Correlation of Infants'Brain and Behavior Response to Temporal Changes in Visual Stimulation

This research was designed to test the hypothesis that a direct, parametric relationship exists between infant attention and the occipital visual evoked potential (VEP) induced by temporal frequency of visual pattern stimulation. Infants (13-weeks-old; N=32) were shown identical checkerboard patterns modulated at different rates of temporal change in a paired-comparison design and durations of orienting responses were measured. Another group of infants (13-weeks-old; N=14) were shown a series of checkerboard patterns, each modulated at a different temporal rate, and the midline occipital brain response was recorded. The results showed that behavioral attention and the signal strength/sec of the VEP are both significantly related to temporal frequency of stimulation. Furthermore, when plotted to the log₂ of temporal rate, both behavioral and neurophysiological response functions were best described by inverted U-shaped curves with similar maxima (4.8 Hz vs 5.8 Hz). These data taken together indicate that infants’visual attention and occipital brain response to temporal frequency covary and that a common neurophysiological mechanism may be involved.     

利用VEP测量视觉系统红,绿通道的反应时间差

本文应用彩色诱发电位（ＣＯＬＯＲ ＶＥＰ）在专门研制的双计算机互连系统，对人眼视觉系统中颜色通道的时间响应特性作初步研究，实验发现，在等主观亮度而颜色不同的棋盘格图形翻转刺激下ＶＥＰ中Ｎ１波的伏期因刺激颜色不同而不同。对实验结果的数据做统计的分析得出人眼颜色并行通道对三基色的响应有明显的差别，绿通道快于红通道。此结果１９９０年ＳＳ．Ｍ．Ｃｏｕｒｔｎｅｙａｎｄ Ｇ．Ｂｕｃｈｓｈａｕｍ提出的视觉颜色的     

Comparison of MEG responses to the sinusoidal flicker and the envelope of amplitude-modulated flicker

For a flickering light with two or more frequency components, the temporal envelope of the flickering light is perceived, although there is no frequency component at the frequency of the envelope. To address the processing of the temporal envelope, we compared cortical responses to the envelope of amplitude-modulated (AM) flickering lights with responses to sinusoidal flickering lights. We measured magnetoencephalographic (MEG) responses to AM and sinusoidal flickering lights while changing the frequency of the temporal envelope of AM flickering light and the stimulus frequency of sinusoidal flickering light. The result showed that the strength of the MEG response to sinusoidal flickering light increased with stimulus frequency in the low frequency range. This probably resulted from the band-pass filtering in the visual system. However, such an increase in the low frequency range was not observed for the envelope of AM flickering light. The absence of the increase in MEG responses suggests that the envelope of AM flickering light is not subject to band-pass filtering in the visual system. It is therefore possible that the envelope is represented after the band-pass filtering stage.     

Neuromagnetic Changes of Brain Rhythm Evoked by Intravenous Olfactory Stimulation in Humans

Summary: To identify the changes in the respective frequency band and brain areas related to olfactory perception, we measured magnetoencephalographic (MEG) signals before and after instilling intravenously thiamine propyl disulfide (TPD) and thiamine tetrahydrofurfuryl disulfide monohydrochloride (TTFD), which evoked a strong and weak sensation of odor, respectively. For the frequency analysis of MEG, a beamformer program, synthetic aperture magnetometry (SAM), was employed and event-related desynchronization (ERD) or synchronization (ERS) was statistically determined. Both strong and weak odors induced ERD in (1) beta band (13–30 Hz) in the right precentral gyrus, and the superior and middle frontal gyri in both hemispheres, (2) low gamma band (30–60 Hz) in the left superior frontal gyrus and superior parietal lobule, and the middle frontal gyrus in both hemispheres, and (3) high gamma band 2 (100–200 Hz) in the right inferior frontal gyrus. TPD induced ERD in the left temporal, parietal and occipital lobes, while TTFD induced ERD in the right temporal, parietal and occipital lobes. The results indicate that physiological functions in several regions in the frontal lobe may change and the strength of the odor may play a different role in each hemisphere during olfactory perception in humans. This study was supported by Japan Space Forum, Grant-in-Aid for Scientific Research on Priority Areas -Higher-Order Brain Functions-from The Ministry of Education, Culture, Sports, Science and Technology, Japan.     

Visual responses of sheep temporal cortex cells to moving and stationary human images

Single-cell extracellular recordings were made from temporal cortical neurones in the conscious sheep. The visual responses of these cells to stationary or moving images of humans were investigated. Results from 6 animals showed that a small population of cells responded preferentially to the sight of humans as opposed to other objects or food. These cells did not respond to visual images of the human face, or to individual body parts (legs or arms) or to the smell of a human. The majority of cells showed direction selectivity, with the most effective stimulus being a human moving towards the animal. Cells did not respond differentially to the front and back view of a human although the side view was less effective. The posture adopted by the human was important, since responses were diminished or absent if the human adopted a quadrupedal as opposed to the normal bipedal posture. These results provide evidence for integrated neural processing of both visual recognition, movement and posture in the sheep temporal cortex.     

Visual responses in the temporal cortex to moving objects with invariant contours

We were interested in how the visual attributes of motion and shape are integrated in the temporal cortex of monkeys. We recorded neural activity in the middle portion of the superior temporal sulcus (STS) of monkeys during a sequential visual discrimination task while the animals maintained fixation. We used images of objects with invariant outlines rotating in 3D space either clockwise or counterclockwise as visual stimuli. In the sequential discrimination task, after the fixation pattern was presented for 1.0 s, the sample stimulus (S1) appeared at the center of the monitor screen for 0.8 s. After a delay period of 0.5-2.0 s, the same stimulus or a new response stimulus appeared on the screen for 0.8 s. In each block, the response stimulus was either a new direction of rotation or a new shape. Of 425 responding neurons isolated in the STS, 202 (48%) showed significant activity when S1 stimuli were presented. Of these visual neurons, 27 (13%) were categorized as motion and shape selective (MS), 69 (34%) as shape selective (S), and 6 (3%) as motion selective (M). Briefer than for MS or S neurons, the latency of the remaining non-selective neurons was 80 ms. Latencies of visual response (110 ms) of both MS and S neurons were similar. On the other hand, MS neurons started responding later (180 ms) to changes in direction. Our findings show that neurons in the STS, responding selectively to changes in shape, do respond to relatively simple motion and that variable contouring is not essential to elicit motion response. The results may also suggest the functional segregation of selective versus non-selective neurons and the later arrival of directional response to MS neurons in the STS.     

基于功能磁共振的人脑视觉皮层V5区功能连通网络变化的研究

利用功能磁共振成像(functional magnetic resonance imaging,f MRI)技术,将空间独立成分分析(spatial independent component analysis,sICA)和时间相关方法相结合研究不同活动状态下人脑视觉运动功能连通网络的变化特性。首先利用sICA处理组块视觉运动刺激的数据,定位V5区;然后分别计算静息和连续视觉运动刺激两种稳态下V5区与其它脑区低频振荡的时间相关,检测出该区的功能连通网络。实验结果表明,静息时V5区的功能连通网络更广泛,且与已知的解剖连通一致;当被试接受连续视觉运动刺激时,与V5区连通的脑区网络局限在视觉皮层,此时的网络特定于处理视觉运动这一任务。     

The Visual ERP Predicts Clinical Response to Methylphenidate in Hyperactive Children

Visual ERP measures have been used to discriminate retrospectively between those hyperactive children who responded well to treatment with methylphenidate (MP) and those who were nonresponders. This study was designed to validate these ERP measures in a prospective study. Visual ERP data were obtained in 20 hyperactive children following 0.33 mg/kg methylphenidate (Ritalin) or a matching placebo. Parent, teacher and physician ratings were then obtained on these same doses in a subsequent double-blind clinical trial. At the conclusion of the trials, children were classified as MP responders or nonresponders based on the pediatrician's blind ratings. Using criteria established in a prior study, a conjoint measure of amplitude and variability statistically discriminated nonresponders from responders. The two clinical groups did not differ on placebo. It was suggested that these predictors are sensitive to nonspecific pharmacological factors.     

An Evaluation of Different Techniques for Removing Eye-Blink Artifact from Visual Evoked Response Recordings

This investigation compared four methods used to control eye-blink artifact in visual evoked response (VER) recordings using the augmenting-reducing paradigm: rejecting trials containing blinks, presenting the stimuli through closed eyelids, and two different techniques for subtracting a proportion of the averaged electro-oculogram (FOG) from the averaged VER. The two subtraction procedures differed in the way in which they estimated the amount of EOG to be subtracted and in the case with which they could be applied. Twenty normal, female subjects were exposed to a series of four different intensity light flashes twice with eyes open and once with eyes closed. Blinking was monitored by recording the EOG and EEG was recorded from three midline electrodes. The results indicated that the two subtraction techniques were very similar. They effectively removed ocular artifact and produced corrected VERs that showed high retest stability. Presenting the flashes through closed lids yielded idiosyncratic data, and rejecting trials contaminated by blinks was found to have limited utility with the VER paradigm used in the present study.     

Single Trial Analysis of Neurophysiological Correlates of the Recognition of Complex Objects and Facial Expressions of Emotion

In an earlier experiment, we have used the BTi twin MAGNES system (2 × 37 channels) to record the evoked magnetic field from five healthy right-handed male volunteers using two tasks: visual recognition of complex objects including faces and facial expressions of emotion. We have repeated the experiment with one of the five subjects using the BTi whole head system (148 channels). Magnetic field tomography (MFT) was used to extract 3D estimates of brain activity millisecond by millisecond from the recorded magnetoencephalographic (MEG) signals. Results from the MFT analysis of the average signals of the five subjects have been reported elsewhere (Streit et al. 1997; Streit et al. 1999). In this paper, we present results of the detailed single trial analysis for the subject recorded from the whole head system. We found activations in areas extending from the occipital pole to anterior areas. Regions of interest (ROIs) were defined entirely on functional criteria and confirmed independently by the location of the maximum activity on the MRI. Activation curves for each ROI were computed and objective statistical measures (Kolmogorov-Smirnov test) were then used to identify time segments for which the ROI activity showed significant differences both within the same and across different object/emotion categories. Emphasis is placed on the quantification of the activity from two ROIs, fusiform gyrus (FG) and amygdala (AM), which have been best studied in the context of processing of faces and facial expressions of emotion, respectively. We found no face-specific area as such, but instead areas like the FG was activated by all complex objects at roughly similar latencies and varying strengths. The amygdala activity was significantly different between 150 and 180 ms for fearful expression, and even earlier for happy expression.     

Reduction of somatosensory evoked fields in the primary somatosensory cortex in a one-back task

In the present study, responses of the somatosensory cortex to sensory input of ten human volunteers were investigated during a one-back task with different conditions of attention. During an condition of attention subjects were requested to detect a predefined sequence of tactile stimuli applied to two different fingers of the dominant hand while a series of visual stimuli was presented simultaneously with an asynchronous stimulus-onset to the tactile stimuli. During an condition of distraction subjects received the identical series of visual and tactile stimuli like in the condition of attention but were now requested to detect a predefined stimulus sequence within the visual stimulus domain. In both conditions, somatosensory evoked magnetic fields (SEFs) to the tactile stimuli were recorded by means of a 31-channel magnetoencephalograph (MEG) from subjects‘ contralateral primary somatosensory cortex. The mean global field power, the dipole strength, the maximum current density, and the first component of the singular value decomposition (SVD) of magnetic fields were used to compare early components of the SEF in the conditions of attention versus distraction. Surprisingly, results revealed significant decreases of measures of all four parameters during the condition of attention as compared to the condition of distraction indicating that early responses of the primary somatosensory cortex became significantly reduced in the condition of attention. We hypothesize that changes in the centre-periphery-relationship of receptive fields in the primary somatosensory cortex may account for this unexpected result.     

Dissociation of summation and peak latencies in visual processing: An MEG study on stimulus eccentricity

Research on the temporal characteristics of visual processing, as measured with critical flicker fusion or the latency of visual evoked potential (VEP), shows controversial results if different eccentricities of visual stimuli are compared. To clarify this question, a direct measure of cortical activity with magnetoencephalography (MEG) was applied to examine the neuronal summation latency and peak latency for both near and far peripheral stimuli. Consistent with cortical magnification, the peak amplitude for less eccentric stimuli was larger than that for more eccentric stimuli. More importantly, the current data also demonstrated longer cortical summation latency and peak latency for more eccentric visual stimuli, but only the summation latency difference between near and far stimuli correlated with the peak amplitude difference between near and far stimuli. These results suggest dissociable mechanisms of summation latency and peak latency with respect to their contributions to the stimulus eccentricity effect, and provide potential explanations for controversial results in previous studies.     

A unique area of the homonculus: the topography of the primary somatosensory cortex in humans following posterior scalp and shoulder stimulation

We recorded somatosensory evoked magnetic field (SEF) to investigate the differentiation in the receptive area for the face, lower part of the posterior scalp (mastoid) and shoulder, which occupy an unique area in the homunculus. We analyzed the location of the equivalent current dipole (ECD) of SEF following electrical stimulation of the skin at the face, mastoid and shoulder in 20 normal subjects. Three deflections (1M, 2M and 3M) were obtained within 50 ms of the stimulation in 16 of 20 subjects. The peak latency of the 1M and 2M was not significantly different at any stimulus sites. The amplitude of the 1M was significantly larger following the face than mastoid stimulation (p<0.05). The 16 subjects were classified according to the locations of the ECD on stimulation of the mastoid: close to that for shoulder stimulation, but significantly (p<0.05) more superior and medial to that following the face stimulation (Type 1, eleven subjects); close to that for face stimulation, but significantly (P<0.05) more inferior and lateral to that following the shoulder stimulation (Type 2, five subjects). The site of the receptive area for the posterior scalp shows interindividual variation, possibly due to anatomical differences.     

Visual evoked potentials in the forebrain of the pigeon

Summary The telencephalon of anaesthetized pigeons was systematically explored for flash evoked potentials. A short latency projection to the hyper striatum was confirmed. A second short latency projection which appears to have a major focus in the medial sector of the neostriatum caudale and a more diffuse representation in the remainder of this structure was also found. Longer latency responses were found in a band of tissue surrounding the ectostriatum although the latency of these potentials was too short to be compatible with their origin in a projection from the thalamic nucleus rotundus. The core of the ectostriatum was not responsive under the conditions of the present study. A previously reported projection to the avian archistriatum was not confirmed and evidence is presented that supposed evoked potentials in this region of the brain were confused with volume conducted electroretinograms. All forebrain evoked potentials were attenuated by repetition rates above 1 hz. The origin of these projections is discussed in conjunction with evoked potentials recorded at lower levels of the pigeon's visual system under the same conditions and in the light of available anatomical and electrophysiological evidence. It is concluded that the information about visual projections to the avian forebrain is as yet too incomplete to be useful as evidence for presumptive avian-mammalian forebrain homologies.     

Responses to Median and Tibial Nerve Stimulation in Patients with Chronic Neuropathic Pain

Somatosensory evoked magnetic fields and electrical potentials were measured in eight patients with unilateral neuropathic pain. After median nerve stimulation on the painful side, the amplitudes of the evoked responses were enhanced 2 to 3 times at a latency of about 100 ms compared to the responses of the contralateral, unaffected side. After posterior tibial nerve stimulation an enhancement was found at latencies around 110 ms and 150 ms. The scalp distribution of the magnetic field at the latencies of abnormal responses was dipolar and the responses could be ascribed to a current dipole. Three (of the eight) patients underwent spinal cord stimulation (SCS) for their pain. The enhancement of the evoked responses to stimulation of the painful side decreased after spinal cord stimulation. After a long period of spinal cord stimulation only (e.g., a year) during which the patient reported to be pain free, these abnormal responses were no longer observed.     

不同范围提示下儿童视觉空间注意的ERP研究

目的:研究儿童在不同范围提示下视觉空间注意的事件相关电位(ERP)特征.方法:采用“提示-目标”的视觉实验范式,以圆圈提示不同等级的搜索范围,对14名儿童进行检测.通过ERP技术分析儿童不同空间注意等级的早成分.结果:随提示范围的减小,反应时加快,后部P1和N1波幅增大,前部P2波幅减小.结论:在空间注意加工的早期阶段,儿童依赖提示等级的有效性调动脑资源;而晚期阶段需要额外的脑资源.     

Visual evoked responses to the upper and lower half-field stimulation in a dark-adapted man

The averaged visual evoked responses (VERs) to flashed blank and checkerboard-patterned (32 checkers) stimulation of the upper and lower half-field of 6° angular subtense were recorded referentially (O_z–A₁₊₂) in seven dark adapted subjects using a luminance range of 3.69 log units (maximum luminance=2220 cd/m²).With the logarithmical rise of stimulation luminance the peak latencies of the maximum positive-negative deflection of the VERs to the upper and lower half-field blank and to the upper half-field patterned stimulation display a monotonick shortening. These three response types do not differ in waveform, polarity and amplitude. Their amplitudes show no significant luminance-dependent changes.The peak latencies of the VERs to the lower half-field patterned stimulation exhibit an U shaped course with the increase of the luminance. At lower luminances they are by about 30 ms shorter in comparison with the VERs to the other three stimulation types, at higher luminances a gradual lengthening is observable. Consequently, at low luminances these VERs have a reversed polarity, at higher luminances the same polarity as the VERs to the other three stimulation types. The amplitude values of the lower half-field patterned responses are the highest and show a triphasic luminance-dependent course.From these and further differences between the VERs to the upper and lower half-field patterned stimulation in connection with the reaction to defocusing and to the subtraction of the luminance-related part of the response it is concluded that the VERs to the lower half-field patterned stimulation only contain a pattern-related component.     

The Effect of Unilateral Alpha Training on Visual Evoked Response in a Dyslexic Adolescent

To further elucidate the possible relationship between alpha waves and the averaged visual evoked response (VER), a pilot study with a dyslexic adolescent was undertaken. Baseline alpha and VER were recorded and bilateral alpha training done. After each trial the VER was recorded. By analysis of variance it was found that alpha training significantly increased the amplitude of VER (p < .001). Baseline values for amplitudes of the VER fluctuated widely from zero but were not correlated with percent alpha. Next a system was devised to train alpha unilaterally. The subject was given a feedback response when he produced 0.5 sec of alpha in the left hemisphere and concurrently 0.5 sec of beta or theta in the right hemisphere. Alpha time on the left significantly increased over the 5 day (4 trials per day) period, as did beta and theta time on the right. Left minus right VER amplitude difference was also increased and correlated (p < .05) with both alpha (L) and beta or theta (R) percent time increases.     

Different Effects of Uncertainty and Complexity on Single Trial Visual ERPs and the SCR-OR in Non-Signal Conditions

Single trial event-related potentials at F_z, C_Z, P₇, and O_Z were measured concurrently with the skin conductance response (SCR) in a habituation paradigm. Half the subjects (26) were told that the same stimulus would be presented a number of times in the middle of a TV screen (“certain condition”), and the other half were not informed about the stimuli (“uncertain condition”). Within each of these groups, half of the subjects received 32 stimuli of 4 bits of information and the other half received 32 stimuli of 60 bits of information. No task-relevance was given to the stimuli. Larger vertex P300 waves were associated with more complex stimuli, but uncertainty had no effect on the P300. A significant complexity × uncertainty × trials interaction was found on a sustained late positive activity, called the Slow Wave (SW), which was maximal at P_z and habituated rapidly. As before, we found that both the SCR and the vertex P300 habituated. No effect of uncertainty or complexity was found on the SCR. The results suggest that the SW is a useful index of information processing, and that the SCR and P300 must be considered to index different aspects of information processing.     

鼻腔内机械振荡刺激对健康人群静息态脑电图相对功率及有效连接的影响

鼻腔内机械振荡刺激(iMVS)是一种新型的无创神经刺激技术,可提升边缘系统内在功能活性从而改善自主神经平衡.通过分析iMVS对健康人群脑电图(EEG)相对功率以及EEG有效连接的影响,探索iMVS的神经生理机制.将22名健康成年被试随机均分为刺激组与对照组,并对11名刺激组被试两侧鼻腔各进行10 min的iMVS,11...