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1.
Geier CF  Garver KE  Luna B 《NeuroImage》2007,35(2):904-915
Extended maintenance delays decrease the accuracy of information stored in spatial working memory. In order to elucidate the network underlying sustained spatial working memory, 16 subjects were scanned using fast event-related fMRI as they performed an oculomotor delayed response task containing trials with "short" (2.5 s) or "long" (10 s) delay periods. Multiple cortical and subcortical regions were common to both delay trial types indicating core task regions. Three patterns of activity were found in a subset of core regions that reflect underlying processes: maintenance-related (e.g., left FEF, right supramarginal gyrus (SMG)), response planning-related (e.g., right FEF, SEF), and motor response-related (e.g., lateral cerebellum (declive)) activation. Several regions were more active during long than short delay trials, including multiple sites in DLPFC (BA 9, 46), indicating a circuitry dynamically recruited to support sustained working memory. Our results suggest that specialized brain processes support extended periods of working memory.  相似文献   

2.
Gould RL  Brown RG  Owen AM  ffytche DH  Howard RJ 《NeuroImage》2003,20(2):1006-1019
We used functional magnetic resonance imaging (fMRI) to assess cortical activations associated with increasing task difficulty (TD) in a visuospatial paired associates learning task. Encoding and retrieval were examined when 100% successful retrieval of three, four, or six object-location pairs had been attained (thus ensuring that performance was matched across subjects). As memory load increased, in general, the number of attempts taken to achieve 100% successful retrieval increased, while the number of trials correctly completed on the first attempt decreased. By modelling parametric variations in working memory load with BOLD signal changes we were able to identify brain regions displaying linear and nonlinear responses to increasing load. During encoding, load-independent activations were found in occipitoparietal cortices (excluding the precuneus for which linear load dependency was demonstrated), anterior cingulate, and cerebellum, while linear load-dependent activations in these same regions were found during retrieval. Nonlinear load-dependent responses, as identified by categorical contrasts between levels of load, were found in the right DLPFC and left inferior frontal gyrus. The cortical response to increasing cognitive demands or TD appears to involve the same, rather than an additional, network of brain regions "working harder."  相似文献   

3.
Cole MW  Schneider W 《NeuroImage》2007,37(1):343-360
Consensus across hundreds of published studies indicates that the same cortical regions are involved in many forms of cognitive control. Using functional magnetic resonance imaging (fMRI), we found that these coactive regions form a functionally connected cognitive control network (CCN). Network status was identified by convergent methods, including: high inter-regional correlations during rest and task performance, consistently higher correlations within the CCN than the rest of cortex, co-activation in a visual search task, and mutual sensitivity to decision difficulty. Regions within the CCN include anterior cingulate cortex/pre-supplementary motor area (ACC/pSMA), dorsolateral prefrontal cortex (DLPFC), inferior frontal junction (IFJ), anterior insular cortex (AIC), dorsal pre-motor cortex (dPMC), and posterior parietal cortex (PPC). We used a novel visual line search task which included periods when the probe stimuli were occluded but subjects had to maintain and update working memory in preparation for the sudden appearance of a probe stimulus. The six CCN regions operated as a tightly coupled network during the 'non-occluded' portions of this task, with all regions responding to probe events. In contrast, the network was differentiated during occluded search. DLPFC, not ACC/pSMA, was involved in target memory maintenance when probes were absent, while both regions became active in preparation for difficult probes at the end of each occluded period. This approach illustrates one way in which a neuronal network can be identified, its high functional connectivity established, and its components dissociated in order to better understand the interactive and specialized internal mechanisms of that network.  相似文献   

4.
Wang L  Zang Y  He Y  Liang M  Zhang X  Tian L  Wu T  Jiang T  Li K 《NeuroImage》2006,31(2):496-504
A selective distribution of Alzheimer's disease (AD) pathological lesions in specific cortical layers isolates the hippocampus from the rest of the brain. However, functional connectivity between the hippocampus and other brain regions remains unclear in AD. Here, we employ a resting state functional MRI (fMRI) to examine changes in hippocampal connectivity comparing 13 patients with mild AD versus 13 healthy age-matched controls. Hippocampal connectivity was investigated by examination of the correlation between low frequency fMRI signal fluctuations in the hippocampus and those in all other brain regions. We found that functional connectivity between the right hippocampus and a set of regions was disrupted in AD; these regions are: medial prefrontal cortex (MPFC), ventral anterior cingulate cortex (vACC), right inferotemporal cortex, right cuneus extending into precuneus, left cuneus, right superior and middle temporal gyrus and posterior cingulate cortex (PCC). We also found increased functional connectivity between the left hippocampus and the right lateral prefrontal cortex in AD. In addition, rightward asymmetry of hippocampal connectivity observed in elderly controls was diminished in AD patients. The disrupted hippocampal connectivity to the MPFC, vACC and PCC provides further support for decreased activity in "default mode network" previously shown in AD. The decreased connectivity between the hippocampus and the visual cortices might indicate reduced integrity of hippocampus-related cortical networks in AD. Moreover, these findings suggest that resting-state fMRI might be an appropriate approach for studying pathophysiological changes in early AD.  相似文献   

5.
Smooth pursuit eye movements (SPEM) are performed to track slowly moving visual targets and are accompanied by saccades whenever foveal representation is lost. In the present study, we correlated the cerebral activation as assessed by functional magnetic resonance imaging with parameters of eye movement performance in order to determine the cortical areas involved in the retinal and extraretinal processing of maintaining smooth pursuit velocity (SPV) and generating saccades in 16 healthy males. The stimulus consisted of a target moving at a constant velocity of 10 degrees/s with and without target blanking. During constant target presentation, SPV was positively correlated with the BOLD signal in the right V5 complex and negatively correlated with the BOLD response in the left dorsolateral prefrontal cortex (DLPFC). In the condition with target blanking, additional negative correlations with SPV were found in the left frontal eye field (FEF), the left parietoinsular vestibular cortex (PIVC) and the left angular gyrus. Saccadic frequency was negatively correlated with activations of the right mesial intraparietal sulcus (IPS) during both conditions and the right premotor area during continuous target presentation. We conclude that V5 is directly related to the maintenance of an optimal smooth pursuit velocity during visual feedback, whereas the FEF, PFC, angular gyrus and PIVC are involved in reconstitution and prediction whenever SPV decreases, especially during maintenance of smooth pursuit in the absence of a visual target. Furthermore, we suggest that parietal areas are related to the suppression of saccades during smooth pursuit.  相似文献   

6.
Frontal and posterior parietal activations have been reported in numerous studies of working memory and visuospatial attention. To directly compare the brain regions engaged by these two cognitive functions, the same set of subjects consecutively participated in tasks of working memory and spatial attention while undergoing functional MRI (fMRI). The working memory task required the subject to maintain an on-line representation of foveally displayed letters against a background of distracters. The spatial attention task required the subject to shift visual attention covertly in response to a centrally presented directional cue. The spatial attention task had no working memory requirement, and the working memory task had no covert spatial attention requirement. Subjects' ability to maintain central fixation was confirmed outside the MRI scanner using infrared oculography. According to cognitive conjunction analysis, the set of activations common to both tasks included the intraparietal sulcus, ventral precentral sulcus, supplementary motor area, frontal eye fields, thalamus, cerebellum, left temporal neocortex, and right insula. Double-subtraction analyses yielded additional activations attributable to verbal working memory in premotor cortex, left inferior prefrontal cortex, right inferior parietal lobule, precuneus, and right cerebellum. Additional activations attributable to covert spatial attention included the occipitotemporal junction and extrastriate cortex. The use of two different tasks in the same set of subjects allowed us to provide an unequivocal demonstration that the neural networks subserving spatial attention and working memory intersect at several frontoparietal sites. These findings support the view that major cognitive domains are represented by partially overlapping large-scale neural networks. The presence of this overlap also suggests that spatial attention and working memory share common cognitive features related to the dynamic shifting of attentional resources.  相似文献   

7.
Visual conjunction search is proposed to be a multicomponent process which involves scaling and successive shifts of attention in space as well as object identification. Here, we first mapped brain areas sustaining the proposed attentional subprocesses and then tested whether their activity was modulated by search load, i.e., the number of shifts, as predicted by serial search models. Search load was manipulated indirectly by precueing a varying number of locations at which relevant objects were shown. Multiple subregions within the intraparietal sulcus (IPS) and the prefrontal cortex were activated after cueing. Activity in the right posterior IPS was modulated by the distance of attention shifts and in the left posterior IPS by "zooming out" to cover a large region of the visual field. More anterior subregions of the left IPS responded to object identification irrespective of the need for serial scanning. Corresponding regions in the right IPS were modulated parametrically with respect to search load, along with the right temporoparietal junction. These results support a functional segregation of subregions of the IPS. The posterior regions participate in large-scale shifts and scaling of the attentional focus and the anterior regions in object identification and rapid serial shifts during search. The sustained activation in the frontal eye fields after cueing suggests a role in maintaining attention in the periphery. Together with the findings in early visual areas from this experiment (Müller et al., 2003) the current observations are best accounted for by hybrid models of visual conjunction search, where parallel processing in visual and temporoparietal regions and serial scanning controlled by the right IPS cooperate.  相似文献   

8.
Movement-associated cortical changes have been shown in several neurological conditions and were found to be associated to the extent of brain and cord damage. Devic's neuromyelitis optica (DNO) is characterized by a severe involvement of the cord and optic nerve, with sparing of the brain. To assess the actual role of cord pathology on the pattern of movement-associated cortical recruitment, we obtained functional magnetic resonance imaging (fMRI) from patients with DNO and investigated whether the extent of brain activation is correlated with the extent of cervical cord damage. We studied 10 right-handed DNO patients and 15 sex- and age-matched healthy controls. The MRI assessment consisted of the following: (a) fMRI during repetitive flexion extension of the last four fingers of the right and left hand, (b) brain and cervical cord conventional MRI, and (c) cervical cord magnetization transfer (MT) MRI. Compared to controls and for both tasks, DNO patients had an increased recruitment of several regions of the sensorimotor network (primary sensorimotor cortex, postcentral gyrus, middle frontal gyrus, rolandic operculum, secondary sensorimotor cortex, precuneus, and cerebellum) and of several other regions mainly in the temporal and occipital lobes, such as MT/V5, the fusiform gyrus, the cuneus, and the parahippocampal gyrus. For both tasks, strong correlations (r values ranging from -0.76 to -0.85) were found between relative activations of cortical sensorimotor areas and the severity of cervical cord damage. This study shows an abnormal pattern of movement-associated cortical activations in patients with DNO, which extends beyond the 'classical' sensorimotor network and also involves visual areas devoted to motion processing. The correlation found between fMRI changes and the extent of cord damage suggests that such functional cortical changes might have an adaptive role in limiting the clinical outcome of DNO structural pathology.  相似文献   

9.
Applying a recently developed method to analyze gyrification with excellent spatial resolution across thousands of points across the lateral and medial cortical surface, we mapped differences in cortical surface anatomy between subjects with Williams syndrome (WS; n=42) and an age-matched sample of healthy subjects (n=40). WS subjects showed increased gyrification bilaterally in occipital regions and over the cuneus. Differences were more pronounced in the left hemisphere than in the right, with additional regions of increased gyrification in WS in the left precuneus, posterior and anterior cingulate, paracentral and mesial frontal lobe. No cortical area was significantly more convoluted in healthy subjects relative to the WS subjects. On the lateral surfaces, the direction and pattern of gyrification asymmetries were similar in WS subjects and controls; posterior brain regions had greater gyrification in the left hemisphere, while anterior brain regions showed greater gyrification in the right hemisphere. On the medial surfaces, control subjects and WS individuals differed considerably with respect to the degree but also direction of gyrification asymmetry. Our findings confirm and extend previous studies measuring cortical complexity at the global whole-brain or hemispheric levels. The observed gyrification abnormalities in individuals with WS might be related to dysfunctions in neuronal circuits and consequently contribute to the distinct cognitive and behavioral profile accompanying the disorder.  相似文献   

10.
The present study evaluated the effect of context on behavior and brain activity during saccade tasks. FMRI and eye movement data were collected while 36 participants completed three runs in a block design: (1) fixation alternating with pro-saccades, (2) fixation alternating with anti-saccades, and (3) pro- alternating with anti-saccades. Two task-related data-driven regressors, identified using independent component analysis, were used in GLM analyses. Brain activity associated with anti- and pro-saccades were compared under both single (runs 1 and 2) and mixed saccade (run 3) conditions. Brain areas consistently associated with anti-saccades in previous studies, including striatum, thalamus, cuneus, precuneus, lateral and medial frontal eye fields (FEF), supplementary eye fields (SEF), and prefrontal cortex (PFC) showed significantly greater percent signal change during the fixation/anti- compared with the fixation/pro-saccade run. During the pro/anti run, however, only precuneus, SEF and FEF showed greater activation during the anti-saccade trials. This is a clear demonstration that the saccade-related neural circuitry is affected by context. Behavioral results suggest that performance on saccade tasks is also affected by context. Participants made more direction errors on pro-trials that followed anti-trials than on pro-trials that followed fixation. Results from this study indicate that precuneus, SEF and FEF, which showed anti-saccade-related activity during both comparisons, may be more important for supporting this complex behavioral response. Other brain regions, such as PFC, however, which showed anti-saccade-related activity during only the single task comparison, may be more involved in response selection and/or context updating.  相似文献   

11.
A lot is known about the neural basis of directing attention based on explicit cues. In real life however, attention shifts are rarely directed by explicit cues but rather generated implicitly, for example on the basis of previous experience with a given situation. Here, we aimed at studying attention shifts dependent on recent trial history. While explicitly cued attention shifts involve activity in cortex of the intraparietal sulcus, whether this region is also involved in shifting attention according to recent history is still unknown. We asked observers to detect targets in a stream of visual stimuli with three feature dimensions: color, shape and motion. Critically, target occurrence probability was always higher in one stimulus dimension than in the others, and probabilities switched between dimensions over blocks of trials. After each probability switch, target detection times decreased exponentially for high-probability targets and increased for low-probability targets, compatible with gradual shifts in attention dependent on trial history since the switch. BOLD signal in left prefrontal and intraparietal sulcus regions was higher in the early phase after the switch, while anterior cingulate, cuneus, precuneus, temporal and more anterior frontal regions showed more activation later after the switch. These findings are compatible with the engagement of regions involved in the establishment and maintenance of attentional sets. BOLD signal in left intraparietal sulcus correlated with the size of the performance changes consecutive to the detected targets, suggesting that it reflects the size of attention shifts induced by updating target probabilities over recent trial history.  相似文献   

12.
We used functional magnetic resonance imaging (fMRI) to investigate cortical activation during the performance of three oculomotor tasks that impose increasing levels of cognitive demand. (1) In a visually guided saccade (VGS) task, subjects made saccades to flashed targets. (2) In a compatible task, subjects made leftward and rightward saccades in response to foveal presentation of the uppercase words "LEFT" or "RIGHT." (3) In a mixed task, subjects made rightward saccades in response to the lowercase word "left" and leftward saccades in response to the lowercase word "right" on incompatible trials (60%). The remaining 40% of trials required compatible responses to uppercase words. The VGS and compatible tasks, when compared to fixation, activated the three cortical eye fields: the supplementary eye field (SEF), the frontal eye field (FEF), and the parietal eye field (PEF). The mixed task, when compared to the compatible task, activated three additional cortical regions proximate to the three eye fields: (1) rostral to the SEF in medial frontal cortex; (2) rostral to the FEF in dorsolateral prefrontal cortex (DLPFC); (3) rostral and lateral to the PEF in posterior parietal cortex. These areas may contribute to the suppression of prepotent responses and in holding novel visuomotor associations in working memory.  相似文献   

13.
目的静息态功能磁共振成像探索鞍区占位视力受损患者引起的脑功能活动改变情况。方法筛选21例鞍区占位视力受损患者,并选择与之年龄和性别相匹配的健康对照者21名。计算ALFF、ReHo、FC值,然后采用双样本t检验统计学方法进行研究。结果与正常对照组相比,鞍区占位视力受损患者组双侧楔叶、左侧舌回、右侧SMA区域ALFF值降低,双侧豆状核ALFF值升高。双侧楔叶ReHo值降低,楔前叶、左侧岛叶皮层和左侧豆状核ReHo值升高,并且楔前叶和左侧岛叶皮层的ReHo值与常规磁共振手动测量的占位的左右直径存在明显正相关性。在功能连接结果中,高级视觉皮层与双侧楔叶、双侧顶上小叶、双侧颞上回、双侧缘上回、中央前回、中央后回及SMA存在功能连接减弱。结论鞍区占位视力受损患者存在视觉以及视觉以外相关脑区神经元活动异常。  相似文献   

14.
目的采用静息态功能磁共振成像(resting state functional MRI,rs-fMRI)低频振幅(amplitude of low-frequency fluctuation,ALFF)方法探究多系统萎缩(multiple system atrophy,MSA)患者认知相关的自发脑活动改变。材料与方法对29例认知功能正常的MSA患者(MSA-normal cognition,MSA-NC)、33例伴轻度认知功能障碍的MSA患者(MSA-mild cognitive impairment,MSA-MCI)与33名健康对照者(healthy control,HC)进行rs-fMRI扫描。应用ALFF方法比较各组间自发脑活动改变,并对患者组间存在差异脑区的ALFF值与认知评分进行相关性分析。结果与HC相比,MSA-NC在左侧角回及右侧颞中回出现ALFF增强;与HC相比,MSA-MCI在双侧背外侧前额叶、内侧前额叶、前扣带回、中扣带回出现ALFF减低,而在双侧颞下回、角回、左侧枕中回、右侧颞中回、楔前叶及右侧小脑、小脑蚓出现ALFF增强。与MSA-NC相比,MSA-MCI在右侧额叶皮层出现ALFF减低,并与蒙特利尔认知评估量表(montreal cognitive assessment scale,MoCA)评分呈正相关(r=0.531,P<0.05);在右侧小脑出现ALFF增强,并与MoCA评分呈负相关(r=-0.499,P<0.05)。结论MSA特异的轻度认知功能障碍是由小脑与额叶皮层损伤共同介导,其中小脑起到代偿作用。  相似文献   

15.
目的 采用激活似然估计(ALE)荟萃分析方法观察长期专业技能训练诱发运动相关专业人员大脑灰质结构的可塑性。方法 于CNKI、PubMed、Web of Science数据库及Google scholar检索2005年1月1日-2020年6月12日基于体素形态学分析(VBM)运动相关专业人员大脑灰质变化的文献,以Ginger ALE软件包对检索结果进行Meta分析。结果 共纳入21项研究,包括396名专业运动员(试验组)和538名健康对照者(对照组)。与对照组相比,试验组左侧脑岛、右侧顶下小叶、右侧额中回、右侧前扣带回、左侧楔前叶及右侧颞上回灰质体积增大;右侧小脑前叶、右侧小脑顶、左侧海马旁回、右侧丘脑、右侧小脑后叶、右侧额上回及左侧楔前叶灰质密度增加。结论 运动相关专业人员多个脑区灰质结构可塑性可能与其所受长期专业技能训练相关。  相似文献   

16.
The cerebellum is thought to be engaged not only in motor control, but also in the neural network dedicated to visual processing of body motion. However, the pattern of connectivity within this network, in particular, between the cortical circuitry for observation of others' actions and the cerebellum remains largely unknown. By combining functional magnetic resonance imaging (fMRI) with functional connectivity analysis and dynamic causal modelling (DCM), we assessed cerebro-cerebellar connectivity during a visual perceptual task with point-light displays depicting human locomotion. In the left lateral cerebellum, regions in the lobules Crus I and VIIB exhibited increased fMRI response to biological motion. The outcome of the connectivity analyses delivered the first evidence for reciprocal communication between the left lateral cerebellum and the right posterior superior temporal sulcus (STS). Through communication with the right posterior STS that is a key node not only for biological motion perception but also for social interaction and visual tasks on theory of mind, the left cerebellum might be involved in a wide range of social cognitive functions.  相似文献   

17.
Although there is clear evidence of alcoholism-related damage to the frontal lobes and cerebellum from neuroimaging, neuropathological, and neuropsychological studies, the functional role of the cerebellum and cerebrocerebellar circuits related to verbal working memory deficits of alcoholics have not been well studied. Alcoholic and nonalcoholic subjects performed a Sternberg verbal working memory task while receiving an fMRI scan in a 3T magnet. This task has been found in previous studies to reliably activate the articulatory control and phonological storage components of the phonological loop (left frontal, left temporal/parietal structures, right superior cerebellar regions) in young healthy controls. We hypothesized that the alcoholics would show a different pattern of activation from the controls, based on the regions of interest (ROIs) identified from a previous study of healthy subjects. Behavioral results showed the alcoholics to be performing at a comparable level to the matched controls in terms of accuracy and median reaction time, with no statistically significant differences. However, analysis of the functional data revealed that the alcoholics exhibited greater activation in the left frontal (BA44/45) and right superior cerebellum (HVI) regions relative to the matched controls. These findings suggest that brain activation in left frontal and right cerebellar regions that support the articulatory control system of verbal working memory may require a compensatory increase in alcoholics in order to maintain the same level of performance as controls.  相似文献   

18.
Working memory (WM) capacity limitations and their neurophysiological correlates are of special relevance for the understanding of higher cognitive functions. Evidence from behavioral studies suggests that restricted attentional resources contribute to these capacity limitations. In an event-related functional magnetic resonance imaging (fMRI) study, we probed the capacity of the human visual WM system for up to four complex nonnatural objects using a delayed discrimination task. A number of prefrontal and parietal areas bilaterally showed increased blood oxygen level-dependent activity, relative to baseline, throughout the task when more than one object had to be held in memory. Monotonic increases in response to memory load were observed bilaterally in the dorsolateral prefrontal cortex (DLPFC) and the presupplementary motor area (pre-SMA). Conversely, activity in the frontal eye fields (FEFs) and in areas along the intraparietal sulcus (IPS) peaked when subjects had to maintain only two or three objects and decreased in the highest load condition. This dissociation of memory load effects on cortical activity suggests that the cognitive operations subserved by the IPS and FEF, which are most likely related to attention, fail to support visual WM when the capacity limit is approached. The correlation of brain activity with performance implies that only the operations performed by the DLPFC and pre-SMA, which support an integrated representation of visual information, helped subjects to maintain a reasonable level of performance in the highest load condition. These results indicate that at least two distinct cortical subsystems are recruited for visual WM, and that their interplay changes when the capacity limit is reached.  相似文献   

19.
目的 采用静息态功能MRI局部一致性(ReHo)的方法,探讨血氨正常高间接胆红素肝硬化患者脑功能的改变。方法 分别对53例血氨正常高间接胆红素肝硬化患者(肝硬化组)及60名健康志愿者(正常对照组)行静息态fMRI,采用ReHo方法分析,比较并获得2组ReHo值的差异性脑区。将2组差异性脑区的ReHo值与间接胆红素浓度进行相关分析。结果 与正常对照组相比较,肝硬化组ReHo值增高的脑区包括左背外侧额上回、左眶部额上回、左顶下缘角回、左中央前回、右尾状核、右豆状壳核、右岛叶、右嗅皮质(P均<0.001),ReHo值降低的脑区包括左枕上回、左枕中回、左楔叶、左岛盖部额下回、右中央旁小叶、右楔前叶、右枕中回、双侧舌回及双侧小脑(P均<0.001)。肝硬化患者右岛叶和右豆状壳核的平均ReHo值与间接胆红素浓度呈正相关(r=0.32,P=0.021)。结论 血氨正常高间接胆红素肝硬化患者静息态脑功能存在增强和减弱,间接胆红素浓度与部分脑区功能相关,高间接胆红素对成人脑功能也有一定的影响。  相似文献   

20.
Previous studies have shown that non‐invasive stimulation of the dorsolateral prefrontal cortex (DLPFC) could modulate experimentally induced pain and working memory (WM) in healthy subjects. However, the two aspects have never been assessed concomitantly. The present study was set up to investigate the effects of transcranial direct current stimulation (tDCS) of the DLPFC on thermal pain and WM in the same population of healthy volunteers. In a randomized and balanced order of different sessions separated by 1 week, 20 min of 2 mA anodal, cathodal or sham tDCS were applied to the left or right DLPFC in two separate experiments. Twelve healthy volunteers were enrolled for each stimulated hemisphere. Warm and cold detection thresholds, heat and cold pain thresholds as well as heat pain tolerance thresholds were measured before, during and following tDCS. WM was assessed by a 2‐back task applied once during cortical stimulation. Anodal tDCS of the right DLPFC led to an increase of tolerance to heat pain. The 2‐back task revealed fewer outliers during cathodal tDCS of the left DLPFC. The present data show an involvement of the DLPFC in the processing of pain and WM. There was no correlation between these findings, suggesting that the analgesic effects of cortical stimulation are not associated with cognitive processing. However, this conclusion is difficult to affirm because of some limitations of the study regarding the parameters of stimulation or a ceiling effect of the 2‐back task for instance.  相似文献   

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