检索结果-内蒙古大学图书馆

Audiograms of five species of rodents: implications for the evolution of hearing and the perception of pitch

HEARING RESEARCH 2001年第1-2期157卷 138-152页

作者： Heffner, RS Koay, G Heffner, HE Univ Toledo Dept Psychol Toledo OH 43606 USA

Behavioral audiograms were determined for five species of rodents: groundhog (Marmota monax), Chipmunk (Tamias striatus), Darwin's leaf-cared mouse (Phyllotis darwinii), golden hamster (Mesocricetus auratus), and Egyptian spiny mouse (Acomys cahirinus). The high-frequency hearing of these animals was found to vary inversely with interaural distance, a typical mammalian pattern. With regard to low-frequency hearing, the animals fell into two groups: those with extended low-frequency hearing (chipmunks, groundhogs, and hamsters hear below 100 Hz) and those with restricted low-frequency hearing (spiny and leaf-eared mice do not hear appreciably below 1 kHz). An analysis of mammalian hearing reveals that the distribution of low-frequency hearing limits is bimodal with the two distributions separated by a gap from 125 to 500 Hz. The correspondence of this dichotomy with studies of temporal coding raises the possibility that mammals that do not hear below 500 Hz do not use temporal encoding for the perception of pitch. (C) 2001 Published by Elsevier Science B.V.

关键词： audiogram evolution frequency coding groundhog chipmunk leaf-eared mouse hamster spiny mouse

来源：评论

学校读者我要写书评

暂无评论

A phylogenetic analysis of the tropidurine lizards (Squamata: Tropiduridae), including new characters of squamation and epidermal micro structure

引用

ZOOLOGICAL JOURNAL OF THE LINNEAN SOCIETY 2000年第2期128卷 189-233页

作者： Harvey, MB Gutberlet, RL Univ Texas Dept Biol Arlington TX 76019 USA

Characters of scale surface microstructure are combined with 'traditional' morphological characters in a phylogenetic analysis of the Tropidurini. Tropidurid lizards show variation in types of coarse and fine scale surface microstructure, in the anatomical distribution of different scale surface features, and in scale organ morphology and distribution. The morphology of the inner surface zone of scales is here described for the first time using scanning electron microscopy. Our phylogeny differs considerably from those proposed in earlier studies. New characters and frequency coding of polymorphic characters help resolve the problematic relationships of several species. Statistical confidence supports recognition of one large cis-Andean and one large trans-Andean clade of species. Based on our results, we synonymize Plesiomicrolophus with Microlophus and Uranoscodon with Tropidurus. The phylogenetic relationships of newly discovered Tropidurus are resolved: T. callathelys is the sister species of I: melanopleurus;I:xanthochilus is the sister species of T. spinulosus. Tropidurus spinulosus is found to be more closely related to I strobilurus and a clade of Amazonian species than to I: melanopleurus. The species previously placed in Uracentron are more closely related to species previously placed in Plica than to T. strobilurus as previously thought. (C) 2000 The Linnean Society or London.

关键词： Tropidurus Uranoscodon Microlophus Plesiomicrolophus microdermatoglyphics epidermis frequency coding systematics

来源：评论

学校读者我要写书评

暂无评论

coding efficiency and information rates in transmembrane signaling

引用

BIOSYSTEMS 2000年第1-3期55卷 15-22页

作者： Prank, K Gabbiani, F Brabant, G Hannover Med Sch Computat Endocrinol Grp Dept Clin Endocrinol D-30625 Hannover Germany CALTECH Computat & Neural Syst Program Div Biol 13974 Pasadena CA 91125 USA

A variety of cell types responds to hormonal stimuli by repetitive spikes in the intracellular concentration of calcium ([Ca2 + ](i)) which have been demonstrated to encode information in their frequency, amplitude, and duration. These [Ca2 + ](i)-spike trains ale able to specifically regulate distinct cellular functions. Using a mathematical model for receptor-controlled [Ca-2 (+) ](i) oscillations in hepatocytes we investigate the encoding of fluctuating hormonal signals in [Ca2 + ](i)-spike trains. The transmembrane information transfer is quantified by using an information-theoretic reverse-engineering approach which allows to reconstruct the dynamic hormonal stimulus from the [Ca2 + ](i)-spike trains. This approach allows to estimate the accuracy of coding as well as the rate of transmembrane information transfer. We found that up to 87% of the dynamic stimulus information can be encoded in the [Ca-2 (+) ](i)-spike train at a maximum information transfer rate of 1.1 bit per [Ca2 + ](i)-spike. These numerical results for humoral information transfer are in the same order as in a number of sensory neuronal systems despite several orders of magnitude different time scales of operation suggesting a universal principle of information processing in both biological systems. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.

关键词： intracellular calcium oscillations hepatocyte stimulus reconstruction information rate frequency coding temporal coding

来源：评论

学校读者我要写书评

暂无评论

The sequential processing of visual motion in the human electroretinogram and visual evoked potential

引用

VISUAL NEUROSCIENCE 2000年第4期17卷 631-646页

作者： Korth, M Rix, R Sembritzki, O Univ Erlangen Nurnberg Dept Ophthalmol D-91054 Erlangen Germany Siemens AG Med Engn Grp D-91052 Erlangen Germany

Mechanisms of motion vision in the human have been studied extensively by psychophysical methods but less frequently by electrophysiological techniques. It is the purpose of the present investigation to study electrical potentials of the eye (electroretinogram, ERG) and of the brain (visual evoked potential, VEP) in response to moving regular square-wave stripe patterns spanning a wide range of contrasts, spatial frequencies, and speeds. The results show that ERG amplitudes increase linearly with contrast while VEPs, in agreement with the literature, show an amplitude saturation at low contrast. Furthermore, retinal responses oscillate with the fundamental temporal stimulus frequency of the moving pattern while brain responses do not. In both the retina and the brain, the response amplitudes are tuned to certain speeds which is in agreement with the nonlinear correlation-type motion detector. Along the ascending slopes (which means increasing amplitudes) of the tuning functions, the ERG curves overlap at all spatial frequencies if plotted as a function of temporal stimulation frequency. The ascending slopes of the tuning functions of the VEP overlap if plotted as a function of speed. The descending slopes (which means decreasing amplitudes) of the tuning functions show little (ERG) or no (VEP) overlap and the waveforms at high speeds approach pattern-offset-onset responses. These observations suggest that in the retina motion processing along the ascending slopes of the tuning curves takes place by coding the temporal stimulation frequency which depends on the spatial frequency of the moving pattern. In the brain, however, motion processing is by speed independent of spatial frequency. Simple calculations show that the VEP information is decoded from the ERG signal into a speed signal.

关键词： visual motion processing electroretinogram visual evoked potential speed coding frequency coding

来源：评论

学校读者我要写书评

暂无评论

Cochlear mechanisms of frequency and intensity coding .1. The place code for pitch

引用

HEARING RESEARCH 1997年第1-2期111卷 65-75页

作者： Chatterjee, M Zwislocki, JJ SYRACUSE UNIV INST SENSORY RESSYRACUSENY 13244

In the past, several researchers have reported a substantial shift in the peak of the tone-evoked excitation pattern toward the base of the cochlea following an increase in the SPL of the stimulating tone. Evidence for such peak shifts has been found in the responses of auditory nerve fibers, cochlear microphonics, and the responses of outer hair cells and supporting cells in the cochlea, as well as in basilar membrane vibration measurements, and indirectly, in psychophysical data. However, direct evidence for such a peak shift in inner hair cell (IHC) responses has been relatively sparse. If the peak shift is preserved in the information conveyed to the auditory nerve fibers by the IHCs, the classical 'place theory' for frequency coding in the cochlea requires modification. In this study, the nature and extent of the SPL-dependent peak shift is examined with the help of recordings in the IHCs and other cells of the organ of Corti in the 0.5-2.5 kHz region of the Mongolian gerbil cochlea. It is demonstrated that the peak shift is a universal phenomenon in the diverse cell types in this region of the cochlea. Most importantly, a large SPL-dependent peak shift is demonstrated in IHC responses. On the other hand, the recordings indicate that the apical cutoff of the spatial excitation pattern is SPL-independent. We conclude, therefore, that the place theory of pitch perception must be abandoned or at least modified.

关键词： cochlea hair cell peak shift pitch frequency coding

来源：评论

学校读者我要写书评

暂无评论

Neural coding in antennal olfactory cells of tsetse flies (Glossina spp.)

引用

CHEMICAL SENSES 1998年第5期23卷 521-530页

作者： Voskamp, KE Noorman, N Mastebroek, HAK Van Schoot, NEG Den Otter, CJ Univ Groningen Dept Anim Physiol NL-9750 AA Haren Netherlands Univ Groningen Dept Biophys NL-9750 AA Haren Netherlands

Spike trains from individual antennal olfactory cells of tsetse flies (Glossina spp.) obtained during steady-state conditions (spontaneous as well as during stimulation with 1-octen-3-ol) and dynamic stimulation with repetitive pulses of 1-octen-3-ol were investigated by studying the spike frequency and the temporal structure of the trains. In general, stimulation changes the intensity of the spike activity but leaves the underlying stochastic structure unaffected. This structure turns out to be a renewal process. The only independently varying parameter in this process is the mean interspike interval length, suggesting that olfactory cells of tsetse flies may transmit information via a frequency coding. In spike records with high firing rates, however, the stationary records had significant negative first-order serial correlation coefficients and were non-renewal. Some cells in this study were capable of precisely encoding the onset of the odour pulses at frequencies up to at least 3 Hz. Cells with a rapid return to pre-stimulus activity at the end of stimulation responded more adequately to pulsed stimuli than cells with a long increased spike frequency. While short-firing cells process information via a frequency code, long-firing cells responded with two distinctive phases: a phasic, non-renewal response and a tonic, renewal response which may function as a memory of previous stimulations.

关键词： M-morsitans Pheromone Adaptation Receptors Responses Neurons Diptera Moths Diptera Moth Pheromones octenol frequency coding spikes Cells Smell spike cells Stimuli Stimulation Glossina Spike Neurons

来源：评论

学校读者我要写书评

暂无评论

Research advances for cochlear implants

引用

Auris Nasus Larynx 1998年第1期25卷 73-87页

作者： Clark, Graeme M. The Hum. Commun. Research Centre Coop. Res. Ctr. Cochlear Implant S. Melbourne Australia The Bionic Ear Institute Melbourne Australia

Considerable progress has been made with speech processing for multiple- channel cochlear implants, with a mean open-set CNC word score of 40% for electrical stimulation alone for the Nucleus SPEAK strategy. Further advances should be achieved through the following: beam-forming dual microphone systems for hearing in noise;better reproduction of the coding of sound frequencies;and taking advantage of plasticity in the central auditory pathways in young children. The reproduction of frequency coding will be facilitated with speech processors such as the Nucleus 24 system which can provide higher stimulus rates, and a new generation of electrode arrays where a greater number of electrodes lie close to the spiral ganglion cells.

关键词： Auditory nerve Beam-forming Cochlear implants Electrical stimulation frequency coding Plasticity Speech processing

来源：评论

学校读者我要写书评

暂无评论

Electrical stimulation of the auditory nerve: The coding of frequency, the perception of pitch and the development of cochlear implant speech processing strategies for profoundly deaf people

引用

CLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY 1996年第9期23卷 766-776页

作者： Clark, GM Special Research Centre for Human Communication Research Department of Otolaryngology The University of Melbourne The Co-operative Research Centre for Cochlear Implant Speech and Hearing Research and The Bionic Ear Institute Melbourne Victoria Australia

1. The development of speech processing strategies for multiple-channel cochlear implants has depended on encoding sound frequencies and intensities as temporal and spatial patterns of electrical stimulation of the auditory nerve fibres so that speech information of most importance for intelligibility could be transmitted, 2. Initial physiological studies showed that rate encoding of electrical stimulation above 200 pulses/s could not reproduce the normal response patterns in auditory neurons for acoustic stimulation in the speech frequency range above 200 Hz and suggested that place coding was appropriate for the higher frequencies, 3. Rate difference limens in the experimental animal were only similar to those for sound up to 200 Hz. 4. Rate difference limens in implant patients were similar to those obtained in the experimental animal. 5. Satisfactory rate discrimination could be made for durations of 50 and 100 ms, but not 25 ms, This made rate suitable for encoding longer duration suprasegmental speech information, but not segmental information, such as consonants, The rate of stimulation could also be perceived as pitch, discriminated at different electrode sites along the cochlea and discriminated for stimuli across electrodes, 6. Place pitch could be scaled according to the site of stimulation in the cochlea so that a frequency scale was preserved and it also had a different quality from rate pitch and was described as tonality, Place pitch could also be discriminated for the shorter durations (25 ms) required for identifying consonants, 7. The inaugural speech processing strategy encoded the second formant frequencies (concentrations of frequency energy in the mid frequency range of most importance for speech intelligibility) as place of stimulation, the voicing frequency as rate of stimulation and the intensity as current level, Our further speech processing strategies have extracted additional frequency information and coded this as place of stimulation,

关键词： auditory nerve cochlear implant electrical stimulation electrophysiology frequency coding psychophysics speech processing

来源：评论

学校读者我要写书评

暂无评论

MULTIfrequency TRELLIS coding WITH LOW-DELAY FOR FADING CHANNELS

引用

IEEE TRANSACTIONS ON COMMUNICATIONS 1993年第10期41卷 1450-1459页

作者： LEUNG, YS WILSON, SG KETCHUM, JW UNIV VIRGINIA DEPT ELECT ENGNCHARLOTTESVILLEVA 22901 GTE LABS INC DEPT MOBILE SYSTWALTHAMMA 02254

The paper describes an L-frequency trellis coding scheme designed for fading channels, which provides diversity up to order L. L-frequency coding is advantageous over channel coding schemes that achieve implicit time-diversity through trellis coding in conjunction with time-interleaving, because it requires negligible end-to-end delay. We will derive an upper-bound for the probability of symbol error of the L-frequency code. Based on this upper-bound, we will then deduce the design criteria for optimum L-frequency codes. A numerical approximation to this upper-bound will also be presented. We have designed a two-state and two four-state, two-frequency codes. Through simulations, we have found that relative to the traditional dual frequency diversity approach, our two-state and four-state codes achieve 3 and 4 dB coding gains, respectively. If desired, we can translate this energy efficiency gain to a spectral efficiency gain. A brief discussion on the difference in code design techniques for the Gaussian channel and the fading channel will also be presented.

关键词： frequency coding spectral efficiency numerical approximation Gaussian channels BISTABILITY Trellis codes Fading channels Codes multiple-frequency DESIGN CRITERIA Uppers

来源：评论

学校读者我要写书评

暂无评论

OPEN CONDUCTOR DETECTOR SYSTEM

引用

IEEE TRANSACTIONS ON POWER DELIVERY 1992年第3期7卷 1643-1651页

作者： WESTROM, AC LINDERS, J JEERINGS, D COKKINIDES, GJ MELIOPOULOS, APS AYOUB, AH GEORGIA INST TECHNOL SCH ELECT ENGNATLANTAGA 30332 UNIV S CAROLINA DEPT ELECT ENGNCOLUMBIASC 29208 GEORGIA POWER CO ATLANTAGA 30302

An open phase conductor detector system is described consisting of one or more transmitters and a receiver which communicate through the distribution line neutral conductor. The transmitter(s) detects the open phase conductor by monitoring the phase conductor voltage using redundant inputs. When an open phase conductor is detected, the transmitter injects a signal to the distribution line neutral conductor by means of a coupling current transformer (CT). The signal is frequency and duration coded. The receiver decodes the signal and generates a trip signal which may activate a breaker, a ground switch, or a recloser causing isolation of the distribution line with the open (downed) phase conductor. The system is presently implemented for single distribution lines. A prototype open conductor detector system has been constructed and field tested on a Georgia Power Company distribution system.

关键词： OPEN CONDUCTOR CURRENT INJECTION CURRENT DETECTION frequency coding

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：