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It is current dogma that neurons in primary visual cortex extract local edges from the scene from which later visual areas reconstruct more meaningful shapes. Recent neuroimaging studies, however, have shown V1 modulations by the degree of structure in the image (shape). These V1 modulations due to the level of shape coherence have been explained in one of two possible ways: due to changes in image statistics or shape-based perceptual influences from higher visual areas. Here we compare both hypotheses using stimuli composed of Gabor arrays constructed to form circular shapes that can be successively degraded by manipulating the orientations of individual Gabors while maintaining local and global statistics. In a first experiment, we confirm that V1 responses are inversely correlated with the degree of structure in the image. In a second experiment, stimulus predictions are compared based on the degree of circular shape or change in the image statistic varied (orientation variance) in the image. We find that these V1 modulations to shape change are correlated with low-level changes in orientation contrast rather than shape perception per se. 相似文献
3.
The functional MRI (fMRI) response to a pair of identical, successively presented stimuli can result in a smaller signal than the presentation of two nonidentical stimuli. This "repetition effect" has become a frequently used tool to make inferences about neural selectivity in specific cortical areas. However, little is known about the mechanism(s) underlying the effect. In particular, despite many successful applications of the technique in higher visual areas, repetition effects in lower visual areas [e.g., primary visual cortex (V1)] have been more difficult to characterize. One property that is well understood in early visual areas is the mapping of visual field locations to specific areas of the cortex (i.e., retinotopy). We used the retinotopic organization of V1 to activate progressively different populations of neurons in a rapid fMRI experimental design. We observed a repetition effect (reduced signal) when localized stimulus elements were repeated in identical locations. We show that this effect is spatially tuned and largely independent of both interstimulus interval (100-800 ms) and the focus of attention. Using the same timing parameters for which we observed a large effect of spatial position, we also examined the response to orientation changes and observed no effect of an orientation change on the response to repeated stimuli in V1 but significant effects in other retinotopic areas. Given these results, we discuss the possible causes of these repetition effects as well as the implications for interpreting other experiments that use this potentially powerful imaging technique. 相似文献
4.
Human cortical representation of oral temperature 总被引:2,自引:0,他引:2
Guest S Grabenhorst F Essick G Chen Y Young M McGlone F de Araujo I Rolls ET 《Physiology & behavior》2007,92(5):975-984
The temperature of foods and fluids is a major factor that determines their pleasantness and acceptability. Studies of nonhuman primates have shown that many neurons in cortical taste areas receive and process not only chemosensory inputs, but oral thermosensory (temperature) inputs as well. We investigated whether changes in oral temperature activate these areas in humans, or middle or posterior insular cortex, the areas most frequently identified for the encoding of temperature information from the human hand. In the fMRI study we identified areas of activation in response to innocuous, temperature-controlled (cooled and warmed, 5, 20 and 50 degrees C) liquid introduced into the mouth. The oral temperature stimuli activated the insular taste cortex (identified by glucose taste stimuli), a part of the somatosensory cortex, the orbitofrontal cortex, the anterior cingulate cortex, and the ventral striatum. Brain regions where activations correlated with the pleasantness ratings of the oral temperature stimuli included the orbitofrontal cortex and pregenual cingulate cortex. We conclude that a network of taste- and reward-responsive regions of the human brain is also activated by intra-oral thermal stimulation, and that the pleasant subjective states elicited by oral thermal stimuli are correlated with the activations in the orbitofrontal cortex and pregenual cingulate cortex. Thus the pleasantness of oral temperature is represented in brain regions shown in previous studies to represent the pleasantness of the taste and flavour of food. Bringing together these different oral representations in the same brain regions may enable particular combinations to influence the pleasantness of foods. 相似文献
5.
Previous studies suggested a relationship between severity of symptoms and the degree of neurofibrillary tangles (NFTs) clustering in different areas of the cortex in Alzheimer's disease (AD). The posterior inferior temporal cortex or Brodmann's area (BA 37) is involved in object naming and recognition memory. But the cellular architecture and connectivity and the NFT pathology of this cortex in AD received inadequate attention. In this report, we describe the laminar distribution and topography of NFT pathology of BA 37 in brains of AD patients by using Thionin staining for Nissl substance, Thioflavin-S staining for NFTs, and phosphorylated tau (AT8) immunohistochemistry. NFTs mostly occurred in cortical layers II, III, V and VI in the area 37 of AD brain. Moreover, NFTs appeared like a patch or in cluster pattern along the cortical layers III and V and within the columns of pyramidal cell layers. The abnormal, intensely labeled AT8 immunoreactive cells were clustered mainly in layers III and V. Based on previously published clinical correlations between cognitive abnormalities in AD and the patterns of laminar distributed NFT cluster pathology in other areas of the brain, we conclude that a similar NFT pathology that severely affected BA 37, may indicate disruption of some forms of naming and object recognition-related circuits in human AD. 相似文献
6.
Object naming is commonly used for demonstrating semantic memory abilities, known to be affected in normal aging. Yet, neuropsychological assessments of older people do not reflect irregularities. The authors used a test with 2 levels of naming complexity by 2 kinds of stimuli: common objects pictured from a conventional viewpoint (usual condition) or from an unconventional viewpoint (unusual condition). The authors studied naming performance with 129 healthy participants, aged 20-85 years. For the usual stimuli, the success rate was high (90.9%), with no reduction in performance until 65 years of age. However, for the unusual stimuli, there was a marked reduction in performance with age. Brain activity was studied on 11 healthy young participants (20-30 years of age) using functional magnetic resonance imaging. The usual condition activated brain regions associated with visual perception, language, and memory. Additional brain regions associated with semantic searching and decision making were obtained in the unusual condition in the prefrontal cortex (Brodmann's area [BA] 9 and BA 47) and anterior cingulate (BA 32). The results suggest that the poor naming performance for unusual-viewed objects in older people might be related to the shrinkage of frontal gray matter with age. 相似文献
7.
Takahiro Ushida Tatsunori Ikemoto Shigeki Tanaka Jun Shinozaki Shinichirou Taniguchi Yoriko Murata Matthew McLaughlin Young-Chang P. Arai Yurie Tamura 《Neuroscience letters》2008
Psychological factors are known to play an extremely important role in the maintenance and development of chronic pain conditions. However, it is unclear how such factors relate to the central neural processing of nociceptive transmission in healthy individuals. To investigate this issue, the activation of the brain was studied in 30 healthy volunteers responding to virtual pain stimuli by fMRI. In the first series of the study (non-preconditioned study), 15 participants were shown a digital video demonstrating an injection needle puncturing the right palm. In the second series of the study (pre-conditioned study), same-task paradigms were used for another 15 participants. Prior to the fMRI session, real needle punctuate stimuli were applied to the right palm of participants for pre-conditioning. fMRI analysis revealed that bilateral activations in anterior insula (BA45), parietal operculum (S2: BA40), premotor area, medial globus pallidus, inferior occipital gyrus (BA18), left temporal association cortex, right fusiform gyrus, right parietal association cortex and cerebellum occurred due to the task in the preconditioned group. On the other hand, right parietal operculum (S2: BA40), premotor area, parietal association cortex, left inferior frontal gyrus and bilateral temporal association cortex were activated in the non-preconditioned group. In addition, activation of anterior insula, inferior frontal gyrus, precentral gyrus and cerebellum significantly increased in the preconditioned group compared with the non-preconditioned group. These results suggest that the virtual needle puncture task caused memory retrieval of unpleasant experiences which is possibly related to empathy for pain, resulting in the activation of specific brain areas. 相似文献
8.
An oblique effect in human primary visual cortex 总被引:6,自引:0,他引:6
Visual perception critically depends on orientation-specific signals that arise early in visual processing. Humans show greater behavioral sensitivity to gratings with horizontal or vertical (0 degrees /90 degrees; 'cardinal') orientations than to other, 'oblique' orientations. Here we used functional magnetic resonance imaging (fMRI) to measure an asymmetry in the responses of human primary visual cortex (V1) to oriented stimuli. We found that neural responses in V1 were larger for cardinal stimuli than for oblique (45 degrees /135 degrees ) stimuli. Thus the fMRI pattern in V1 closely resembled subjects' behavioral judgments; responses in V1 were greater for those orientations that yielded better perceptual performance. 相似文献
9.
Kathleen Vancleef Johan Wagemans Glyn W. Humphreys 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》2013,230(1):41-57
We examined the relations between texture segregation and contour integration in patients with deficits in spatial attention leading to left or right hemisphere extinction. Patients and control participants were presented with texture and contour stimuli consisting of oriented elements. We induced regularity in the stimuli by manipulating the element orientations resulting in an implicit texture border or explicit contour. Participants had to discriminate curved from straight shapes without making eye movements, while the stimulus presentation time was varied using a QUEST procedure. The results showed that only patients with right hemisphere extinction had a spatial bias, needing a longer presentation time to determine the shape of the border or contour on the contralesional side, especially for borders defined by texture. These results indicate that texture segregation is modulated by attention-related brain areas in the right posterior parietal cortex. 相似文献
10.
Sokolov EN Satinskas R Stabinyte D Pleskacauskas A Vaitkevicius H Stanikunas R Shvegzda A 《Neuroscience and behavioral physiology》2007,37(4):395-402
Analysis of matrixes consisting of the numbers of spikes evoked by the movement of simple and complex stimuli in cat visual
cortex neurons by the principal components method demonstrated vector encoding. The responses of direction detectors to the
movement of points and orientation detectors to changes in the angle of a line were encoded independently in areas V1 and
V2 of the cortex. Each type of detector was represented by excitation of two cardinal neurons generating sine and cosine functions.
The responses of neurons in the associative cortex with selectivity for the direction of movement of specifically oriented
bars depended on four cardinal neurons formed by summation of the excitations of the cardinal neurons of the directional and
orientational channels.
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Translated from Zhurnal Vysshei Nervnoi Deyatel’nosti imeni I. P. Pavlova, Vol. 56, No. 2, pp. 228–235, March–April, 2006. 相似文献
11.
Ai Miyanari Yoshiki Kaneoke Yasuki Noguchi Manabu Honda Norihiro Sadato Yasuyuki Sagara Ryusuke Kakigi 《Neuroscience letters》2007
To identify the BOLD effects related to olfaction in humans, we recorded functional magnetic resonance imaging (fMRI) scans in response intravenously instilled thiamine propyl disulfide (TPD) and thiamine tetrahydrofurfuryl disulfide monohydrochloride (TTFD). TPD and TTFD evoked a strong and weak odor sensation, respectively. Since we did not spray the odor stimuli directly, this method is expected to reduce the effect caused by direct stimulation of the trigeminal nerve. For the analysis of fMRI data, statistical parametric mapping (SPM2) was employed and the areas significantly activated during olfactory processing were located. Both strong and weak odorants induced brain activities mainly in the orbitofrontal gyrus (Brodmann's area: BA 11) in the left hemisphere. TPD (a strong odorant) induced activity in the subthalamic nucleus in the left hemisphere and the precentral gyrus (BA 6) and insula in the right hemisphere. TTFD (a weak odorant) induced activity in the superior frontal gyrus (BA 11) in the right hemisphere. In both circumstances, there was an increase in blood flow at the secondary olfactory cortex (SOC) but not the primary olfactory cortex (POC), probably due to a habituation effect in the POC. From the present results, we found brain activity in not only odor-specific regions but also regions whose levels of activity were changed by an intensity difference of odor stimuli. 相似文献
12.
Hierarchy of cortical responses underlying binocular rivalry 总被引:2,自引:0,他引:2
During binocular rivalry, physical stimulation is dissociated from conscious visual awareness. Human brain imaging reveals a tight linkage between the neural events in human primary visual cortex (V1) and the dynamics of perceptual waves during transitions in dominance during binocular rivalry. Here, we report results from experiments in which observers' attention was diverted from the rival stimuli, implying that: competition between two rival stimuli involves neural circuits in V1, and attention is crucial for the consequences of this neural competition to advance to higher visual areas and promote perceptual waves. 相似文献
13.
Maria Stylianou-Korsnes Miriam Reiner Svein J. Magnussen Marcus W. Feldman 《Brain structure & function》2010,214(4):355-359
Previous literature suggest that processing of visually presented shapes and textures starts in the early visual areas, but
subsequently follow different pathways. The purpose of this experiment was to further investigate differential activation
for shapes and textures in order elucidate the pathways involved in visual shape and texture matching. In the present study,
brain areas involved in discrimination of shapes and textures are mapped, using the same set of stimuli for shape and texture
decisions. Texture matching activates more prefrontal regions than shape matching, particularly regions in the left middle
frontal gyrus and bilateral inferior frontal gyrus. Shape specific activation includes an occipital/temporal region which
is associated with multimodal object matching. The pattern of results suggests that recognition of textures may be based upon
different ordering conditions in memory, which involve a prefrontal network and require a great deal more workload than the
holistic representation of shape. 相似文献
14.
Uylings HB Rajkowska G Sanz-Arigita E Amunts K Zilles K 《Anatomy and embryology》2005,210(5-6):423-431
In human brain imaging studies, it is common practice to use the Talairach stereotaxic reference system for signifying the
convergence of brain function and structure. In nearly all neuroimaging reports, the studied cortical areas are specified
further with a Brodmann Area (BA) number. This specification is based upon macroscopic extrapolation from Brodmann’s projection
maps into the Talairach atlas rather than upon a real microscopic cytoarchitectonic study. In this review we argue that such
a specification of Brodmann area(s) via the Talairach atlas is not appropriate. Cytoarchitectonic studies reviewed in this
paper show large interindividual differences in 3-D location of primary sensory cortical areas (visual cortex) as well as
heteromodal associational areas (prefrontal cortical areas), even after correction for differences in brain size and shape.
Thus, the simple use of Brodmann cortical areas derived from the Talairach atlas can lead to erroneous results in the specification
of pertinent BA. This in turn can further lead to wrong hypotheses on brain system(s) involved in normal functions or in specific
brain disorders. In addition, we will briefly discuss the different ‘Brodmann’ nomenclatures which are in use for the cerebral
cortex. 相似文献
15.
Wouter Schellekens Richard J. A. van Wezel Natalia Petridou Nick F. Ramsey Mathijs Raemaekers 《Brain structure & function》2016,221(2):879-890
The current study investigates if early visual cortical areas, V1, V2 and V3, use predictive coding to process motion information. Previous studies have reported biased visual motion responses at locations where novel visual information was presented (i.e., the motion trailing edge), which is plausibly linked to the predictability of visual input. Using high-field functional magnetic resonance imaging (fMRI), we measured brain activation during predictable versus unpreceded motion-induced contrast changes during several motion stimuli. We found that unpreceded moving dots appearing at the trailing edge gave rise to enhanced BOLD responses, whereas predictable moving dots at the leading edge resulted in suppressed BOLD responses. Furthermore, we excluded biases in directional sensitivity, shifts in cortical stimulus representation, visuo-spatial attention and classical receptive field effects as viable alternative explanations. The results clearly indicate the presence of predictive coding mechanisms in early visual cortex for visual motion processing, underlying the construction of stable percepts out of highly dynamic visual input. 相似文献
16.
Selective attention operates in visual cortex by facilitating processing of selected stimuli and by filtering out unwanted information from nearby distracters over circumscribed regions of visual space. The neural representation of unattended stimuli outside this focus of attention is less well understood. We studied the neural fate of unattended stimuli using functional magnetic resonance imaging by dissociating the activity evoked by attended (target) stimuli presented to the periphery of a visual hemifield and unattended (distracter) stimuli presented simultaneously to a corresponding location of the contralateral hemifield. Subjects covertly directed attention to a series of target stimuli and performed either a low or a high attentional-load search task on a stream of otherwise identical stimuli. With this task, target-search-related activity increased with increasing attentional load, whereas distracter-related activity decreased with increasing load in areas V4 and TEO but not in early areas V1 and V2. This finding presents evidence for a load-dependent push-pull mechanism of selective attention that operates over large portions of the visual field at intermediate processing stages. This mechanism appeared to be controlled by a distributed frontoparietal network of brain areas that reflected processes related to target selection during spatially directed attention. 相似文献
17.
Seung-Hyun Jin Byung-Joo Ham Soo Yong Kim 《International journal of psychophysiology》2005,56(3):249-259
The purpose of this study is to investigate the effects of photic and auditory stimuli on brain functions in schizophrenics by investigating the functional cluster (FC) of EEGs. We recorded EEGs using 16 electrodes on 10 schizophrenic patients and on 10 normal controls during photic and auditory stimuli. We estimated FC would characterize the strongly interactive brain regions among many brain regions. FC refers to the brain regions that interact much more strongly among themselves than with the rest of the brain. Brain regions that belong to the same cluster are therefore all functionally involved while, presumably, the regions that belong to separate clusters are functionally unrelated. When photic and auditory stimuli are applied, the schizophrenic patients have a very similar cluster composed of the right temporal and occipital regions for both conditions, whereas the normal controls show the normally driven information stream from the posterior areas to the prefrontal cortex. Our findings may suggest that in schizophrenics the right temporal and occipital regions strongly interact with neuronal activities not only in the resting condition but also during the stimulation condition. In addition, this strong interaction supports the abnormal brain functional connectivity and the dysfunction of the cortical structure during photic and auditory stimuli. Our study shows the existence and different pattern of FCs for normal controls and schizophrenics. Thus, FC analysis would be a potential tool to investigate the simultaneous neuronal activity of human EEGs. 相似文献
18.
In this paper, the temporal pattern of activity and approximate locations of brain areas related to selective attention and
visual working memory processes were studied with event related potential (ERP) recordings in healthy humans. Three experimental
series included pairs of the following conditions: Face comparison (familiar faces), Pattern comparison (abstract dot patterns),
and Passive viewing. Participants compared pairs of consecutive targets presented in composite images on a computer screen.
Spatio-temporal multiple dipole models were developed for 128-channel ERPs. Keeping dipole locations and orientations constant,
we compared the source activities for ERPs recorded (1) in different tasks for task-specificity of activations, (2) after
the first and second stimuli in the pair, i.e. on the encoding and comparison stages of the task, and (3) after the first
stimulus in different series to compare encoding in different conditions. Sources located in the inferotemporal brain areas,
especially in the left hemisphere, showed increased activity after 200 ms from the first stimulus onset that may indicate
encoding into visual working memory. The anterior sources, located near midline and showing activity around or after 300 ms,
presumably reflect non-specific memory processes and attentional control. Major task-specific differences were observed in
the temporo-parieto-occipital region in 250–500 ms. 相似文献
19.
A direct quantitative relationship between the functional properties of human and macaque V5 总被引:19,自引:0,他引:19
The nature of the quantitative relationship between single-neuron recordings in monkeys and functional magnetic resonance imaging (fMRI) measurements in humans is crucial to understanding how experiments in these different species are related, yet it remains undetermined. We measured brain activity in humans attending to moving visual stimuli, using blood oxygenation level-dependent (BOLD) fMRI. Responses in V5 showed a strong and highly linear dependence on increasing strength of motion signal (coherence). These population responses in human V5 had a remarkably simple mathematical relationship to previously observed single-cell responses in macaque V5. We provided an explicit quantitative estimate for the interspecies comparison of single-neuron activity and BOLD population responses. Our data show previously unknown dissociations between the functional properties of human V5 and other human motion-sensitive areas, thus predicting similar dissociations for the properties of single neurons in homologous areas of macaque cortex. 相似文献
20.
Hemispheric lateralization of somatosensory processing 总被引:9,自引:0,他引:9
Processing of both painful and nonpainful somatosensory information is generally thought to be subserved by brain regions predominantly contralateral to the stimulated body region. However, lesions to right, but not left, posterior parietal cortex have been reported to produce a unilateral tactile neglect syndrome, suggesting that components of somatosensory information are preferentially processed in the right half of the brain. To better characterize right hemispheric lateralization of somatosensory processing, H(2)(15)O positron emission tomography (PET) of cerebral blood flow was used to map brain activation produced by contact thermal stimulation of both the left and right arms of right-handed subjects. To allow direct assessment of the lateralization of activation, left- and right-sided stimuli were delivered during separate PET scans. Both innocuous (35 degrees C) and painful (49 degrees C) stimuli were employed to determine whether lateralized processing occurred in a manner related to perceived pain intensity. Subjects were also scanned during a nonstimulated rest condition to characterize activation that was not related to perceived pain intensity. Pain intensity-dependent and -independent changes in activation were identified in separate multiple regression analyses. Regardless of the side of stimulation, pain intensity--dependent activation was localized to contralateral regions of the primary somatosensory cortex, secondary somatosensory cortex, insular cortex, and bilateral regions of the cerebellum, putamen, thalamus, anterior cingulate cortex, and frontal operculum. No hemispheric lateralization of pain intensity-dependent processing was detected. In sharp contrast, portions of the thalamus, inferior parietal cortex (BA 40), dorsolateral prefrontal cortex (BA 9/46), and dorsal frontal cortex (BA 6) exhibited right lateralized activation during both innocuous and painful stimulation, regardless of the side of stimulation. Thus components of information arising from the body surface are processed, in part, by right lateralized systems analogous to those that process auditory and visual spatial information arising from extrapersonal space. Such right lateralized processing can account for the left somatosensory neglect arising from injury to brain regions within the right cerebral hemisphere. 相似文献