Electrotactile and vibrotactile displays for sensory substitutionsystems

Sensory substitution systems provide their users with environmental information through a human sensory channel (eye, ear, or skin) different from that normally used, or with the information processed in some useful way. We review the methods used to present visual, auditory, and modified tactile information to the skin. First, we discuss present and potential future applications of sensory substitution, including tactile vision substitution (TVS), tactile auditory substitution, and remote tactile sensing or feedback (teletouch). Next, we review the relevant sensory physiology of the skin, including both the mechanisms of normal touch and the mechanisms and sensations associated with electrical stimulation of the skin using surface electrodes (electrotactile (also called electrocutaneous) stimulation). We briefly summarize the information-processing ability of the tactile sense and its relevance to sensory substitution. Finally, we discuss the limitations of current tactile display technologies and suggest areas requiring further research for sensory substitution systems to become more practical.     

In Vivo Electrical Stimulation Using Multichannel Photolithographic Electrode Atrays

Multichannel electrical stimulation of the auditory nerve is demonstrated in a cat model using photolithographic electrode arrays. Evoked potentials from the auditory cortex are used to map the location of fibers activated by different electrodes in the array. The evoked responses obtained are equivalent to those produced by fine wire electrodes currently used for functional stimulation of the auditory system.     

Neuromagnetic localization using magnetic resonance images

Ionic flow associated with neural activation of the brain produces a magnetic field, called the neuromagnetic field, that can be measured outside the head using a highly sensitive superconducting quantum interference device (SQUID)-based neuromagnetometer. Under certain conditions, the sources producing the neuromagnetic field can be localized from a sampling of the neuromagnetic field. Neuromagnetic measurements alone, however, do not contain sufficient information to visualize brain structure. Thus, it is necessary to combine neuromagnetic localization with an anatomical imaging technique such as magnetic resonance imaging (MRI) to visualize both function and anatomy in vivo. Using experimentally measured human neuromagnetic fields and magnetic resonance images, the authors have developed a technique to register accurately these two modalities and have applied the registration procedure to portray the spatiotemporal distribution of neural activity evoked by auditory stimulation.     

Fast wavelet estimation of weak biosignals

Wavelet-based signal processing has become commonplace in the signal processing community over the past decade and wavelet-based software tools and integrated circuits are now commercially available. One of the most important applications of wavelets is in removal of noise from signals, called denoising, accomplished by thresholding wavelet coefficients in order to separate signal from noise. Substantial work in this area was summarized by Donoho and colleagues at Stanford University, who developed a variety of algorithms for conventional denoising. However, conventional denoising fails for signals with low signal-to-noise ratio (SNR). Electrical signals acquired from the human body, called biosignals, commonly have below 0 dB SNR. Synchronous linear averaging of a large number of acquired data frames is universally used to increase the SNR of weak biosignals. A novel wavelet-based estimator is presented for fast estimation of such signals. The new estimation algorithm provides a faster rate of convergence to the underlying signal than linear averaging. The algorithm is implemented for processing of auditory brainstem response (ABR) and of auditory middle latency response (AMLR) signals. Experimental results with both simulated data and human subjects demonstrate that the novel wavelet estimator achieves superior performance to that of linear averaging.     

Coil design for real and sham transcranial magnetic stimulation

Transcranial magnetic stimulation (TMS) can be used to excite the human cortex noninvasively. TMS also activates scalp muscles and sensory receptors; additionally, the loud sound from the stimulating coil activates auditory pathways. These side effects complicate the interpretation of the results of TMS studies. For control experiments, we have designed a coil that can produce both real and sham stimulation without moving the coil. The sham TMS is similar to the real TMS, except for the different relative direction of the currents in the two loops of the figure-of-eight coil. While the real TMS elicited activation of hand muscles, sham TMS had no such effect; however, the auditory-evoked potentials were similar.     

Closed-loop stimulation of hypoglossal nerve in a dog model of upper airway obstruction

Electrical stimulation of upper airway (UAW) muscles has been under investigation as a treatment method for obstructive sleep apnea (OSA). Particular attention has been given to the electrical activation of the genioglossal muscle, either directly or via the stimulation of the hypoglossal nerve (HG), since the genioglossus is the main tongue protrusor muscle. Regardless of the stimulation site or method, an implantable electrical stimulation device for OSA patients will require a reliable method for detection of obstructive breaths to apply the stimulation when needed. In this paper, we test the hypothesis that the activity of the HG nerve can be used as a feedback signal for closed-loop stimulation of the HG nerve in an animal model of UAW obstruction where a force is applied on the submental region to physically narrow the airways. As an advantage, the method uses a single electrode for both recording and stimulation of the HG nerve. Simple linear filtering techniques were found to be adequate for producing the trigger signal for the electrical stimulation from the HG recordings. Esophageal pressure, which was used to estimate the size of the UAW passage, returned to the preloading values during closed-loop stimulation of the HG nerve. The data demonstrate the feasibility of the closed-loop stimulation of the HG nerve using its activity as the feedback signal.     

Electrocutaneous Stimulation for Sensory Communication in Rehabilitation Engineering

Physiological and psychophysical functions underlying electrocutaneous stimulation are discussed, including a comparative review of stimulus parameters and coding formats. Procedures are recommended for implementing electrotactile displays and for generating reliable, painfree sensations with a useful communications bandwidth.     

Independent component analysis of noninvasively recorded cortical magnetic DC-fields in humans

We apply a recently developed multivariate statistical data analysis technique--so called blind source separation (BSS) by independent component analysis--to process magnetoencephalogram recordings of near-dc fields. The extraction of near-dc fields from MEG recordings has great relevance for medical applications since slowly varying dc-phenomena have been found, e.g., in cerebral anoxia and spreading depression in animals. Comparing several BSS approaches, it turns out that an algorithm based on temporal decorrelation successfully extracted a dc-component which was induced in the auditory cortex by presentation of music. The task is challenging because of the limited amount of available data and the corruption by outliers, which makes it an interesting real-world testbed for studying the robustness of ICA methods.     

A CMOS implantable multielectrode auditory stimulator for the deaf

Describes an implantable multielectrode neural stimulator developed for electrical stimulation of the auditory nerves with the aim of producing a sensation of sound in sensory deaf ears. Power and digitally coded amplitude and frequency data are transcutaneously transmitted to the implantable stimulator using an inductively coupled RF link and an ultrasonic link, respectively. A novel low-power low-component count CMOS charge-redistribution digital-to-analog (D/A) demultiplexer which produces a high resolution neuro-compatible charge output is described. An extended missing pulse code is developed which assures higher reliability and protection against excess and erroneous stimulations. An experimental 4-electrode system capable of stimulating up to a 5-kHz rate and consuming less than 10 mW of power is presented.     

Enhancement of Spatial Learning-Memory in Developing Rats via Mozart Music

This paper studies the effect of musical stimulations on the capability of the spatial learningmemory in developing rats by behavioral and electrophysiological techniques. Rats, which are exposed to Mozart's Sonata for Two Pianos in D Major, complete learning tasks of the Moriss water maze with significantly shorter latencies, and the power spectrum of alpha band of electrohippocampogram (EHG) significantly increase, compared with the control rats and rats exposed to the horror music. The results indicate that if given the stimulation of Mozart music in the developmental period of the auditory cortex, the capability of the spatial learning-memory can be significantly changed. The enhancement of alpha band of EHG may be related to the change of this function mainly.     

Enhancement of Spatial Learning-Memory in Developing Rats via Mozart Music

This paper studies the effect of musical stimulations on the capability of the spatial learningmemory in developing rats by behavioral and electrophysiological techniques. Rats, which are exposed to Mozart＇s Sonata for Two Pianos in D Major, complete learning tasks of the Moriss water maze with significantly shorter latencies, and the power spectrum of alpha band of electrohippocampogram （EHG） significantly increase, compared with the control rats and rats exposed to the horror music. The results indicate that if given the stimulation of Mozart music in the developmental period of the auditory cortex, the capability of the spatial learning-memory can be significantly changed. The enhancement of alpha band of EHG may be related to the change of this function mainly.     

Photolithographic Fabrication and Physiological Performance of Microelectrode Arrays for Neural Stimulation

The development of an auditory cochlear prosthesis which works by direct electrical stimulation of the auditory nerve creates the need for a multielectrode stimulation array which is small in size, rugged, resistant to electrolysis, and stable and reproducible in its electrical and mechanical properties. This paper describes the fabrication of such microelectrode arrays using planar lithographic techniques.     

基于听觉模型的汉语耳语音声调检测

 从听觉感知出发,分析了听觉外周模型对于语音激励的主要响应过程,采取听神经平均发放率为声调感知线索,提出了一种汉语耳语音声调的识别方法.其理论基础是听神经发放信息是听觉中枢的唯一信息来源,它是对于语音激励中声强、频谱、共振峰等多种特征的综合反应,因此适合用作耳语音的声调特征.采用BP神经网络对大量汉语元音耳语四声样本进行训练、识别,得到65.1%的平均识别率,达到了改善汉语耳语音声调识别效果的目的.     

Frequency domain dipole localization: extensions of the method andapplications to auditory and visual evoked potentials

A statistical frequency domain approach to localizing equivalent dipole generators of human brain evoked potentials is described. The frequency domain representation allows considerable data reduction, constrains the magnitude function of the dipoles to be smooth, and accounts for the statistical properties of the background EEG. A general model in which dipole orientation can vary over time, and which includes multiple dipole generators is considered. The varying orientation model has the practical advantage of being more nearly linear and more flexible than a fixed orientation model, which facilitates convergence of the iterative fitting algorithm. A measure of goodness-of-fit that compares the likelihood of the dipole model with the likelihoods of saturated and null models is suggested. The results of fitting the model report recorded auditory and visual evoked potentials are reported. A single dipole with fixed orientation seems to be an adequate model of the auditory midlatency response, while two dipoles with varying orientation are needed to fit the later P200 component. Analysis of the visual P100 response to unilateral stimulation localized a generator in the contralateral occipital cortex, as expected from anatomical considerations     

Auditory perception and cognition

In this article, the essential process of auditory perception and advocated for the integration of structural and functional knowledge of the auditory system is reviewed. A perspective, called the constructionist's paradigm, is suggested which looks at the neuron-anatomical structure for auditory perception in three essential stages with intermediate signal representations that allow interchangeable coupling to accommodate new and improved models within each individual stage. This article introduces to the signal processing audience the exciting new frontiers in auditory research, particularly functional neuroimaging. The discussion and collaboration among researchers in various disciplines is motivated for the ultimate understanding of the human auditory perception process which will eventually lead to many practical applications.     

Pain Suppression by Transcutaneous Electronic Stimulation

Electrical stimulation applied to the skin has been observed to relieve pain. Although transcutaneous nerve stimulation devices are quite simple, certain constraints must be met, particularly in electrode design, in order to maximize effectiveness.     

Optimal electrical stimulation modality for cortical esophageal evoked potentials: transmural or intraesophageal?

Esophageal electrical stimulation using short and a relatively small number of (200 micros, 0.2 Hz, n = 25) electrical pulses generates a characteristic and well defined cortical evoked potential response (EP). There are two methods of stimulation: either through intraesophageal electrodes or with transmural electrodes. The objective of this paper is to compare EP response, sensations and heart rate variability power spectra elicited by both stimulation modalities in healthy volunteers. Our results suggest that transmural stimulation is more accurately perceived and at lower intensities, produces more reproducible peaks of higher amplitude than during intraesophageal stimulation. During either mode of esophageal stimulation, power within the high-frequency component of the heart rate variability power spectrum is enhanced.     

人体行为识别的研究

人们通常用形体动作,表情等对外界的刺激作出反应,传送某种信息,这些称为行为能力。近年来人工智能的研究取得了一定的进展,机器视觉是人工智能的一个重要分支,而人体行为识别就是其中的一个研究方面。机器视觉是通过图像摄取装置（比如摄像头）将摄取的目标转换成图像信号,然后对图像信号进行相关运算,抽取目标特征,根据判别的结果进行相应的操作过程。     

Neuronal activities related to higher brain functions-theoreticaland experimental implications

The activities of several single units (6-10) were recorded simultaneously in the auditory cortex and in frontal cortical areas of cats and monkeys. The response properties of the single units and the interaction between them were studied. It is shown that single units in both areas may participate in prolonged processes and be involved in more than one process. Adjacent neurons need not function in unison; while some neurons are activated, others may stay inactive. The interactions among adjacent neurons are weak, and can be modulated by sensory stimulation, and by arousal and behavioral states. These properties lead us to hypothesize that information is represented in the cortex by coactivation of sets of neurons rather than by independent modulation of the single-unit firing rate. A single unit may be a member of several representing sets. Thus, each neuron may participate in more than one function and each small cortical area may contain members of several functional sets. A mechanism for computing and transmitting information, based on converging-diverging links, between neuronal sets is described and tested by simulations and analysis of experimental data.     

A study of the properties of the structures with Al nanoclusters incorporated into the GaAs matrix

It is shown that organometallic vapor-phase epitaxy can be used to form an artificial medium that constitutes a matrix of single-crystal GaAs with incorporated Al nanoparticles. Electrical and optical properties of this medium are studied.