共查询到20条相似文献，搜索用时 31 毫秒
1.
Stephan KE Marshall JC Friston KJ Rowe JB Ritzl A Zilles K Fink GR 《Science (New York, N.Y.)》2003,301(5631):384-386
The principles underlying human hemispheric specialization are poorly understood. We used functional magnetic resonance imaging of letter and visuospatial decision tasks with identical word stimuli to address two unresolved problems. First, hemispheric specialization depended on the nature of the task rather than on the nature of the stimulus. Second, analysis of frontal candidate regions for cognitive control showed increased coupling between left anterior cingulate cortex (ACC) and left inferior frontal gyrus during letter decisions, whereas right ACC showed enhanced coupling with right parietal areas during visuospatial decisions. Cognitive control is thus localized in the same hemisphere as task execution. 相似文献
2.
In a group of normal adults, averaged cortical evoked responses to natural speech stimuli were recorded from scalp electrodes placed symmetrically over the two cerebral hemispheres at frontal, Rolandic, and temporoparietal leads. The amplitude of the most prominent component was consistently larger in left hemisphere derivations, with the major hemisphere difference observed in the temporoparietal records. These electrophysiological measures may be sensitive indicators of hemispheric specialization of function. 相似文献
3.
R Cohen 《Science (New York, N.Y.)》1971,172(983):599-601
Psychophysiological measurements have indicated that the right cerebral hemisphere processes noises and other nonverbal data and that the left cerebral hemisphere processes verbal material. Direct physiological measurements, as expressed in summated auditory evoked cortical responses, unequivocally demonstrate that click noises show a greater amplitude of initial output over the right brain, and that verbal stimuli produce either equal or higher amplitudes of output over the left cerebral hemisphere. 相似文献
4.
马瑞雪 《甘肃农业大学学报》2004,39(3):355-358
语言意义和语言形式的平衡发展是语言教学的理想目标。任务型教学法通过让学习者完成一定的任务从而实现兼顾语意和形式的教学思想。通过对学生两种任务类型写作的调查,统计了大学生英语写作错误在两种任务类型各个维度上的不同表现,并分析了两种任务类型作文对学生写作的影响。 相似文献
5.
Paulesu E Démonet JF Fazio F McCrory E Chanoine V Brunswick N Cappa SF Cossu G Habib M Frith CD Frith U 《Science (New York, N.Y.)》2001,291(5511):2165-2167
The recognition of dyslexia as a neurodevelopmental disorder has been hampered by the belief that it is not a specific diagnostic entity because it has variable and culture-specific manifestations. In line with this belief, we found that Italian dyslexics, using a shallow orthography which facilitates reading, performed better on reading tasks than did English and French dyslexics. However, all dyslexics were equally impaired relative to their controls on reading and phonological tasks. Positron emission tomography scans during explicit and implicit reading showed the same reduced activity in a region of the left hemisphere in dyslexics from all three countries, with the maximum peak in the middle temporal gyrus and additional peaks in the inferior and superior temporal gyri and middle occipital gyrus. We conclude that there is a universal neurocognitive basis for dyslexia and that differences in reading performance among dyslexics of different countries are due to different orthographies. 相似文献
6.
William M. Clapham James M. FeddersKim Beeman James P.S. Neel 《Computers and Electronics in Agriculture》2011,76(1):96-104
Estimating forage intake by free-grazing livestock is difficult and expensive. Previous approaches include behavioral observation, ratio techniques using indigestible markers, mechanical recording of ingestive jaw motion, and acoustic recording of ingestive behaviors. Acoustic recording shows great potential but has been limited by the difficulty and time required to manually identify and classify ingestive events. We present an acoustic recording and analysis system that automatically detects, classifies, and quantifies ingestive events in free-grazing beef cattle. The system utilizes a wide-frequency acoustic microphone close to the animal's mouth, mathematical signal analysis to detect and measure ingestive events, and streaming data analysis capable of handling an unlimited amount of data. Analysis parameters can be reconfigured for different animals, forages and other changing conditions. The system measures the acoustic parameters of ingestive events, such as duration, amplitude, spectrum and energy, which can support further event classification and become the inputs to a forage intake model. We validated our detection and classification technique against the results of trained human observers based on field studies with grazing steer. The software detected 95% of manually identified bites in an event-by-event comparison. Field observations and sound attenuation analysis indicate that sounds from adjacent livestock and ambient pastoral environments have an insignificant effect upon the integrity of the recorded acoustic data set. We conclude that wideband acoustic analysis allows us to identify ingestive events accurately and automatically over extended periods of time. 相似文献
7.
EEG alpha activity reflects attentional demands, and beta activity reflects emotional and cognitive processes 总被引：9，自引：0，他引：9
Two experiments were designed to examine the effects of attentional demands on the electroencephalogram during cognitive and emotional tasks. We found an interaction of task with hemisphere as well as more overall parietal alpha for tasks not requiring attention to the environment, such as mental arithmetic, than for those requiring such attention. Differential hemispheric activation for beta was found most strongly in the temporal areas for emotionally positive or negative tasks and in the parietal areas for cognitive tasks. 相似文献
8.
Although the variability of averaged evoked potentials as recorded from cortex in man has been a constant source of concern among investigators, the degree of variability has not received systematic treatment. The authors have accordingly undertaken an exploratory study of reliable differences that may occur in the first 300 msec of the averaged evoked response over long periods of time. Computer analysis of visually evoked responses in seven subjects over several weeks indicated stability of the response of each individual, with reliable intra-individual correlations. Inter-individual differences, however, were large. The evoked responses of different individuals were found to be unique. 相似文献
9.
针对木材损伤断裂过程中声发射(AE)信号识别的问题,提出一种基于瞬时频率的AE信号辨识方法。首先,采用三点弯曲的方式对马尾松试件做损伤试验,利用采样频率为500 kHz的4通道NI USB-6366采集卡收集原始AE信号。然后,通过小波分析的方法对采集的原始信号降噪处理,并对降噪后的信号进行频率分析,再根据频率范围及产生原因的不同定义了两类AE信号。最后,通过Hilbert变换分别获得两类AE信号的瞬时频率,并统计两类AE事件频率。试验结果表明,基于瞬时频率统计的AE事件频率能够客观反映试件的应力水平,同时,木材损伤过程中主要产生断裂AE和变形AE信号,且断裂AE信号的频率范围明显高于变形AE信号的频率范围。 相似文献
10.
The average visual evoked potentials elicited from relaxed human subjects are different for a blank visual field and one containing a geometric form, are different for different geometric forms of equal area, are similar for versions of the same geometric fortn of unequal area, and are different for two printed words equated for total letter area. These findings suggest that the waveform of evoked responses is not determined solely by the set of peripheral receptors which is stimulated, but it also reflects the perceptual content of the stimulus. 相似文献
11.
Induction of synaptic potentiation in hippocampus by patterned stimulation involves two events 总被引：16，自引：0，他引：16
Electrical stimulation of axons in the hippocampus with short high-frequency bursts that resemble in vivo activity patterns produces stable potentiation of postsynaptic responses when the bursts occur at intervals of 200 milliseconds but not 2 seconds. When a burst was applied to one input and a second burst applied to a different input to the same target neuron 200 milliseconds later, only the synapses activated by the second burst showed stable potentiation. This effect was observed even when the two inputs innervated completely different regions of the postsynaptic cells; but did not occur when the inputs were stimulated simultaneously or when the second burst was delayed by 2 seconds. Intracellular recordings indicated that the first burst extended the decay phase of excitatory postsynaptic potentials evoked 200 milliseconds later. These results suggest that a single burst of axonal stimulation produces a transient, spatially diffuse "priming" effect that prolongs responses to subsequent bursts, and that these altered responses trigger spatially restricted synaptic modifications. The similarity of the temporal parameters of the priming effect and the theta rhythm that dominates the hippocampal electroencephalogram (EEG) during learning episodes suggests that this priming may be involved in behaviorally induced synaptic plasticity. 相似文献
12.
Prelinguistic infants recognized structural correspondences in acoustic and optic properties of synchronized, naturally spoken disyllables, but did so only when they were looking to their right sides. This result suggests that intermodal speech perception is facilitated by rightward orientation of attention and subserved by the left hemisphere. 相似文献
13.
Evoked potential correlates of auditory signal detection 总被引：11，自引：0，他引：11
A long-latency comnponent of the averaged evoked potential recorded from the human scalp varied in close relationship with subjects' perceptual reports in an auditory signal detection task. Detected signals evoked potentials several times larger than did undetected signals, falsely reported signals, or correctly reported nonsignals. The threshold signal intensity at which detection perfornmance exceeded chance levels was identical with concurrently obtained electro-physiological measures of threshold. 相似文献
14.
Three adult cats were deprived of rapid eye movement sleep for six separate periods of up to 32 days. Animals were allowed normal amouints of sleeping time during which rapid eye movement sleep was interrupted, whenever it occurred, by human observers who continually monitored the animals and their electrocortical activity. Cortical responses evoked by pairs of acoustic clicks were recorded during wakefulness. Recovery functions derived from these data were facilitated during periods of deprivation of rapid eye movement sleep and returned to base-line values when animals were allowed normal amounts of this sleep phase. This change was noted repeatedly within, as well as between, subjects. It did not occur during control periods when non-rapid eye movement sleep was interrupted on identical schedules, nor did it occur when the cats were deprived of all sleep for 22 hours a day for 5 days. 相似文献
15.
Dogs given opportunities to base their instrumental conditioned responses in differentiation learning on either the quality of the auditory conditioned stimulus (for example, metronome versus buzzer) or the direction of its source (in front or behind) choose different cues in different tasks. In S(1)--> R(1), S(2)-->R(2) (left leg-right leg) differentiation they exclusively use directional cues and are almost unable to learn this task when only quality cues are available. When confronted with Pavlovian S +--> R, S ---> no R (go-no go) differentiation, however, they generally learn on the basis of quality cues, although some animals also attend to the directional cues. Thus an animal's success or failure in a given differentiation procedure depends not only on its ability to discriminate the stimuli but also on the task with which it is confronted. 相似文献
16.
17.
Common pathogenetic mechanism for three tumor types in bilateral acoustic neurofibromatosis 总被引：20，自引：0，他引：20
B R Seizinger G Rouleau L J Ozelius A H Lane P St George-Hyslop S Huson J F Gusella R L Martuza 《Science (New York, N.Y.)》1987,236(4799):317-319
Bilateral acoustic neurofibromatosis (BANF) is a genetic defect associated with multiple tumors of neural crest origin. Specific loss of alleles from chromosome 22 was detected with polymorphic DNA markers in two acoustic neuromas, two neurofibromas, and one meningioma from BANF patients. This indicates a common pathogenetic mechanism for all three tumor types. The two neurofibromas were among three taken from the same patient, and both showed loss of identical alleles demonstrating that the same chromosome suffered deletion in both tumors. The third neurofibroma from this patient showed no detectable loss of heterozygosity, which suggests the possibility of a more subtle mutational event that affects chromosome 22. In the two acoustic neuromas, only a portion of chromosome 22 was deleted, narrowing the possible chromosomal location of the gene that causes BANF to the region distal to the D22S9 locus in band 22q11. The identification of progressively smaller deletions on chromosome 22 in these tumor types may well provide a means to clone and characterize the defect. 相似文献
18.
采用NI高速采集设备构建木材声发射信号采集平台,通过铅芯折断的方式在马尾松胶合木表面模拟产生AE源。然后对采集的原始信号进行5层小波分解并重构AE信号波形,进而获得AE信号的时频域特征。最后,根据信号相关性分析和时差定位方法,研究AE信号沿胶接横纹和指接横纹方向上的传播速率。研究表明,AE信号在胶合木表面传播时,AE信号中频率较低的成分在通过胶层时能量衰减更加显著,并且在胶接横纹和指接横纹方向上的传播速率存在明显差异,进一步指出指接胶层对信号传播速率的影响比胶接胶层更明显。 相似文献
19.
加利福尼亚湾茎柔鱼(Dosidicus gigas)渔场声学调查方法 总被引：1，自引：0，他引：1
唐峰华 吴祖立 杨嘉樑 黄洪亮 蒋科技 ESTEFANIAGonzalez Maiez Violeta ARREOLAJuan Pedro Vela 《中国农业科技导报》2022,24(4):185-192
声学方法已成为海洋生物资源评估的重要手段,水声学调查与数据分析作为海洋生物资源声学评估的关键,直接影响渔业资源评估结果.通过对数据处理过程中的目标强度、噪声剔除、物种判别问题进行分析,探究墨西哥加利福尼亚湾的茎柔鱼(Dosidicus gigas)资源水声学调查方法,进而为系统了解和掌握加利福尼亚湾渔场经济品种的资源量... 相似文献
20.
Responses from motor cortex evoked by cerebellar stimulation have been recorded with chronically implanted electrodes from cats in different states of arousal. The response, which in the waking cat consists of a short latency biphasic component followed by one or more slower waves, was attenuated, or abolished completely, in association with electroencephalographic and behavioral signs of decreased arousal. In contrast, responses in primary somatosensory cortex evoked by stimulating the bulbar trigeminal nucleus were enhanced during periods of decreased alertness. 相似文献