脊椎体感诱发电位中的高频抑制

本文介绍了脊椎体感诱发电位的记录装置及记录方法,并在家兔脊椎处体表记录到了体感诱发电位波形。研究了高频脉冲电刺激所引起的神经兴奋对诱发电位刺激所引起的神经兴奋在脊髓发生的影响,证明了高频抑制在脊髓就能发生。同时也阐明了体表记录的脊椎体感诱发电位完全能反映出脊髓中高频抑制这样的电活动,这对理解体表记录的诱发电位所能表示的生理信息量是很有意义的。     

The Effects of Stimulus Expectancy on Evoked Brain Potentials

The effects of self-generated expectancy of stimulus content on the visual evoked potential to physically identical stimuli were studied in college students. The subject set up his own internal expectant; by choosing to see either a bright or dim Hash. When a bright or dim Hash was anticipated, the potentials evoked by u medium stimulus intensity resembled the responses elicited by an actual bright or dim flash, respectively. Significant differences in visual evoked potential amplitude were obtained between identical medium intensity stimuli depending on the stimulus intensity expected, despite (he constant physical properties of the stimulus. 1 In1 results suggest that a subject's expectancy of certain physical parameters of a stimulus are as important In determining (he resultant visual evoked potential as the actual physical features of the stimulus.     

Visual Evoked Potentials Before and After Kraepelin Performance Test in Schizophrenia

Visual evoked potentials of a group of 25 schizophrenic patients, a group of 13 neurotics, and a group of 24 healthy subjects were recorded before and after Kraepelin performance test. Soon after performance of the addition test for 15 min. amplitudes of later components (waves IV, V, and VI) of the potential were reduced in schizophrenics, while neurotic patients and healthy subjects did not show such changes.     

Orientation-Specific and Luminance Effects: Interocular Suppression of Visual Evoked Potentials in Man

The interocular transfer of orientation-specific effects was investigated using visual evoked potentials (VEPs). Monocular VEPs were obtained to either diffuse light or grids of 0° or 45° orientations flashed to one eye. The other eye continuously viewed either darkness, diffuse light or grids of 0°, 15°, 30°, or 45° orientations. Changing the continuous stimulus from darkness to diffuse light interocularly reduced the amplitude of a late VEP component (P200). Changing the orientation of the continuous stimulus primarily affected an earlier VEP component (N110). This interocular effect was orientation specific: the more similar the orientation of the flashed and continuously presented grids, the smaller the amplitude of the VEP components. The 1/2 bandwidths at 1/2 amplitude of the orientation tuning functions were 45° and 32° for the vertical and oblique test flashes respectively. This orientation-specific interocular suppression was discussed in terms of electrophysiological and psychophysical data indicating binocular orientation channels and the interactions among these channels.     

Cross-Modal Selective Attention Effects on Retinal, Myogenic, Brainstem, and Cerebral Evoked Potentials

Short latency evoked potentials were recorded during a cross-modal selective attention task to evaluate recent proposals that sensory transmission in the peripheral auditory and visual pathways can be modified selectively by centrifugal mechanisms in humans. Twenty young adult subjects attended in turn to either left-ear tones or right-field flashes presented in a randomized sequence, in order to detect infrequent, lower-intensity targets. Attention-related enhancement of longer-latency components, including the visual P105 and the auditory N1/Nd waves and T-complex, showed that subjects were able to adopt a selective sensory set toward either modality. Neither the auditory evoked brainstem potentials nor the early visual components (electroretinogram, occipito-temporal N40, P50, N70 waves) were significantly affected by attention. Measures of retinal B-waves were significantly reduced in amplitude when attention was directed to the flashes, but concurrent recordings of eyelid electromyographic activity and the electro-oculogram indicated that this effect may have resulted from contamination of the retinal recordings by blink microreflex activity. A trend toward greater positivity in the 15-50 ms latency range for auditory evoked potentials to attended tones was observed. These results provide further evidence that the earliest levels of sensory transmission are unaffected by cross-modal selective attention, but that longer latency exogenous and endogenous potentials are enhanced to stimuli in the attended modality.     

Operant Conditioning of Visual Evoked Potentials in Man

The operant conditioning technique was used to produce visual evoked response modifications in man. Our results show that: 1) 50% of our subjects are able to modify a definite component of their evoked potential. 2) These modifications still occur with irregular evoked potential intervals. 3) The criterion segment is the only part of the response which is modified; other components are not affected. 4) All components ranging from 90 to 385 msec can be modified; however, the second part of the response (after 200 msec) seems to be more easily modified.     

Cerebral Evoked Potentials to Noxious Dental Stimulation: Relationship to Subjective Pain Report

The relationship between subjective pain report and dental evoked potentials (DEP) was evaluated in 11 subjects. Brief electrical shocks were delivered to healthy, unfilled teeth and evoked potentials were recorded at three levels of pain intensity. Amplitude of major components increased with increasing pain report. Latency of major components did not change with pain report. Since intradental nerve endings consist mainly of high-threshold fibers generally associated with nociception, these results suggest that the DEP may be a useful physiological index of the acute pain experience in man.     

Stimulus Intensity Expectation and Visual Evoked Brain Potentials

In a sample of 32 adult subjects, we examined the relationship between amplitude measures of the visual evoked potential (VEP) and a subject's expectation that a stimulus would be either brighter or dimmer than the others in a series. It was found that when subjects expected a bright light flash, the VEP waveform changed in the direction associated with a stimulus intensity increase even though no actual intensity change occurred. Conversely, when subjects expected a dim light flash, the VEP waveform changed in the direction associated with a stimulus intensity decrease even though no actual intensity change occurred. The amplitude changes to the expected stimulus intensities occurred in specific VEP peaks and were related to the position of the stimulus in the sequence.     

Conditioning of Evoked Potentials in Children of Differing Intelligence

This study compared the conditioning of averaged evoked potentials in three groups of children (average age 11 yrs): (I) normals, (II) IQ between 50 and 60, (III) IQ between 20 and 50. Sound was the conditioned stimulus, light the unconditioned stimulus, 68 sessions were recorded in 34 children. Decrease in the number and in the amplitude of potentials evoked by sound was observed from group I to group III, whereas generalized slow waves increased from group I to group III. Conditioning was different in the three groups. In the normal child it modified the conditioned evoked potential to sound. In the mentally retarded child, it modified generalized slow waves and brought about the reproduction of a temporal sequence.     

Auditory Evoked Potentials and Divided Attention

In a multi-channel divided attention task, 8 subjects listened to a sequence of tones delivered at one of two stimulation rates and at one of three spatial locations (channels): left ear, right ear, and an apparent position midway between left and right ears. Subjects were instructed to monitor one, two, or all three channels and detect slightly louder target tones in the monitored channel(s). Seven listening conditions were used, three in which subjects monitored one channel and ignored the others, another three in which two channels were simultaneously monitored and the third ignored, and a further condition in which all three channels were monitored. With a high stimulation rate, the N1 component of the vertex evoked potential (latency 70–130 msec) in both attended and unattended channels significantly decreased in amplitude with an increase in the number of monitored channels. At the same time, N1 was significantly larger when a channel was attended than when it was ignored. There were no significant effects under slow stimulation rate conditions. Like N1, target detectability (d') declined with increasing monitoring load only with a fast stimulation rate, but the correspondence between these two measures was not upheld in every condition. The results indicate that with a high “information load” in a multi-channel task, selective attention increases the vertex response in all attended channels, while divided attention decreases the response in both attended and unattended channels, thus suggesting that the N1 component of the auditory evoked potential reflects the apparent division of attentional capacity among competing auditory inputs.     

Effects of Amplitude-Frequency Characteristics of a Noise-Masked Test Stimulus on the Shapes of Visual Evoked Potentials

Visual evoked potentials produced in response to a reversive checkerboard pattern presented in conditions of additive noise were recorded. Changes induced by noise in both the shapes of evoked potentials and the structure of the test stimulus were compared. The nature of changes in the shapes of evoked potentials was found to correlate with the nature of changes in the amplitude-frequency spectrum of the stimulus. These results support the gestalt psychology point of view that the visual system uses spatial frequency rather than discrete means for describing information. Translated from Rossiiskii Fiziologicheskii Zhurnal imeni I. M. Sechenova, Vol. 94, No. 8, pp. 928–944, August, 2008.     

Effects of Light Intensity and Edge Density on Visually Evoked Potentials in Rhesus Monkeys

Visually evoked potentials were recorded from bipolar electrodes implanted in the foveal and parafoveal striate, prestriate and inferotemporal cortices of mature rhesus monkeys (Macaca mulatta). The stimuli used were a blank field and three checkerboard patterns containing checks whose sizes were 2° 24′, 36′, and 9′ of visual arc. In addition to the size of the checks within the patterns, the intensity at which the stimuli were presented was also varied. In all four regions studied, check size had a significant effect on the amplitude of the average evoked potential, but intensity showed an effect only in the two striate regions. Certain regions of the visual cortex can apparently process two dimensions of a stimulus concurrently, and the same mass of neuronal tissue can participate in the processing of different dimensions of a stimulus at different times. The results are discussed in the context of existing literature concerning the evoked potential as an indicator of sensory information processing.     

葛根素对豚鼠卡那霉素耳中毒听觉诱发电位的影响

观察葛根素在豚鼠卡那霉素耳中毒中的作用。将豚鼠 30只随机分两组 :对照组 15只 ,肌注卡那霉素 40 0mg/kg/d ,共 12天 ;葛根素组 15只 ,除肌注卡那霉素 40 0mg/kg/d外 ,腹腔注射葛根素 10mg/kg/d ,共 12天。以听觉诱发电位为指标进行组间比较 ,听觉诱发电位阈值对照组明显高于葛根素组 (P <0 0 5 ) ;对照组诱发电位各波幅值则明显低于葛根素组 (P <0 0 1)。葛根素能减轻卡那霉素耳毒性 ,对卡那霉素耳中毒具有一定的保护作用 ,为耳毒性抗生素致聋的防治提供了一条新的研究途径     

Visual Evoked Potentials and Reaction Time in Normal and Dyslexic Children

This investigation compared the visual evoked responses (VERs) and reaction time (RT) performance of 24 dyslexic boys and 24 controls at four different age levels (7, 9, 11, and 13 yrs). Prescreening and matching techniques were used to eliminate differences due to social or educational deprivation, gross sensory-motor handicaps, specific neurological deficiencies, or intellectual impairment. The VER was recorded from four scalp locations (O₁, O₂, P₃, and P₄) referenced to the vertex during a detection task in which subjects were required to respond to dim flashes occurring in a train of brighter flashes. An overall hemispheric asymmetry in VER amplitude (right > left) was observed in both experimental and control subjects. Dyslexics exhibited an increased amplitude to unattended stimuli and a slower RT to attended stimuli. Normals exhibited significant correlations between RT and VER latency, dyslexics did not. There were no significant VER-IQ correlations. The results are discussed in terms of an attentional deficit hypothesis.     

Visual Evoked Potentials to Illusory Reversals of the Necker Cube

Sensory adaptation and cognitive evaluation have been proposed as explanations of illusory figure reversals. The effect of variations in the perceived orientation of a Necker cube on visual evoked potentials (VEPs) was studied to test these two hypotheses. VEPs associated with perceptual reversals and non-reversals of a Necker cube were compared with VEPs elicited by a sequence of physically varying cubical figures. Amplitude differences in the early VEP components consistent with adaptation effects were not detected. Both types of reversals were associated with a late positive component (400–700 ms), which was smaller in amplitude in the illusory condition. The late positivity to illusory reversals was also distinguished by a broad (200–700 ms) positive component over frontal and central recording sites which was absent over Oz. These findings suggest that illusory reversals are more difficult to discriminate than physical reversals, and require additional cognitive resources for evaluation.     

Contingent Negative Variation, P3 Evoked Potentials, and Antisocial Behavior

While initial investigations have found significantly lower contingent negative variation (CNV) amplitudes in adult, institutionalised antisocial groups, others have found either no group differences or significantly higher amplitudes. This study attempts to circumvent some methodological and conceptual problems in previous stud its by assessing CNV in a classical forewarned reaction time experiment in two samples of non-institutionalised normal adolescents where behavioral ratings and self-report measures were used to define Antisocial and Pro social groups. A trend toward higher P3 amplitudes to the warning stimulus (SI) observed in a previous study was also investigated by recording evoked potentials to SI. Results indicated no significant group differences in CNV and Nl amplitudes, but a significantly larger P3 amplitude in the Antisocial group in both subject samples. This latter result was viewed as consistent with Jutai and Hare's (1983) finding that psychopathic anti socials have a heightened capacity to attend to events of immediate interest.     

诱发电位快速提取方法及进展

每次刺激所产生的诱发电位的峰值和潜伏期以至波形是时变信号。随着信号处理技术的发展,诱发电位的提取方法由传统的平均叠加方法,向逐步减少累加次数,最终实现单次提取诱发响应波形,实现动态提取诱发电位的方向发展,因此对诱发电位的少次以至单次提取成为生物医学信号处理领域备受关注的一个研究课题。对近年来快速提取诱发电位的信号处理方法进行了简要的回顾,并分别从自适应滤波、小波变换、神经网络及独立成分分析等4个方面对算法进行了介绍。     

Human Brainstem Auditory Evoked Potentials Fail to Provide Evidence of Efferent Modulation of Auditory Input During Attentional Tasks

Efferent modulation of auditory input at the level of the brainstem during attention-demanding tasks has been described in animal studies. Attempts to demonstrate these effects in humans have produced conflicting results, however. These studies are reviewed with particular reference to those animal experiments that have demonstrated peripheral effects. The human experiments have used a number of attentional conditions which have not been related either to each other or to the successful animal work. Two of the most important conditions in these studies--the use of an intermodal attention task and the manipulation of attentional states--have been examined rarely or not at all in the human research. Two experiments were conducted to investigate the possibility of attention-related effects on the human brainstem auditory evoked potential. These experiments were designed to examine experimental conditions common to both successful and unsuccessful attempts to demonstrate attention-driven efferent modulation at the periphery in humans. Also examined was the gradation of attention effects on efferent modulation demonstrated in animals but never studied in humans. No significant changes in either the latency or the amplitude of the brainstem auditory evoked potential were found in any of the attention-demanding conditions. Results are discussed in terms of psychophysiological theories of attention. Also, the interpretation of the most recent animal work is questioned.     

Augmenting and Reducing of Visual Evoked Potentials in High- and Low-Sensation Seeking Humans, Cats, and Rats

High- and low-sensation seeking behaviors in human and cat are shown to be correlated with visual evoked potential (VEP) augmenting and reducing, respectively. Demonstration of this relationship in RHA/Verh and RLA/Verh rats provides a heuristic animal model with which to investigate the physiological and genetic basis of this relationship. Recent work is described which shows that VEP augmenting and reducing is a true cortical phenomenon and not merely a reflection of differences occurring at the thalamus. Recent evidence is discussed that suggests the role of diffuse subcortical monoaminergic projections to the cortex as the neurochemical basis for sensation seeking behaviors controlled by prefrontal and limbic cortex and perhaps the correlated VEP augmenting/reducing responses recorded from the posterior cortex.     

Comparing Principal Components Analyses of Evoked Potentials Recorded from Heterogeneous Groups of Subjects

Principal components analysis of evoked potentials differing between groups presents an interpretive problem, particularly in psychiatric research. Two sets of principal components and associated factor scores may appear to differ. The issue is to determine the extent to which visually differing principal components and resultant factor scores span the same factor space. Sets of evoked potentials from controls and from schizophrenics were each subjected to principal components analysis, from which factor score coefficients were computed for all subjects. This allowed determination of the extent to which (1) the two sets of basis waves were similar and (2) the factor scores resulting from the set of basis waves derived from principal components analysis of the control subjects' evoked potential data adequately represented those of the schizophrenics and vice-versa. Canonical correlation analyses indicated substantial similarities between the principal component structures (sets of basis waves). Multiple correlational analyses confirmed that the basis waves from either group spanned the other group's factor space. Factor scores from either set of basis waves were highly correlated. These results suggest that principal component structures derived from evoked potentials of a control group may be used in computing evoked potential factor scores of psychiatrically diverse populations even though the average evoked potentials of the groups may differ in several ways.