Showing papers by "Olivier F. Bertrand published in 2014"

Selective modulation of auditory cortical alpha activity in an audiovisual spatial attention task.

Abstract: Despite substantial research on attentional modulations of visual alpha activity, doubts remain as to the existence and functional relevance of auditory cortical alpha-band oscillations. It has been argued that auditory cortical alpha does not exist, cannot be measured noninvasively, or that it is dependent on visual alpha generators. This study aimed to address these remaining doubts concerning auditory cortical alpha. A magnetoencephalography study was conducted using a combined audiovisual spatial cueing paradigm. In each trial, a cue indicated the side (left or right) and the modality (auditory or visual) to attend, followed by a short lateralized auditory or visual stimulus. Participants were instructed to respond to the stimuli by a button press. Results show that auditory cortical alpha power is selectively modulated by the audiospatial, but not the visuospatial, attention task. These findings provide further evidence for a distinct auditory cortical alpha generator, which can be measured noninvasively.

Balloon-assisted tracking: a must-know technique to overcome difficult anatomy during transradial approach.

Abstract: Objective To examine the use and outcomes of balloon-assisted tracking (BAT) technique for dealing with complexities of arm and chest vasculature during transradial approach (TRA) at a single high volume radial center. Background TRA has been used for coronary angiography and percutaneous coronary interventions (PCI) around the world. Different techniques have been described to address the anatomical issues and tortuosities for successful completion of coronary angiography and PCI. This study describes the use of BAT technique and associated outcomes during real world clinical practice. Methods Subjects comprised 63 patients, (out of total 8,245 patients between January 2011 and December 2012) in whom we encountered significantly complex anatomical course in radial, brachial, or subclavian region, leading to difficult advancement of a diagnostic or a guide catheter despite trying all standard maneuvers. In all of them BAT technique was used and they were retrospectively analyzed for the purpose of this study. Results About 63 (0.76%) of 8,245 patients met the study criteria. Twenty-five (39.7%) patients had very small RA. Twenty-two (34.9%) had severe RA tortuosity. Four (6.3%) had complex RA loops. Six (9.5%) had severe RA spasm and six (9.5%) had severe subclavian tortuosity and/or stenosis. We encountered technical failure in three (4.8%) patients (two had very small RA and one had 360 degree RA loop). Conclusion BAT technique was useful to address the anatomical issues and tortuosities of radial, brachial, and subclavian vasculature during TRA. © 2013 Wiley Periodicals, Inc.

Brain Reactivity Differentiates Subjects with High and Low Dream Recall Frequencies during Both Sleep and Wakefulness

Abstract: The neurophysiological correlates of dreaming remain unclear. According to the “arousal-retrieval” model, dream encoding depends on intrasleep wakefulness. Consistent with this model, subjects with high and low dream recall frequency (DRF) report differences in intrasleep awakenings. This suggests a possible neurophysiological trait difference between the 2 groups. To test this hypothesis, we compared the brain reactivity (evoked potentials) of subjects with high (HR, N= 18) and low (LR, N= 18) DRF during wakefulness and sleep. During data acquisition, the subjects were presented with sounds to be ignored (first names randomly presented among pure tones) while they were watching a silent movie or sleeping. Brain responses to first names dramatically differed between the 2 groups during both sleep and wakefulness. During wakefulness, the attention-orienting brain response (P3a) and a late parietal response were larger in HR than in LR. During sleep, we also observed between-group differences at the latency of the P3a during N2 and at later latencies during all sleep stages. Our results demonstrate differences in the brain reactivity of HR and LR during both sleep and wakefulness. These results suggest that the ability to recall dreaming is associated with a particular cerebral functional organization, regardless of the state of vigilance.

Oscillatory Alpha Modulations in Right Auditory Regions Reflect the Validity of Acoustic Cues in an Auditory Spatial Attention Task

Abstract: Anticipation of targets in the left or right hemifield leads to alpha modulations in posterior brain areas. Recently using magnetoencephalography, we showed increased right auditory alpha activity when attention was cued ipsilaterally. Here, we investigated the issue how cue validity itself influences oscillatory alpha activity. Acoustic cues were presented either to the right or left ear, followed by a compound dichotically presented target plus distractor. The preceding cue was either informative (75% validity) or uninformative (50%) about the location of the upcoming target. Cue validity × siderelated alpha modulations were identified in pre- and posttarget periods in a right lateralized network, comprising auditory and nonauditory regions. This replicates and extends our previous finding of the right hemispheric dominance of auditory attentional modulations. Importantly, effective connectivity analysis showed that, in the pretarget period, this effect is accompanied by a pronounced and timevarying connectivity pattern of the right auditory cortex to the right intraparietal sulcus (IPS), with influence of IPS on superior temporal gyrus dominating at earlier intervals of the cue–target period. Our study underlines the assumption that alpha oscillations may play a similar functional role in auditory cortical regions as reported in other sensory modalities and suggests that these effects may be mediated via IPS.

Functional connectivity of insular efferences

Abstract: Objectives The aim of our study was to explore the functional connectivity between the insula and other cortical regions, in human, using cortico-cortical evoked potentials (CCEPs) Experimental design We performed intra-cerebral electrical stimulation in eleven patients with refractory epilepsy investigated with depth electrodes, including 39 targeting the insula. Electrical stimulation consisted of two series of 20 pulses of 1-ms duration, 0.2-Hz frequency, and 1-mA intensity delivered at each of the 39 insular bipoles. Rates of connectivity were reported whenever a noninsular cortical region was tested by at least ten stimulating/recording electrode pairs in three or more patients Results Significant CCEPs were elicited in 193 of the 578 (33%) tested connections, with an average latency of 33 ± 5 ms. The highest connectivity rates were observed with the nearby perisylvian structures (59%), followed by the pericentral cortex (38%), the temporal neocortex (28%), the lateral parietal cortex (26%), the orbitofrontal cortex (25%), the mesial temporal structures (24%), the dorsolateral frontal cortex (15%), the temporal pole (14%), and the mesial parietal cortex (11%). No connectivity was detected in the mesial frontal cortex or cingulate gyrus. The pattern of connectivity also differed between the five insular gyri, with greater connectivity rate for the posterior short gyrus (49%), than for the middle short (29%), and two long gyri (28 and 33%) Conclusion The human insula is characterized by a rich and complex connectivity that varies as a function of the insular gyrus and appears to partly differ from the efferences described in nonhuman primates. Hum Brain Mapp 35:5279–5294, 2014. © 2014 Wiley Periodicals, Inc.

Intrainsular functional connectivity in human.

Abstract: Objectives The anatomical organization of the insular cortex is characterized by its rich and heterogeneous cytoarchitecture and its wide network of connections. However, only limited knowledge is available regarding the intrainsular connections subserving the complex integrative role of the insular cortex. The aim of this study was to analyze the functional connectivity within- and across-insular subregions, at both gyral and functional levels. Experimental design We performed intracerebral electrical stimulation in 10 patients with refractory epilepsy investigated with depth electrodes, 38 of which were inserted in the insula. Bipolar electrical stimulation, consisting of two series of 20 pulses of 1-ms duration, 0.2-Hz frequency, and 1-mA intensity, was delivered at each insular contact. For each stimulated insular anatomical region, we calculated a rate of connectivity, reflecting the proportion of other insular contacts, showing significant evoked potentials. Results Statistically significant evoked potentials were recorded in 74% of tested connections, with an average latency of 26 ± 3 ms. All insular gyri were interconnected, except the anterior and posterior short gyri. Most connections were reciprocal, showing no clear anterior to posterior directionality. No connection was observed between the right and the left insula. Conclusions These findings point to specific features of human insula connectivity as compared to non-Human primates, and remain consistent with the complex integration role devoted to the human insula in many cognitive domains. Hum Brain Mapp 35:2779–2788, 2014. © 2013 Wiley Periodicals, Inc.

Frequency of radial artery occlusion after transradial access in patients receiving warfarin therapy and undergoing coronary angiography.

Abstract: The efficacy of warfarin-induced anticoagulation in reducing radial artery occlusion (RAO) after transradial access is not known. The present case-control study compared the incidence of early (24 hours) and late (30 days) RAO in patients undergoing transradial diagnostic coronary angiography during therapeutic warfarin anticoagulation (group 1) with that of a matched (3:1) cohort of patients not receiving warfarin and receiving intraprocedural heparin (group 2). All patients underwent transradial diagnostic coronary angiography using a 5F hydrophilic introducer sheath. The patients in group 2 received an intravenous heparin bolus (50 IU/kg) immediately after sheath insertion. After sheath removal, hemostasis was obtained using the TR-band (Terumo Interventional Systems, Terumo Medical, Tokyo, Japan) and a plethysmography-guided patent hemostasis technique. We included 86 patients receiving warfarin with an international normalized ratio of 2 to 4 in group 1 and 250 matched patients in group 2. No significant differences were present in the demographic and procedural variables between the 2 groups. Early RAO occurred in 18.6% of the patients in group 1 compared with 9.6% of patients in group 2 (p = 0.024). The incidence of late RAO remained significantly higher in group 1 compared with group 2 (13.9% vs 5.2%, p = 0.01). All patients with RAO remained asymptomatic. In conclusion, patients receiving chronic oral anticoagulation with warfarin and undergoing transradial coronary angiography without parenteral anticoagulation had a higher incidence of early and late RAO compared with patients receiving standard intravenous heparin therapy.

Toward a New Application of Real-Time Electrophysiology: Online Optimization of Cognitive Neurosciences Hypothesis Testing

Abstract: Brain-computer interfaces (BCIs) mostly rely on electrophysiological brain signals. Methodological and technical progress has largely solved the challenge of processing these signals online. The main issue that remains, however, is the identification of a reliable mapping between electrophysiological measures and relevant states of mind. This is why BCIs are highly dependent upon advances in cognitive neuroscience and neuroimaging research. Recently, psychological theories became more biologically plausible, leading to more realistic generative models of psychophysiological observations. Such complex interpretations of empirical data call for efficient and robust computational approaches that can deal with statistical model comparison, such as approximate Bayesian inference schemes. Importantly, the latter enable the optimization of a model selection error rate with respect to experimental control variables, yielding maximally powerful designs. In this paper, we use a Bayesian decision theoretic approach to cast model comparison in an online adaptive design optimization procedure. We show how to maximize design efficiency for individual healthy subjects or patients. Using simulated data, we demonstrate the face- and construct-validity of this approach and illustrate its extension to electrophysiology and multiple hypothesis testing based on recent psychophysiological models of perception. Finally, we discuss its implications for basic neuroscience and BCI itself.

Characteristics of trabeculated myocardium burden in young and apparently healthy adults.

Abstract: Increased myocardial trabeculations define noncompaction cardiomyopathy (NCC). Imaging advancements have led to increasingly common identification of prominent trabeculations with unknown implications. We quantified and determined the impact of trabeculations' burden on cardiac function and stretch in a population of healthy young adults. One hundred adults aged 18 to 35 years (28 ± 4 years, 55% women) without known cardiovascular disease were prospectively studied by cardiovascular magnetic resonance. Left ventricular (LV) volumes, segmental function, and ejection fraction (EF) and left atrial volumes were determined. Thickness and area of trabeculated (T) and dense (D) myocardium were measured for each standardized LV segment. N-terminal pro-brain natriuretic peptide (Nt-pro-BNP) was measured. Eighteen percent of the subjects had ≥1 positive traditional criteria for NCC, and 11% meet new proposed NCC cardiovascular magnetic resonance criteria. Trabeculated over dense myocardium ratio (T/D) ratios were uniformly greater at end-diastole versus end-systole (0.90 ± 0.25 vs 0.42 ± 0.13, p

Scalp current density mapping in the analysis of mismatch negativity paradigms.

Abstract: MMN oddball paradigms are frequently used to assess auditory (dys)functions in clinical populations, or the influence of various factors (such as drugs and alcohol) on auditory processing. A widely used procedure is to compare the MMN responses between two groups of subjects (e.g. patients vs controls), or between experimental conditions in the same group. To correctly interpret these comparisons, it is important to take into account the multiple brain generators that produce the MMN response. To disentangle the different components of the MMN, we describe the advantages of scalp current density (SCD)—or surface Laplacian—computation for ERP analysis. We provide a short conceptual and mathematical description of SCDs, describe their properties, and illustrate with examples from published studies how they can benefit MMN analysis. We conclude with practical tips on how to correctly use and interpret SCDs in this context.

Feasibility of Using a Sheathless Guiding Catheter for Left Ventricular Endomyocardial Biopsy Performed by Transradial Approach

Abstract: The role of endomyocardial biopsy (EMB) in the diagnosis and treatment of adults presenting a newly unexplained car- diomyopathy remains controversial and the clinical indication varies among di�耀erent centers. Furthermore, the choice of the ventric- ular site for EMB is still under debate. The right ventricular EMB is commonly used due to safety features and le�耀 ventricle (LV) EMB has not yet gained acceptance because of concerns about possible complications. Of note, when LV-EMB is performed, the femoral artery is usually the access site. There is a large body of evidence supporting the safety and feasibility of transradial approach in a broad spectrum of patients and settings in the catheterization laboratory. Therefore, the aim of the present manuscript is to report the feasibility of performing a LV-EMB by the transradial approach using a sheathless guiding catheter as an ad hoc procedure.

Predictors and prognosis of early ischemic mitral regurgitation in the era of primary percutaneous coronary revascularisation

Abstract: Studies assessing ischemic mitral regurgitation (IMR) comprised of heterogeneous population and evaluated IMR in the subacute setting. The incidence of early IMR in the setting of primary PCI, its progression and clinical impact over time is still undetermined. We sought to determine the predictors and prognosis of early IMR after primary percutaneous coronary intervention (PCI) for ST-elevation myocardial infarction (STEMI). Using our primary PCI database, we screened for patients who underwent ≥2 transthoracic echocardiograms early (1–3 days) and late (1 year) following primary PCI. The primary outcomes were: (1) major adverse events (MACE) including death, ischemic events, repeat hospitalization, re-vascularization and mitral repair or replacement (2) changes in quantitative echocardiographic assessments. From January 2006 to July 2012, we included 174 patients. Post-primary PCI IMR was absent in 95 patients (55%), mild in 60 (34%), and moderate to severe in 19 (11%). Early after primary PCI, IMR was independently predicted by an ischemic time > 540 min (OR: 2.92 [95% CI, 1.28 – 7.05]; p = 0.01), and female gender (OR: 3.06 [95% CI, 1.42 – 6.89]; p = 0.004). At a median follow-up of 366 days [34–582 days], IMR was documented in 44% of the entire cohort, with moderate to severe IMR accounting for 15%. During follow-up, MR regression (change ≥ 1 grade) was seen in 18% of patients. Moderate to severe IMR remained an independent predictor of MACE (HR: 2.58 [95% CI, 1.08 – 5.53]; p = 0.04). After primary PCI, IMR is a frequent finding. Regression of early IMR during long-term follow-up is uncommon. Since moderate to severe IMR post-primary PCI appears to be correlated with worse outcomes, close follow-up is required.

Fusion proteins and immunoconjugates and uses thereof

Abstract: The present invention relates to isolated VHHs directed against human Glycophorin A. The present invention also relates to fusion proteins comprising the VHH according to the invention that is fused to at least one heterologous polypeptide and immunogonjugates comprising the VHH according to the invention that is conjugated to at least one chemical compound and their use in therapeutic or diagnostic methods.

Outcomes following surgical correction of pure aortic regurgitation in presence or absence of significant functional mitral regurgitation.

Abstract: Background Functional mitral regurgitation (MR) can occur secondary to severe aortic regurgitation (AR). However, data on the overall impact of mitral surgical intervention after aortic valve replacement (AVR) are scarce. We sought to study the left ventricular (LV) remodeling process and determine predictors of clinical outcomes of patients with pure severe AR in presence or absence of significant functional MR. Methods Patients were categorized into AR-MR group (≤ mild MR; n = 51, 76%) and AR + MR group (≥ moderate MR; n = 16, 24%). All patients in the AR + MR group underwent AVR and MR correction. Serial echocardiographic measurements and clinical follow-up up to 5 years were obtained in all patients. Results Significant reverse LV remodeling occurred in both groups compared with baseline. No 30-day deaths occurred. Mortality and heart failure-related hospitalization rates, at follow-up, were significantly higher in the AR + MR group (19% vs. 2%, P = 0.04 and 38% vs. 12% P = 0.03, respectively), but a similar proportion of patients from both groups was in New York Heart Association class I or II (87% vs. 92%, P = 0.62). Preoperative indexed stroke volume (SV) <50 mL/m2 was the only independent predictor of death and/or rehospitalization after surgery (odds ratio: 61.1, [95% CI, 12.6–425.2]; P < 0.0001). Conclusion Despite being a higher risk population, patients with moderate-to-severe functional MR secondary to severe AR experience similar postoperative mortality at the expense of a moderately higher 5-year overall mortality, rate of hospitalization for congestive heart failure, and medication use. Preoperative indexed SV < 50 mL/m2 may be helpful in predicting long-term outcomes.

Fusion proteins and immunoconjugates and uses thereof which are specific for glycophorin A

Abstract: The present invention relates to isolated VHHs directed against human Glycophorin A. The present invention also relates to fusion proteins comprising the VHH according to the invention that is fused to at least one heterologous polypeptide and immunoconjugates comprising the VHH according to the invention that is conjugated to at least one chemical compound and their use in therapeutic or diagnostic methods.

Development of a Metallic Biodegradable Stent Based on Microgalvanic Corrosion

Abstract: Coronary angioplasty is commonly used as a treatment for myocardial infarction. Initial challenges of bare metallic stents (BMS), e.g., early thrombosis and in stent restenosis (ISR) from proliferation and migration of vascular smooth muscle cell (SMC) are treated with anticlotting drugs and drug eluting stents (DES), respectively. But very late stent thrombosis (ST) is another challenge which causes restenosis of the stenotic arteries [1]. Improvement of reduced in stent restenosis (ISR) rate from 20–25% to around 8.6% using DES instead of BMS is hampered by stent fracture (SF) associated with DES [2]. Moreover, BMS shows very late ST (>5 years), whereas improved DES shows late ST (>1 year). In addition, clinically silent DES SF is associated with ISR and ST and pathologic investigation indicates 29% incidence of SF with about additional 5% incidence associated with adverse effect, e.g., inflammation, ulceration, avulsion, etc. [3]. Use of long overlapping stents with severe angulation, balloon overexpansion and vessel tortuosity reveal potential predictors of stent fracture in addition to stent design [4]. This indicates a fatigue process occurring under cyclic loading associated with the heart beats which inevitably will lead to Severe SF for any material and stent design. Long term problems of permanent stents require to improve material strength or biodegradability [5]. Due to lower ultimate tensile strength with polymeric stents, current research is directed to develop degradable metals and alloys for stents. Currently, iron and magnesium based alloys are investigated as degradable stent material [6]. Cold spray, introduced in this work, provides smaller grain size and good mechanical integrity as compared to powder metallurgy technique. Since cold spray coating deposition occurs at much lower temperature than powders melting point, it reduces thermally induced harmful effects commonly observed in conventional thermal spray coatings [7]. In this work, galvanic or bimetallic corrosion is introduced on the coating at the particle level, thus generating micro galvanic corrosion. In order to achieve this, a metal is selected with a nonreactive alloy which maintains a galvanic gap or potential difference in the galvanic table. Selected metals need to be available in powder form and cold spray able.