Imagined speech event detection from electrocorticography and its transfer between speech modes and subjects.

Speech brain-computer interfaces aim to support communication-impaired patients by translating neural signals into speech. While impressive progress was achieved in decoding performed, perceived and attempted speech, imagined speech remains elusive, mainly due to the absence of behavioral output. Nevertheless, imagined speech is advantageous since it does not depend on any articulator movements that might become impaired or even lost throughout the stages of a neurodegenerative disease. In this study, we analyzed electrocortigraphy data recorded from 16 participants in response to 3 speech modes: performed, perceived (listening), and imagined speech. We used a linear model to detect speech events and examined the contributions of each frequency band, from delta to high gamma, given the speech mode and electrode location. For imagined speech detection, we observed a strong contribution of gamma bands in the motor cortex, whereas lower frequencies were more prominent in the temporal lobe, in particular of the left hemisphere. Based on the similarities in frequency patterns, we were able to transfer models between speech modes and participants with similar electrode locations.

Current state of the art of traditional and minimal invasive epilepsy surgery approaches.

Introduction: Open resective surgery remains the main treatment modality for refractory epilepsy, but is often considered a last resort option due to its invasiveness. Research question: This manuscript aims to provide an overview on traditional as well as minimally invasive surgical approaches in modern state of the art epilepsy surgery. Materials and methods: This narrative review addresses both historical and contemporary as well as minimal invasive surgical approaches in epilepsy surgery. Peer-reviewed published articles were retrieved from PubMed and Scopus. Only articles written in English were considered for this work. A range of traditional and minimally invasive surgical approaches in epilepsy surgery were examined, and their respective advantages and disadvantages have been summarized. Results: The following approaches and techniques are discussed: minimally invasive diagnostics in epilepsy surgery, anterior temporal lobectomy, functional temporal lobectomy, selective amygdalohippocampectomy through a transsylvian, transcortical, or subtemporal approach, insulo-opercular corticectomies compared to laser interstitial thermal therapy, radiofrequency thermocoagulation, stereotactic radiosurgery, neuromodulation, high intensity focused ultrasound, and disconnection surgery including callosotomy, hemispherotomy, and subpial transections. Discussion and conclusion: Understanding the benefits and disadvantages of different surgical approaches and strategies in traditional and minimal invasive epilepsy surgery might improve the surgical decision tree, as not all procedures are appropriate for all patients.

Functional hemispheric disconnection procedures for chronic epilepsy: history, indications, techniques, complications and current practice in Europe. A consensus statement on behalf of the EANS functional neurosurgery section.

Introduction: The surgical procedure for severe, drug-resistant, unilateral hemispheric epilepsy is challenging. Over the last decades the surgical landscape for hemispheric disconnection procedures changed from anatomical hemispherectomy to functional hemispherotomy with a reduction of complications and stable good seizure outcome. Here, a task force of European epilepsy surgeons prepared, on behalf of the EANS Section for Functional Neurosurgery, a consensus statement on different aspects of the hemispheric disconnection procedure. Research question: To determine history, indication, timing, techniques, complications and current practice in Europe for hemispheric disconnection procedures in drug-resistant epilepsy. Material and methods: Relevant literature on the topic was collected by a literature search based on the PRISMA 2020 guidelines. Results: A comprehensive overview on the historical development of hemispheric disconnection procedures for epilepsy is presented, while discussing indications, timing, surgical techniques and complications. Current practice for this procedure in European epilepsy surgery centers is provided. At present, our knowledge of long-term seizure outcomes primarily stems from open surgical disconnection procedures. Although minimal invasive surgical techniques in epilepsy are rapidly developing and reported in case reports or small case series, long-term seizure outcome remain uncertain and needs to be reported. Discussion and conclusion: This is the first paper presenting a European consensus statement regarding history, indications, techniques and complications of hemispheric disconnection procedures for different causes of chronic, drug-resistant epilepsy. Furthermore, it serves as the pioneering document to report a comprehensive overview of the current surgical practices regarding this type of surgery employed in renowned epilepsy surgery centers across Europe.

Chronic subthreshold cortical stimulation: A promising therapy for motor cortex seizures.

Chronic subthreshold cortical stimulation (CSCS) is a form of neurostimulation consisting of continuous or cyclic, open-loop, subthreshold electrical stimulation of a well-defined epileptogenic zone (EZ). CSCS has seen limited clinical use but could be a safe and effective long-term treatment of focal drug resistant epilepsy, in particular when the EZ is located in the motor cortex. We present a case of a 49-year-old woman suffering from debilitating focal motor seizures. Treatment with CSCS resulted in significant clinical improvement, enabling her to walk unaided for the first time in years.

Deep Brain Stimulation of the Anterior Nucleus of the Thalamus in Drug-Resistant Epilepsy in the MORE Multicenter Patient Registry.

BACKGROUND AND OBJECTIVES: The efficacy of deep brain stimulation of the anterior nucleus of the thalamus (ANT DBS) in patients with drug-resistant epilepsy (DRE) was demonstrated in the double-blind Stimulation of the Anterior Nucleus of the Thalamus for Epilepsy randomized controlled trial. The Medtronic Registry for Epilepsy (MORE) aims to understand the safety and longer-term effectiveness of ANT DBS therapy in routine clinical practice. METHODS: MORE is an observational registry collecting prospective and retrospective clinical data. Participants were at least 18 years old, with focal DRE recruited across 25 centers from 13 countries. They were followed for at least 2 years in terms of seizure frequency (SF), responder rate (RR), health-related quality of life (Quality of Life in Epilepsy Inventory 31), depression, and safety outcomes. RESULTS: Of the 191 patients recruited, 170 (mean [SD] age of 35.6 [10.7] years, 43% female) were implanted with DBS therapy and met all eligibility criteria. At baseline, 38% of patients reported cognitive impairment. The median monthly SF decreased by 33.1% from 15.8 at baseline to 8.8 at 2 years (p < 0.0001) with 32.3% RR. In the subgroup of 47 patients who completed 5 years of follow-up, the median monthly SF decreased by 55.1% from 16 at baseline to 7.9 at 5 years (p < 0.0001) with 53.2% RR. High-volume centers (>10 implantations) had 42.8% reduction in median monthly SF by 2 years in comparison with 25.8% in low-volume center. In patients with cognitive impairment, the reduction in median monthly SF was 26.0% by 2 years compared with 36.1% in patients without cognitive impairment. The most frequently reported adverse events were changes (e.g., increased frequency/severity) in seizure (16%), memory impairment (patient-reported complaint, 15%), depressive mood (patient-reported complaint, 13%), and epilepsy (12%). One definite sudden unexpected death in epilepsy case was reported. DISCUSSION: The MORE registry supports the effectiveness and safety of ANT DBS therapy in a real-world setting in the 2 years following implantation. CLASSIFICATION OF EVIDENCE: This study provides Class IV evidence that ANT DBS reduces the frequency of seizures in patients with drug-resistant focal epilepsy. TRIAL REGISTRATION INFORMATION: MORE ClinicalTrials.gov Identifier: NCT01521754, first posted on January 31, 2012.

Cognitive tasks propagate the neural entrainment in response to a visual 40 Hz stimulation in humans.

Introduction: Alzheimer's disease is one of the great challenges in the coming decades, and despite great efforts, a widely effective disease-modifying therapy in humans remains elusive. One particular promising non-pharmacological therapy that has received increased attention in recent years is based on the Gamma ENtrainment Using Sensory stimulation (GENUS), a high-frequency neural response elicited by a visual and/or auditory stimulus at 40 Hz. While this has shown to be effective in animal models, studies on human participants have reported varying success. The current work hypothesizes that the varying success in humans is due to differences in cognitive workload during the GENUS sessions. Methods: We recruited a cohort of 15 participants who underwent a scalp-EEG recording as well as one epilepsy patient who was implanted with 50 subdural surface electrodes over temporo-occipital and temporo-basal cortex and 14 depth contacts that targeted the hippocampus and insula. All participants completed several GENUS sessions, in each of which a different cognitive task was performed. Results: We found that the inclusion of a cognitive task during the GENUS session not only has a positive effect on the strength and extent of the gamma entrainment, but also promotes the propagation of gamma entrainment to additional neural areas including deep ones such as hippocampus which were not recruited when no cognitive task was required from the participants. The latter is of particular interest given that the hippocampal complex is considered to be one of the primary targets for AD therapies. Discussion: This work introduces a possible improvement strategy for GENUS therapy that might contribute to increasing the efficacy of the therapy or shortening the time needed for the positive outcome.

MRI-Compatible and Conformal Electrocorticography Grids for Translational Research.

Intraoperative electrocorticography (ECoG) captures neural information from the surface of the cerebral cortex during surgeries such as resections for intractable epilepsy and tumors. Current clinical ECoG grids come in evenly spaced, millimeter-sized electrodes embedded in silicone rubber. Their mechanical rigidity and fixed electrode spatial resolution are common shortcomings reported by the surgical teams. Here, advances in soft neurotechnology are leveraged to manufacture conformable subdural, thin-film ECoG grids, and evaluate their suitability for translational research. Soft grids with 0.2 to 10 mm electrode pitch and diameter are embedded in 150 µm silicone membranes. The soft grids are compatible with surgical handling and can be folded to safely interface hidden cerebral surface such as the Sylvian fold in human cadaveric models. It is found that the thin-film conductor grids do not generate diagnostic-impeding imaging artefacts (<1 mm) nor adverse local heating within a standard 3T clinical magnetic resonance imaging scanner. Next, the ability of the soft grids to record subdural neural activity in minipigs acutely and two weeks postimplantation is validated. Taken together, these results suggest a promising future alternative to current stiff electrodes and may enable the future adoption of soft ECoG grids in translational research and ultimately in clinical settings.

Survival impact of incidental subventricular zone irradiation in IDH-wildtype glioblastoma.

BACKGROUND AND PURPOSE: The subventricular zone (SVZ) is an important niche for neural stem cells but probably also for brain tumor propagating cells, including the glioblastoma stem cell. The SVZ may become a target for radiation therapy in glioblastoma patients. However, reports studying the effect of irradiation of the SVZ on glioblastoma patient survival show conflicting results. We studied the correlation between incidental SVZ radiation dose and survival in a cohort of isocitrate dehydrogenase-wildtype (IDHwt) glioblastoma patients with inclusion of important survival prognosticators. PATIENTS AND METHODS: In this retrospective analysis, only adult patients with supratentorial IDHwt glioblastoma were included who were treated with temozolomide-based chemoradiotherapy after surgery. The SVZ was contoured on the radiotherapy planning imaging. Cox proportional regression overall survival (OS) analysis was used to study the correlation between SVZ dose and survival. Age, Karnofsky Performance Score, extent of resection and O6-methylguanine-methyl-DNA-transferase gene promoter (MGMTp) methylation were used as covariates in multivariate analysis. RESULTS: In total, 137 patients were included. Median OS was 13.3 months. The MGMTp methylation was present in 40% of cases. Ipsilateral SVZ (iSVZ) mean dose was 44.4 Gy and 27.2 Gy for the contralateral SVZ (cSVZ). Univariate survival analysis showed an inverse relationship between cSVZ mean dose and OS (HR 1.029 (1.003-1.057); p= .032). However, there was no correlation between cSVZ mean dose and OS in multivariate analysis. iSVZ dose did not correlate with survival. CONCLUSION: In this cohort of 137 IDHwt glioblastoma patients, iSVZ did not correlate with OS. Higher cSVZ dose was inversely correlated with OS in univariate survival analysis but lost its significance in multivariate analysis, including MGMTp-methylation. Hence, the correlation between SVZ radiation and glioblastoma patient survival remains unclear. Carefully designed prospective studies are needed to provide unequivocal results on this controversial topic.

Partial resection offers an overall survival benefit over biopsy in MGMT-unmethylated IDH-wildtype glioblastoma patients.

Background Isocitrate dehydrogenase (IDH)-wildtype glioblastoma patients with O6-methylguanine-DNA-methyltransferase (MGMT)-unmethylated tumors have the worst outcome of all glioblastoma patients. The overall survival (OS) benefit of partial resection of glioblastoma compared to biopsy only remains controversial specifically in relation to molecular factors. In this report, we analyzed the effect of incomplete resection on OS compared to biopsy only in a cohort of IDH-wildtype glioblastoma patients who were uniformly treated with temozolomide-based chemoradiotherapy (TMZ-CR) after surgery. Material & Methods A retrospective study was conducted including only glioblastoma patients who were treated with TMZ-CR after surgery from two centers. Surgical groups were defined as biopsy only, partial resection (PR) or gross total resection depending on the presence of contrast-enhancing tumor on postoperative imaging. IDH-mutation was determined using next generation sequencing technique and MGMT-methylation was analyzed with semi-quantitative methylation-specific polymerase chain reaction. Next to descriptive statistics, univariate and multivariate survival analyses were performed using Kaplan-Meier estimates and Cox regression models. Results In total, 159 patients were included. 37 patients underwent biopsy only and 73 partial resections. 99 patients (62.3%) harbored unmethylated tumors. Median OS for the whole patient group was 13.4 months. In the subgroup of patients with unmethylated tumors, PR yielded a median OS of 12.2 months vs 7.6 months for biopsy patients (P = 0.003). PR proved an independent beneficial prognostic factor in multivariate Cox regression model, together with age, Karnofsky Performance Score and MGMT-methylation. Conclusion In IDH-wildtype glioblastoma patients with MGMT-unmethylated tumors, treated with chemoradiotherapy after surgery, PR yields a significant OS benefit compared to biopsy.

Localization of deep brain activity with scalp and subdural EEG.

To what extent electrocorticography (ECoG) and electroencephalography (scalp EEG) differ in their capability to locate sources of deep brain activity is far from evident. Compared to EEG, the spatial resolution and signal-to-noise ratio of ECoG is superior but its spatial coverage is more restricted, as is arguably the volume of tissue activity effectively measured from. Moreover, scalp EEG studies are providing evidence of locating activity from deep sources such as the hippocampus using high-density setups during quiet wakefulness. To address this question, we recorded a multimodal dataset from 4 patients with refractory epilepsy during quiet wakefulness. This data comprises simultaneous scalp, subdural and depth EEG electrode recordings. The latter was located in the hippocampus or insula and provided us with our "ground truth" for source localization of deep activity. We applied independent component analysis (ICA) for the purpose of separating the independent sources in theta, alpha and beta frequency band activity. In all patients subdural- and scalp EEG components were observed which had a significant zero-lag correlation with one or more contacts of the depth electrodes. Subsequent dipole modeling of the correlating components revealed dipole locations that were significantly closer to the depth electrodes compared to the dipole location of non-correlating components. These findings support the idea that components found in both recording modalities originate from neural activity in close proximity to the depth electrodes. Sources localized with subdural electrodes were ~70% closer to the depth electrode than sources localized with EEG with an absolute improvement of around ~2cm. In our opinion, this is not a considerable improvement in source localization accuracy given that, for clinical purposes, ECoG electrodes were implanted in close proximity to the depth electrodes. Furthermore, the ECoG grid attenuates the scalp EEG, due to the electrically isolating silastic sheets in which the ECoG electrodes are embedded. Our results on dipole modeling show that the deep source localization accuracy of scalp EEG is comparable to that of ECoG. SIGNIFICANCE STATEMENT: Deep and subcortical regions play an important role in brain function. However, as joint recordings at multiple spatial scales to study brain function in humans are still scarce, it is still unresolved to what extent ECoG and EEG differ in their capability to locate sources of deep brain activity. To the best of our knowledge, this is the first study presenting a dataset of simultaneously recorded EEG, ECoG and depth electrodes in the hippocampus or insula, with a focus on non-epileptiform activity (quiet wakefulness). Furthermore, we are the first study to provide experimental findings on the comparison of source localization of deep cortical structures between invasive and non-invasive brain activity measured from the cortical surface.

High-gamma oscillations precede visual steady-state responses: A human electrocorticography study.

The robust steady-state cortical activation elicited by flickering visual stimulation has been exploited by a wide range of scientific studies. As the fundamental neural response inherits the spectral properties of the gazed flickering, the paradigm has been used to chart cortical characteristics and their relation to pathologies. However, despite its widespread adoption, the underlying neural mechanisms are not well understood. Here, we show that the fundamental response is preceded by high-gamma (55-125 Hz) oscillations which are also synchronised to the gazed frequency. Using a subdural recording of the primary and associative visual cortices of one human subject, we demonstrate that the latencies of the high-gamma and fundamental components are highly correlated on a single-trial basis albeit that the latter is consistently delayed by approximately 55 ms. These results corroborate previous reports that top-down feedback projections are involved in the generation of the fundamental response, but, in addition, we show that trial-to-trial variability in fundamental latency is paralleled by a highly similar variability in high-gamma latency. Pathology- or paradigm-induced alterations in steady-state responses could thus originate either from deviating visual gamma responses or from aberrations in the neural feedback mechanism. Experiments designed to tease apart the two processes are expected to provide deeper insights into the studied paradigm.

Modeling brain dynamics after tumor resection using The Virtual Brain.

Brain tumor patients scheduled for tumor resection often face significant uncertainty, as the outcome of neurosurgery is difficult to predict at the individual patient level. Recently, simulation of the activity of neural populations connected according to the white matter fibers, producing personalized brain network models, has been introduced as a promising tool for this purpose. The Virtual Brain provides a robust open source framework to implement these models. However, brain network models first have to be validated, before they can be used to predict brain dynamics. In prior work, we optimized individual brain network model parameters to maximize the fit with empirical brain activity. In this study, we extend this line of research by examining the stability of fitted parameters before and after tumor resection, and compare it with baseline parameter variability using data from healthy control subjects. Based on these findings, we perform the first "virtual neurosurgery", mimicking patient's actual surgery by removing white matter fibers in the resection mask and simulating again neural activity on this new connectome. We find that brain network model parameters are relatively stable over time in brain tumor patients who underwent tumor resection, compared with baseline variability in healthy control subjects. Concerning the virtual neurosurgery analyses, use of the pre-surgery model implemented on the virtually resected structural connectome resulted in improved similarity with post-surgical empirical functional connectivity in some patients, but negligible improvement in others. These findings reveal interesting avenues for increasing interactions between computational neuroscience and neuro-oncology, as well as important limitations that warrant further investigation.

The single nucleotide variant n.60G>C in the microRNA-146a associated with susceptibility to drug-resistant epilepsy.

OBJECTIVE: The aim of this study was to evaluate single nucleotide variants (SNVs) n.-411A > G (rs57095329) and n.60 G > C (rs2910164) in microRNA (miR)-146a, related to suppressing of TRAF6 with risk for epilepsy, as well as miR-146a and TRAF6 levels. METHODS: DNAs were extracted from epileptogenic tissues and blood leukocytes from drug-resistant epilepsy patients and healthy-individuals, respectively. Genotypes were identified by real-time PCR. Hardy-Weinberg equilibrium (HWE) and Fisher or X2 tests evaluated the difference between groups. The disease risk was assessed by odds ratio (OR) with 95 % confidence interval (95 %CI). The prognostic impact on probability seizure-free survival (PSF) was evaluated by Kaplan-Meier and log-rank tests. RESULTS: For rs57095329 both control and patient samples were not in HWE (p < 0.05) and the genotypes prevalence was similar in patients and controls (p>0.05). For rs2910164, control samples were in HWE (p = 0.61), contrasting with patients (p = 0.03), and similar frequencies of wild-type homozygous (GG) (43.4 % vs. 34.4 %, p = 0.2) and variant (CC) genotypes (8.0 % vs. 6.6 %, p = 0.6) were observed in patients and controls, respectively. However, increased frequency of heterozygous (GC) was observed in patients compared to controls (59.0 % vs. 42.7 %, p = 0.04) with 1.98 (95 %CI=1.09-3.57) risk for epilepsy. The miR-146a expression level in the epileptogenic tissues was lower in the GC (p = 0.02) and CC (p = 0.09) compared to GG genotype. TRAF6 expression level was higher in CC than in GG genotype (p = 0.09). Interestingly, there was an increased frequency of patients harboring GC genotype and less time until surgery compared to patients harboring GG or CC (36.06 % vs. 11.5 %, p = 0.01), confirmed by PSF (p = 0.04). CONCLUSIONS: The GC genotype for SNV rs2910164 appears associated with susceptibility to drug-resistant epilepsy due to the decreased MIR146a expression, favoring NF-kB pathway through TRAF6.

Invasive Neuromodulation as a Treatment for Tinnitus: A Systematic Review.

OBJECTIVE: Although the prevalence and burden of tinnitus is high, none of the available tinnitus treatments has been proven to be effective for the majority of tinnitus patients so far. Neuromodulation is currently gaining more interest to explore as tinnitus treatment. Because noninvasive neuromodulation has been shown to be effective in some tinnitus patients in the short term, more invasive techniques have been applied with variable success and without clear clinical applicability. As new insights into the neuropathophysiology of tinnitus arise, it seems essential to recapitulate the current evidence of invasive neuromodulation for tinnitus, to assess the quality of the available studies and identify gaps in this research domain. DATA SOURCES: MEDLINE, Embase, Web of Science and Clinical Trial Register. MATERIALS AND METHODS: We conducted a systematic review following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement. Studies since 2005 that reported on adult human subjects with chronic subjective tinnitus, who underwent some form of invasive neuromodulation, were included. Quality evaluation was performed using the modified Downs and Black checklist. RESULTS AND CONCLUSION: Twenty-one studies were included. Studies were often of low quality due to low sample sizes, lack of controlled designs, or investigating tinnitus as a secondary indication of neuromodulation. Current research results provide insufficient evidence to generally recommend invasive neuromodulation as an alternative treatment alternative for intractable tinnitus, although some promising effects are mentioned. Further research must be encouraged to gain more insight in this treatment including optimization of the technique, and standardization of tinnitus evaluation in subgroups.

Semantic and perceptual priming activate partially overlapping brain networks as revealed by direct cortical recordings in humans.

Facilitation of object processing in the brain due to a related context (priming) can be influenced by both semantic connections and perceptual similarity. It is thus important to discern these two when evaluating the spatio-temporal dynamics of primed object processing. The repetition-priming paradigm frequently used to study perceptual priming is, however, unable to differentiate between the mentioned priming effects, possibly leading to confounded results. In the current study, we recorded brain signals from the scalp and cerebral convexity of nine patients with refractory epilepsy in response to related and unrelated image-pairs, all of which shared perceptual features while only related ones had a semantic connection. While previous studies employing a repetition-priming paradigm observed largely overlapping networks between semantic and perceptual priming effects, our results suggest that this overlap is only partial (both temporally and spatially). These findings stress the importance of controlling for perceptual features when studying semantic priming.

Vestibular schwannoma: natural growth and possible predictive factors.

Background: Prediction of vestibular schwannoma (VS) growth would allow for a more differentiated follow-up protocol. Objectives: The natural course of a VS and predictive factors of growth are investigated. Methods: Sixty-two sporadic VS cases diagnosed between 2003 and 2015 were included in this retrospective cohort study. After initial surveillance, active therapy was initiated in 31/62 patients. Regular magnetic resonance images (MRIs) were performed. Two mm/year linear difference was the cut-off value for significant growth. The STROBE guidelines have been implemented. Results: Growth of the tumor was detected in 56% of patients and mainly observed in the first three years of follow-up. Tumor size remained stable in 34% and decreased in 10% of patients. No baseline information, symptom, or sign was found to be predictive for growth. Conclusions: In 56% of the initially conservatively managed VSs growth was observed and active treatment was initiated. Eighty-seven percent of the growing VSs were identified during the first three years of follow-up. The initially larger VSs seemed to grow faster and needed active treatment earlier during follow-up. No predicting factors for growth identified from the literature could be confirmed in the present study. Serial MRI remains the appropriate method to detect tumor growth.

Preparing for hard times: Scalp and intracranial physiological signatures of proactive cognitive control.

Based on reward and difficulty information, people can strategically adjust proactive cognitive control. fMRI research shows that motivated proactive control is implemented through fronto-parietal control networks that are triggered by reward and difficulty cues. Here, we investigate electrophysiological signatures of proactive control. Previously, the contingent negative variation (CNV) in the ERPs and oscillatory power in the theta (4-8 Hz) and alpha band (8-14 Hz) have been suggested as signatures of control implementation. However, experimental designs did not always separate control implementation from motor preparation. Critically, we used a mental calculation task to investigate effects of proactive control implementation on the CNV and on theta and alpha power, in absence of motor preparation. In the period leading up to task onset, we found a more negative CNV, increased theta power, and decreased alpha power for hard versus easy calculations, showing increased proactive control implementation when a difficult task was expected. These three measures also correlated with behavioral performance, both across trials and across subjects. In addition to scalp EEG in healthy participants, we collected intracranial local field potential recordings in an epilepsy patient. We observed a slow-drift component that was more pronounced for hard trials in a hippocampal location, possibly reflecting task-specific preparation for hard mental calculations. The current study thus shows that difficulty information triggers proactive control in absence of motor preparation and elucidates its neurophysiological signatures.

Is the Human Brain Capable of Controlling Seven Degrees of Freedom?

BACKGROUND: Conventional rigid laparoscopic instruments offer five degrees of freedom (DOF). Robotic instruments add two independent DOFs allowing unconstrained directional steering. Several nonrobotic instruments have been developed with the additional DOFs, but with these devices, surgeon's wrist movements are not intuitively transmitted into tip movements. In this study, a new articulated instrument has been evaluated. The aim of the study was to compare learning curves and performances of conventional laparoscopic instruments, the da Vinci system and Steerable devices in a crossover study. MATERIALS AND METHODS: A total of 16 medical students without any laparoscopic experience were trained for 27 h to operate all of a rigid, a robotic, and a new Steerable instrument in a random order. Learning curves and ultimate experience scores were determined for each instrument. Strain in wrist and shoulders was assessed with a visual analog score. RESULTS: Performing the suturing task with rigid and robot instruments required 4 h of training, compared with 6 h to master the Steerable instrument. After 9 h of training with each instrument, completing the complex suturing pattern required 662 ± 308 s with rigid instruments, 279 ± 90 s with the da Vinci system, and 279 ± 53 s with the Steerable instrument. Pain scores were significantly higher after using the rigid instruments compared with the Steerable instruments. CONCLUSIONS: Transmission of torque and the presence of additional two DOFs in combination with reduced crosstalk significantly improved the instrument dexterity where the Steerable platform is concerned. Although the learning curve is longer, once mastered, it provides enhanced surgical freedom.

Articulated Instruments and 3D Visualization: A Synergy? Evaluation of Execution Time, Errors, and Visual Fatigue.

Objective. The introduction of advanced endoscopic systems, such as the Storz Image1S and the Olympus Endoeye, heralds a new era of 3-dimensional (3D) visualization. The aim of this report is to provide a comprehensive overview of the neurophysiology of 3D view, its relevance in videoscopy, and to quantify the benefit of the new 3D technologies for both rigid and articulated instruments. Method. Sixteen medical students without any laparoscopic experience were trained each for a total of 27 hours. Proficiency scores were determined for rigid and articulated instruments under 2D and 3D visualization conditions. Results. A reduction in execution time of 14%, 28%, and 36% was seen for the rigid instruments, the da Vinci, and Steerable instruments, respectively. A reduction in errors of 84%, 92%, and 87% was seen for the rigid instruments, the da Vinci, and Steerable instruments, respectively. Conclusion. 3D visualization greatly augments endoscopic procedures. The advanced endoscopic systems employed in the recent study caused no visual fatigue or discomfort. The benefit of 3D was most distinct with articulated instruments.

A new dynamic model for in vitro evaluation of intravascular devices.

INTRODUCTION:: A dynamic model to evaluate thrombus formation on intravascular catheters in vitro is presented. The model enables fluid infusion, variation in the catheter orientation, and variable flow conditions. It was applied on a catheter used to shunt cerebrospinal fluid to a vein, a dural venous sinus, for the treatment of hydrocephalus. METHODS:: Fresh human blood-filled circuits were circulated in a non-occlusive roller pump. A catheter infused either with cerebrospinal fluid, Ringer's lactate, or no fluid (control) was inserted through each circuit's wall. Sixteen circuits (six cerebrospinal fluid, six Ringer's lactate, four control) ran for 60 min. Qualitative assessment was performed by measuring viscoelastic properties of blood at the start and end of the experiment; quantitative evaluation of clot formation by scanning electron microscope. RESULTS:: Average blood velocity was 79 mm/s, with a pressure wave between 5 and 15 mm Hg. At the experiment's end, the infused fluid represented 5.88% of the blood/infusion volume in the circuit. The control circuits showed no statistical difference between the start and end for viscoelastic testing, whereas both Ringer's lactate and cerebrospinal fluid enhanced coagulation, most pronounced for the latter. Most thrombus material was observed on catheters in the cerebrospinal fluid group. Clot formation was less pronounced on the surface of the catheter facing the blood flow. DISCUSSION:: A dynamic model for intravascular catheter testing mimics better clinical conditions when evaluating blood-material interaction. Catheter position, blood flow around the catheter, and infusion fluid all have a potential impact on the hemocompatibility of a given catheter.