Auditory evoked response: meaningfulness of stimuli and interhemispheric asymmetry

Interhemispheric asymmetries of different magnitudes were observed in human cortical auditory evoked responses to speech and sound-effect stimuli. The wave with peak asymmetry occurred 100 milliseconds after signal onset. The amount of asymmetry of the amplitude of this wave was related to the meaningfulness to the subject of the auditory stimulus rather than to the mere use of verbal versus nonverbal materials.     

Auditory evoked potentials during speech perception

Neural responses evoked by the same binaural speech signal were recorded from ten right-handed subjects during two auditory identification tasks. One task required analysis of acoustic parameters important for making a linguistic distinction, while the other task required analysis of an acoustic parameter which provides no linguistic information at the phoneme level. In the time interval between stimulus onset and the subjects' identification responses, evoked potentials from the two tasks were significantly different over the left hemisphere but identical over the right hemisphere. These results indicate that different neural events occur in the left hemisphere during analysis of linguistic versus nonlinguistic parameters of the same acoustic signal.     

Electrical signs of selective attention in the human brain

Auditory evoked potentials were recorded from the vertex of subjects who listened selectively to a series of tone pips in one ear and ignored concurrent tone pips in the other ear. The negative component of the evoked potential peaking at 80 to 110 milliseconds was substantially larger for the attended tones. This negative component indexed a stimulus set mode of selective attention toward the tone pips in one ear. A late positive component peaking at 250 to 400 milliseconds reflected the response set established to recognize infrequent, higher pitched tone pips in the attended series.     

Electrographic evidence of impaired brain function in chronically anxious patients

In a study of cerebral function by electroencephalographic techniques the following observations have been made. (i) In intact subjects, repeated stimulation with bright light causes a predictable change (alpha blocking) in the electroencephalogram, whereas repeated auditory stimulation does not. (ii) If, however, an auditory stimulus is presented repeatedly just before the visual stimulus, the sound temporarily but predictably acquires the property of the light to suppress the alpha activity. (iii) This linkage between sound and light occurs much less frequently in human subjects with known amounts of structural brain damage. (iv) A similar electrophysiological defect, implying impairment of brain function, occurs in patients showing severe anxiety during prolonged periods of difficulty in over-all adaptation.     

Neural mechanisms of sound localization in an echolocating bat

The mustache bat emits a three-harmonic echolocation pulse. At the external ear, large interaural intensity differences are generated only when a sound originates within a limited area of two-dimensional space, and this area is different for each pulse harmonic. As a consequence, the external ear generates pronounced binaural spectral cues containing two-dimensional spatial information. This information is encoded in the inferior colliculus by neurons tuned to one of the harmonics and sensitive to interaural intensity differences.     

Somatically evoked magnetic fields of the human brain

The human brain is found to produce a magnetic field near the scalp which varies in synchrony with periodic electrical stimulation applied to a finger. Use of a highly sensitive superconducting quantum interference device as a magnetic field detector reveals that the brain's field is sharply localized over the primary projection area of the sensory cortex contralateral to the digit being stimulated. The phase of the response at the stimulus frequency varies monotonically with the repetition rate and at intermediate frequencies yields a latency of approximately 70 milliseconds for cortical response.     

Entrainment of circadian rhythms by sound in Passer domesticus

The circadian locomotor rhythm of house sparrows was entrained by a sound stimulus. The birds were maintained at a constant temperature in, dim green light. The entraining agent was 4 (1/2) 12 hours of tape-recorded bird song ,played each day. Variations in the response to this stimulus have been correlated with individual variations in free-running period. This is the first clear demonstration that a biological clock can be influenced by sound stimuli.     

Separation of signal transduction and adaptation functions of the aspartate receptor in bacterial sensing

In order to investigate the functions of stimulus recognition, signal transduction, and adaptation, the aspartate receptor gene for bacterial chemotaxis in Salmonella typhimurium has been sequenced and modified. A carboxyl-terminal truncated receptor was shown to bind aspartate and to transmit a signal to change motility behavior. However, the truncated receptor showed greatly reduced methyl-accepting capacity, and did not allow adaptation to the sensory stimulation. The separation of receptor functions by alteration of primary structure emphasizes that the receptor is directly involved in adaptation and is not solely a device for transmitting a signal across a membrane.     

Nonresonant multiple spin echoes

Nonresonant manipulation of nuclear spins can probe large volumes of sample situated in inhomogeneous fields outside a magnet, a geometry suitable for mobile sensors for the inspection of roads, buildings, and geological formations. However, the interference by Earth's magnetic field causes rapid decay of the signal within a few milliseconds for protons and is detrimental to this method. Here we describe a technique to suppress the effects of Earth's field by using adiabatic rotations and sudden switching of the applied fields. We observed hundreds of spin echo signals lasting for more than 600 milliseconds and accurately measured the relaxation times of a liquid sample.     

Activity and responsivity in rats after magnesium pemoline injections

Rats injected intraperitoneally with magnesium pemoline avoided a buzzing sound (conditioned stimulus) associated with an electric shock to the feet (unconditioned stimulus) more frequently than controls. Drug-injected rats did not avoid the foot shock more frequently than controls, although the experi mental rats did have shorter response latencies fn the active avoidance task. In sub sequent experiments which measured activity changes and response to the buzzing sound alone, it was found that magnesium pemoline caused a lesser decrease in activity level and a more sustained responsivity to the buzzer's. sound than did control injections of tragacanth. This may account for the latency differences observed in the avoidance task.     

Evoked potentials and auditory reaction time in monkeys

Monkeys with bipolar stimulating and recording electrodes in primary auditory cortex were trained to release a key to the onset of a pure tone. Substitution of direct cortical stimulation for the pure tone resulted in a reduction of 15 milliseconds In the latency of the behavioral response. This changed latency agreed with the latency of the primary evoked potential recorded from the animals. Systematic related changes in the amplitude of the central response and in the latency of the behavioral response followed changes in the intensity and frequency of the acoustic stimulus.     

Attention shifts in a maintained discrimination

Pigeons received lights of varying wavelengths paired with sounds of varying frequencies; pecking was reinforced only at one stimulus combination. Then either the light or the sound was held constant at its reinforced value, while the other stimulus continued to vary. Subsequent tests showed that the constant stimulus had lost much of its control over the birds' responses.     

管道金属蚀失量检测聚焦信号加载理论研究

针对瞬变电磁法(TEM)在埋地金属管道金属蚀失量检测中,由于每个检测点覆盖的管道距离较长,难以满足实际检测精度需求的现状,对磁场信号的聚焦加载技术进行研究.基于经颅脑刺激用磁聚焦线圈技术,设计了一种适用于埋地金属管道检测的线圈阵列,并利用遗传算法对线圈阵列的电流大小及相位进行优化,给出了线圈阵列在计算区域内的磁场分布和二维等高线图,数值计算结果表明:该线圈阵列在计算区域产生的磁场具有良好的聚焦功能,可用于埋地金属管道腐蚀检测.     

Rats smell in stereo

It has been hypothesized that rats and other mammals can use stereo cues to localize odor sources, but there is limited behavioral evidence to support this hypothesis. We found that rats trained on an odor-localization task can localize odors accurately in one or two sniffs. Bilateral sampling was essential for accurate odor localization, with internasal intensity and timing differences as directional cues. If the stimulus arrived at the correct point of the respiration cycle, internasal timing differences as short as 50 milliseconds sufficed. Neuronal recordings show that bulbar neurons responded differentially to stimuli from the left and stimuli from the right.     

利用PC机实现B&K2230型声级计性能的拓展

利用 PC机和 B& K2 2 30声级计内部相关电路组成新测量系统 ,通过声级计对系列稳定纯音的测量实现对该新系统的标定 .在此基础上 ,应用信号数字处理技术进行编程 ,使系统具有音频信号频谱分析、图形显示和打印等功能 .结果表明 ,在测量精度不变的前提下 ,新测量系统在测量和数据处理方面明显优于原声级计     

鸡舍多功能程序控制仪的研制

介绍适用于鸡舍光、声刺激程序控制仪的结构、工作原理、特点以及初步试验结果。     

A neural map of auditory space in the owl

Auditory units that responded to sound only when it originated from a limited area of space were found in the lateral and anterior portions of the midbrain auditory nucleus of the owl (Tyto alba). The areas of space to which these units responded (their receptive fields) were largely independent of the nature and intensity of the sound stimulus. The units were arranged systematically within the midbrain auditory nucleus according to the relative locations of their receptive fields, thus creating a physiological map of auditory space.     

Detection thresholds as a function of interval separation between two successive targets

Detection thresholds for two successive targets varied systematically with the interval between the two puclses. At intervals of 10 to 30 milliseconds, and again at 80 to 200 milliseconds, the threshold was lowered as compared to that for a single target, while at a separation of 50 to 60 milliseconds, the threshold was raised.     

输气管道泄漏音波的产生及传播特性

对输气管道泄漏音波的产生和传播特性进行研究,分析了泄漏音波产生的形式,获得了音波信号的时域、频域及时频特征。结果显示：泄漏音波主要由介质与管道相互作用产生的单极子、偶极子和四极子声源所引起,表现为时域上能量突变,但所占时域较窄,所占频域较宽,主要能量集中在0-100Hz。利用软件对泄漏音波在特殊管件（弯管、变径、分支）中的传播特性进行模拟研究,并利用高压输气管道泄漏装置进行试验研究,分析了泄漏音波信号的传播规律,确定了影响音波信号衰减的主要因素。结果显示：音波在管内以平面波形式传播,随着传播距离的增大,音波基本呈指数规律衰减,在较低泄漏量下,泄漏音波信号幅值基本与泄漏孔径无关：音波信号经弯管和直管的损失基本为0,经分支和变径管损失较大。根据拟合计算结果,对于现有型号的音波传感器,其理论安装距离可达100km,利于长输管道的泄漏检测。     

Binocular unmasking: an analog to binaural unmasking?

A visual analog to binaural unmasking was explored. The observer's task was to detect, under stereoscopic viewing conditions, an apertured sinusoidal grating added to a square patch of visual noise. In the experimental condition, the square patch of noise was presented within a frame such that the right-eye noise was a shifted version of the left-eye noise. Because of the disparity in the noise images, subjects perceived, under stereoscopic viewing conditions, that the noise patch was located behind the frame. When sinusoidal signals were added to this noise patch, the signals were clearly more detectable when the signal disparity was zero than when the signal disparity equaled that of the noise patch, demonstrating the existence of visual unmasking. Hence, under appropriate circumstances, binocular processing, in addition to providing information about depth, can also enhance the detectability of visual patterns.