中川 誠司

Many studies involving the application of geophysical methods in the field of gas hydrates have focused on determining rock-physics relationships for hydrate-bearing sediments, with the goal being to delineate the boundaries of gas-hydrate accumulations and to estimate the quantities of gas hydrate that such accumulations contain using remote-sensing techniques. However, the potential for using time-lapse geophysical methods to monitor the evolution of hydrate accumulations during production and, thus, to manage production has not been investigated. In this work, we begin to examine the feasibility of using time-lapse seismic methods specifically, the vertical-seismic-profiling (VSP) method for monitoring changes in hydrate accumulations that are predicted to occur during production of natural gas. A feasibility study of this nature is made possible through the coupled simulation of large-scale production in hydrate accumulations and time-lapse geophysical (seismic) surveys. We consider a hydrate accumulation in the Gulf of Mexico that may represent a promising target for production. Although the current study focuses on one seismic method (VSP), this approach can be extended easily to other geophysical methods, including other seismic methods (e.g., surface seismic or crosshole measurements) and electromagnetic surveys. In addition to examining the sensitivity of seismic attributes and parameters to the changing conditions in hydrate accumulations, our long-term goals in this work are to determine optimal sampling strategies (e.g., source frequency, time interval for data acquisition) and measurement configurations (e.g., source and receiver spacing for VSP), while taking into account uncertainties in rock-physics relationships. The numerical-modeling strategy demonstrated in this study may be used in the future to help design cost-effective geophysical surveys to track the evolution of hydrate properties. Here, we describe the modeling procedure and present some preliminary results.

Poroelastic analysis has traditionally focused on the relationship between dry and drained constants, which are assumed known, and the saturated or undrained constants, which are assumed unknown. However, there are many applications in this field of study for which the main measurements can only be made on the saturated/undrained system, and then it is uncertain what the effects of the fluids were on the system, since the drained constants remain a mystery. The work presented here shows how to deduce drained constants from undrained constants for anisotropic systems having symmetries ranging from isotropic to orthotropic. Laboratory ultrasound data are then inverted for the drained constants in three granular packings: one of glass beads, and two others for distinct types of more or less angular sand grain packings. Experiments were performed under uniaxial stress, which resulted in hexagonal (transversely isotropic) symmetry of the poroelastic response. One important conclusion from the general analysis is that the drained constants are uniquely related to the undrained constants, assuming that porosity, grain bulk modulus, and pore fluid bulk modulus are already known. Since the resulting system of equations for all the drained constants is linear, measurement error in undrained constants also propagates linearly into the computed drained constants.

<jats:p> Acoustic fields/vibrations in the external auditory meatus (ear canal) and tympanic membrane (TM) under bone-conducted ultrasonic stimulation were measured to elucidate the contributions of the osseotympanic and inertial routes to bone-conducted ultrasonic (BCU) perception. Evidence showing nonlinear distortions, especially the generation of audible subharmonics in the outer and middle ear, was examined. In the results, we did not find any audible signals corresponding to the subjective pitch of a BCU tone in the acoustic fields for the auditory meatus and TM vibrations. This suggests that nonlinear distortions in the osseotympanic and inertial routes do not contribute to bone-conducted ultrasonic perception. Specific properties of perception may be related to mechanisms in the cochlea or afferent neural pathway. </jats:p>

Speech recognition tends to be influenced by noise in the air. Body-conducted speech offers a robust signal extraction method from noisy environments, particularly because body-conducted speech is a propagated sound and not easily influenced by noise. However, when body-conducted speech is extracted with an accelerator, the typical frequency component of 2 kHz or more decreases compared with normal speech. Thus, we investigated a technique combining differential acceleration and noise reduction to estimate a clear signal using only body-conducted speech from a noisy room. The recognition rate confirmed about 3-4% is improved with proposed method. © 2010 Inderscience Enterprises Ltd.

Bone-conducted ultrasound (BCU) is perceived even by the profoundly sensorineural deaf. We have been developing a novel hearing-aid using BCU perception, which transmits a 30-kHz bone-conducted carrier that is amplitude-modulated by speech. The fundamental capabilities of the BCU hearing-aid (BCUHA) were objectively assessed by magnetoencephalography. Frequency- and temporal-resolution were assessed by measuring mismatch fields (MMFs). As well, the capability to discriminate two-channel BCUs presented to the left and right mastoids was verified by the laterality of auditory evoked magnetic field N1m. In the frequency-discrimination tests, amplitude-modulated BCU (AM-BCU) and air-conducted sound (AC) showed almost the same MMF-magnitudes when frequency/modulation-frequency of the standard-stimuli were 1.0 kHz, even though MMF-magnitudes for BCU were smaller than those of AC at 0.125 kHz. In the temporal-discrimination tests, MMFs for changes of stimulus-duration were measured. MMF-magnitudes for AM-BCUs reached more than 80% of those for air-conducted sounds (ACs). In addition, in the laterality-discrimination tests, N1m evoked by contralateral stimuli were larger in amplitude and shorter in latency than those evoked by ipsilateral stimuli for both AM-BCUs and ACs. This result agrees with earlier reports of AC auditions, and suggests that two-BCU channels presented to the left and right mastoid were separately localized. These findings objectively indicate that the BCUHA has practical frequency- and temporal resolution, and give a rationale for the development of a multi-channel (at least two) BCUHA.

For a sinusoidal flickering light amplitude-modulated (AM) sinusoidally, flicker with a periodicity of a temporal envelope (modulation-frequency) of the light is perceived even though there is no such frequency component. However, the mechanisms underlying the perception are still unclear. In human visual system, it is known that there are two temporal channels with a lower and a higher peak frequency. Therefore, we investigated whether the two temporal channels affected the perception of the envelope of the AM flickering light. Visual sensitivity and magnetoenceplialographic (MEG) responses to the envelope periodicity were measured when the sensitivity of each of the temporal channel was reduced by adaptation. Sinusoidal flickering lights with a low (2 Hz) and a high (16 Hz) temporal frequency were used as adapting stimuli. The sinusoidal flickering lights of 2 and 16 Hz and an AM flickering light with a modulation-frequency of 2 Hz and a carrier-frequency of 16 Hz were presented as test stimuli. The results showed that the sensitivity and MEG responses to the sinusoidal flickering light decreased more when the sensitivity of the temporal channel tuned for the test stimulus frequency was reduced than when that of the other temporal channel was reduced. On the other hand, the sensitivity and MEG responses to the envelope periodicity decreased more when the sensitivity to the frequency corresponding to the envelope periodicity was reduced than when that to the carrier frequency was reduced, even though a frequency component corresponding to the envelope periodicity did not exist in the stimulus. The results indicated that the envelope component of AM flickering light was affected by the low-frequency channel and suggest the possibility that the envelope component arises before or while the AM flickering signal passes the low-frequency channel.

To reduce cost, implant levels usually use masks fabricated with older generation mask tools, such as laser writers, which are known to introduce significant mask errors. In fact, for the same implant photolithography process, Optical Proximity Correction (OPC) models have to be developed separately for the negative and positive mask tones to account for the resulting differences from the mask making process. However, in order to calibrate a physical resist model, it is ideal to use single resist model to predict the resist performance under the two mask polarities. In this study, we show our attempt to de-convolute mask error from the Correct Positive (CP) and Correct Negative (CN) tone CD data collected from bare Si wafer and derive a single resist model. Moreover, we also present the predictability of this resist model over a patterned substrate by comparing simulated CD/profiles against wafer data of various features.

骨導超音波刺激下での生体鼓膜振動をレーザードップラ振動計により計測し、骨導による超音波知覚が外耳や中耳系での非線形歪みに起因する可聴音の発生によるものか検証した。計測時に生じた光学系ノイズを効果的に除去し、観測信号のS/N比の向上を図る信号処理手法を構築した。30kHzの骨導超音波刺激下で、ノイズの重畳していない場合の代表的な鼓膜振動の時間波形と周波数特性の計測状況は良好で、目立った光学系ノイズが発生しなかった。次に、同じく30kHzの骨導超音波刺激下で、ノイズが重畳した場合、周波数全域に渡ってノイズが乗り、30kHzの刺激信号はこのノイズの中に埋もれた。これに対して、この時間波形にノイズ除去処理を施した後の周波数特性はノイズフロアが全体的に低下し、30kHzの刺激信号の存在が明確になり、良好な計測状況で得られた信号の周波数特性と遜色ないS/N比が得られた。

To investigate the perception of a temporal envelope of flickering light is important for understanding nonlinear temporal processing in the visual system. The influence of the frequency components of a flickering light on the perception of the envelope remains unclear, with few studies having investigated the cortical activities for the envelope. We investigated the detection thresholds, brightness, and magnetoencephalographic responses related to amplitude-modulated (AM) flickering lights. The results showed that the sensitivity to flicker at the envelope periodicity of the AM flickering light was lower for a high-frequency carrier (40 Hz) than for a lower-frequency one (10, 20, or 30 Hz). Also, the primary visual cortex responded at the frequency corresponding to the envelope periodicity of the AM flickering light, and the strength of the cortical response reflected the brightness of the flicker at the envelope periodicity. (C) 2009 Optical Society of America

CONCLUSION: N1m growth indicates the differences in central auditory processing between bone-conducted ultrasound and air-conducted audible sound. OBJECTIVES: Bone conduction enables ultrasound to be heard by the human ear. Despite many studies, the perceptual mechanism of bone-conducted ultrasound has not yet been clarified completely. Therefore, this study investigated the ultrasonic perception of humans, especially as regards the effects of stimulus intensity or loudness. SUBJECTS AND METHODS: The effect of the stimulus level on N1m amplitude was measured over the psycho-acoustical dynamic range. RESULTS: The dynamic range for 30 kHz bone-conducted ultrasound (18.2 +/- 3.3 dB) was found to be significantly narrower than that for 1 kHz air-conducted sound (85.9 +/- 11.9 dB). As the stimulus level increased, the N1m amplitude in response to bone-conducted ultrasound grew faster than that to air-conducted sound. Although the growth of the N1m amplitude for air-conducted sound saturated below the uncomfortable loudness level (UCL), that for bone-conducted ultrasound continued to grow above the UCL.

The aim of this study was to determine whether the amplitude and/or latency of the N1m deflection of auditory-evoked magnetic fields are influenced by the level and frequency of sound. The results indicated that the amplitude of the N1m increased with sound level. The growth in amplitude with increasing sound level was almost constant with low frequencies (250-1000 Hz); however, this growth decreased with high frequencies (> 2000 Hz). The behavior of the amplitude may reflect a difference in the increase in the activation of the peripheral and/or central auditory systems. NeuroReport 20:548-552 (C) 2009 Wolters Kluwer Health vertical bar Lippincott Williams & Wilkins.

Several studies have reported that bone-conducted ultrasound (BCU) is even perceived by the profoundly sensorineural deaf; however, the mechanisms involved remain unclear. We previously reported some unique characteristics of BCU perception that suggest unique neurophisiological mechanisms. For example: (1) the pitch of BCU is 10-odd kHz and is independent of its frequency; (2) no beats occur between BCU and 10-odd-kHz air-conducted sinusoids; (3) BCU masks 10-14 kHz air-conducted sounds; and (4) the dynamic range of loudness for BCU is less than 20 dB. In the present study, several electrophysiological measurements were carried out to clarify the neural pathway involved in BCU perception. Specifically, auditory brainstem responses (ABRs), middle latency responses (MLRs), and cortical magnetic activities evoked by BCU were measured in humans. Substantial ABRs (wave I-V) and MLRs were evoked by BCU as well as air-conducted audible sound. In terms of cortical activities, clear N1m responses were elicited by BCU, with their sources being localized in the auditory cortices. However, BCU showed later, smaller, more posterior, and more lateral sources than audible-frequency sounds, and therefore did not appear to follow a tonotopic organization at the cortical level. These results indicate that: (1) the cochlea substantially contributes to BCU perception; (2) BCU goes through the normal auditory pathway and there is no special organ for BCU perception; and (3) some differences in the inner ear mechanisms may exist between audible sounds and BCU.

Conclusion: N1m growth indicates the differences in central auditory processing between bone-conducted ultrasound and air-conducted audible sound. Objectives: Bone conduction enables ultrasound to be heard by the human ear. Despite many studies, the perceptual mechanism of bone-conducted ultrasound has not yet been clarified completely. Therefore, this study investigated the ultrasonic perception of humans, especially as regards the effects of stimulus intensity or loudness. Subjects and methods: The effect of the stimulus level on N1m amplitude was measured over the psycho-acoustical dynamic range. Results: The dynamic range for 30 kHz bone-conducted ultrasound (18.2 +/- 3.3 dB) was found to be significantly narrower than that for 1 kHz air-conducted sound (85.9 +/- 11.9 dB). As the stimulus level increased, the N1m amplitude in response to bone-conducted ultrasound grew faster than that to air-conducted sound. Although the growth of the N1m amplitude for air-conducted sound saturated below the uncomfortable loudness level (UCL), that for bone-conducted ultrasound continued to grow above the UCL.

Human listeners can perceive speech signals from a voice-modulated ultrasonic carrier which is presented through a bone-conduction stimulator, even if they are sensorineural hearing loss patients. As an application of this phenomenon, we have been developing a bone-conducted ultrasonic hearing aid (BCUHA). This research examined whether formant space and F(0) can be cues of speaker discrimination in BCU hearing as well as via air-conduction (AC) hearing. A series of speaker discrimination experiments revealed that both formant space and F(0) can act as cues for speaker discrimination even via BCUHA. However, sensitivity to formant space in BCU hearing is less than in AC hearing.

Resist process challenges for 32-nm node and beyond are discussed in this paper. For line and space (L/S) logic patterns, we examine ways to balance the requirements of resolution-enhancement techniques (RETs). In 32-nm node logic patterning, two-dimensional (2D) layout pattern deformation becomes more severe with stronger RET (e.g., narrow angle CQUAD illumination). Also pattern collapse more frequently happens in 2D-pattern layouts when stronger RET is used. In contrast, milder RET (annular illumination) does not induce the severe pattern collapse in 2D-pattern layout. For 2D-pattern layouts, stronger RET seems to worsen image contrast and results in high background-light in the resist pattern, which induces more pattern collapse. For the minimum-pitch L/S pattern in 32-nm node logic, annular illumination is acceptable for patterning with NA1.35 scanner when high contrast resist is used. For contact/via patterns, it is necessary to expand the overlapping CD process window. Better process margin is realized through the combination of hole-shrink technique and precise acid-diffusion control in an ArF chemically amplified resist.

Several studies have reported that bone-conducted ultrasound (BCU) is even perceived by the profoundly sensorineural deaf; however, the mechanisms involved remain unclear. We previously reported some unique characteristics of BCU perception that suggest unique neurophisiological mechanisms. For example: (1) the pitch of BCU is 10-odd kHz and is independent of its frequency; (2) no beats occur between BCU and 10-odd-kHz air-conducted sinusoids; (3) BCU masks 10-14 kHz air-conducted sounds; and (4) the dynamic range of loudness for BCU is less than 20 dB. In the present study, several electrophysiological measurements were carried out to clarify the neural pathway involved in BCU perception. Specifically, auditory brainstem responses (ABRs), middle latency responses (MLRs), and cortical magnetic activities evoked by BCU were measured in humans. Substantial ABRs (wave I-V) and MLRs were evoked by BCU as well as air-conducted audible sound. In terms of cortical activities, clear N1m responses were elicited by BCU, with their sources being localized in the auditory cortices. However, BCU showed later, smaller, more posterior, and more lateral sources than audible-frequency sounds, and therefore did not appear to follow a tonotopic organization at the cortical level. These results indicate that: (1) the cochlea substantially contributes to BCU perception; (2) BCU goes through the normal auditory pathway and there is no special organ for BCU perception; and (3) some differences in the inner ear mechanisms may exist between audible sounds and BCU.

Speech-recognition rates decrease in noisy environments. The body-conducted speech, conducted in solids such as body and skins, has a noise-robust characteristics and can be served for recognition systems even in 98 -dBSPL (20 dBSNR) noise environments. However, the body-conduction can not capture high frequency sounds. Conventional methods to improve sound quality of body-conducted speeches need both speeches themselves and body-conducted speeches. In this paper, a new body-conducted speech retrieval technique in sound quality without a speech signal itself is proposed. First, high-frequency components in the body-conducted speech were emphasized using differential acceleration. Second, a conventional noise reduction method was adopted to make a clear body-conducted speech from a retrieval speech which contains constant noise. The recognition experiments using the proposed method showed that it improved recognition rate in all speakers.

The intention of this study is to develop an immersion lithography process using advanced track solutions to achieve world class critical dimension (CD) and defectivity performance in a state of the art manufacturing facility. This study looks at three important topics for immersion lithography: defectivity, CD control, and wafer backside contamination. The topic of defectivity is addressed through optimization of coat, develop, and rinse processes as well as implementation of soak steps and bevel cleaning as part of a comprehensive defect solution. Develop and rinse processing techniques are especially important in the effort to achieve a zero defect solution. Improved CD control is achieved using a biased hot plate (BHP) equipped with an electrostatic chuck. This electrostatic chuck BHP (eBHP) is not only able to operate at a very uniform temperature, but it also allows the user to bias the post exposure bake (PEB) temperature profile to compensate for systematic within-wafer (WiW) CD non-uniformities. Optimized CD results, pre and post etch, are presented for production wafers. Wafer backside particles can cause focus spots on an individual wafer or migrate to the exposure tool's wafer stage and cause problems for a multitude of wafers. A basic evaluation of the cleaning efficiency of a backside scrubber unit located on the track was performed as a precursor to a future study examining the impact of wafer backside condition on scanner focus errors as well as defectivity in an immersion scanner.

Effects of center frequency on the binaural auditory filter in the human auditory cortex were examined using auditory-evoked magnetic fields. Two tones with different frequency separations, which were presented dichotically to the left and right ears, were used as the sound stimuli. Eight normal-hearing participants took part in the study. The amplitudes of the N1m components of auditory-evoked magnetic fields were approximately constant when the frequency separation was less than 10-20% of the center frequency; however, the N1m amplitudes increased with increasing frequency separation when the frequency separation was greater than 10-20% of the center frequency. This indicates that binaural auditory filter bandwidth is approximately 10-20% of the center frequency. NeuroReport 19:1709-1713 (C) 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins.

The effects of the bandwidth of high-frequency sounds oil loudness are investigated. Loudness matches are obtained using a two-interval, adaptive forced-choice procedure converging on the point of subjective equality by following a simple 1-up, 1-down rule. Loudness increases significantly when the sound has a 1/3 octave band compared with smaller bandwidth sounds, confirming the effect of bandwidth of high-frequency sounds. (C) 2008 Elsevier Ltd. All rights reserved.

According to previous studies, ultrasound can be perceived through bone conduction and ultrasound amplitude modulated by different speech sounds can be discriminated by some profoundly deaf subjects as well as the normal-hearing. These findings suggest the usefulness of development of a bone-conducted ultrasonic hearing aid (BCUHA) for profoundly deaf subjects. In this study, with a view to developing a frequency modulation system in a BCUHA, the capability to discriminate the frequency of sinusoidal bone-conducted ultrasound (BCU) was evaluated by measuring mismatch fields (MMF). We compared MMFs between BCU (standard stimuli were 30 kHz, and deviant stimuli were 27 and 33 kHz) and air-conducted audible sound (ACAS; standard stimuli were 1 kHz, and deviant stimuli were 900 and 1100 Hz). MMFs were observed in all subjects for ACAS, however, not observed in a few subjects for BCU. Further, the mean peak amplitudes of MMF for BCU were significantly less than those for ACAS. These findings indicate that the discrimination capability of frequency of sinusoidal BCU is inferior to that of ACAS. It was also demonstrated that normal hearing could to some extent discriminate differences in frequency in sinusoidal BCU. The results indicate a possibility of transmission system for language information making use of frequency discrimination. (C) 2008 Elsevier Ireland Ltd. All rights reserved.

The aim of this paper was to determine whether the latency and/or amplitude of the NIm deflection of the auditory-evoked magnetic fields are influenced by the delay and number of iterations of iterated rippled noise, which are related to pitch and pitch strength, respectively. The results indicate that the NIm amplitude decreased sharply for delays between 16 and 32 ms, suggesting that the NIm amplitude reflects the lower limit of the audible pitch range. The NIm latency increases with increasing delay of up to 8-16 ms and then decreases again for delays longer than 16 ms. The behavior of the latency may reflect the balance between the pitch-related component of the NIm and a specific pitch-unrelated component.

The AKARI satellite (formerly known as ASTRO-F) is Japan's first infrared astronomical satellite. AKARI is equipped with the infrared camera (IRC) and the far-infrared surveyor (FIS), which are cooled below 7 K. The AKARI's 68.5 cm telescope, which is made of SiC, is also cooled below 7 K. A unique feature of the AKARI cryostat is that it uses both cryogen and mechanical coolers. Using mechanical coolers, the helium lifetime can be greater than one year with 170 L of liquid helium. AKARI was launched on February 21, 2006 (UT), from the Uchinoura Space Center (USC). It has been performing successfully in orbit. (C) 2008 Elsevier Ltd. All rights reserved.

In this paper we review the current status of VERA (VLBI Exploration of Radio Astrometry) project. First, we present an overview of VERA, and then we report on recent results from VERA, particularly the parallax measurement of Galactic star forming region S269 at the distance of 5.3 kpc.

The effects of the binaural auditory filter in the human auditory cortex were examined by auditory-evoked magnetic fields. Two tones with different frequency separations, which were presented dichotically to the left and right ears, were used as the sound stimuli, with all signals presented at sound pressure level of 60 dB. The results indicated that the NIm amplitudes were approximately constant when the frequency separation was less than IOOHz; however, the NIm amplitudes increased with increasing frequency separation when the frequency separation was greater than 200 Hz. These findings indicate that binaural auditory filter-like behavior might be reflected in NIm amplitudes.

Permeability of a fracture can affect how the fracture interacts with seismic waves. To examine this effect, a simple mathematical model that describes the poroelastic nature of wave-fracture interaction is useful. In this paper, a set of boundary conditions is presented which relate wave-induced particle velocity (or displacement) and stress including fluid pressure across a compliant, fluid-bearing fracture. These conditions are derived by modeling a fracture as a thin porous layer with increased compliance and finite permeability. Assuming a small layer thickness, the boundary conditions can be derived by integrating the governing equations of poroelastic wave propagation. A finite jump in the stress and velocity across a fracture is expressed as a function of the stress and velocity at the boundaries. Further simplification for a thin fracture yields a set of characteristic parameters that control the seismic response of single fractures with a wide range of mechanical and hydraulic properties. These boundary conditions have potential applications in simplifying numerical models such as finite-difference and finite-element methods to compute seismic wave scattering off nonplanar (e.g., curved and intersecting) fractures.

This study examined the loudness of iterated rippled noises (IRNs) with different number of iterations under conditions of equal sound pressure. The scale values of loudness were obtained using a paired-comparison method. The results showed that the loudness of IRNs was not constant, even though the sound pressure level was equivalent. The loudness of IRNs increased with increasing iteration number. This indicated that repetitive components of sounds might affect their loudness. (C) 2007 Elsevier Ltd. All rights reserved.

Few have reported the activities of auditory cortices to high-frequency sounds over 5000 Hz though several studies have reported that bone-conducted ultrasounds (BCUs) are perceived even by those who are profoundly sensorineural deaf. Brain magnetic fields evoked by air- and bone-conducted sounds with frequency variations in an audible to ultrasonic range were recorded to clarify differences of perception mechanisms between (i) low- and high-frequency sounds, (ii) air- and bone-conducted sounds, and (iii) BCU and 12-kHz air-conducted sound, which had almost same pitch and loudness as BCU. Auditory-evoked magnetic fields evoked by air-conducted audible sounds (ACs 500-16,000 Hz), bone-conducted audible sounds (BCs 500-16,000 Hz), and a BCU (30,000 Hz) were measured and following results were obtained (1) for all stimuli, substantial N1m responses were observed and equivalent current dipoles (ECDs) were localized in the Heschl's gyrus or the planum temporale. (2) Generally, the latencies increased and the ECD moments decreased as the frequency increased. (3) ACs and BCs produced by the same frequency sounds showed no differences in N1m latency and ECD moment below 8000 Hz on the other hand, BCs showed larger latencies and smaller ECD moments than ACs over 12,000 Hz. (4) BCUs showed a larger latency and smaller ECD moments, and more posterior and lateral location than all ACs and BCs. Especially, BCU was different from 12-kHz AC in ECD moment, latency, and source location. (5) With all kinds of stimuli, the contralateral stimuli showed faster and larger N1m than the ipsilateral stimuli. These results suggest that air- and bone-conducted sounds are processed similarly below 8000 Hz, but high-frequency bone-conducted sounds over 12,000 Hz are processed differently. Considering the previous reports, the differences in the perception mechanisms possibly exists in the inner ear. © 2007 Elsevier B.V. All rights reserved.

We previously demonstrated that late electromyographic responses with a latency of 100 ms were evoked bilaterally in soleus muscles following transcranial magnetic stimulation over the left cerebellum. Efferent fibers from the left cerebellum modulate vestibulospinal tract influences on the extensor muscles of the left hindlimb. Here, we investigated whether the vestibulospinal tract mediates this late response. We activated the vestibulospinal tract by optokinetic stimulation. Our results show that the latency of the soleus electromyographic response is shortened by optokinetic stimulation, but the latency of the motor response evoked by the corticospinal tract is unchanged. These findings support our hypothesis that vestibulospinal tracts mediate late electromyographic responses, and allow the development of techniques to assess the human vestibulospinal system function.

Although several studies have reported that the rise-time of sound stimulus affects on auditory evoked magnetic fields, effects of each parameter which vary in connection with rise-time&mdash;whole energy, rising-speed (dL/dt), spectrum&mdash;have not been clarified. In this study, N1m amplitudes and latencies were examined using noise-bursts with varying rise-time and constant energy or rising-speed. The results showed that N1m increased in amplitude and decreased in latency as rise-time increased (i.e, energy increased) under the rising-speed-constant condition. In contrast, N1m amplitudes and latencies did not vary significantly as rise-time increased (i.e., rising-speed decreased) under the energy-constant condition. These results indicate that sound energy has greater effects on N1m amplitude and latency than rising-speed.

Bone-conducted ultrasound (BCU) is perceived even by those who are profoundly sensorineural deaf. A novel hearing-aid using BCU perception, which transmits amplitude-modulated ultrasound by bone-conduction, has been developed for the profoundly deaf. To assess and optimize the bone-conducted ultrasonic hearing-aid (BCUHA), the characteristics of BCU perception need to be better specified. This study verified the discrimination capability of two-channel BCUs presented to the both left and right mastoids in the both normal-hearing and profoundly deaf subjects by evaluating the laterality of the auditory evoked cortical activities. In normal-hearing subjects, N1m responses, the most prominent deflections peaking about 100 ms after the sound onset, evoked by the contralateral stimuli were larger in amplitude and shorter in latency than those evoked by the ipsilateral stimuli for BCUs as well as audible sounds. The same phenomena were also observed for BCUs in profoundly deaf subjects. These results suggest that two-channel BCUs were separately localized and provide a rationale to develop a two-channel BCUHA.