Exploiting the PIR Sensor Analog Behavior as Thermoreceptor: Movement Direction Classification Based on Spiking Neurons.

Pyroelectric infrared sensors (PIR) are widely used as infrared (IR) detectors due to their basic implementation, low cost, low power, and performance. Combined with a Fresnel lens, they can be used as a binary detector in applications of presence and motion control. Furthermore, due to their features, they can be used in autonomous intelligent devices or included in robotics applications or sensor networks. In this work, two neural processing architectures are presented: (1) an analog processing approach to achieve the behavior of a presynaptic neuron from a PIR sensor. An analog circuit similar to the leaky integrate and fire model is implemented to be able to generate spiking rates proportional to the IR stimuli received at a PIR sensor. (2) An embedded postsynaptic neuron where a spiking neural network matrix together with an algorithm based on digital processing techniques is introduced. This structure allows connecting a set of sensors to the post-synaptic circuit emulating an optic nerve. As a case study, the entire neural processing approach presented in this paper is applied to optical flow detection considering a four-PIR array as input. The results validate both the spiking approach for an analog sensor presented and the ability to retrieve the analog information sent as spike trains in a simulated optic nerve.

Performance of parallel FDTD method for shared- and distributed-memory architectures: Application tobioelectromagnetics.

This work provides an in-depth computational performance study of the parallel finite-difference time-domain (FDTD) method. The parallelization is done at various levels including: shared- (OpenMP) and distributed- (MPI) memory paradigms and vectorization on three different architectures: Intel's Knights Landing, Skylake and ARM's Cavium ThunderX2. This study contributes to prove, in a systematic manner, the well-established claim within the Computational Electromagnetic community, that the main factor limiting FDTD performance, in realistic problems, is the memory bandwidth. Consequently a memory bandwidth threshold can be assessed depending on the problem size in order to attain optimal performance. Finally, the results of this study have been used to optimize the workload balancing of simulation of a bioelectromagnetic problem consisting in the exposure of a human model to a reverberation chamber-like environment.

Design of coils for lateralized TMS on mice.

OBJECTIVE: Translational studies on animals play a vital role in the advancement of transcranial magnetic stimulation (TMS) as clinical technique. Nonetheless the relevance of these procedures is frequently limited by the lack of TMS systems specifically designed for small animals capable of producing comparable stimulation conditions to those found in human TMS. In this work, we propose to take advantage of the versatility of recently introduced TMS coil design methods to produce optimal rodent-specific TMS stimulators. APPROACH: A stream function inverse boundary element method (IBEM) has been used for producing three small sized mice-specific TMS coils of different geometries. They have been created for unilateral hemispheric stimulation of the rodent brain, and several constraints have been considered in the design process to satisfy essential performance requirements, such as minimum stored magnetic energy, minimum power dissipation, optimised maximum current density or minimization of the undesired electric field induced in non-target regions. In order to validate the presented strategy, three prototype coils have been built. The performance of each prototype has also been numerically investigated, where the electric field induced in a mouse model has been found by using an existing computational forward technique. MAIN RESULTS: Stream function IBEM represents an ideally suited approach for designing specific TMS coils for small animals, capable of fulfilling many essential functional and technical requirements. The prototypes produced in this work focally stimulate the right hemisphere of the mouse brain, and so they can be successfully used in lateralized TMS experiments. SIGNIFICANCE: The design scheme proposed here can be used to produce efficient TMS stimulators for small animals, which can overcome some of the existing limitations found when producing more reliable translational experiments.

Design of TMS coils with reduced Lorentz forces: application to concurrent TMS-fMRI.

OBJECTIVE: Interleaving TMS (transcranial magnetic stimulation) with fMRI (functional Magnetic Resonance Imaging) is a promising technique to study functional connectivity in the human brain, but its development is being restricted by technical limitations, such as that due to the interaction of the TMS current pulses with the magnetic fields of an MRI scanner. In this work, a TMS coil design method capable of controlling Lorentz forces experienced by the coil in the presence of static magnetic fields is presented. APPROACH: The suggested approach is based on an existing inverse boundary element method (IBEM) for TMS coil design, in which new electromagnetic computational models of the Lorentz forces have been included to be controlled in the design process. MAIN RESULTS: To demonstrate the validity of this technique, it has been used for the design and simulation of TMS coils wound on rectangular flat, spherical and hemispherical surfaces with improved mechanical stability. The obtained results confirm that TMS coils with reduced Lorentz forces inside the static main field of an MRI scanner can be produced, which is achieved to the detriment of other coil performance parameters. SIGNIFICANCE: The proposed approach provides an efficient tool to design TMS stimulators of a wide range of coil geometries with improved mechanical stability, which can be extremely useful to overcome current limitations for interleaved TMS-fMRI.

Calculation of the electric field resulting from human body rotation in a magnetic field.

A number of recent studies have shown that the electric field and current density induced in the human body by movement in and around magnetic resonance imaging installations can exceed regulatory levels. Although it is possible to measure the induced electric fields at the surface of the body, it is usually more convenient to use numerical models to predict likely exposure under well-defined movement conditions. Whilst the accuracy of these models is not in doubt, this paper shows that modelling of particular rotational movements should be treated with care. In particular, we show that v × B rather than -(v · ∇)A should be used as the driving term in potential-based modelling of induced fields. Although for translational motion the two driving terms are equivalent, specific examples of rotational rigid-body motion are given where incorrect results are obtained when -(v · ∇)A is employed. In addition, we show that it is important to take into account the space charge which can be generated by rotations and we also consider particular cases where neglecting the space charge generates erroneous results. Along with analytic calculations based on simple models, boundary-element-based numerical calculations are used to illustrate these findings.