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Several neuroimaging studies have shown the somatotopy of body part representations in primary somatosensory cortex (S1), but the functional hierarchy of distinct subregions in human S1 has not been adequately addressed. The current study investigates the functional hierarchy of cyto-architectonically distinct regions, Brodmann areas BA3, BA1, and BA2, in human S1. During functional MRI experiments, we presented participants with vibrotactile stimulation of the fingertips at three different vibration frequencies. Using population Receptive Field (pRF) modeling of the fMRI BOLD activity, we identified the hand region in S1 and the somatotopy of the fingertips. For each voxel, the pRF center indicates the finger that most effectively drives the BOLD signal, and the pRF size measures the spatial somatic pooling of fingertips. We find a systematic relationship of pRF sizes from lower-order areas to higher-order areas. Specifically, we found that pRF sizes are smallest in BA3, increase slightly towards BA1, and are largest in BA2, paralleling the increase in visual receptive field size as one ascends the visual hierarchy. Additionally, we find that the time-to-peak of the hemodynamic response in BA3 is roughly 0.5 s earlier compared to BA1 and BA2, further supporting the notion of a functional hierarchy of subregions in S1. These results were obtained during stimulation of different mechanoreceptors, suggesting that different afferent fibers leading up to S1 feed into the same cortical hierarchy. [ABSTRACT FROM AUTHOR]

Applications such as brain computer interfaces require recordings of relevant neuronal population activity with high precision, for example, with electrocorticography (ECoG) grids. In order to achieve this, both the placement of the electrode grid on the cortex and the electrode properties, such as the electrode size and material, need to be optimized. For this purpose, it is essential to have a reliable tool that is able to simulate the extracellular potential, i.e., to solve the so-called ECoG forward problem, and to incorporate the properties of the electrodes explicitly in the model. In this study, this need is addressed by introducing the first open-source pipeline, FEMfuns (finite element method for useful neuroscience simulations), that allows neuroscientists to solve the forward problem in a variety of different geometrical domains, including different types of source models and electrode properties, such as resistive and capacitive materials. FEMfuns is based on the finite element method (FEM) implemented in FEniCS and includes the geometry tessellation, several electrode-electrolyte implementations and adaptive refinement options. The Python code of the pipeline is available under the GNU General Public License version 3 at https://github.com/meronvermaas/FEMfuns. We tested our pipeline with several geometries and source configurations such as a dipolar source in a multi-layer sphere model and a five-compartment realistically-shaped head model. Furthermore, we describe the main scripts in the pipeline, illustrating its flexible and versatile use. Provided with a sufficiently fine tessellation, the numerical solution of the forward problem approximates the analytical solution. Furthermore, we show dispersive material and interface effects in line with previous literature. Our results indicate substantial capacitive and dispersive effects due to the electrode-electrolyte interface when using stimulating electrodes. The results demonstrate that the pipeline presented in this paper is an accurate and flexible tool to simulate signals generated on electrode grids by the spatiotemporal electrical activity patterns produced by sources and thereby allows the user to optimize grids for brain computer interfaces including exploration of alternative electrode materials/properties. [ABSTRACT FROM AUTHOR]

The sensorimotor cortex is responsible for the generation of movements and interest in the ability to use this area for decoding speech by brain-computer interfaces has increased recently. Speech decoding is challenging however, since the relationship between neural activity and motor actions is not completely understood. Non-linearity between neural activity and movement has been found for instance for simple finger movements. Despite equal motor output, neural activity amplitudes are affected by preceding movements and the time between movements. It is unknown if neural activity is also affected by preceding motor actions during speech. We addressed this issue, using electrocorticographic high frequency band (HFB; 75-135 Hz) power changes in the sensorimotor cortex during discrete vowel generation. Three subjects with temporarily implanted electrode grids produced the /i/ vowel at repetition rates of 1, 1.33 and 1.66 Hz. For every repetition, the HFB power amplitude was determined. During the first utterance, most electrodes showed a large HFB power peak, which decreased for subsequent utterances. This result could not be explained by differences in performance. With increasing duration between utterances, more electrodes showed an equal response to all repetitions, suggesting that the duration between vowel productions influences the effect of previous productions on sensorimotor cortex activity. Our findings correspond with previous studies for finger movements and bear relevance for the development of brain-computer interfaces that employ speech decoding based on brain signals, in that past utterances will need to be taken into account for these systems to work accurately. [ABSTRACT FROM AUTHOR]

The increasing understanding of human brain functions makes it possible to directly interact with the brain for therapeutic purposes. Implantable brain computer interfaces promise to replace or restore motor functions in patients with partial or complete paralysis. We postulate that neuronal states associated with gestures, as they are used in the finger spelling alphabet of sign languages, provide an excellent signal for implantable brain computer interfaces to restore communication. To test this, we evaluated decodability of four gestures using high-density electrocorticography in two participants. The electrode grids were located subdurally on the hand knob area of the sensorimotor cortex covering a surface of 2.5-5.2 cm. Using a pattern-matching classification approach four types of hand gestures were classified based on their pattern of neuronal activity. In the two participants the gestures were classified with 97 and 74 % accuracy. The high frequencies (>65 Hz) allowed for the best classification results. This proof-of-principle study indicates that the four gestures are associated with a reliable and discriminable spatial representation on a confined area of the sensorimotor cortex. This robust representation on a small area makes hand gestures an interesting control feature for an implantable BCI to restore communication for severely paralyzed people. [ABSTRACT FROM AUTHOR]

Of 319 pediatric patients treated with bone marrow transplantation (BMT) during a 10-year period, 27 developed pulmonary fungal infections (PFI). Only 2 patients (7%) survived. Twenty-three patients (85%) had been treated with systemic antifungal therapy immediately before or at the time of diagnosis. Nineteen patients (70%) were neutropenic, and 4 of the 8 patients who were not neutropenic were being treated with systemic steroids for graft vs. host disease (GVHD). Seven patients (26%) died within 7 days of diagnosis. The diagnosis was made ante-mortem in 9 patients (33%). Radiographic abnormalities were variable. At the onset of chest X-ray (CXR) change, the pulmonary infiltrates were unilateral in 14 patients (52%) and, at diagnosis, bilateral in 18 (66%). At diagnosis the infiltrates were interstitial in 3 patients (11%), alveolar in 20 (74%) and mixed in 4 (15%). Six patients (22%) developed cavitary lesions. The infecting agents were Aspergillus in 21 patients (78%), Candida in 7 (26%), Mucormycosis in 3 (11%), and Fusarium in 1 (4%). Five patients (19%) had mixed fungal infections and 7 (26%) had concurrent cytomegalovirus (CMV) pulmonary infections. Although the radiographic changes are often nonspecific in PFI, alveolar or nodular infiltrates in neutropenic patients or in those being treated for GVHD should strongly suggest a fungal etiology. [ABSTRACT FROM AUTHOR]

Objectives: To assess the reliability of diffusion tensor imaging (DTI)-based fibre tractography (FT), which is a prerequisite for clinical applications of this technique. Here we assess the test-retest reproducibility of the architectural and microstructural features of two clinically relevant tracts reconstructed with DTI-FT.Methods: The corticospinal tract (CST), arcuate fasciculus (AF) and its long segment (AFl) were reconstructed in 17 healthy subjects imaged twice using a deterministic approach. Coefficients of variation (CVs) of diffusion-derived tract values were used to assess the microstructural reproducibility. Spatial correlation and fibre overlap were used to assess the architectural reproducibility.Results: Spatial correlation was 68 % for the CST and AF, and 69 % for the AFl. Overlap was 69 % for the CST, 61 % for the AF, and 59 % for the AFl. This was comparable to 2-mm tract shift variability. CVs of diffusion-derived tract values were at most 3.4 %.Conclusions: The results showed low architectural and microstructural variability for the reconstruction of the tracts. The architectural reproducibility results encourage the further investigation of the use of DTI-FT for neurosurgical planning. The high microstructural reproducibility results are promising for using DTI-FT in neurology to assess or predict functional recovery. [ABSTRACT FROM AUTHOR]

The early history of magnetic resonance to around 1950 is discussed from the point of view of a participant in it. I. I. Rabi's theory of space quantization in a gyrating magnetic field and his molecular beam experiments in the 1930s laid the foundation of the magnetic resonance method, which he and his associates subsequently pursued and developed further at Columbia University, leading eventually to the development of NMR after World War II and the invention of the separated oscillatory fields method in 1950. [ABSTRACT FROM AUTHOR]

It is an honor to contribute to this celebration of the hundredth anniversary of the birth of Otto Stern, who developed molecular beams to become one of the most nowerful and fruitful physics research methods. [ABSTRACT FROM AUTHOR]

The methods of separated or successive oscillatory fields (often called Ramsey methods) are described for radio, microwave and optical coherent radiation. The methods are initially described qualitatively. The quantitative theories of the methods are also given. For a two-level system at radio frequencies exact expressions for the transition probability amplitudes for an arbitrary number of successive oscillatory regions can be found in terms of products of successive transformation matrices. The expressions are greatly simplified if the oscillatory-field regions are very short. If there are only two oscillatory-field regions the situation is similar to a Young's two-slit interference pattern except that the two paths are separated in spin space rather than normal space. Some results from more than two oscillatory regions are discussed. The extensions of the methods and the theories to optical frequencies are described. The advantages and disadvantages of the methods are given as are the many extensions of the method beyond the original concept. [ABSTRACT FROM AUTHOR]

For people suffering from severe paralysis, communication can be difficult or nearly impossible. Technology systems called brain-computer interfaces (BCIs) are being developed to assist these people with communication by using their brain activity to control a computer without any muscle activity. To benefit the development of BCIs that employ neural activity related to speech, we investigated if neural activity patterns related to different articulator movements can be distinguished from each other. We recorded with electrocorticography (ECoG), the neural activity related to different articulator movements in 4 epilepsy patients and classified which articulator participants moved based on the sensorimotor cortex activity patterns. The same was done for different movement directions of a single articulator, the tongue. In both experiments highly accurate classification was obtained, on average 92% for different articulators and 85% for different tongue directions. Furthermore, the data show that only a small part of the sensorimotor cortex is needed for classification (ca. 1 cm2). We show that recordings from small parts of the sensorimotor cortex contain information about different articulator movements which might be used for BCI control. Our results are of interest for BCI systems that aim to decode neural activity related to (actual or attempted) movements from a contained cortical area. [ABSTRACT FROM AUTHOR]