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1.
Inferior temporal (IT) cortex is critical for visual memory, but it is not known how IT neurons retain memories while new information is streaming into the visual system. Single neurons were therefore recorded from IT cortex of two rhesus monkeys performing tasks that required them to hold items in memory while concurrently viewing other items. The neuronal response to an incoming visual stimulus was attenuated if it matched a stimulus actively held in working memory, even when several other stimuli intervened. The neuronal response to novel stimuli declined as the stimuli became familiar to the animal. IT neurons appear to function as adaptive mnemonic "filters" that preferentially pass information about new, unexpected, or not recently seen stimuli. 相似文献
2.
The circuitry and function of mammalian visual cortex are shaped by patterns of visual stimuli, a plasticity likely mediated by synaptic modifications. In the adult cat, asynchronous visual stimuli in two adjacent retinal regions controlled the relative spike timing of two groups of cortical neurons with high precision. This asynchronous pairing induced rapid modifications of intracortical connections and shifts in receptive fields. These changes depended on the temporal order and interval between visual stimuli in a manner consistent with spike timing-dependent synaptic plasticity. Parallel to the cortical modifications found in the cat, such asynchronous visual stimuli also induced shifts in human spatial perception. 相似文献
3.
Self-stimulation alters human sensory brain responses 总被引：3，自引：0，他引：3
Human electrocortical potentials evoked by self-administered auditory and visual stimuli manifest much smaller amplitude and faster poststimulus timing than do average brain responses evoked by identical machine-delivered stimuli. Auditory evoked potentials show this "self-stimulation effect" to a greater degree than do visual responses. For visual evoked potentials, the effect appears greater at the vertex association area than over the occipital cortex. Individual differences in the magnitude of the "self-stimutlation effect" relate to level of intelligence. 相似文献
4.
de Gelder B 《Science (New York, N.Y.)》2000,289(5482):1148-1149
A single event may elicit several different sensory stimuli such as vision, sound, and touch. But how does the brain know which of the many different stimuli arriving in the sensory cortex of the brain are connected? In her Perspective, de Gelder discusses new findings showing that when a touch is applied on the same side of the body as a visual cue, vision is enhanced (Macaluso et al.). She explains that this effect is due to neurons projecting from the somatosensory (touch) area of the sensory cortex back to the visual cortex. These neurons keep the visual cortex informed about tactile stimuli elicited at the same time as the visual stimuli. 相似文献
5.
The ability to group stimuli into meaningful categories is a fundamental cognitive process. To explore its neural basis, we trained monkeys to categorize computer-generated stimuli as "cats" and "dogs." A morphing system was used to systematically vary stimulus shape and precisely define the category boundary. Neural activity in the lateral prefrontal cortex reflected the category of visual stimuli, even when a monkey was retrained with the stimuli assigned to new categories. 相似文献
6.
Selective attention gates visual processing in the extrastriate cortex 总被引：56，自引：0，他引：56
Single cells were recorded in the visual cortex of monkeys trained to attend to stimuli at one location in the visual field and ignore stimuli at another. When both locations were within the receptive field of a cell in prestriate area V4 or the inferior temporal cortex, the response to the unattended stimulus was dramatically reduced. Cells in the striate cortex were unaffected by attention. The filtering of irrelevant information from the receptive fields of extrastriate neurons may underlie the ability to identify and remember the properties of a particular object out of the many that may be represented on the retina. 相似文献
7.
The neural encoding of serial order was studied in the motor cortex of monkeys performing a context-recall memory scanning task. Up to five visual stimuli were presented successively on a circle (list presentation phase), and then one of them (test stimulus) changed color; the monkeys had to make a single motor response toward the stimulus that immediately followed the test stimulus in the list. Correct performance in this task depends on memorization of the serial order of the stimuli during their presentation. It was found that changes in neural activity during the list presentation phase reflected the serial order of the stimuli; the effect on cell activity of the serial order of stimuli during their presentation was at least as strong as the effect of motor direction on cell activity during the execution of the motor response. This establishes the serial order of stimuli in a motor task as an important determinant of motor cortical activity during stimulus presentation and in the absence of changes in peripheral motor events, in contrast to the commonly held view of the motor cortex as just an "upper motor neuron." 相似文献
8.
Whereas gamma-band neuronal oscillations clearly appear integral to visual attention, the role of lower-frequency oscillations is still being debated. Mounting evidence indicates that a key functional property of these oscillations is the rhythmic shifting of excitability in local neuronal ensembles. Here, we show that when attended stimuli are in a rhythmic stream, delta-band oscillations in the primary visual cortex entrain to the rhythm of the stream, resulting in increased response gain for task-relevant events and decreased reaction times. Because of hierarchical cross-frequency coupling, delta phase also determines momentary power in higher-frequency activity. These instrumental functions of low-frequency oscillations support a conceptual framework that integrates numerous earlier findings. 相似文献
9.
Reorganization of retinotopic cortical maps in adult mammals after lesions of the retina 总被引：23，自引：0，他引：23
J H Kaas L A Krubitzer Y M Chino A L Langston E H Polley N Blair 《Science (New York, N.Y.)》1990,248(4952):229-231
The organization of the visual cortex has been considered to be highly stable in adult mammals. However, 5 degrees to 10 degrees lesions of the retina in the contralateral eye markedly altered the systematic representations of the retina in primary and secondary visual cortex when matched inputs from the ipsilateral eye were also removed. Cortical neurons that normally have receptive fields in the lesioned region of the retina acquired new receptive fields in portions of the retina surrounding the lesions. The capacity for such changes may be important for normal adjustments of sensory systems to environmental contingencies and for recoveries from brain damage. 相似文献
10.
Dommett E Coizet V Blaha CD Martindale J Lefebvre V Walton N Mayhew JE Overton PG Redgrave P 《Science (New York, N.Y.)》2005,307(5714):1476-1479
Unexpected, biologically salient stimuli elicit a short-latency, phasic response in midbrain dopaminergic (DA) neurons. Although this signal is important for reinforcement learning, the information it conveys to forebrain target structures remains uncertain. One way to decode the phasic DA signal would be to determine the perceptual properties of sensory inputs to DA neurons. After local disinhibition of the superior colliculus in anesthetized rats, DA neurons became visually responsive, whereas disinhibition of the visual cortex was ineffective. As the primary source of visual afferents, the limited processing capacities of the colliculus may constrain the visual information content of phasic DA responses. 相似文献
11.
Retinal cells have been induced to project into the medial geniculate nucleus, the principal auditory thalamic nucleus, in newborn ferrets by reduction of targets of retinal axons in one hemisphere and creation of alternative terminal space for these fibers in the auditory thalamus. Many cells in the medial geniculate nucleus are then visually driven, have large receptive fields, and receive input from retinal ganglion cells with small somata and slow conduction velocities. Visual cells with long conduction latencies and large contralateral receptive fields can also be recorded in primary auditory cortex. Some visual cells in auditory cortex are direction selective or have oriented receptive fields that resemble those of complex cells in primary visual cortex. Thus, functional visual projections can be routed into nonvisual structures in higher mammals, suggesting that the modality of a sensory thalamic nucleus or cortical area may be specified by its inputs during development. 相似文献
12.
Responses of human somatosensory cortex to stimuli below threshold for conscious sensation 总被引：5，自引：0，他引：5
Averaged evoked responses of somatosensory cortex, recorded subdurally, appeared with stimuli (skin, ventral posterolateral nucleus, cortex) which were subthreshold for sensation. Such responses were deficient in late components. Subthreshold stimuli could elicit sensation with suitable repetition. The primary evoked response was not sufficient for sensation. These facts bear on the problems of neurophysiological correlates of conscious and unconscious experience, and of "subliminal perception." 相似文献
13.
目的:利用电生理学技术探讨Long Evans大鼠视皮层眼优势柱可塑性的发育性变化。方法:取22d Long Evans大鼠7只和100d Long Evans大鼠5只,通过缝合一侧眼睑建立单眼剥夺大鼠动物模型。利用电生理学技术检测22 d正常大鼠、22 d单眼剥夺大鼠、100 d正常大鼠、100 d单眼剥夺大鼠眼优势柱的分布。结果:正常22 d Long Evans大鼠、正常100 d Long Evans大鼠和100 d单眼剥夺大鼠视皮层眼优势柱分布为对侧眼优势,22 d单眼剥夺大鼠视皮层眼优势柱分布为同侧眼优势。结论:正常视觉环境下发育的Long Evans大鼠,其眼优势柱的分布为对侧眼优势,幼年Long Evans大鼠视皮层具有可塑性,异常的视觉环境能影响其眼优势柱的分布;成年Long Evans大鼠视觉可塑性终止,异常的视觉环境不能再影响其眼优势柱的分布。 相似文献
14.
Theoretical studies suggest that primary visual cortex (area V1) uses a sparse code to efficiently represent natural scenes. This issue was investigated by recording from V1 neurons in awake behaving macaques during both free viewing of natural scenes and conditions simulating natural vision. Stimulation of the nonclassical receptive field increases the selectivity and sparseness of individual V1 neurons, increases the sparseness of the population response distribution, and strongly decorrelates the responses of neuron pairs. These effects are due to both excitatory and suppressive modulation of the classical receptive field by the nonclassical receptive field and do not depend critically on the spatiotemporal structure of the stimuli. During natural vision, the classical and nonclassical receptive fields function together to form a sparse representation of the visual world. This sparse code may be computationally efficient for both early vision and higher visual processing. 相似文献
15.
The functional organization of the second cortical visual area was examined with three different anatomical markers: 2-[14C]deoxy-D-glucose, cytochrome oxidase, and various myelin stains. All three markers revealed strips running throughout the area, parallel to the cortical surface. The boundaries of these strips provide an anatomical criterion for defining the borders of this extrastriate region. Further, the demonstration of these strips allows a functional and anatomical analysis of modules in the area, just as the recent demonstration of spots in the primary visual cortex has allowed an analysis of modules there. The strips differ structurally and functionally from interstrip regions and these differences are similar to those seen between the spots and the interspot regions in the primary visual cortex. In the macaque the strips and spots differ with regard to binocular organization. 相似文献
16.
Monocular deprivation during early postnatal development remodels the circuitry of the primary visual cortex so that most neurons respond poorly to stimuli presented to the deprived eye. This rapid physiological change is ultimately accompanied by a matching anatomical loss of input from the deprived eye. This remodeling is thought to be initiated at the thalamocortical synapse. Ocular dominance plasticity after brief (24 hours) monocular deprivation was analyzed by intrinsic signal optical imaging and by targeted extracellular unit recordings. Deprived-eye responsiveness was lost in the extragranular layers, whereas normal binocularity in layer IV was preserved. This finding supports the hypothesis that thalamocortical organization is guided by earlier changes at higher stages. 相似文献
17.
Whitney D Goltz HC Thomas CG Gati JS Menon RS Goodale MA 《Science (New York, N.Y.)》2003,302(5646):878-881
Although the visual cortex is organized retinotopically, it is not clear whether the cortical representation of position necessarily reflects perceived position. Using functional magnetic resonance imaging (fMRI), we show that the retinotopic representation of a stationary object in the cortex was systematically shifted when visual motion was present in the scene. Whereas the object could appear shifted in the direction of the visual motion, the representation of the object in the visual cortex was always shifted in the opposite direction. The results show that the representation of position in the primary visual cortex, as revealed by fMRI, can be dissociated from perceived location. 相似文献
18.
Neurons in the pericruciate cortex of the cat were tested with moving visual stimuli for responses to specific properties of the visual receptive field. Specific response patterns were shown by cells of origin of the pyramidal tract as well as by other cells. 相似文献
19.
R Spehlmann 《Science (New York, N.Y.)》1969,165(891):404-405
Sinigle neurons in cat visual cortex were driven by afferent stimuli to determine the effects of drugs liberated from multibarreled micropipettes on synaptic transmission. Acetylcholine increased, and atropine decreased, the number of neuron discharges fired in response to stimulation of the mesencephalic reticular formation without necessarily affecting responses to other stimuli or affecting spontaneous firing. 相似文献
20.
Relationships between the M and P retino-geniculo-cortical visual pathways and "dorsal" visual areas were investigated by measuring the sources of local excitatory input to individual neurons in layer 4B of primary visual cortex. We found that contributions of the M and P pathways to layer 4B neurons are dependent on cell type. Spiny stellate neurons receive strong M input through layer 4Calpha and no significant P input through layer 4Cbeta. In contrast, pyramidal neurons in layer 4B receive strong input from both layers 4Calpha and 4Cbeta. These observations, along with evidence that direct input from layer 4B to area MT arises predominantly from spiny stellates, suggest that these different cell types constitute two functionally specialized subsystems. 相似文献