Measurement of axonal excitability: Consensus guidelines

Measurement of axonal excitability provides an in vivo indication of the properties of the nerve membrane and of the ion channels expressed on these axons. Axonal excitability techniques have been utilised to investigate the pathophysiological mechanisms underlying neurological diseases. This document presents guidelines derived for such studies, based on a consensus of international experts, and highlights the potential difficulties when interpreting abnormalities in diseased axons. The present manuscript provides a state-of-the-art review of the findings of axonal excitability studies and their interpretation, in addition to suggesting guidelines for the optimal performance of excitability studies.

The laryngoscope and nineteenth-century British understanding of laryngeal movements

The source of the human voice is obscured from view. The development of the laryngoscope in the late 1850s provided the potential to see the action of the vocal folds during speaking for the first time. This new instrument materially contributed to the understanding of vocal fold neuroanatomy, neurophysiology, and neuropathology. The laryngoscope led to elaborated understanding of disorders that previously were determined by changes in sound. The objective of this paper is to detail the consequences of this novel visualization of the larynx, and to trace how it aided in the development of understanding of the movements of the vocal folds. This is demonstrated through an examination of the activities and practices of a group of London clinicians in the second half of the nineteenth century.

Elastocapillary self-assembled neurotassels for stable neural activity recordings

Implantable neural probes that are mechanically compliant with brain tissue offer important opportunities for stable neural interfaces in both basic neuroscience and clinical applications. Here, we developed a Neurotassel consisting of an array of flexible and high-aspect ratio microelectrode filaments. A Neurotassel can spontaneously assemble into a thin and implantable fiber through elastocapillary interactions when withdrawn from a molten, tissue-dissolvable polymer. Chronically implanted Neurotassels elicited minimal neuronal cell loss in the brain and enabled stable activity recordings of the same population of neurons in mice learning to perform a task. Moreover, Neurotassels can be readily scaled up to 1024 microelectrode filaments, each with a neurite-scale cross-sectional footprint of 3 × 1.5 μm², to form implantable fibers with a total diameter of ~100 μm. With their ultrasmall sizes, high flexibility, and scalability, Neurotassels offer a new approach for stable neural activity recording and neuroprosthetics.

A Low-Power Current-Reuse Analog Front-End for High-Density Neural Recording Implants

Studying brain activity in vivo requires collecting bioelectrical signals from several microelectrodes simultaneously in order to capture neuron interactions. In this work, we present a new current-reuse analog front-end (AFE), which is scalable to very large numbers of recording channels, thanks to its small implementation silicon area and its low-power consumption. This current-reuse AFE, which is including a low-noise amplifier (LNA) and a programmable gain amplifier (PGA), employs a new fully differential current-mirror topology using fewer transistors, and improving several design parameters, such as power consumption and noise, over previous current-reuse amplifier circuit implementations. We show that the proposed current-reuse amplifier can provide a theoretical noise efficiency factor (NEF) as low as 1.01, which is the lowest reported theoretical NEF provided by an LNA topology. A foue-channel current-reuse AFE implemented in a CMOS 0.18-μm technology is presented as a proof-of-concept. T-network capacitive circuits are used to decrease the size of input capacitors and to increase the gain accuracy in the AFE. The measured performance of the whole AFE is presented. The total power consumption per channel, including the LNA and the PGA stage, is 9 μW (4.5 μW for LNA and 4.5 μW for PGA), for an input referred noise of 3.2 μV_rms, achieving a measured NEF of 1.94. The entire AFE presents three selectable gains of 35.04, 43.1, and 49.5 dB, and occupies a die area of 0.072 mm² per channel. The implemented circuit has a measured inter-channel rejection ratio of 54 dB. In vivo recording results obtained with the proposed AFE are reported. It successfully allows collecting low-amplitude extracellular action potential signals from a tungsten wire microelectrode implanted in the hippocampus of a laboratory mouse.

Ultrasensitive gold micro-structured electrodes enabling the detection of extra-cellular long-lasting potentials in astrocytes populations

Ultra-sensitive electrodes for extracellular recordings were fabricated and electrically characterized. A signal detection limit defined by a noise level of 0.3-0.4 μV for a bandwidth of 12.5 Hz was achieved. To obtain this high sensitivity, large area (4 mm2) electrodes were used. The electrode surface is also micro-structured with an array of gold mushroom-like shapes to further enhance the active area. In comparison with a flat gold surface, the micro-structured surface increases the capacitance of the electrode/electrolyte interface by 54%. The electrode low impedance and low noise enable the detection of weak and low frequency quasi-periodic signals produced by astrocytes populations that thus far had remained inaccessible using conventional extracellular electrodes. Signals with 5 μV in amplitude and lasting for 5-10 s were measured, with a peak-to-peak signal-to-noise ratio of 16. The electrodes and the methodology developed here can be used as an ultrasensitive electrophysiological tool to reveal the synchronization dynamics of ultra-slow ionic signalling between non-electrogenic cells.

Design of a Closed-Loop, Bidirectional Brain Machine Interface System With Energy Efficient Neural Feature Extraction and PID Control

This paper presents a bidirectional brain machine interface (BMI) microsystem designed for closed-loop neuroscience research, especially experiments in freely behaving animals. The system-on-chip (SoC) consists of 16-channel neural recording front-ends, neural feature extraction units, 16-channel programmable neural stimulator back-ends, in-channel programmable closed-loop controllers, global analog-digital converters (ADC), and peripheral circuits. The proposed neural feature extraction units includes 1) an ultra low-power neural energy extraction unit enabling a 64-step natural logarithmic domain frequency tuning, and 2) a current-mode action potential (AP) detection unit with time-amplitude window discriminator. A programmable proportional-integral-derivative (PID) controller has been integrated in each channel enabling a various of closed-loop operations. The implemented ADCs include a 10-bit voltage-mode successive approximation register (SAR) ADC for the digitization of the neural feature outputs and/or local field potential (LFP) outputs, and an 8-bit current-mode SAR ADC for the digitization of the action potential outputs. The multi-mode stimulator can be programmed to perform monopolar or bipolar, symmetrical or asymmetrical charge balanced stimulation with a maximum current of 4 mA in an arbitrary channel configuration. The chip has been fabricated in 0.18 μ m CMOS technology, occupying a silicon area of 3.7 mm ². The chip dissipates 56 μW/ch on average. General purpose low-power microcontroller with Bluetooth module are integrated in the system to provide wireless link and SoC configuration. Methods, circuit techniques and system topology proposed in this work can be used in a wide range of relevant neurophysiology research, especially closed-loop BMI experiments.

A Neural Probe With Up to 966 Electrodes and Up to 384 Configurable Channels in 0.13 $\mu$m SOI CMOS

In vivo recording of neural action-potential and local-field-potential signals requires the use of high-resolution penetrating probes. Several international initiatives to better understand the brain are driving technology efforts towards maximizing the number of recording sites while minimizing the neural probe dimensions. We designed and fabricated (0.13- μm SOI Al CMOS) a 384-channel configurable neural probe for large-scale in vivo recording of neural signals. Up to 966 selectable active electrodes were integrated along an implantable shank (70 μm wide, 10 mm long, 20  μm thick), achieving a crosstalk of [Formula: see text] dB. The probe base (5 × 9 mm ² ) implements dual-band recording and a 171.6 Mbps digital interface. Measurement results show a total input-referred noise of 6.4 μ V _rms and a total power consumption of 49.1  μW/channel.

Multiplexed neural recording along a single optical fiber via optical reflectometry

We introduce the design and theoretical analysis of a fiber-optic architecture for neural recording without contrast agents, which transduces neural electrical signals into a multiplexed optical readout. Our sensor design is inspired by electro-optic modulators, which modulate the refractive index of a waveguide by applying a voltage across an electro-optic core material. We estimate that this design would allow recording of the activities of individual neurons located at points along a 10-cm length of optical fiber with 40-μm axial resolution and sensitivity down to 100  μV using commercially available optical reflectometers as readout devices. Neural recording sites detect a potential difference against a reference and apply this potential to a capacitor. The waveguide serves as one of the plates of the capacitor, so charge accumulation across the capacitor results in an optical effect. A key concept of the design is that the sensitivity can be improved by increasing the capacitance. To maximize the capacitance, we utilize a microscopic layer of material with high relative permittivity. If suitable materials can be found—possessing high capacitance per unit area as well as favorable properties with respect to toxicity, optical attenuation, ohmic junctions, and surface capacitance—then such sensing fibers could, in principle, be scaled down to few-micron cross-sections for minimally invasive neural interfacing. We study these material requirements and propose potential material choices. Custom-designed multimaterial optical fibers, probed using a reflectometric readout, may, therefore, provide a powerful platform for neural sensing.

Preliminary methods for wearable neuro-vascular assessment with non-invasive, active sensing

In this study, a non-invasive and active sensing scheme that is ultimately aimed to be integrated in a wearable system for neuro-vascular health assessment is presented with preliminary results. With this system, vascular tone is modulated by local heating and cooling of the palm, and the resulting changes in local hemodynamics are monitored via impedance plethysmography (IPG) and photoplethysmography (PPG) sensors interfaced with custom analog electronics. Proof-of-concept measurements were conducted on three subjects using hot packs/ice bags to modulate the palmar skin temperature. From ensemble averaged and smoothed versions of pulsatile IPG and PPG signals, the effects of local changes in skin temperature on a series of parameters associated with neuro-vascular mechanisms (heart rate, blood volume, blood flow rate, blood volume pulse inflection point area ratio, and local pulse transit time) have been observed. The promising experimental results suggest that, with different active temperature modulation schemes (consisting of heating/cooling cycles covering different temperature ranges at different rates), it would be possible to enhance the depth and specificity of the information associated with neuro-vascular health by using biosensors that can fit inside a wearable device (such as a sleeve). This study sets the foundation for future studies on designing and testing such a wearable neuro-vascular health assessment system employing active sensing.

Braincubator: an incubation system to extend brain slice lifespan for use in neurophysiology

In vitro brain slice preparations are instrumental in developing our understanding of the nervous system. However, the current lifespan of an acute brain slice is limited to approximately 6-12 hours. This reduces potential experimentation time and leads to considerable waste of neural tissue. We have designed, developed and tested a novel incubation system capable of extending the lifespan of these brain slices. This is done by controlling the temperature and pH of the artificial cerebral spinal fluid in which the slices are incubated while continuously passing the fluid through a UVC filtration system. This system is capable of maintaining extremely low bacterial levels and significantly extending the brain slice lifespan to at least 24 hours. Brain slice viability was validated through electrophysiological recordings as well as live/dead cell assays.

Neuromechanical sensor fusion yields highest accuracies in predicting ambulation mode transitions for trans-tibial amputees

Advances in battery and actuator technology have enabled clinical use of powered lower limb prostheses such as the BiOM Powered Ankle. To allow ambulation over various types of terrains, such devices rely on built-in mechanical sensors or manual actuation by the amputee to transition into an operational mode that is suitable for a given terrain. It is unclear if mechanical sensors alone can accurately modulate operational modes while voluntary actuation prevents seamless, naturalistic gait. Ensuring that the prosthesis is ready to accommodate new terrain types at first step is critical for user safety. EMG signals from patient's residual leg muscles may provide additional information to accurately choose the proper mode of prosthesis operation. Using a pattern recognition classifier we compared the accuracy of predicting 8 different mode transitions based on (1) prosthesis mechanical sensor output (2) EMG recorded from residual limb and (3) fusion of EMG and mechanical sensor data. Our findings indicate that the neuromechanical sensor fusion significantly decreases errors in predicting 10 mode transitions as compared to using either mechanical sensors or EMG alone (2.3±0.7% vs. 7.8±0.9% and 20.2±2.0% respectively).

Multiple frequency audio signal communication as a mechanism for neurophysiology and video data synchronization

BACKGROUND

Current methods for aligning neurophysiology and video data are either prepackaged, requiring the additional purchase of a software suite, or use a blinking LED with a stationary pulse-width and frequency. These methods lack significant user interface for adaptation, are expensive, or risk a misalignment of the two data streams.

NEW METHOD

A cost-effective means to obtain high-precision alignment of behavioral and neurophysiological data is obtained by generating an audio-pulse embedded with two domains of information, a low-frequency binary-counting signal and a high, randomly changing frequency. This enabled the derivation of temporal information while maintaining enough entropy in the system for algorithmic alignment.

RESULTS

The sample to frame index constructed using the audio input correlation method described in this paper enables video and data acquisition to be aligned at a sub-frame level of precision.

COMPARISONS WITH EXISTING METHOD

Traditionally, a synchrony pulse is recorded on-screen via a flashing diode. The higher sampling rate of the audio input of the camcorder enables the timing of an event to be detected with greater precision.

CONCLUSIONS

While on-line analysis and synchronization using specialized equipment may be the ideal situation in some cases, the method presented in the current paper presents a viable, low cost alternative, and gives the flexibility to interface with custom off-line analysis tools. Moreover, the ease of constructing and implements this set-up presented in the current paper makes it applicable to a wide variety of applications that require video recording.

Nonlinear Signal-Specific ADC for Efficient Neural Recording in Brain-Machine Interfaces

A nonlinear ADC dedicated to the digitization of neural signals in implantable brain-machine interfaces is presented. Benefitting from an exponential quantization function, effective resolution of the proposed ADC in the digitization of action potentials is almost 2 bits more than its physical number of bits. Hence, it is shown in this paper that the choice of a proper nonlinear quantization function helps reduce the outgoing bit rate carrying the recorded neural data. Another major benefit of digitizing neural signals using the proposed signal-specific ADC is the considerable reduction in the background noise of the neural signal. The 8-b exponential ADC reported in this paper digitizes large action potentials with maximum resolution of 10.5 bits , while quantizing the small background noise is performed with a resolution of as low as 3 bits. Fully-integrated version of the circuit was designed and fabricated in a 0.18-μm CMOS process, occupying 0.036 mm(2) silicon area. Designed based on a two-step successive-approximation register ADC architecture, the proposed ADC employs a piecewise-linear approximation of the target exponential function for quantization. Operating at a sampling frequency of 25 kS/s (typical for intra-cortical neural recording) and with a supply voltage of 1.8 V, the entire chip, including the ADC and reference circuits, dissipates 87.2 μW. According to the experiments, Noise-Content-Reduction Ratio (NCRR) of the ADC is 41.1 dB.

A 515 nW, 0-18 dB Programmable Gain Analog-to-Digital Converter for In-Channel Neural Recording Interfaces

This paper presents a low-area low-power Switched-Capacitor (SC)-based Programmable-Gain Analog-to-Digital Converter (PG-ADC) suitable for in-channel neural recording applications. The PG-ADC uses a novel implementation of the binary search algorithm that is complemented with adaptive biasing techniques for power saving. It has been fabricated in a standard CMOS 130 nm technology and only occupies 0.0326 mm(2). The PG-ADC has been optimized to operate under two different sampling modes, 27 kS/s and 90 kS/s. The former is tailored for raw data conversion of neural activity, whereas the latter is used for the on-the-fly feature extraction of neural spikes. Experimental results show that, under a voltage supply of 1.2 V, the PG-ADC obtains an ENOB of 7.56 bit (8-bit output) for both sampling modes, regardless of the gain setting. The amplification gain can be programmed from 0 to 18 dB. The power consumption of the PG-ADC at 90 kS/s is 1.52 μW with a FoM of 89.49 fJ/conv, whereas at 27 kS/s it consumes 515 nW and obtains a FoM of 98.31 fJ/conv .

An open source 3-d printed modular micro-drive system for acute neurophysiology

Current, commercial, electrode micro-drives that allow independent positioning of multiple electrodes are expensive. Custom designed solutions developed by individual laboratories require fabrication by experienced machinists working in well equipped machine shops and are therefore difficult to disseminate into widespread use. Here, we present an easy to assemble modular micro-drive system for acute primate neurophysiology (PriED) that utilizes rapid prototyping (3-d printing) and readily available off the shelf-parts. The use of 3-d printed parts drastically reduces the cost of the device, making it available to labs without the resources of sophisticated machine shops. The direct transfer of designs from electronic files to physical parts also gives researchers opportunities to easily modify and implement custom solutions to specific recording needs. We also demonstrate a novel model of data sharing for the scientific community: a publicly available repository of drive designs. Researchers can download the drive part designs from the repository, print, assemble and then use the drives. Importantly, users can upload their modified designs with annotations making them easily available for others to use.

A dual slope charge sampling analog front-end for a wireless neural recording system

This paper presents a novel dual slope charge sampling (DSCS) analog front-end (AFE) architecture, which amplifies neural signals by taking advantage of the charge sampling concept for analog signal conditioning, such as amplification and filtering. The presented DSCS-AFE achieves amplification, filtering, and sampling in a simultaneous fashion, while consuming very small amount of power. The output of the DSCS-AFE produces a pulse width modulated (PWM) signal that is proportional to the input voltage amplitude. A circular shift register (CSR) utilizes time division multiplexing (TDM) of the PWM pulses to create a pseudo-digital TDM-PWM signal that can feed a wireless transmitter. The 8-channel system-on-a-chip was fabricated in a 0.35-μm CMOS process, occupying 2.4 × 2.1 mm(2) and consuming 255 μW from a 1.8V supply. Measured input-referred noise for the entire system, including the FPGA in order to recover PWM signal is 6.50 μV(rms) in the 288 Hz~10 kHz range. For each channel, sampling rate is 31.25 kHz, and power consumption is 31.8 μW.

Quantitative assessment of multiple sclerosis using inertial sensors and the TUG test

Multiple sclerosis (MS) is a progressive neurological disorder affecting between 2 and 2.5 million people globally. Tests of mobility form part of clinical assessments of MS. Quantitative assessment of mobility using inertial sensors has the potential to provide objective, longitudinal monitoring of disease progression in patients with MS. The mobility of 21 patients (aged 25-59 years, 8 M, 13 F), diagnosed with relapsing-remitting MS was assessed using the Timed up and Go (TUG) test, while patients wore shank-mounted inertial sensors. This exploratory, cross-sectional study aimed to examine the reliability of quantitative measures derived from inertial sensors during the TUG test, in patients with MS. Furthermore, we aimed to determine if disease status (as measured by the Multiple Sclerosis Impact Scale (MSIS-29) and the Expanded Disability Status Score (EDSS)) can be predicted by assessment using a TUG test and inertial sensors. Reliability analysis showed that 32 of 52 inertial sensors parameters obtained during the TUG showed excellent intrasession reliability, while 11 of 52 showed moderate reliability. Using the inertial sensors parameters, regression models of the EDSS and MSIS-29 scales were derived using the elastic net procedure. Using cross validation, an elastic net regularized regression model of MSIS yielded a mean square error (MSE) of 334.6 with 25 degrees of freedom (DoF). Similarly, an elastic net regularized regression model of EDSS yielded a cross-validated MSE of 1.5 with 6 DoF. Results suggest that inertial sensor parameters derived from MS patients while completing the TUG test are reliable and may have utility in assessing disease state as measured using EDSS and MSIS.

A switched-capacitor front-end for velocity-selective ENG recording

Multi-electrode cuffs (MECs) have been proposed as a means for extracting additional information about the velocity and direction of nerve signals from multi-electrode recordings. This paper discusses certain aspects of the implementation of a system for velocity selective recording (VSR) where multiple neural signals are matched and summed to identify excited axon populations in terms of velocity. The approach outlined in the paper involves the replacement of the digital signal processing stages of a standard delay-matched VSR system with analogue switched-capacitor (SC) delay lines which promises significant savings in both size and power consumption. The system specifications are derived and two circuits, each composed of low-noise preamplifiers connecting to a 2nd rank SC gain stage, are evaluated. One of the systems provides a single-ended SC stage whereas the other system is fully differential. Both approaches are shown to provide the low-noise, low-power operation, practically identical channel gains and sample delay range required for VSR. Measured results obtained from chips fabricated in 0.8 μ m CMOS technology are reported.

A low-power configurable neural recording system for epileptic seizure detection

This paper describes a low-power configurable neural recording system capable of capturing and digitizing both neural action-potential (AP) and fast-ripple (FR) signals. It demonstrates the functionality of epileptic seizure detection through FR recording. This system features a fixed-gain, variable-bandwidth (BW) front-end circuit and a sigma-delta ADC with scalable bandwidth and power consumption. The ADC employs a 2nd-order single-bit sigma-delta modulator (SDM) followed by a low-power decimation filter. Direct impulse-response implementation of a sinc(3) filter and 8-cycle data pipelining in an IIR filter are proposed for the decimation filter design to improve the power and area efficiency. In measurements, the front end exhibits 39.6-dB DC gain, 0.8 Hz to 5.2 kHz of BW, 5.86- μVrms input-referred noise, and 2.4- μW power consumption in AP mode, while showing 38.5-dB DC gain, 250 to 486 Hz of BW, 2.48- μVrms noise, and 4.5- μW power consumption in FR mode. The noise efficiency factor (NEF) is 2.93 and 7.6 for the AP and FR modes, respectively. At 77-dB dynamic range (DR), the ADC has a peak SNR and SNDR of 75.9 dB and 67 dB, respectively, while consuming 2.75-mW power in AP mode. It achieves 78-dB DR, 76.2-dB peak SNR, 73.2-dB peak SNDR, and 588- μW power consumption in FR mode. Both analog and digital power supply voltages are 2.8 V. The chip is fabricated in a standard 0.6- μm CMOS process. The die size is 11.25 mm(2).

The isometric pull task: a novel automated method for quantifying forelimb force generation in rats

Reach-to-grasp tasks are commonly used to assess forelimb function in rodent models. While these tasks have been useful for investigating several facets of forelimb function, they are typically labor-intensive and do not directly quantify physiological parameters. Here we describe the isometric pull task, a novel method to measure forelimb strength and function in rats. Animals were trained to reach outside the cage, grasp a handle attached to a stationary force transducer, and pull with a predetermined amount of force to receive a food reward. This task provides quantitative data on operant forelimb force generation. Multiple parameters can be measured with a high degree of accuracy, including force, success rate, pull attempts, and latency to maximal force. The task is fully automated, allowing a single experimenter to test multiple animals simultaneously with usually more than 300 trials per day, providing more statistical power than most other forelimb motor tasks. We demonstrate that an ischemic lesion in primary motor cortex yields robust deficits in all forelimb function parameters measured with this method. The isometric pull task is a significant advance in operant conditioning systems designed to automate the measurement of multiple facets of forelimb function and assess deficits in rodent models of brain damage and motor dysfunction.

A low-power programmable neural spike detection channel with embedded calibration and data compression

This paper reports a programmable 400 μm pitch neural spike recording channel, fabricated in a 130 nm standard CMOS technology, which implements amplification, filtering, digitization, analog spike detection plus feature extraction, and self-calibration functionalities. It can operate in two different output modes: 1) signal tracking, in which the neural signal is sampled and transmitted as raw data; and 2) feature extraction, in which the spikes of the neural signal are detected and encoded by piece-wise linear curves. Additionally, the channel offers a foreground calibration procedure in which the amplification gain and the passband of the embedded filter can be self-adjusted. The amplification stage obtains a noise efficiency factor of 2.16 and an input referred noise of 2.84 μVrms over a nominal bandwidth of 167 Hz-6.9 kHz. The channel includes a reconfigurable 8-bit analog-to-digital converter combined with a 3-bit controlled programmable gain amplifier for adjusting the input signal to the full scale range of the converter. This combined block achieves an overall energy consumption per conversion of 102 fJ at 90 kS/s. The energy consumed by the circuit elements which are strictly related to the digitization process is 14.12 fJ at the same conversion rate. The complete channel consumes 2.8 μW at 1.2 V voltage supply when operated in the signal tracking mode, and 3.1 μW when the feature extraction mode is enabled.

A multichannel integrated circuit for electrical recording of neural activity, with independent channel programmability

Since a few decades, micro-fabricated neural probes are being used, together with microelectronic interfaces, to get more insight in the activity of neuronal networks. The need for higher temporal and spatial recording resolutions imposes new challenges on the design of integrated neural interfaces with respect to power consumption, data handling and versatility. In this paper, we present an integrated acquisition system for in vitro and in vivo recording of neural activity. The ASIC consists of 16 low-noise, fully-differential input channels with independent programmability of its amplification (from 100 to 6000 V/V) and filtering (1-6000 Hz range) capabilities. Each channel is AC-coupled and implements a fourth-order band-pass filter in order to steeply attenuate out-of-band noise and DC input offsets. The system achieves an input-referred noise density of 37 nV/√Hz, a NEF of 5.1, a CMRR > 60 dB, a THD < 1% and a sampling rate of 30 kS/s per channel, while consuming a maximum of 70 μA per channel from a single 3.3 V. The ASIC was implemented in a 0.35 μm CMOS technology and has a total area of 5.6 × 4.5 mm². The recording system was successfully validated in in vitro and in vivo experiments, achieving simultaneous multichannel recordings of cell activity with satisfactory signal-to-noise ratios.

Animal experiments with the microelectronics neural bridge IC

The combination of the neural science and the microelectronics science offers a new way to restore the function of central nervous system. A neural regeneration module is used to be implanted into body to bridge the damaged nerve. A microelectronics neural bridge IC designed in CSMC 0.5□m CMOS process which can detect the neural signal and stimulate the nerve is presented. The neural regeneration module is composed of the microelectronics neural bridge IC and some discrete devices. An animal experiment has been done to check whether the neural signal can be transmitted with the chip normally or not. The animal experiment results suggest that the neural regeneration module can make the neural signal transmit normally.

Identification of directed interactions in networks

Multichannel data collection in the neurosciences is routine and has necessitated the development of methods to identify the direction of interactions among processes. The most widely used approach for detecting these interactions in such data is based on autoregressive models of stochastic processes, although some work has raised the possibility of serious difficulties with this approach. This article demonstrates that these difficulties are present and that they are intrinsic features of the autoregressive method. Here, we introduce a new method taking into account unobserved processes and based on coherence. Two examples of three-process networks are used to demonstrate that although coherence measures are intrinsically non-directional, a particular network configuration will be associated with a particular set of coherences. These coherences may not specify the network uniquely, but in principle will specify all network configurations consistent with their values and will also specify the relationships among the unobserved processes. Moreover, when new information becomes available, the values of the measures of association already in place do not change, but the relationships among the unobserved processes may become further resolved.

Autonomous head-mounted electrophysiology systems for freely behaving primates

Recent technological advances have led to new light-weight battery-operated systems for electrophysiology. Such systems are head mounted, run for days without experimenter intervention, and can record and stimulate from single or multiple electrodes implanted in a freely behaving primate. Here we discuss existing systems, studies that use them, and how they can augment traditional, physically restrained, 'in-rig' electrophysiology. With existing technical capabilities, these systems can acquire multiple signal classes, such as spikes, local field potential, and electromyography signals, and can stimulate based on real-time processing of recorded signals. Moving forward, this class of technologies, along with advances in neural signal processing and behavioral monitoring, have the potential to dramatically expand the scope and scale of electrophysiological studies.

A microfluidic brain slice perfusion chamber for multisite recording using penetrating electrodes

To analyze the spatiotemporal dynamics of network activity in a brain tissue slice, it is useful to record simultaneously from multiple locations. When obtained from laminar structures such as the hippocampus or neocortex, multisite recordings also yield information about subcellular current distributions via current source density analysis. Multisite probes developed for in vivo recordings could serve these purposes in vitro, allowing recordings to be obtained from brain slices at sites deeper within the tissue than currently available surface recording methods permit. However, existing recording chambers do not allow for the insertion of lamina-spanning probes that enter through the edges of brain slices. Here, we present a novel brain slice recording chamber design that accomplishes this goal. The device provides a stable microfluidic perfusion environment in which tissue health is optimized by superfusing both surfaces of the slice. Multichannel electrodes can be inserted parallel to the surface of the slice, at any depth relative to the surface. Access is also provided from above for the insertion of additional recording or stimulating electrodes. We illustrate the utility of this recording configuration by measuring current sources and sinks during theta burst stimuli that lead to the induction of long-term potentiation in hippocampal slices.

Chronic detachable headphones for acoustic stimulation in freely moving animals

A growing number of studies of auditory processing are being carried out in awake, behaving animals, creating a need for precisely controlled sound delivery without restricting head movements. We have designed a system for closed-field stimulus presentation in freely moving ferrets, which comprises lightweight, adjustable headphones that can be consistently positioned over the ears via a small, skull-mounted implant. The invasiveness of the implant was minimized by simplifying its construction and using dental adhesive only for attaching it to the skull, thereby reducing the surgery required and avoiding the use of screws or other anchoring devices. Attaching the headphones to a chronic implant also reduced the amount of contact they had with the head and ears, increasing the willingness of the animals to wear them. We validated sound stimulation via the headphones in ferrets trained previously in a free-field task to localize stimuli presented from one of two loudspeakers. Noise bursts were delivered binaurally over the headphones and interaural level differences (ILDs) were introduced to allow the sound to be lateralized. Animals rapidly transferred from the free-field task to indicate the perceived location of the stimulus presented over headphones. They showed near perfect lateralization with a 5 dB ILD, matching the scores achieved in the free-field task. As expected, the ferrets' performance declined when the ILD was reduced in value. This closed-field system can easily be adapted for use in other species, and provides a reliable means of presenting closed-field stimuli whilst monitoring behavioral responses in freely moving animals.

Low-cost, high-fidelity, adaptive cancellation of periodic 60 Hz noise

A common method to eliminate unwanted power line interference in neurobiology laboratories where sensitive electronic signals are measured is with a notch filter. However a fixed-frequency notch filter cannot remove all power line noise contamination since inherent frequency and phase variations exist in the contaminating signal. One way to overcome the limitations of a fixed-frequency notch filter is with adaptive noise cancellation. Adaptive noise cancellation is an active approach that uses feedback to create a signal that when summed with the contaminated signal destructively interferes with the noise component leaving only the desired signal. We have implemented an optimized least mean square adaptive noise cancellation algorithm on a low-cost 16 MHz, 8-bit microcontroller to adaptively cancel periodic 60 Hz noise. In our implementation, we achieve between 20 and 25 dB of cancellation of the fundamental 60 Hz noise component.

Biomechanical approaches applied to the lower and upper limb for the measurement of spasticity: A systematic review of the literature

PURPOSE

To review and characterise biomechanical approaches for the measurement of spasticity as one component of the upper motor neurone syndrome.

METHOD

Systematic literature searches based on defined constructs and a four-step review process of approaches used or described to measure spasticity, its association with function or associated phenomena. Most approaches were limited to individual joints and therefore, to reflect this trend, references were grouped according to which body joint(s) were investigated or whether it addressed a functional activity. For each joint, references were further sub-divided into the types of measurement method described.

RESULTS

A database of 335 references was established for the review process. The knee, ankle and elbow joints were the most popular, perhaps reflecting the assumption that they are mono-planar in movement and therefore simpler to assess. Seven measurement methods were identified: five involving passive movement (manual, controlled displacement, controlled torque, gravitational and tendon tap) and two involving active movement (voluntary and functional). Generally, the equipment described was in an experimental stage and there was a lack of information on system properties, such as accuracy or reliability. Patient testing was either by cohort or case studies. The review also conveyed the myriad of interpretations of the concept of spasticity.

CONCLUSIONS

Though biomechanical approaches provide quantitative data, the review highlighted several limitations that have prevented them being established as an appropriate method for clinical application to measure spasticity.

A method for recording resistance changes non-invasively during neuronal depolarization with a view to imaging brain activity with electrical impedance tomography

Electrical impedance tomography (EIT) is a recently developed medical imaging method which has the potential to produce images of fast neuronal depolarization in the brain. The principle is that current remains in the extracellular space at rest but passes into the intracellular space during depolarization through open ion channels. As current passes into the intracellular space across the capacitance of cell membranes at higher frequencies, applied current needs to be below 100 Hz. A method is presented for its measurement with subtraction of the contemporaneous evoked potentials which occur in the same frequency band. Neuronal activity is evoked by stimulation and resistance is recorded from the potentials resulting from injection of a constant current square wave at 1 Hz with amplitude less than 25% of the threshold for stimulating neuronal activity. Potentials due to the evoked activity and the injected square wave are removed by subtraction. The method was validated with compound action potentials in crab walking leg nerve. Resistance changes of -0.85+/-0.4% (mean+/-SD) occurred which decreased from -0.97+/-0.43% to -0.46+/-0.16% with spacing of impedance current application electrodes from 2 to 8 mm but did not vary significantly with applied currents of 1-10 microA. These tallied with biophysical modelling, and so were consistent with a genuine physiological origin. This method appears to provide a reproducible and artefact free means for recording resistance changes during neuronal activity which could lead to the long-term goal of imaging of fast neural activity in the brain.

A novel device to measure power grip forces in squirrel monkeys

Understanding the neural bases for grip force behaviors in both normal and neurologically impaired animals is imperative prior to improving treatments and therapeutic approaches. The present paper describes a novel device for the assessment of power grip forces in squirrel monkeys. The control of grasping and object manipulation represents a vital aspect of daily living by allowing the performance of a wide variety of complex hand movements. However, following neurological injury such as stroke, these grasping behaviors are often severely affected, resulting in persistent impairments in strength, grip force modulation and kinematic hand control. While there is a significant clinical focus on rehabilitative strategies to address these issues, there exists the need for translational animal models. In the study presented here, we describe a simple grip force device designed for use in non-human primates, which provides detailed quantitative information regarding distal grip force dynamics. Adult squirrel monkeys were trained to exceed a specific grip force threshold, which was rewarded with a food pellet. One of these subjects then received an infarct of the M1 hand representation area. Results suggest that the device provides detailed and reliable information on grip behaviors in healthy monkeys and can detect deficits in grip dynamics in monkeys with cortical lesions (significantly longer release times). Understanding the physiological and neuroanatomical aspects of grasping function following neurological injury may lead to more effective rehabilitative interventions.

Bump time-frequency toolbox: a toolbox for time-frequency oscillatory bursts extraction in electrophysiological signals

BACKGROUND

oscillatory activity, which can be separated in background and oscillatory burst pattern activities, is supposed to be representative of local synchronies of neural assemblies. Oscillatory burst events should consequently play a specific functional role, distinct from background EEG activity - especially for cognitive tasks (e.g. working memory tasks), binding mechanisms and perceptual dynamics (e.g. visual binding), or in clinical contexts (e.g. effects of brain disorders). However extracting oscillatory events in single trials, with a reliable and consistent method, is not a simple task.

RESULTS

in this work we propose a user-friendly stand-alone toolbox, which models in a reasonable time a bump time-frequency model from the wavelet representations of a set of signals. The software is provided with a Matlab toolbox which can compute wavelet representations before calling automatically the stand-alone application.

CONCLUSION

The tool is publicly available as a freeware at the address: http://www.bsp.brain.riken.jp/bumptoolbox/toolbox_home.html.

Implantable microelectrode arrays for simultaneous electrophysiological and neurochemical recordings

Implantable microfabricated microelectrode arrays represent a versatile and powerful tool to record electrophysiological activity across multiple spatial locations in the brain. Spikes and field potentials, however, correspond to only a fraction of the physiological information available at the neural interface. In urethane-anesthetized rats, microfabricated microelectrode arrays were implanted acutely for simultaneous recording of striatal local field potentials, spikes, and electrically evoked dopamine overflow on the same spatiotemporal scale. During these multi-modal recordings we observed (1) that the amperometric method used to detect dopamine did not significantly influence electrophysiological activity, (2) that electrical stimulation in the medial forebrain bundle (MFB) region resulted in electrochemically transduced dopamine transients in the striatum that were spatially heterogeneous within at least 200 microm, and (3) following MFB stimulation, dopamine levels and electrophysiological activity within the striatum exhibited similar temporal profiles. These neural probes are capable of incorporating customized microelectrode geometries and configurations, which may be useful for examining specific spatiotemporal relationships between electrical and chemical signaling in the brain.

[Detection of episodes of ischemic tissue hypoxia by means of the combined intraoperative neurophysiologic monitoring with the tissue oxygenation monitoring in aneurysm surgery]

INTRODUCTION

Intraoperative neuromonitoring in aneurysm surgery can be very useful to determine inadequate positions of the vascular clip that cause partial or complete compromise of the cerebral sanguineous flow in the vascular territories irrigated by the arteries related to aneurysm. The direct visualization of these arteries after the application of the surgical clip can be insufficient in detecting this potentially detrimental situation. Knowing this circumstance on the onset would allow the neurosurgeon to correct it and to avoid, therefore, cerebral ischemic tissue hypoxia. We show the utility of the intraoperative monitoring of the oxygen tissue pressure (PtiO2) and the somatosensorial evoked potential (SSEP) for the detection of these situations with the example of a clinical case.

CLINICAL CASE

We present the case of a 62 year-old woman, that presented with subarachnoid hemorrhage of aneurysmal origin. The cerebral arteriography demonstrated the existence of an aneurysm of the posterior communicating artery that was treated initially by endovascular procedure with partial exclusion of the aneurysm. For this reason it was decided to complete the treatment with a programmed surgery. The patient was put on an intraoperative monitoring system with a PtiO2 sensor located in the risk area and with SSEP. After positioning the surgical clip the partial oxygen pressure decreased rapidly, as well as the amplitude of the cortical potential of the left posterior tibial nerve. The knowledge of this situation allowed the detection of a trapped posterior communicating artery. After correcting this situation by replacing the surgical clip, both variables recovered to their basal values.

CONCLUSIONS

The intraoperative PtiO2 monitoring, combined with neurophysiologic monitoring during aneurysm surgery offers a fast and trustworthy form of early detection of ischemic phenomena caused by bad positioning of the surgical clip.

Applying Double Magnetic Induction to Measure Two-Dimensional Head-Unrestrained Gaze Shifts in Human Subjects

This study compares the performance of a newly developed gaze (eye-in-space) measurement technique based on double magnetic induction (DMI) by a custom-made gold-plated copper ring on the eye with the classical scleral search coil (SSC) technique to record two-dimensional (2D) head-unrestrained gaze shifts. We tested both systems simultaneously during head-free saccades toward light-emitting diodes (LEDs) within the entire oculomotor range (±35 deg). The absence of irritating lead wires in the case of the DMI method leads to a higher guarantee of success (no coil breakage) and to less irritation on the subject's eye, which results in a longer and more comfortable measurement time. Correlations between DMI and SSC signals for horizontal and vertical eye position, velocity, and acceleration were close to 1.0. The difference between the SSC signal and the DMI signal remains within a few degrees. In our current setup the resolution was about 0.3 deg for the DMI method versus 0.2 deg for the SSC technique. The DMI method is an especially good alternative in the case of patient and laboratory animal gaze control studies where breakage of the SSC lead wires is particularly cumbersome.

Todd, Faraday and the electrical basis of brain activity

The origins of our understanding of brain electricity and electrical discharges in epilepsy can be traced to Robert Bentley Todd (1809-60). Todd was influenced by his contemporary in London, Michael Faraday (1791-1867), who in the 1830 s and 1840 s was laying the foundations of our modern understanding of electromagnetism. Todd's concept of nervous polarity, generated in nerve vesicles and transmitted in nerve fibres (neurons in later terminology), was confirmed a century later by the Nobel Prize-winning work of Hodgkin and Huxley, who demonstrated the ionic basis of neuro-transmission, involving the same ions which had had been discovered by Faraday's mentor, Sir Humphry Davy (1778-1829).

A method of extracellular recording of neuronal activity in swimming mice

The design of a removable miniature microdrive-headstage waterproof assembly for extracellular recordings of single unit activity with high-impedance electrodes in swimming mice is presented. The assembly provides perfect protection of the critical components and electric contacts from water. Neuronal activity may be recorded even if the animal is diving and swimming under the water surface. The advantages of this construction include simple installation and removal of the electrodes, rapid attachment of the assembly to the animal's skull, and rapid removal after recording. The device provides precise vertical positioning of the electrode without rotation or lateral shift, stable recordings of single units for several hours and the possibility to change the penetration track many times in the same animal. The assembly weight is less than 160mg. This work is the first successful attempt to record neuronal activity in mice performing spatial task in water maze.

A lamprey striatal brain slice preparation for patch-clamp recordings

Striatum, the input layer of the basal ganglia is important for functions such as the selection of motor behaviour. The lamprey, a lower vertebrate, is particularly well suited as a model system for the control of motor functions as its central nervous system is similar to that of higher vertebrates and exhibits a lower level of complexity. Therefore, studies in lamprey preparations enable cellular and synaptic mechanisms to be correlated with behaviour. The lamprey brain slice preparation presented has been developed to study the striatal microcircuits and input/output systems with patch-clamp recordings. The method involves dissection of the central nervous system, brain slice preparation, identification of the striatum, visual identification of striatal neurons and patch-clamp recordings. By combining studies in the slice preparation presented here and other lamprey preparations such as the semi-intact lamprey, we will be able to correlate striatal mechanisms on the cellular, synaptic and network levels with striatal output and motor behaviour. The method can be adapted to produce similar slice preparations from other areas of the lamprey brain.

Weighted least squares fitting with multiple templates for detection of small spontaneous signals

Cultured neurons have been used for investigating synaptic plasticity due to their accessibility to biochemical and immunochemical assays. In addition, recording spontaneous postsynaptic miniature events provides important information about the mechanisms involved in the modulation of synaptic transmission. To automatically detect the spontaneous events, we developed a technique in which a weighted least squares algorithm was used instead of an ordinary one. In addition, multiple templates were used simultaneously to scan the data to increase the accuracy of the fit between the data and templates. An important outcome of the weighted template technique is that the detection rate is not as sensitive to the length of templates and this technique is capable of detection overlapping events reliably.

A CMOS-based microelectrode array for interaction with neuronal cultures

We report on the system integration of a CMOS chip that is capable of bidirectionally communicating (stimulation and recording) with electrogenic cells such as neurons or cardiomyocytes and that is targeted at investigating electrical signal propagation within cellular networks in vitro. The overall system consists of three major subunits: first, the core component is a 6.5 mm x 6.5 mm CMOS chip, on top of which the cells are cultured. It features 128 bidirectional electrodes, each equipped with dedicated analog filters and amplification stages and a stimulation buffer. The electrodes are sampled at 20 kHz with 8-bit resolution. The measured input-referred circuitry noise is 5.9 microV root mean square (10 Hz to 100 kHz), which allows to reliably detect the cell signals ranging from 1 mVpp down to 40 microVpp. Additionally, temperature sensors, a digital-to-analog converter for stimulation, and a digital interface for data transmission are integrated. Second, there is a reconfigurable logic device, which provides chip control, event detection, data buffering and an USB interface, capable of processing the 2.56 million samples per second. The third element includes software that is running on a standard PC performing data capturing, processing, and visualization. Experiments involving the stimulation of neurons with two different spatio-temporal patterns and the recording of the triggered spiking activity have been carried out. The response patterns have been successfully classified (83% correct) with respect to the different stimulation patterns. The advantages over current microelectrode arrays, as has been demonstrated in the experiments, include the capability to stimulate (voltage stimulation, 8 bit, 60 kHz) spatio-temporal patterns on arbitrary sets of electrodes and the fast stimulation reset mechanism that allows to record neuronal signals on a stimulating electrode 5 ms after stimulation (instantaneously on all other electrodes). Other advantages of the overall system include the small number of needed electrical connections due to the digital interface and the short latency time that allows to initiate a stimulation less than 2 ms after the detection of an action potential in closed-loop configurations.

EEG mu rhythm and imitation impairments in individuals with autism spectrum disorder

Imitation ability has consistently been shown to be impaired in individuals with autism. A dysfunctional execution/observation matching system has been proposed to account for this impairment. The EEG mu rhythm is believed to reflect an underlying execution/observation matching system. This study investigated evidence of differential mu rhythm attenuation during the observation, execution, and imitation of movements and examined its relation to behaviorally assessed imitation abilities. Fourteen high-functioning adults with autism spectrum disorder (ASD) and 15 IQ- and age-matched typical adults participated. On the behavioral imitation task, adults with ASD demonstrated significantly poorer performance compared to typical adults in all domains of imitation ability. On the EEG task, both groups demonstrated significant attenuation of the mu rhythm when executing an action. However, when observing movement, the individuals with ASD showed significantly reduced attenuation of the mu wave. Behaviorally assessed imitation skills were correlated with degree of mu wave attenuation during observation of movement. These findings suggest that there is execution/observation matching system dysfunction in individuals with autism and that this matching system is related to degree of impairment in imitation abilities.

Test-retest reliability of knee kinesthesia in healthy adults

Background

Sensory information from mechanoreceptors in the skin, muscles, tendons, and joint structures plays an important role in joint stability. A joint injury can lead to disruption of the sensory system, which can be measured by proprioceptive acuity. When evaluating proprioception, assessment tools need to be reliable. The aim of this study was to assess the test-retest reliability of a device designed to measure knee proprioception.

Methods

Twenty-four uninjured individuals (14 women and 10 men) were examined with regard to test-retest reliability of knee kinesthesia, measured by the threshold to detection of passive motion (TDPM). Measurements were performed towards extension and flexion from the two starting positions, 20 degrees and 40 degrees knee joint flexion, giving four variables. The mean difference between test and retest together with the 95% confidence interval (test 2 minus test 1), the intraclass correlation coefficient (ICC_2,1), and Bland and Altman graphs with limits of agreement, were used as statistical methods for assessing test-retest reliability.

Results

The intraclass correlation coefficients ranged from 0.59 to 0.70 in all variables except one. No difference was found between test and retest in three of the four TDPM variables. TDPM would need to decrease between 10% and 38%, and increase between 17% and 24% in groups of uninjured subjects to be 95% confident of detecting a real change. The limits of agreement were rather wide in all variables. The variables associated with the 20-degree starting position tended to have higher intraclass correlation coefficients and narrower limits of agreement than those associated with 40 degrees.

Conclusion

Three TDPM variables were considered reliable for observing change in groups of subjects without pathology. However, the limits of agreement revealed that small changes in an individual's performance cannot be detected. The higher intraclass correlation coefficients and the narrower limits of agreement in the variables associated with the starting position of 20 degrees knee joint flexion, indicate that these variables are more reliable than those associated with 40 degrees. We, therefore, recommend that the TDPM be measured with a 20-degree starting position.

J.-M. Charcot and simulated neurologic disease: Attitudes and diagnostic strategies

BACKGROUND

Neurologists have long wrestled with the diagnosis of elaborated or feigned disease. Studies have not focused on early techniques utilized to diagnose malingering.

OBJECTIVE

To analyze cases of purposeful neurologic malingering among patients treated by the 19th century neurologist J.-M. Charcot, describe his attitudes, and study his methods to separate malingering from primary neurologic diseases.

METHODS

A study was conducted of Charcot's printed and original documents from the Bibliothèque Charcot, Paris, and added documents on American neurology.

RESULTS

Charcot recognized that purposeful simulation occurred in isolation as well as in established neurologic disorders. Charcot was strict with subjects motivated by greed or spite, but showed forbearance and wonder in those who created illness as "art for art's sake." Charcot developed diagnostic equipment that measured inspiratory depth and muscle activity as a strategy to identify malingerers. His approach strikingly contrasted with contemporary military medical treatises on malingering and S.W. Mitchell's civilian neurologic approaches that unmasked patients through more aggressive strategies.

CONCLUSION

Charcot provided an academically professional approach to the assessment of neurologic malingering, with a stern, often patronizing attitude, but without categorical condemnation. His diagnostic techniques are echoed by contemporary approaches and emphasized an attention to enhanced and inconsistent patterns of behaviors by malingerers.

A new method for wide frequency range dynamic olfactory stimulation and characterization

Sensory receptors often receive strongly dynamic, or time varying, inputs in their natural environments. Characterizing their dynamic properties requires control and measurement of the stimulus over a frequency range that equals or exceeds the receptor response. Techniques for dynamic stimulation of olfactory receptors have lagged behind other major sensory modalities because of difficulties in controlling and measuring the concentration of odorants at the receptor. We present a new method for delivering olfactory stimulation that gives linear, low-noise, wide frequency range control of odorant concentration. A servo-controlled moving bead of silicone elastomer occludes the tip of a Pasteur pipette that releases odorant plus tracer gas into a flow tube. Tracer gas serves as a surrogate indicator of odorant concentration and is measured by a photoionization detector. The system has well-defined time-dependent behavior (frequency response and impulse response functions) and gives predictable control of odorant over a significant volume surrounding the animal. The frequency range of the system is about 0-100 Hz. System characterization was based on random (white noise) stimulation, which allows more rapid and accurate estimation of dynamic behavior than deterministic signals such as sinusoids or step functions. Frequency response functions of Drosophila electroantennograms stimulated by fruit odors were used to demonstrate a typical application of the system.

A comparative study of the effects of repetitive paired transcranial magnetic stimulation on motor cortical excitability

OBJECTIVES

Various methods of application of repetitive transcranial magnetic stimulation (TMS) have been evaluated for their potential capacity to alter motor cortical excitability. Initial research suggests that the repetitive application of paired TMS pulses (repetitive paired pulse TMS (rppTMS)) may have greater effects on cortical excitability, perhaps through the facilitation of I-wave interaction. We aimed to compare the post-train effects of 15 min trains of rppTMS to investigate the potential therapeutic application of this technique as well as to compare it to a standard high frequency repetitive TMS paradigm.

METHODS

Ten normal subjects received three 15 min sessions of rppTMS, 5 Hz high frequency rTMS and sham TMS in randomised order. rppTMS consisted of a single train of 180 pulse pairs (0.2 Hz, 1.5 ms inter-stimulus interval, supra-threshold intensity) administered over 15 min. The rTMS condition involved 750 pulses provided in 5s 5 Hz trains with a 25s inter-train interval at 90% of the RMT. Motor evoked potential size and cortical silent period duration were assessed before and after each session.

RESULTS

There were no significant changes in cortical excitability produced by any of the stimulation conditions. Five hertz rTMS produced an increase in cortical silent period duration (p=0.004) which was not affected by rppTMS.

CONCLUSIONS

Fifteen minutes trains of 1.5ms rppTMS do not substantially increase post train cortical excitability. Repetitive brief trains of 5Hz rTMS also do not alter excitability but appear to effect cortical inhibition.

[Knee joint proprioception evaluation with own construction device]

Proprioception is a term covering together joint position sense, kinesthesia and integration of these stimuli in the central nervous system which is needed to keep homeosthasis of joints during motion. The aim of this study is to present authors originally created measuring device working according to the principles of Barrett, aiming at evaluation of proprioception of the knee. The construction of this device is based on the Summer chair, model UPR-01B, working in connection with Bosh goniometer DWM-40L measuring angles with a precision of 0,1 degree. The device presented in this study fulfills all criteria required for this kind of apparatus and may be an alternative to other constructs produced commercially and available on the market.

Three-dimensional reconstruction of stained histological slices and 3D non-linear registration with in-vivo MRI for whole baboon brain

The correlation between post-mortem data and in-vivo brain images is of high interest for studying neurodegenerative diseases. This paper describes a protocol that matches a series of stained histological slices of a baboon brain with an anatomical MRI scan of the same subject using an intermediate 3D-consistent volume of "blockface" photographs taken during the sectioning process. Each stained histological section of the baboon brain was first registered to its corresponding blockface photograph using a novel "hemi-rigid" transformation. This piecewise rigid 2D transformation was specifically adapted to the registration of slices which contained both hemispheres. Subsenquently, to correct the global 3D deformations of the brain caused by histological preparation and fixation, a 3D elastic transformation was estimated between the blockface volume and the MRI data. This 3D elastic transformation was then applied to the histological volume previously aligned using the hemi-rigid method to complete the registration of the series of stained histological slices with the MRI data. We assessed the efficacy of our method by evaluating the quality of matching of anatomical features as well as the difference of volume measurements between the MRI and the histological images. Two complete baboon brains (with the exception of cerebellum) were successfully processed using our protocol.

The CatWalk gait analysis in assessment of both dynamic and static gait changes after adult rat sciatic nerve resection

Functional repair of neurotmesis has been proven most challenging in regenerative medicine. Progress in this field has shown that functional repair not only requires axon regeneration, but also selectivity in target reinnervation. Although selectivity in target reinnervation still involves relatively unexplored avenues, evidence-based medicine, in the end, requires behavioral proof of repair. Therefore, there is a need for tests assessing behavioral deficits after neurotmesis. To date, behavioral tests for detecting both dynamic and static parameters are limited. The CatWalk gait analysis has been shown to detect a multitude of speed-controlled dynamic and static gait deficits after experimental spinal cord injury. Therefore, we here evaluated its use in detecting both dynamic and static gait deficits after neurotmesis. After rat sciatic nerve resection CatWalk testing was performed for 8 weeks. A large amount of dynamic and static gait parameters were detected to be immediately and severely affected in the ipsilateral paw, sometimes reaching levels of only 15% of those of the unaffected paw. We conclude that the CatWalk objectively detects dynamic and static gait impairments after sciatic nerve resection and future experiments are now required to prove which of these parameters are of particular interest to detect functional repair.

Neurosonography in the second half of fetal life: a neonatologist's point of view

This article reviews the interpretation of the fetal motor repertoire in the light of neurophysiology and clinical neurology. The continuity of the maturative process from the fetus to the neonate allows us to speculate on the predictive value of optimal and non-optimal neurological function as observed in the fetus and their morphological consequences. Neonatologists know that early prediction concerning outcome is reliable only at the two ends of the spectrum, e.g., optimal and very abnormal situations. However, in intermediate situations the quality of observations achieved by 3D-4D ultrasonography already allows to demonstrate the prenatal onset of brain damage, based on morphologic and functional signs. Their identification during the second half of pregnancy may serve as a retrospective marker of a prenatal insult.