Performance monitoring for brain-computer-interface actions.

When presented with a difficult perceptual decision, human observers are able to make metacognitive judgements of subjective certainty. Such judgements can be made independently of and prior to any overt response to a sensory stimulus, presumably via internal monitoring. Retrospective judgements about one's own task performance, on the other hand, require first that the subject perform a task and thus could potentially be made based on motor processes, proprioceptive, and other sensory feedback rather than internal monitoring. With this dichotomy in mind, we set out to study performance monitoring using a brain-computer interface (BCI), with which subjects could voluntarily perform an action - moving a cursor on a computer screen - without any movement of the body, and thus without somatosensory feedback. Real-time visual feedback was available to subjects during training, but not during the experiment where the true final position of the cursor was only revealed after the subject had estimated where s/he thought it had ended up after 6s of BCI-based cursor control. During the first half of the experiment subjects based their assessments primarily on the prior probability of the end position of the cursor on previous trials. However, during the second half of the experiment subjects' judgements moved significantly closer to the true end position of the cursor, and away from the prior. This suggests that subjects can monitor task performance when the task is performed without overt movement of the body.

Oscillatory neural responses evoked by natural vestibular stimuli in humans.

While there have been numerous studies of the vestibular system in mammals, less is known about the brain mechanisms of vestibular processing in humans. In particular, of the studies that have been carried out in humans over the last 30 years, none has investigated how vestibular stimulation (VS) affects cortical oscillations. Here we recorded high-density electroencephalography (EEG) in healthy human subjects and a group of bilateral vestibular loss patients (BVPs) undergoing transient and constant-velocity passive whole body yaw rotations, focusing our analyses on the modulation of cortical oscillations in response to natural VS. The present approach overcame significant technical challenges associated with combining natural VS with human electrophysiology and reveals that both transient and constant-velocity VS are associated with a prominent suppression of alpha power (8-13 Hz). Alpha band suppression was localized over bilateral temporo-parietal scalp regions, and these alpha modulations were significantly smaller in BVPs. We propose that suppression of oscillations in the alpha band over temporo-parietal scalp regions reflects cortical vestibular processing, potentially comparable with alpha and mu oscillations in the visual and sensorimotor systems, respectively, opening the door to the investigation of human cortical processing under various experimental conditions during natural VS.

Learning to integrate contradictory multisensory self-motion cue pairings.

Humans integrate multisensory information to reduce perceptual uncertainty when perceiving the world and self. Integration fails, however, if a common causality is not attributed to the sensory signals, as would occur in conditions of spatiotemporal discrepancies. In the case of passive self-motion, visual and vestibular cues are integrated according to statistical optimality, yet the extent of cue conflicts that do not compromise this optimality is currently underexplored. Here, we investigate whether human subjects can learn to integrate two arbitrary, but co-occurring, visual and vestibular cues of self-motion. Participants made size comparisons between two successive whole-body rotations using only visual, only vestibular, and both modalities together. The vestibular stimulus provided a yaw self-rotation cue, the visual a roll (Experiment 1) or pitch (Experiment 2) rotation cue. Experimentally measured thresholds in the bimodal condition were compared with theoretical predictions derived from the single-cue thresholds. Our results show that human subjects combine and optimally integrate vestibular and visual information, each signaling self-motion around a different rotation axis (yaw vs. roll and yaw vs. pitch). This finding suggests that the experience of two temporally co-occurring but spatially unrelated self-motion cues leads to inferring a common cause for these two initially unrelated sources of information about self-motion. We discuss our results in terms of specific task demands, cross-modal adaptation, and spatial compatibility. The importance of these results for the understanding of bodily illusions is also discussed.

Self-motion leads to mandatory cue fusion across sensory modalities.

When perceiving properties of the world, we effortlessly combine multiple sensory cues into optimal estimates. Estimates derived from the individual cues are generally retained once the multisensory estimate is produced and discarded only if the cues stem from the same sensory modality (i.e., mandatory fusion). Does multisensory integration differ in that respect when the object of perception is one's own body, rather than an external variable? We quantified how humans combine visual and vestibular information for perceiving own-body rotations and specifically tested whether such idiothetic cues are subjected to mandatory fusion. Participants made extensive size comparisons between successive whole body rotations using only visual, only vestibular, and both senses together. Probabilistic descriptions of the subjects' perceptual estimates were compared with a Bayes-optimal integration model. Similarity between model predictions and experimental data echoed a statistically optimal mechanism of multisensory integration. Most importantly, size discrimination data for rotations composed of both stimuli was best accounted for by a model in which only the bimodal estimator is accessible for perceptual judgments as opposed to an independent or additive use of all three estimators (visual, vestibular, and bimodal). Indeed, subjects' thresholds for detecting two multisensory rotations as different from one another were, in pertinent cases, larger than those measured using either single-cue estimate alone. Rotations different in terms of the individual visual and vestibular inputs but quasi-identical in terms of the integrated bimodal estimate became perceptual metamers. This reveals an exceptional case of mandatory fusion of cues stemming from two different sensory modalities.

A randomized, controlled trial of endovenous thermal ablation using the 810-nm wavelength laser and the ClosurePLUS radiofrequency ablation methods for superficial venous insufficiency of the great saphenous vein.

BACKGROUND: Great saphenous vein (GSV) incompetence is the most common cause of superficial venous insufficiency. Radiofrequency catheter ablation (RFA) is superior to conventional ligation and stripping, and endovenous laser treatment (EVL) has emerged as an effective alternative to RFA. This randomized study evaluated RFA and EVL for superficial venous insufficiency due to GSV incompetence and compared early and 1-year results. METHODS: Between June 2006 and May 2008, patients with symptomatic primary venous insufficiency due to GSV incompetence were randomized to RFA or EVL. Patients with bilateral disease were randomized for treatment of the first leg and received the alternative method on the other. Pretreatment examination included a leg assessment using the Venous Clinical Severity Score (VCSS) and CEAP classification. Patients completed the Chronic Venous Insufficiency Questionnaire 2 (CIVIQ2). RFA was performed with the ClosurePlus system (VNUS Medical Technologies, Sunnyvale, Calif). EVL was performed with the EVLT system (AngioDynamics Inc, Queensbury, NY). Early (1-week and 1-month) postoperative results of pain, bruising, erythema, and hematoma were recorded. Duplex ultrasound (DU) imaging was used at 1 week and 1 year to evaluate vein status. VCSS scores and CEAP clinical class were recorded at each postoperative visit, and quality of life (QOL) using CIVIQ2 was assessed at 1 month and 1 year. RESULTS: The study enrolled 118 patients (141 limbs): 46 (39%) were randomized to RFA and 48 (40%) to EVL, and 24 (20%) had bilateral GSV incompetence. At 1 week, one patient in the RFA group had an open GSV and was deemed a failure. More bruising occurred in the EVL group (P = .01) at 1 week, but at 1 month, there was no difference in bruising between groups. At 1 year, DU imaging showed evidence of recanalization with reflux in 11 RFA and 2 EVL patients (P = .002). The mean VCSS score change from baseline to 1 week postprocedure was higher for RFA than EVL (P = .002), but there was no difference between groups at 1 month (P = .07) and 1 year (P = .9). Overall QOL mean score improved over time for all patients (P < .001). CEAP clinical class scores of >or=3 were recorded in 21 RFA (44%) and 24 EVL patients (44%) pretreatment, but at 1-year, 9 RFA (19%) and 12 EVL patients (24%) had scores of >or=3 (P < .001). This represented a significant improvement in all patients compared with baseline. CONCLUSION: Both methods of endovenous ablation effectively reduce symptoms of superficial venous insufficiency. EVL is associated with greater bruising and discomfort in the perioperative period but may provide a more secure closure over the long-term than RFA.

Optimal visuo-vestibular integration for self-motion perception in patients with unilateral vestibular loss.

Unilateral vestibular loss (UVL) is accompanied by deficits in processing of visual and vestibular self-motion cues. The present study examined whether multisensory integration of these two types of information is, nevertheless, intact in such patients. Patients were seated on a rotating platform with a screen simulating 3D rotation in front of them and asked to judge the relative magnitude of two successive rotations in the yaw plane in three conditions: vestibular stimulation, visual stimulation and bimodal stimulation (congruent stimuli from both modalities together). Similar to findings in healthy controls, UVL patients exhibited optimal multisensory integration during both ipsi- and contralesional rotations. The benefit of multisensory integration was more pronounced on the ipsilesional side. These results show that visuo-vestibular integration for passive self-motion is automatic and suggests that it functions without additional cognitive mechanisms, unlike more complex multisensory tasks such as postural control and spatial navigation, previously shown to be impaired in UVL patients.

Chronic venous insufficiency due to great saphenous vein incompetence treated with radiofrequency ablation: an effective and safe procedure in the elderly.

Chronic venous insufficiency (CVI) with the resultant clinical sequelae significantly reduces quality of life. Most elderly patients with CVI are treated nonoperatively owing to concerns of increased operative risk and therefore suffer more advanced disease. Radiofrequency ablation (RFA) has emerged as a minimally invasive procedure to treat patients with superficial venous insufficiency (SVI) due to great saphenous vein (GSV) incompetence. The purpose of this study was to review our experience using RFA of the GSV to treat CVI due to superficial disease in elderly patients compared to younger patients in terms of procedure-related morbidity and severity of disease at time of treatment. RFA treatment of the GSV was performed in 490 extremities of 421 patients with SVI between March 2001 and December 2002. Indications, medical history, and outcome (operative complications and hospital stay) were compared between 2 groups: Group I:41 extremities of 35 patients, 70 years if age or older (mean 75 +/-4); and Group II:449 limbs of 386 patients younger than 70 years (mean 47 +/-11). The incidence of skin pigmentation and healed/nonhealed ulcers (CEAP 4-6) was significantly higher in the elderly than in the younger group (41% vs 16%, p <0.05). Hypertension, diabetes, and previous myocardial infarction were 2.8, 5.4, and 6.7 times more prevalent in the elderly (p <0.05), respectively. There were no major postoperative complications in either group; 97% of all patients were discharged on the day of operation and there was no difference between the 2 groups in overnight hospital stay. There is a treatment bias against operative management in elderly patients with SVI, as evidenced by their more advanced disease at the time of definitive treatment than their younger cohort. However, operative morbidity is no different compared to the younger subset. RFA is a safe and effective procedure for older patients; therefore, the threshold for operative management of older patients should be lowered.

Visual Feedback Dominates the Sense of Agency for Brain-Machine Actions.

Recent advances in neuroscience and engineering have led to the development of technologies that permit the control of external devices through real-time decoding of brain activity (brain-machine interfaces; BMI). Though the feeling of controlling bodily movements (sense of agency; SOA) has been well studied and a number of well-defined sensorimotor and cognitive mechanisms have been put forth, very little is known about the SOA for BMI-actions. Using an on-line BMI, and verifying that our subjects achieved a reasonable level of control, we sought to describe the SOA for BMI-mediated actions. Our results demonstrate that discrepancies between decoded neural activity and its resultant real-time sensory feedback are associated with a decrease in the SOA, similar to SOA mechanisms proposed for bodily actions. However, if the feedback discrepancy serves to correct a poorly controlled BMI-action, then the SOA can be high and can increase with increasing discrepancy, demonstrating the dominance of visual feedback on the SOA. Taken together, our results suggest that bodily and BMI-actions rely on common mechanisms of sensorimotor integration for agency judgments, but that visual feedback dominates the SOA in the absence of overt bodily movements or proprioceptive feedback, however erroneous the visual feedback may be.

Percutaneous venous valve bioprosthesis: initial observations.

Chronic deep venous insufficiency remains a major health problem in the United States and worldwide. Selected patients benefit from direct deep vein valve repair or valve transplantation; however, most are not candidates for these procedures. Experience with the bovine monocusp venous valve surgically inserted into the common femoral vein (CFV) demonstrates potential benefit and good long-term patency. A venous valve placed distal to the CFV via percutaneous access has great appeal and potential for further improving venous hemodynamics, as well as reducing ambulatory venous hypertension and ulceration. Two patients were treated with a percutaneous venous valve bioprosthesis as part of a Phase I trial. The primary objective was to evaluate the safety, patency, and efficacy of the percutaneous venous valve bioprosthesis to restore competency to the deep venous system.

Fate of great saphenous vein after radio-frequency ablation: detailed ultrasound imaging.

Radio-frequency ablation (RFA) of the great saphenous vein (GSV) is an endovascular alternative to stripping. To determine long-term effectiveness, the fate of GSV treated for valvular insufficiency with RFA was evaluated in detail with ultrasound imaging (US). One hundred lower extremities were examined with high-resolution color flow US, an average of 8 months after RFA treatment of an incompetent GSV. For every cm of the RFA-treated segment, the US observation was classified as follows: absent, occluded, or recanalized. Lengths of vein segments in each class were added and percentages of absent, occluded, or recanalized segments were calculated. Five groups were identified. Group I (n = 15): segment of treated GSV was absent. Group II (n = 4): segment of treated GSV was visualized and occluded (these vein segments had no flow and were shrunk and "fibrotic" or thrombosed without clear evidence of significant shrinkage). Group III (n = 1): segment of treated GSV was recanalized. Group IV (n = 27): segment of treated GSV was obstructed (absent or occluded). Group V (n = 53): segment of treated GSV was partially recanalized, on average being 53% absent, 32% occluded, and 15% recanalized. Maximum recanalization was 50% of treated segment. RFA was successful in obliterating all of the GSV treated segment in 46% of veins (groups I, 15%, plus II, 4%, plus IV, 27%) and obliterated more than half of the treated vein segment in 53% of the cases (group V). A dynamic process of recanalization and thrombosis warrants further evaluation to determine if and how a collateral network may develop.

DOMINATE Wounds.

Chronic wounds are a significant health problem worldwide. Often they are initially managed with various focal treatments until a specialist becomes involved, sometimes weeks or months after treatment has begun. Even at the specialist level, practices and guidelines are inconsistent due to a lack of high-level evidence. A disease management system for chronic wounds that is simple, practical, and adoptable by a variety of wound care practitioners is needed. Such a system would guide wound care providers to address the critical aspects of wound care in a prioritized, systematic sequence, leading to faster healing of simple wounds, and timely advancement to more complex therapies for wounds that require such treatment. This paper describes an empirically developed wound care management system that has been successfully implemented and provides evidence-based rationale for each of its components. Relatively simple and practical, this system organizes an approach to any type of wound, routine or complex.

Technique of contemporary iliofemoral and infrainguinal venous thrombectomy.

Patients with acute deep vein thrombosis involving the iliofemoral venous system experience the most severe postthrombotic sequelae. Treatment designed to reduce or eliminate the postthrombotic syndrome must necessarily remove thrombus to eliminate obstruction. Unfortunately, currently published guidelines do not recommend venous thrombectomy and actually recommend against its use because of the poor results initially reported. However, recent reports of venous thrombectomy and the long-term results of a large randomized trial confirm the significant benefit compared with anticoagulation alone. The technique of contemporary venous thrombectomy follows basic vascular surgical principles and offers patients the opportunity for complete or nearly complete thrombus extraction, thereby avoiding the significant morbidity of their anticipated postthrombotic syndrome. The techniques described herein represent the authors' approach to patients with few alternatives to clear the venous system. Because the patient benefit is well established, vascular surgeons should include contemporary venous thrombectomy as part of their routine operative armamentarium, offering this procedure to patients with extensive deep vein thrombosis involving the iliofemoral venous system, especially if other options are not available or have failed.

Ultrasound findings after radiofrequency ablation of the great saphenous vein: descriptive analysis.

OBJECTIVE: As an emerging endovascular alternative to ligation and stripping of the incompetent greater saphenous vein (GSV), radiofrequency ablation was monitored with ultrasound scanning to evaluate anatomic results. Neovascularization and inflammation are potential consequences that lead to the appearance of small vessels. The natural history of the below-knee untreated GSV segment may be important in our understanding of ongoing chronic venous disease. An ultrasound follow-up study was conducted to determine the prevalence of small vessel networks, defined as veins and arteries less than 2 mm in diameter, adjacent to the saphenofemoral junction (SFJ); prevalence of small vessel networks adjacent to the treated GSV in the thigh; and fate of the below-knee untreated GSV distal to the ablated segment. METHODS: One hundred six extremities with radiofrequency ablation of the GSV for treatment of superficial venous insufficiency were followed up with high-resolution ultrasound imaging 4 to 25 months (median, 9 months) after the procedure. Ninety-three limbs had concomitant ligation and division of the SFJ and its tributaries, and 13 limbs underwent radiofrequency ablation without SFJ ligation. Ultrasound was used to evaluate patients for small vessel networks, and concomitant findings of small vessel networks and recanalization at the SFJ and adjacent to the treated GSV. The status of the below-knee segment of untreated GSV was evaluated for patency and reflux. Data analysis compared the findings in the ligation group with those in the no-ligation group, with the chi 2 test and Fisher exact test. RESULTS: We found small vessel networks in 65% (n = 69) of extremities: 15% (n = 16) at the SFJ only, 26% (n = 28) in the thigh only, and 24% (n = 25) at both the SFJ and thigh, resulting in a small vessel network prevalence of 39% (n = 41) at the SJF and 50% (n = 53) in the thigh. The prevalence of small vessel networks at the SFJ was significantly less after radiofrequency ablation with SFJ ligation (34%, 32 of 93) than after radiofrequency ablation without ligation (69%, 9 of 13; P = .035). Small vessel networks and GSV recanalization at the SFJ was more common in patients undergoing radiofrequency ablation without ligation (46%, 6 of 13) than after radiofrequency ablation with ligation (14%, 13 of 93; P = .014). The prevalence of small vessel networks in the thigh was not affected by SFJ ligation. The below-knee GSV was patent in 79% (84 of 106), and 58% (61 of 106) demonstrated reflux, a decrease from the pre-radiofrequency ablation rate of 71% (75 of 106), possibly because thrombosis extended distally beyond the ablated segment in 16% (17 of 106) of the legs. CONCLUSIONS: Small vessel networks were detected adjacent to or in connection with most of the radiofrequency ablation-treated GSVs. SFJ ligation was associated with fewer small vessel networks and proximal GSV recanalization. Most below-knee untreated GSV segments remained patent, and most exhibited reflux.