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ABSTRACT: This paper proposes and evaluates an intramouth vibrating voice-generation system we have developed to aid alaryngeal speech.
The system fixes a vibrator in artificial teeth as a substitute for a glottal sound source, and proper sound control improves
the speech. With this system, we controlled the substitute glottal sound with intraoral pressure, which increases for voiceless
consonants, for clearer speech. In addition, the system controls the pitch of speech using pressure from a finger. This concise
pitch control is available to all patients for more natural speech. We tested two methods of pitch control by finger pressure:
one in which finger pressure directly determines the pitch, and the other in which finger pressure is converted into binary
commands of voice and accent that execute pitch pattern generation. Conventional pitch control with expiration pressure served
as a reference. Without voicing control, less than 50% of syllables were identified correctly. Voicing control improved this
rate to 60%. Similarly, voicing control improved misidentification of voiceless consonants to corre-sponding voiced ones from
30% to 10%. Binary pitch control with finger pressure performed better than direct pitch control and was perceived as natural
as direct pitch control with expiration pressure.
Journal of Artificial Organs 04/2012; 4(4):288-294. · 1.59 Impact Factor
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ABSTRACT: We studied the effect of the duty ratio, i.e., the ratio of hill width to pitch, of patterned diamondlike carbon (DLC) surfaces on Ar gas cluster ion beam (GCIB) planarization effect. The patterns of 40 nm depth were fabricated on Si substrates by electron beam lithography and CHF3 reactive-ion etching. The pitch of the line-and-space pattern was 300 nm and three duty ratios were adopted. Then, refilling materials were deposited to 50 nm thickness on the patterned substrates. The test samples were irradiated by Ar-GCIB and the resultant surface profiles were measured by atomic force microscopy. The acceleration energy for one cluster was 20 keV. The dose was set in the range from 5×1014 to 5×1016 ion/cm2. Although there was a difference in the dose, the patterns clearly disappeared upon irradiating GCIB. The reduction rate of the peak-to-valley height decreased as the width of the hill increased. We indicated that GCIB irradiation is effective for the planarization of patterned surfaces with various duty ratios.
Journal of Applied Physics 03/2011; 109(7):07B733-07B733-3. · 2.17 Impact Factor
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ABSTRACT: Light addressing is an emerging technique to optically address a virtual electrode on a photoconductive substrate. A thinner photoconductive layer of a light-addressable planar electrode can improve the spatial resolution of the light-addressed electrode. Voltage application to the electrode, however, causes a strong electric field across the thin photoconductive layer with a significant avalanche effect, which induces an undesired increase of dark current. In order to overcome this problem, we investigated how photoconductive-layer thickness and passivation-layer conductivity affect voltage-application-induced bright and dark charge densities. Suppression of the dark charge density with a thick photoconductive layer and a low-conductive passivation layer is found to be a key factor for optimization of the light-addressable electrode. With this design strategy, we developed a novel light-addressable electrode using titanium dioxide as a photoconductor. To suppress the avalanche effect, the thickness of the titanium-dioxide layer was designed to be 1.5 μm. The fabricated electrode turned out to have sufficient photoelectric properties: the bright charge density reached 70 μC/cm2 and the bright-to-dark charge density ratio was greater than 10, which allows stimulation to cultured dissociated neurons. © 2010 Wiley Periodicals, Inc. Electron Comm Jpn, 94(1): 61–68, 2011; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/ecj.10241
Electronics and Communications in Japan 12/2010; 94(1):61 - 68. · 0.08 Impact Factor
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ABSTRACT: High-aspect-ratio nanostructures are thermally imprinted with dynamic heating of the mold surface. A thin-film current heater located at the back of the mold realized rapid heating, and an upper punch and a heater substrate as coolants make the cooling time short. This heater is applied to stamping-type imprinting and injection molding. The authors demonstrated imprinting nanostructures with aspect ratios of 2–3 in the cycle time of 15 s. This equipment concept is practical for high-throughput and low-energy thermal nanoimprinting.
Journal of vacuum science & technology. B, Microelectronics and nanometer structures: processing, measurement, and phenomena: an official journal of the American Vacuum Society 12/2010; · 1.34 Impact Factor
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ABSTRACT: Information transfer among neuronal populations has a directional bias. Some past studies demonstrated that microstructure could bias the direction of information transfer at a cellular level. However, the transfer at a population level has hardly been controlled to date. In order to control the information transfer, we attempt to bias the direction of neurite outgrowth of cultured neurons using a three-dimensional asymmetric microstructure. The proposed microstructure is an embossed barrier with a right-triangle cross section, namely, an ascending slope and vertical wall. Because of the asymmetricity, the neurite growth rate from the wall-side to the slope-side is expected to be lower than that of the slope-to-wall. We fabricated the microstructure on a polystyrene substrate by hot pressing, simultaneously embedding line electrodes for probing stimulation. To confirm the impact of the microstructure on neurite outgrowth, and thus the signal transfer direction between neuronal populations separated by the structure, we stimulated cultured neurons on both sides of the structure. There was a difference in neuronal responses to wall-side stimulation and slope-side stimulation, demonstrating the directional characteristic of information transfer. © 2010 Wiley Periodicals, Inc. Electron Comm Jpn, 93(12): 17–25, 2010; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/ecj.10240
Electronics and Communications in Japan 11/2010; 93(12):17 - 25. · 0.08 Impact Factor
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ABSTRACT: Recently, intrinsic signal optical imaging has been widely used as a routine procedure for visualizing cortical functional maps. We do not, however, have a well-established imaging method for visualizing cortical functional connectivity indicating spatio-temporal patterns of activity propagation in the cerebral cortex. In the present study, we developed a novel experimental setup for investigating the propagation of neural activities combining the intracortical microstimulation (ICMS) technique with voltage sensitive dye (VSD) imaging, and demonstrated the feasibility of this setup applying to the measurement of time-dependent intra- and inter-hemispheric spread of ICMS-evoked excitation in the cat visual cortices, areas 17 and 18. A microelectrode array for the ICMS was inserted with a specially designed easy-to-detach electrode holder around the 17/18 transition zones (TZs), where the left and right hemispheres were interconnected via the corpus callosum. The microelectrode array was stably anchored in agarose without any holder, which enabled us to visualize evoked activities even in the vicinity of penetration sites as well as in a wide recording region that covered a part of both hemispheres. The VSD imaging could successfully visualize ICMS-evoked excitation and subsequent propagation in the visual cortices contralateral as well as ipsilateral to the ICMS. Using the orientation maps as positional references, we showed that the activity propagation patterns were consistent with previously reported anatomical patterns of intracortical and interhemispheric connections. This finding indicates that our experimental system can serve for the investigation of cortical functional connectivity.
Journal of Neural Engineering 10/2009; 6(6):066002. · 3.84 Impact Factor
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ABSTRACT: Surface planarization and modification of a patterned surface were demonstrated using gas cluster ion beam (GCIB). Grooves with 100–400 nm intervals were formed on amorphous carbon films using focused ion beams to study the special frequency dependence of the planarization. Also, line and space patterns were fabricated on Si substrates, and amorphous carbons were deposited as a model structure of discrete track media. Subsequently, surface planarization using Ar-GCIB was carried out. After GCIB irradiations, all of the grooves were completely removed, and a flat surface was realized. And it showed that GCIB irradiation planarized grooves without huge thickness loss. From the power spectrum density of an atomic force microscope, GCIB preferentially removed grooves with small intervals. It was found from energy dispersive x-ray spectroscopy that surface planarization without severe damage in the amorphous carbon and magnetic layers was carried out with GCIB.
Journal of Applied Physics 05/2009; · 2.17 Impact Factor
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ABSTRACT: The authors propose a single-pass forming technique for three-dimensional microstructures by shearing multilayer thin films. At a high strain rate, when strain is applied to a material at a speed higher than that of plastic wave propagation, the material is generally fractured without plastic deformation. In their experiment, a punch freely falling onto the back of a microfabricated mold allowed a high strain rate to be applied to the substrate. Multilayer thin films of eight evaporated layers of 250-nm-thick Si and SiO were successfully deformed to the bottom layer when the strain rate was over 1000–1500 s <sup>-1</sup> .
Journal of vacuum science & technology. B, Microelectronics and nanometer structures: processing, measurement, and phenomena: an official journal of the American Vacuum Society 10/2008; · 1.34 Impact Factor
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ABSTRACT: In normal speech, coordinated activities of intrinsic laryngeal muscles suspend a glottal sound at utterance of voiceless consonants, automatically realizing a voicing control. In electrolaryngeal speech, however, the lack of voicing control is one of the causes of unclear voice, voiceless consonants tending to be misheard as the corresponding voiced consonants. In the present work, we developed an intra-oral vibrator with an intra-oral pressure sensor that detected utterance of voiceless phonemes during the intra-oral electrolaryngeal speech, and demonstrated that an intra-oral pressure-based voicing control could improve the intelligibility of the speech. The test voices were obtained from one electrolaryngeal speaker and one normal speaker. We first investigated on the speech analysis software how a voice onset time (VOT) and first formant (F1) transition of the test consonant-vowel syllables contributed to voiceless/voiced contrasts, and developed an adequate voicing control strategy. We then compared the intelligibility of consonant-vowel syllables among the intra-oral electrolaryngeal speech with and without online voicing control. The increase of intra-oral pressure, typically with a peak ranging from 10 to 50 gf/cm2, could reliably identify utterance of voiceless consonants. The speech analysis and intelligibility test then demonstrated that a short VOT caused the misidentification of the voiced consonants due to a clear F1 transition. Finally, taking these results together, the online voicing control, which suspended the prosthetic tone while the intra-oral pressure exceeded 2.5 gf/cm2 and during the 35 milliseconds that followed, proved efficient to improve the voiceless/voiced contrast.
Journal of Voice 08/2008; 22(4):420-9. · 1.39 Impact Factor
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ABSTRACT: Neural prostheses for restoring lost functions can benefit from selective activation of nerves with limited number and density of electrodes. Here, we show by simulations and animal experiments that multipoint simultaneous stimulation with a surface electrode array can selectively activate nerves in a bundle at a desired location in between the array or at a desired depth, which are referred to as lateral or depth-wise gating stimulation, respectively. The stimulation broadly generates action potentials with cathodic source electrodes, and simultaneously blocks unnecessary propagation with downstream anodic gate electrodes. In general, stimulation with a small diameter electrode can affect a nearly hemispherical region, while a large electrode is effective at a more vertically compressed region, i.e., a surface of nerve bundle. The gating stimulation takes advantage of the size effects by utilizing an asymmetrical electrode array. The array of the lateral gating stimulation is designed to have four electrodes; a pair of large source electrodes and a pair of small gate electrodes. The depth-wise gating stimulation array consists of two electrodes; a large gate and small source electrodes. The simulation first demonstrated that appropriate combination of currents at the source and gate electrodes can change recruitment patterns of nerves with lateral or depth-wise selectivity as desired. We then applied the lateral gating stimulation on the rat spinal cords and obtained a preliminary support for the feasibility.
IEEE Transactions on Biomedical Engineering 04/2007; 54(3):563-9. · 2.28 Impact Factor
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ABSTRACT: The authors propose a light-addressable planar electrode with a simple three-layer laminated structure that can induce pinpoint neuronal activation on the culture substrate. The structure consists of a tin oxide ( Sn O <sub>2</sub>) , hydrogenated amorphous silicon (a- Si : H ) , and passivation layer. The passivation layer was a spin-coated low-conductive zinc antimonate ( Zn O Sb <sub>2</sub> O <sub>5</sub>) -dispersed epoxy, which was proved to be effective for preventing penetration of culture medium and thus avoiding deterioration of a- Si : H layer. Illumination to the electrode locally elevated the conductivity with 60-fold stimulus charge density. The fluo-4 calcium imaging of neurons cultured on the developed electrode showed that the neuronal activation was confined around the illuminated location, thus demonstrating the light-addressing capability of the proposed electrode.
Applied Physics Letters 03/2007; · 3.84 Impact Factor
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ABSTRACT: We developed a fabrication method and a liquid filling method for a nano chemical reactor that used Y-shaped nanochannels specially designed for mixing and reacting. In order to reduce the pressure loss and to utilize the characteristics of the nanochannel, inlet microchannels were fabricated just beside the nanochannels. We investigated an initial liquid filling method into the nanochannels that ensured there were no air bubbles that could cause a flow stack due to the capillary pressure. In our method, the micro- and nanochannels were filled with carbon dioxide and any remaining air during the initial liquid introduction was dissolved utilizing the high solubility of carbon dioxide. We propose that chemical reactions in nanospaces can be realized by utilizing these fabrication and liquid introduction techniques.
Analytical Sciences 05/2006; 22(4):529-32. · 1.25 Impact Factor
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ABSTRACT: Auditory evoked potentials (AEPs) in the temporal cortex have typical slow positive/negative (P1/N1) biphasic waves, which are occasionally associated with an additional earlier small deflection (P0/N0). In the present paper, we attempted to address the neural origin of P0/N0 deflection by the independent component analysis (ICA) of densely mapped cortical AEPs of rats. The ICA results suggest that the deflection appears when subcortical contribution to AEP is equal to or larger than cortical contribution.
Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 02/2006; 1:2284-7.
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ABSTRACT: Conventional multielectrode arrays (MEAs) cannot always access desired neurons due to low electrode density and small number of electrode. To overcome this problem, we propose a light-addressable planar electrode on a glass substrate. The electrode has a 3-layer structure, namely a transparent SnO2 layer, an hydrogenated amorphous silicon (a-Si:H) layer, and a passivation layer. Illumination to the a-Si:H layer increases the conductivity of a-Si:H and creates a virtual electrode at the surface of the illuminated site. In the present study, we developed a low-conductive zinc antimonate-dispersed epoxy layer. This layer could successfully prevent penetration of culture medium and thus deterioration of a-Si:H layer. A fluo-4 calcium imaging demonstrated that, when the whole area of electrode was illuminated, negative-monophasic voltage-controlled pulses could also successfully activate neurons cultured on the electrode. Moreover, the focused illumination to the electrode resulted in the selective activation of neurons around the illuminated area.
Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 02/2006; 1:648-51.
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ABSTRACT: Existing studies have demonstrated interfield differences in functional organizations and neuronal responsive properties at a single neuron level in the auditory cortex, suggesting complicated encoding of sound frequency and intensity. The objective of present work is, by characterizing cortical auditory evoked potentials (AEPs), to bridge neural characteristics between a single neuron and field levels and to identify the interfield differences in the auditory cortex specifically in terms of spatial representation, which will be useful in guiding future unit studies. The AEP mapping found that each of auditory fields, which could be identified by a different tonotopic representation, showed interfield differences in an intensity-dependent spatial change, amplitude, latency, and amplitude-SPL (sound pressure level) function. These results also showed that many aspects of cortical representation were based on the cochlear properties, yet some were inconsistent. The intensity-dependent shift of activation in AI paralleled the tonotopic axis, which was similar to the place code in cochlea, while the shift in AAF and VAF did not parallel. Nevertheless, the amplitude-SPL function suggested that an underlying mechanism of all these shifts can be a compressive nonlinearity to CF tone, which is possibly formed in the cochlea and still preserved in the cortex. These results suggest that each field modifies the representation to handle a different aspect of sound information, which can be better analyzed than the cochlear representation.
Hearing Research 01/2006; 210(1-2):9-23. · 2.70 Impact Factor
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ABSTRACT: Auditory brainstem implants (ABI) that electrically stimulate the surface of cochlear nucleus have been clinically used for the rehabilitation of deaf patients with bilateral vestibular schwannomas. The change of pitch perception with an active electrode location is not as clear in ABIs as in cochlear implants, a factor which might play a role in poorer speech performance in ABIs. The objective of present work was to develop an animal ABI model that could provide physiological data for future ABI development and optimization. The experimental system included a penetrating microelectrode array for microstimulation of the cochlear nucleus and a surface microelectrode array for mapping evoked potentials over the auditory cortex. We first obtained tone-evoked cortical activation patterns, which represented a place code of the frequency and intensity of test tones, i.e., the ampli-tonotopic organization, and compared the patterns with those evoked by cochlear nuclear microstimulation. Our experimental results demonstrated that microstimulation of both the dorsal and ventral cochlear nucleus (DCN and VCN) could access the cortical ampli-tonotopic organization as acoustic stimuli did. We also found that the cortical dynamic range was wider for the DCN than VCN stimulation and for the low-frequency than for the high-frequency pathway. The present results have great implications for improved ABI performance.
IEEE Transactions on Biomedical Engineering 08/2005; 52(7):1333-44. · 2.28 Impact Factor
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ABSTRACT: We developed and evaluated an intra-oral electrolaryngeal speech aid system for those who could not acquire common alaryngeal speech or for early post-surgery speech rehabilitation. Our system consisted of a denture-base intra-oral vibrator, a wireless miniature fingertip switch and a controller. To produce natural speech, the fingertip switch produced binary commands of voicing and accent and the controller implemented the pitch generation model using the commands. We first estimated the intelligibility of consonant-vowel syllables produced by our system. We then obtained the feedback about the system from the Japanese users on the basis of their daily life use, and evaluated the possibility and acceptability as an alaryngeal speech aid. Although the users were less satisfied at the intra-oral electrolarynx, the intelligibility of the intra-oral electrolarygeal speech was comparable to that of transcervical electrolaryngeal speech, and most of them were willing to employ it if they lost their current electrolaryngeal speech. According to the feedbacks from the users, a completely wire-free system and less eye-catching designs would make the prosthesis more acceptable. These results placed the intra-oral electrolarynx as a useful option of alaryngeal speech aids and encouraged the further development of the intra-oral electrolarynx.
Auris Nasus Larynx 07/2005; 32(2):157-62. · 0.76 Impact Factor
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ABSTRACT: This paper provides a detailed process flow for fabricating an easy-to-prepare, inexpensive, dense array of tungsten microelectrodes. We designed the process flow to minimize routine tasks by separating an initial preparation of a master mold from a routine preparation of substrate replication, array assembly and tip processing. Sandblast processing first produced a glass mold with a pattern of a series of protruding lines at a requested interval of a few hundred micrometers. Copying the groove pattern onto polystyrene mass-produced a replica substrate. Tungsten probes were then aligned on the substrate, and the tips of probes were finely processed in the block.
IEEE Transactions on Biomedical Engineering 06/2005; 52(5):952-6. · 2.28 Impact Factor
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ABSTRACT: Prevailing studies of auditory systems pay most attention to the dynamic temporal changes of sound intensity, but poorly enlighten the encoding of steady-state aspects. Using tone bursts as test stimuli, we epipially map auditory evoked potentials over the rat auditory cortex and investigate how the cortex represents the dynamic and steady states. Our results demonstrate that all of the auditory fields investigated potentially have at least two strategies to represent the two states; a temporal combination of early and late components of the potentials, and a spatial combination of an arbitrary component. In addition, the optimal combination that can distinguish between the two states differs across auditory fields, suggesting robust analyses of sound intensity in the auditory cortex.
Neuroreport 03/2005; 16(2):137-40. · 1.66 Impact Factor
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ABSTRACT: We epipially mapped tone-burst-evoked potentials over the rat auditory cortex, and investigated the representation of intensity information. The experiments were designed to elucidate how the auditory cortex represents a steady-state plateau sound pressure level (SPL) and dynamic onset temporal structure, i.e., the rate of pressure change (in Pa/s), and how the representations differ across the auditory fields. The anterior and ventral fields have spatial axes of the rate of pressure change. Characteristic frequency (CF) locations mainly handle the dynamic state, while off-CF locations have the potential to code the steady state. Each field represents the intensity information differently, particularly at the off-CF locations. These results suggest that intensity information is distributed in various aspects in the multiple auditory fields.
Neuroreport 10/2004; 15(13):2061-5. · 1.66 Impact Factor
