatosensory stimuli of different type.     

Artificial feedback for invasive brain–computer interfaces

During the last two decades, considerable progress has been made in the studies of brain–computer interfaces (BCIs)—devices in which motor signals from the brain are registered by multi-electrode arrays and transformed into commands for artificial actuators such as cursors and robotic devices. This review is focused on one problem. Voluntary motor control is based on neurophysiological processes, which strongly depend on the afferent innervation of skin, muscles, and joints. Thus, invasive BCI has to be based on a bidirectional system in which motor control signals are registered by multichannel microelectrodes implanted in motor areas, whereas tactile, proprioceptive, and other useful signals are transported back to the brain through spatiotemporal patterns of intracortical microstimulation (ICMS) delivered to sensory areas. In general, the studies of invasive BCIs have advanced in several directions. The progress of BCIs with artificial sensory feedback will not only help patients, but will also expand base knowledge in the field of human cortical functions.     

Age-related changes in tactile spatial resolution from 6 to 16 years old

The aim of this study was to determine age-related changes in tactile spatial resolution from 6 to 16 years old. Two hundred and twenty-two healthy children (105 boys and 117 girls) were assessed. The tactile spatial resolution threshold was determined using a classic set of JVP domes with a procedure adapted for children. Preadolescence appears to be an important step in tactile spatial resolution since children aged between 6 and 9 years old had a worse tactile spatial resolution than older children. Both peripheral and central explanations for this improvement of tactile spatial resolution with age are considered. The authors suggest that cortical maturational processes are likely to explain the better results of older children.     

moBeat: Using Interactive Music to Guide and Motivate Users During Aerobic Exercising

An increasing number of people are having trouble staying fit and maintaining a healthy bodyweight because of lack of physical activity. Getting people to exercise is crucial. However, many struggle with developing healthy exercising habits, due to hurdles like having to leave the house and the boring character of endurance exercising. In this paper, we report on a design project that explores the use of audio to motivate and provide feedback and guidance during exercising in a home environment. We developed moBeat, a system that provides intensity-based coaching while exercising, giving real-time feedback on training pace and intensity by means of interactive music. We conducted a within-subject comparison between our moBeat system and a commercially available heart rate watch. With moBeat, we achieved a comparable success rate: our system has a significant, positive influence on intrinsic motivation and attentional focus, but we did not see significant differences with regard to either perceived exertion or effectiveness. Although promising, future research is needed.