Electrical stimulation induces propagated colonic contractions in an experimental model.

BACKGROUND: Direct colonic electrical stimulation may prove to be a treatment option for specific motility disorders such as chronic constipation. The aim of this study was to provoke colonic contractions using electrical stimulation delivered from a battery-operated device. METHODS: Electrodes were inserted into the caecal seromuscular layer of eight anaesthetized pigs. Contractions were induced by a neurostimulator (Medtronic 3625). Caecal motility was measured simultaneously by video image analysis, manometry and a technique assessing colonic transit. RESULTS: Caecal contractions were generated using 8-10 V amplitude, 1000 micros pulse width, 120 Hz frequency for 10-30 s, with an intensity of 7-15 mA. The maximal contraction strength was observed after 20-25 s. Electrical stimulation was followed by a relaxation phase of 1.5-2 min during which contractions propagated orally and aborally over at least 10 cm. Spontaneous and stimulated caecal motility values were significantly different for both intraluminal pressure (mean(s.d.) 332(124) and 463(187) mmHg respectively; P < 0.001, 42 experiments) and movement of contents (1.6(0.9) and 3.9(2.8) mm; P < 0.001, 40 experiments). CONCLUSION: Electrical stimulation modulated caecal motility, and provoked localized and propagated colonic contractions.

Assessment of quadriceps muscle inactivation with a new electrical stimulation paradigm.

INTRODUCTION: In this study we evaluated the validity of garment-based quadriceps stimulation (GQS) for assessment of muscle inactivation in comparison with femoral nerve stimulation (FNS). METHODS: Inactivation estimates (superimposed doublet torque), self-reported discomfort, and twitch and doublet contractile properties were compared between GQS and FNS in 15 healthy subjects. RESULTS: Superimposed doublet torque was significantly lower for GQS than for FNS at 20% and 40% maximum voluntary contraction (MVC) (P < 0.01), but not at 60%, 80%, and 100% MVC. Discomfort scores were systematically lower for GQS than for FNS (P < 0.05). Resting twitch and doublet peak torque were lower for GQS, and time to peak torque was shorter for GQS than for FNS (P < 0.01). CONCLUSIONS: GQS can be used with confidence for straightforward evaluation of quadriceps muscle inactivation, whereas its validity for assessment of contractile properties remains to be determined. Muscle Nerve 51: 117-124, 2015.

Cross validation of experts versus registration methods for target localization in deep brain stimulation.

In the last five years, Deep Brain Stimulation (DBS) has become the most popular and effective surgical technique for the treatent of Parkinson's disease (PD). The Subthalamic Nucleus (STN) is the usual target involved when applying DBS. Unfortunately, the STN is in general not visible in common medical imaging modalities. Therefore, atlas-based segmentation is commonly considered to locate it in the images. In this paper, we propose a scheme that allows both, to perform a comparison between different registration algorithms and to evaluate their ability to locate the STN automatically. Using this scheme we can evaluate the expert variability against the error of the algorithms and we demonstrate that automatic STN location is possible and as accurate as the methods currently used.

Auditory stimulation does not induce implicit memory during anaesthesia

Background and aim of the study: Formation of implicit memory during general anaesthesia is still debated. Perceptual learning is the ability to learn to perceive. In this study, an auditory perceptual learning paradigm, using frequency discrimination, was performed to investigate the implicit memory. It was hypothesized that auditory stimulation would successfully induce perceptual learning. Thus, initial thresholds of the frequency discrimination postoperative task should be lower for the stimulated group (group S) compared to the control group (group C). Material and method: Eighty-seven patients ASA I-III undergoing visceral and orthopaedic surgery during general anaesthesia lasting more than 60 minutes were recruited. The anaesthesia procedure was standardized (BISR monitoring included). Group S received auditory stimulation (2000 pure tones applied for 45 minutes) during the surgery. Twenty-four hours after the operation, both groups performed ten blocks of the frequency discrimination task. Mean of the thresholds for the first three blocks (T1) were compared between groups. Results: Mean age and BIS value of group S and group C are respectively 40 } 11 vs 42 } 11 years (p = 0,49) and 42 } 6 vs 41 } 8 (p = 0.87). T1 is respectively 31 } 33 vs 28 } 34 (p = 0.72) in group S and C. Conclusion: In our study, no implicit memory during general anaesthesia was demonstrated. This may be explained by a modulation of the auditory evoked potentials caused by the anaesthesia, or by an insufficient longer time of repetitive stimulation to induce perceptual learning.

Nouvelles techniques de stimulation cérébrale: perspectives thérapeutiques en psychiatrie [Novel brain stimulation techniques: therapeutic perspectives in psychiatry]

Recent advances have allowed the development of new physical techniques in neurology and psychiatry, such as Transcranial Magnetic Stimulation (TMS), Vagus Nerve Stimulation (VNS), and Deep Brain Stimulation (DBS). These techniques are already recognized as therapeutic approaches in several late stage refractory neurological disorders (Parkinson's disease, tremor, epilepsy), and currently investigated in psychiatric conditions, refractory to medical treatment (obsessive-compulsive disorder, resistant major depression). In Paralell, these new techniques offer a new window to understand the neurobiology of human behavior.

Prepupal Building Behavior in Drosophila melanogaster and Its Evolution under Resource and Time Constraints.

Structures built by animals are a widespread and ecologically important 'extended phenotype'. While its taxonomic diversity has been well described, factors affecting short-term evolution of building behavior within a species have received little experimental attention. Here we describe how, given the opportunity, wandering Drosophila melanogaster larvae often build long tunnels in agar substrates and embed their pupae within them. These embedded larvae are characterized by a longer egg-to-pupariation developmental time than larvae that pupate on the surface. Assuming that such building behaviors are likely to be energetically costly and/or time consuming, we hypothesized that they should evolve to be less pronounced under resource or time limitation. In accord with this prediction, larvae from populations evolved for 160 generations under a regime that combines larval malnutrition with limited developmental time dug shorter tunnels than larvae from control unselected populations. However, the proportion of larvae that embedded before pupation did not differ between the malnutrition-adapted and control populations, suggesting that tunnel length and likelihood of embedding before pupation are controlled by different genetic loci. The behaviors exhibited by wandering larvae of Drosophila melanogaster prior to pupation offer a model system to study evolution of animal building behaviors because the tunneling and embedding phenotypes are simple, facultative and highly variable.

Closed loop electrical muscle stimulation in spinal cord injured rehabilitation

The effect of motor training using closed loop controlled Functional Electrical Stimulation (FES) on motor performance was studied in 5 spinal cord injured (SCI) volunteers. The subjects trained 2 to 3 times a week during 2 months on a newly developed rehabilitation robot (MotionMaker?). The FES induced muscle force could be adequately adjusted throughout the programmed exercises by the way of a closed loop control of the stimulation currents. The software of the MotionMaker? allowed spasms to be detected accurately and managed in a way to prevent any harm to the SCI persons. Subjects with incomplete SCI reported an increased proprioceptive awareness for motion and were able to achieve a better voluntary activation of their leg muscles during controlled FES. At the end of the training, the voluntary force of the 4 incomplete SCI patients was found increased by 388% on their most affected leg and by 193% on the other leg. Active mobilisation with controlled FES seems to be effective in improving motor function in SCI persons by increasing the sensory input to neuronal circuits involved in motor control as well as by increasing muscle strength.

Influence of the implanted pulse generator as reference electrode in finite element model of monopolar deep brain stimulation.

Electrical deep brain stimulation (DBS) is an efficient method to treat movement disorders. Many models of DBS, based mostly on finite elements, have recently been proposed to better understand the interaction between the electrical stimulation and the brain tissues. In monopolar DBS, clinically widely used, the implanted pulse generator (IPG) is used as reference electrode (RE). In this paper, the influence of the RE model of monopolar DBS is investigated. For that purpose, a finite element model of the full electric loop including the head, the neck and the superior chest is used. Head, neck and superior chest are made of simple structures such as parallelepipeds and cylinders. The tissues surrounding the electrode are accurately modelled from data provided by the diffusion tensor magnetic resonance imaging (DT-MRI). Three different configurations of RE are compared with a commonly used model of reduced size. The electrical impedance seen by the DBS system and the potential distribution are computed for each model. Moreover, axons are modelled to compute the area of tissue activated by stimulation. Results show that these indicators are influenced by the surface and position of the RE. The use of a RE model corresponding to the implanted device rather than the usually simplified model leads to an increase of the system impedance (+48%) and a reduction of the area of activated tissue (-15%).

Cutting edge: stimulation with the cognate self-antigen induces expression of the Ly49A receptor on self-reactive T cells which modulates their responsiveness.

NK cell self-tolerance is maintained by inhibitory receptors specific for MHC class I molecules. Inhibitory NK receptors are also expressed on memory CD8 T cells but their biological relevance on T cells is unclear. In this study, we describe the expression of the Ly49A receptor on a subset of autoreactive T cells which persist in mice double-transgenic for the lymphocytic choriomeningitis virus-derived peptide gp33 and a TCRalphabeta specific for the gp33. No Ly49A-expressing cells are found in TCRalphabeta single-transgenic mice, indicating that the presence of the autoantigen is required for Ly49A induction. Direct evidence for an Ag-specific initiation of Ly49A expression has been obtained in vitro after stimulation of autoreactive TCRalphabeta T cells with the cognate self-Ag. This expression of Ly49A substantially reduces Ag-specific activation of autoreactive T cells. These findings thus suggest that autoantigen-specific induction of inhibitory NK cell receptors on T cells may contribute to peripheral self-tolerance.

Behavioral changes in brain-injured critical care adults with different levels of consciousness during nociceptive stimulation: an observational study.

PURPOSE: The primary objective of this study was to describe the frequency of behaviors observed during rest, a non-nociceptive procedure, and a nociceptive procedure in brain-injured intensive care unit (ICU) patients with different levels of consciousness (LOC). Second, it examined the inter-rater reliability and discriminant and concurrent validity of the behavioral checklist used. METHODS: The non-nociceptive procedure involved calling the patient and shaking his/her shoulder. The nociceptive procedure involved turning the patient. The frequency of behaviors was recorded using a behavioral checklist. RESULTS: Patients with absence of movement, or stereotyped flexion or extension responses to a nociceptive stimulus displayed more behaviors during turning (median 5.5, range 0-14) than patients with localized responses (median 4, range 0-10) or able to self-report their pain (median 4, range 0-10). Face flushing, clenched teeth, clenched fist, and tremor were more frequent in patients with absence of movement, or stereotyped responses to a nociceptive stimulus. The reliability of the checklist was supported by a high intra-class correlation coefficient (0.77-0.92), and the internal consistency was acceptable in all three groups (KR 20, 0.71-0.85). Discriminant validity was supported as significantly more behaviors were observed during nociceptive stimulation than at rest. Concurrent validity was confirmed as checklist scores were correlated to the patients' self-reports of pain (r s = 0.53; 95 % CI 0.21-0.75). CONCLUSION: Brain-injured patients reacted significantly more during a nociceptive stimulus and the number of observed behaviors was higher in patients with a stereotyped response.

Traitement de la douleur chronique: rôle de la stimulation transcrânienne du cortex moteur [Treatment of chronic pain: transcranial stimulation of the motor cortex?].

Chronic pain refractory to medical therapy poses a therapeutic challenge. The repetitive Transcranial Magnetic Stimulation (rTMS) and transcranial Direct Current Stimulation (tDCS) modulate brain activity offering a new approach. Current evidence suggests a potential therapeutic efficacy of motor cortex stimulation for the treatment of pain, but does not (yet) support their recommendation for clinical practice. These methods allow to deepen our knowledge in the pathophysiology of chronic pain while providing new therapeutic approaches.

Long duration response to levodopa in advanced Parkinson's disease patients treated with subthalamic deep brain stimulation

Résumé La levodopa (LD) est le traitement antiparkinsonien le plus efficace et le plus répandu. Son effet est composé d'une réponse de courte (quelques heures) et de longue durée (jours à semaines). La persistance de cette dernière dans les phases avancées de la maladie de Parkinson est controversée, et sa mesure directe n'a jamais été faite en raison des risques liés à un sevrage complet de LD. La stimulation du noyau sous-thalamique est un nouveau traitement neurochirurgical de la maladie de Parkinson, indiqué dans les formes avancées, qui permet l'arrêt complet du traitement médicamenteux chez certains patients. Nous avons étudié 30 patients qui ont bénéficié d'une telle stimulation, et les avons évalués avant l'intervention sans médicaments, et à 6 mois postopératoires, sans médicaments et sans stimulation. Chez 19 patients, la médication a pu être complètement arrêtée, alors qu'elle a dû être réintroduite chez les 11 patients restants. Au cours des 6 mois qui ont suivi l'intervention, le parkinsonisme s'est aggravé de façon significative dans le groupe sans LD, et non dans le groupe avec LD. Cette différence d'évolution s'explique par la perte de l'effet à long terme de la LD dans le groupe chez qui ce médicament a pu être arrêté. En comparant cette aggravation à la magnitude de l'effet à court terme, la réponse de longue durée correspond environ à 80 pourcent de la réponse de courte durée, et elle lui est inversement corrélée. Parmi les signes cardinaux de la maladie, la réponse de longue durée affecte surtout la bradycinésie et la rigidité, mais pas le tremblement ni la composante axiale. La comparaison du parkinsonisme avec traitement (stimulation et LD si applicable) ne montre aucune différence d'évolution entre les 2 groupes, suggérant que la stimulation compense tant la réponse de courte que de longue durée. Notre travail montre que la réponse de longue durée à la LD demeure significative chez les patients parkinsoniens après plus de 15 ans d'évolution, et suggère que la stimulation du noyau sous-thalamique compense les réponses de courte et de longue durée. Abstract Background: Long duration response to levodopa is supposed to decrease with Parkinson's disease (PD) progression, but direct observation of this response in advanced PD has never been performed. Objective: To study the long duration response to levodopa in advanced PD patients treated with subthalamic deep-brain stimulation. Design and settings: We studied 30 consecutive PD patients who underwent subthalamic deep-brain stimulation. One group had no antiparkinsonian treatment since surgery (no levodopa), while medical treatment had to be reinitiated in the other group (levodopa). Main outcome measures: motor Unified Parkinson's Disease Rating Scale (UPDRS). Results: In comparison with preoperative assessment, evaluation six months postoperatively with stimulation turned off for three hours found a worsening of the motor part of UPDRS in the no-levodopa group. This worsening being absent in the levodopa group, it most probably reflected the loss of the long duration response to levodopa in the no-levodopa group. Stimulation turned on, postoperative motor UPDRS in both groups were similar to preoperative on medication scores, suggesting that subthalamic deep-brain stimulation compensated for both the short and long duration responses to levodopa. Conclusions: Our results suggest that the long duration response to levodopa remains significant even in advanced PD, and that subthalamic deep-brain stimulation compensates for both the short and the long duration resposes to levodopa.