Cellular Classes in the Human Brain Revealed In Vivo by Heartbeat-Related Modulation of the Extracellular Action Potential Waveform

Determining cell types is critical for understanding neural circuits but remains elusive in the living human brain. Current approaches discriminate units into putative cell classes using features of the extracellular action potential (EAP); in absence of ground truth data, this remains a problematic procedure. We find that EAPs in deep structures of the brain exhibit robust and systematic variability during the cardiac cycle. These cardiac-related features refine neural classification. We use these features to link bio-realistic models generated from in vitro human whole-cell recordings of morphologically classified neurons to in vivo recordings. We differentiate aspiny inhibitory and spiny excitatory human hippocampal neurons and, in a second stage, demonstrate that cardiac-motion features reveal two types of spiny neurons with distinct intrinsic electrophysiological properties and phase-locking characteristics to endogenous oscillations. This multi-modal approach markedly improves cell classification in humans, offers interpretable cell classes, and is applicable to other brain areas and species

Supplemental protocol for liana censuses

Lianas affect many aspects of tropical forest dynamics and thus the study of their ecology is critical for a comprehensive understanding of tropical forest ecology. Recently, we initiated a complete census of all lianas ≥1 cm diameter in the 50 ha forest dynamics plot on Barro Colorado Island, Panama using the census protocol developed by Gerwing et al. [Gerwing, J.J., Schnitzer, S.A., Burnham, R.J., Bongers, F., Chave, J., DeWalt, S.J., Ewango, C.E.N., Foster, R., Kenfack, D., Martinez-Ramos, M., Parren, M., Parthasarathy, N., Perez-Salicrup, D.R., Putz, F.E., Thomas, D.W., 2006. A standard protocol for liana censuses. Biotropica 38, 256–261]. This protocol marked an important advance in the study of lianas by providing a standard methodology that can be used for liana censuses worldwide, thereby making accurate comparisons among studies possible. During the course of our census, however, we encountered a number of recurring situations that were critical for accurate and repeatable liana censuses but were not covered in the protocol of Gerwing and colleagues. In this paper, we present a supplemental protocol that covers these additional situations. Our supplement, combined with the protocol developed by Gerwing et al., provides a more complete set of methods with provisions for situations commonly encountered in liana censuses

Morphometric versus densitometric assessment of coronary vasomotor tone-an overview

The main advantage of the morphometric approach is that the spatial orientation of the vessel with respect to the image intensifier is not very important. Its most severe limitations are that reasonable accuracy can only be obtained with circular lumina, and that accuracy decreases rapidly with the vessel diameter. The densitometric approach is much less dependent on the shape of the lumen and on the correct identification of the vessel wall in the image. A further essential advantage is that one measures directly the cross-sectional area of the vessel instead of a ‘diameter' of low haemodynamic relevance. Severe requirements must however be met if the potential accuracy of densitometry is to be fully exploited. The morphometric approach seems thus preferable for absolute or relative diameter measurements on intact vessels, while densitometry is superior in case of irregular or small lumina. Morphometric calibration using the injection catheter can induce non-negligible errors in both approaches. Grid calibration is probably more accurate, but also more tedious. In the densitometric approach, ‘3D-calibration' by help of a cube of known size allows also determination of the spatial orientation of the vessel in space. This solution requires however biplane imagin

Safety and Utility of Hybrid Depth Electrodes for Seizure Localization and Single-Unit Neuronal Recording

Background: Invasive electrode monitoring provides more precise localization of epileptogenic foci in patients with medically refractory epilepsy. The use of hybrid depth electrodes that include microwires for simultaneous single-neuron monitoring is becoming more widespread. Objective: To determine the safety and utility of hybrid depth electrodes for intracranial monitoring of medically refractory epilepsy. Methods: We reviewed the medical charts of 53 cases of medically refractory epilepsy operated on from 2006 to 2017, where both non-hybrid and hybrid microwire depth electrodes were used for intracranial monitoring. We assessed the localization accuracy and complications that arose to assess the relative safety and utility of hybrid depth electrodes compared with standard electrodes. Results: A total of 555 electrodes were implanted in 52 patients. The overall per-electrode complication rate was 2.3%, with a per-case complication rate of 20.8%. There were no infections or deaths. Serious or hemorrhagic complications occurred in 2 patients (0.4% per-electrode risk). Complications did not correlate with the use of any particular electrode type, and hybrids were equally as reliable as standard electrodes in localizing seizure onset zones. Conclusions: Hybrid depth electrodes appear to be as safe and effective as standard depth electrodes for intracranial monitoring and provide unique opportunities to study the human brain at single-neuron resolution

A NWB-based dataset and processing pipeline of human single-neuron activity during a declarative memory task

A challenge for data sharing in systems neuroscience is the multitude of different data formats used. Neurodata Without Borders: Neurophysiology 2.0 (NWB:N) has emerged as a standardized data format for the storage of cellular-level data together with meta-data, stimulus information, and behavior. A key next step to facilitate NWB:N adoption is to provide easy to use processing pipelines to import/export data from/to NWB:N. Here, we present a NWB-formatted dataset of 1863 single neurons recorded from the medial temporal lobes of 59 human subjects undergoing intracranial monitoring while they performed a recognition memory task. We provide code to analyze and export/import stimuli, behavior, and electrophysiological recordings to/from NWB in both MATLAB and Python. The data files are NWB:N compliant, which affords interoperability between programming languages and operating systems. This combined data and code release is a case study for how to utilize NWB:N for human single-neuron recordings and enables easy re-use of this hard-to-obtain data for both teaching and research on the mechanisms of human memory

Digital videodensitometric measurement of aortic regurgitation

A videodensitometric method for quantification of aortic regurgitation which requires neither measurement of cardiac output nor determination of enddiastolic and endsystolic left ventricular volumes has been developed. The injection of 20 ml of contrast medium into the left ventricle is digitally recorded at 25 images s−1 during 20 s using an equipment for digital subtraction angiography (Digitron 2, Siemens). The Digitron computes 2 ‘time dilution curves' (TDC) from the unsubtracted image sequence, for 2 regions of interest drawn around the angiographic enddiastolic and endsystolic left ventricular silhouettes. Enddiastolic and endsystolic points of the TDC are then entered into a VAX-750 computer, which calculates the ejection fraction (EF), the forward ejection fraction (FEF) and the regurgitant fraction (RGF). This is performed by a complex fitting algorithm based on a physical model of the washout process of contrast medium, which reconstructs the two best enddiastolic and endsystolic baselines in the washout parts of the two TDC. The EF, FEF and RGF obtained in 9 regurgitant and 11 nonregurgitant patients have been compared with the corresponding values EFv, FEFv and RGFv obtained by a conventional technique (Cardiogreen and biplane LV area-length volumetry). Regression analysis yielded: EF = 0.88 × EFv (regression line forced through the origin), r = 0.77, FEF = 0.76 × FEFv + 3, r = 0.96, RGF = 0.94 × RGFv + 5, r = 0.98 (v stands for volumetry

Long-term (10 years) prognostic value of a normal thallium-201 myocardial exercise scintigraphy in patients with coronary artery disease documented by angiography

In order to assess the prognostic significance of normal exercise thallium-210 myocardial scintigraphy in patients with documented coronary artery disease, we studied the incidence of cardiac death and non-fatal myocardial infarction in 69 symptomatic patients without prior Q wave myocardial infarction, who demonstrated one or more significant coronary lesions (stenosis ≤70%) on an angiogram performed within 3 months of scintigraphy (Group 1). These patients were compared to a second group of 136 patients with an abnormal exercise scintigram, defined by the presence of reversible defect(s) and angiographically proven coronary artery disease (Group 2), and to a third group of 102 patients with normal exercise scintigraphy without significant coronary lesions (stenosis ≥30%) or with normal coronary angiography (Group 3). In contrast to coronary lesions observed in Group 2, patients in Group I presented more frequently with single- vessel disease (83% vs 35%, P>0·0001) and with more distal lesions (55% vs 23%, P>0·0001). Over a mean follow-up period of 8·6 years, one fatal and eight non-fatal cases of myocardial infarction were observed in Group 1. The majority of patients in Group 1 were treated medically: only 24 (35%) underwent myocardial revascularization, usually by coronary angioplasty. There was no significant difference in the incidence of combined major cardiac events (cardiac death, non-fatal myocardial infarction) in patients with normal exercise scintigraphy, with or without documented coronary artery disease (Groups 1 and 3), while the incidence was higher in Group 2. However, while the mortality remained very low in Group 1, the incidence of non-fatal myocardial infraction was not different from that of Group 2, where most patients underwent revascularization procedures. In conclusion, patients with coronary artery disease and a normal exercise thallium-201 myocardial scintigram usually have mild coronary lesions (single-vessel disease, distal location) and good long-term prognosis, with a low incidence of cardiac deat

Magnetoliposomes: opportunities and challenges

Combining liposomes with magnetic nanoparticles is an intriguing approach to create multifunctional vesicles for medical applications, which range from controlled drug delivery vehicles to diagnostic imaging enhancers. Over the past decade, significant effort has been invested in developing such hybrids - widely known as magnetoliposomes - and has led to numerous new concepts. This review provides an overview on of the current state of the art in this field. The concept of magnetic fluid hyperthermia and stimuli-responsive nanoparticles for drug delivery is briefly recapitulated. The materials needed for these hybrids are addressed as well. The three typically followed approaches to associate magnetic nanoparticles to the liposomes are described and discussed more in detail. The final chapters are dedicated to the analytical methods used to characterize these hybrids and to theoretical considerations relevant for bilayer-embedded nanoparticle