Vernier But Not Grating Acuity Contributes to an Early Stage of Visual Word Processing / 神经科学通报·英文版

The process of reading words depends heavily on efficient visual skills, including analyzing and decomposing basic visual features. Surprisingly, previous reading-related studies have almost exclusively focused on gross aspects of visual skills, while only very few have investigated the role of finer skills. The present study filled this gap and examined the relations of two finer visual skills measured by grating acuity (the ability to resolve periodic luminance variations across space) and Vernier acuity (the ability to detect/discriminate relative locations of features) to Chinese character-processing as measured by character form-matching and lexical decision tasks in skilled adult readers. The results showed that Vernier acuity was significantly correlated with performance in character form-matching but not visual symbol form-matching, while no correlation was found between grating acuity and character processing. Interestingly, we found no correlation of the two visual skills with lexical decision performance. These findings provide for the first time empirical evidence that the finer visual skills, particularly as reflected in Vernier acuity, may directly contribute to an early stage of hierarchical word processing.

Attention and Working Memory Task-Load Dependent Activation Increase with Deactivation Decrease after Caffeine Ingestion

PURPOSE: Caffeine is the most widely consumed psychostimulant. It is often adopted as a tool to modulate brain activations in fMRI studies. However, its pharmaceutical effect on task-induced deactivation has not been fully examined in fMRI. Therefore, the purpose of this study was to examine the effect of caffeine on both activation and deactivation under sustained attention. MATERIALS AND METHODS: Task fMRI was acquired from 26 caffeine naive healthy volunteers before and after taking caffeine pill (200 mg). RESULTS: Statistical analysis showed an increase in cognition-load dependent task activation but a decrease in load dependent de-activation after caffeine ingestion. Increase of attention and memory task activation and its load-dependence suggest a beneficial effect of caffeine on the brain even though it has no overt behavior improvement. The reduction of deactivation by caffeine and its load-dependence indicate reduced facilitation from task-negative networks. CONCLUSION: Caffeine affects brain activity in a load-dependent manner accompanied by a disassociation between task-positive network and task-negative network.

The neural mechanism of left hemiparalexia and left hemialexia in reading Chinese characters / 中华物理医学与康复杂志

Objective To investigate the underlying neural mechanism of left hemiparalexia and left hemialexia in reading Chinese characters. Methods A patient with reading disorders caused by brain infarctions at the left ventralis medialis occipitotemporal lobe and the splenium of the corpus callosum was studied. A series of neuropsychological tests, such as reading Chinese characters presented in the central foveal field or in the left and right half of the foveal field, were conducted with the patient, and neuroimaging techniques including high spatial resolution 3D-MRI and diffusion tensor tractography (DTT) were used to examine whether or not there were lesions of the neural pathway. Results The patient showed left hemiparalexia, which was characterized by making substitution or omission mistakes, mostly in the left parts of Chinese characters, and also left hemialexia(alexia for characters presented in left visual field). 3D-MRI demonstrated infarctions in the left ventral mesial occipitotemporal area and in the left side of the splenium of the corpus callosum. The left lateral mid-fusiform cortex, which has been identified as the visual word form area(VWFA), was almost intact. DTT indicated the major forceps fibers running through the splenium were all disconnected due to the infarction of the left splenium. Conclusion As a result of disruption of the splemium-major forceps pathway, visual character information in the left visual field which is initially projected to the right occipital cortex cannot be transferred from the right visual cortex to the left VWFA. This mechanism of left hemiparalexia and left hemialexia in reading Chinese characters is similar to that in reading English words.

Pre-surgical evaluation of the cerebral tumor in the left language related areas by functional MRI / 中华放射学杂志

Objective To evaluate the application of combination of BOLD-fMRI and diffusion tensor tractography (DTT) in pre-operative evaluation of cerebral tumors located at the left language related areas.Methods A non-vocal button pressing semantic judging paradigm was developed and validated in 10 right-handed volunteers at 3 T.After validation, this protocol combined with DTI were applied to 15 patients with left cerebral tumor prior to surgical resection, and 3 of them had aphasia fMRI data analysis was on subject-specific basis by one-sampled t-test.The distance from the tumor to Broca area and pre-central "hand-knot" area were measured separately.Functional language laterality index (LI) was calculated by taking out Broca area and Wernicke area.Three dimensional architecture of frontal lobe white matter fibers, especially arcuate fasciculus, were visualized using diffusion tensor tractography on Volume-one software.The images demonstrating relationship among tumor, language activation areas and white matter fibers were reviewed by neurosurgeons as part of pre-operative planning.One year after the operation, patients were followed up with MRI and language function test Results The non-vocal semantic judging paradigm successfully detect Broca area, Wernicke area and pre-central "hand-knot" area In 12 of 15 patients, the relationship of Broca area and pre-central motor area to the left brain tumor in language related areas was identified, which make the pre-operative neurosurgical plan applicable to minimize the disruption of language and motor.8 patients had the left language dominant hemisphere, 3 patients with the right language dominant hemisphere and 1 patient with bilateral dominance.The other 3 patients' fMRI data were corrupted by patients' motion.Diffusion tensor images were corrupted by motion in 1 patient but demonstrated the impact of tumor on left arcuate fasciculus in 14 patients.Diffusion tensor tractography showed disruption of left arcuate fasciculus in 3 patients, deviation/deformation in 6 cases and unaffected by tumor in the remaining 5 cases.Pre-operative review of language activation maps and diffusion tensor tractography of arcuate fasciculus influenced the surgical approach in all 12 patients.Post-operatively, one patient died accidentally, the remaining 14 patients showed no tumor recurrence after one year follow-up.No patient showed deterioration of language function, though 3 patients who had aphasia pre-operation improved slightly.Conclusion The combination of fMRI and diffusion tensor tractography is helpful for identifying the relationship of brain tumors with language cortex and white matter fibers, which is important for sparing language function during individually surgical plan.

Function connectivity MRI to evaluate the changes of the motorial nerve net in patients with brain tumors adjacent to the central sulcus occurred with reorganization of motor function / 中华放射学杂志

Objective We investigated the changes of the motorial network in patients suffered from brain tumors adjacent to the central sulcus occurred with reorganization of motor function using function connectivity MRI(fcMRI)technique in order to provide the new evidence for the compensational hypothesis of the reorganization caused by focal lesions.Methods Using 1.5 T MRI unit,14 patients with brain tumors in the vicinity of the central sulcus occurred with reorganization of motor function and 6 normal volunteers were examined with fcMRI technique while the subjects performed no task.By selecting seed voxels(region of interest)in the regions showing the most activation in M1 area on the activated map and cross correlating with every voxel within the brain,the fcMRI maps based on unilateral primary motor(M1)area were calculated.The location,extent and volume of the region showing significant connectivity to the several seed voxel,such as left/right M1 area in the health group and affected/unaffected M1 area in the patient group were evaluated on the fcMRI map.Results In healthy group,the extent and volume of the region showing significant connectivity to the left M1 area[(9514.17±186.92)mm3]were almost similar to those to the right M1 area [(9364.67±382.75)mm3].There showed no significant difference in motor connectivity between the two groups(P>0.05).In the tumor group,the volume of regions showing significant connectivity to the M1 area located in the affected hemisphere [(11193.14±811.29)mm3]was obviously higher than that of regions based on the seed voxel in the unaffected side[(6549.86±400.94)mm3](t=20.383,P＜0.01).The volume was significantly different among the regions showing high connectivity to the M1 of the affected side in patient group.those showing significant connectivity to the left M1 and fight M1 in health group(P＜0.01),the former was the biggest(P＜0.01).The extent of the regions showing connectivity to the affected M1 was consistent with the reorganization area of motor function revealed by fMRI.The volume of regions showing significant connectivity to M1 area of unaffected hemisphere in patient group showed significant difference compared with those showing significant connectivity to the left M1 and right M1 in health group(P＜0.01),the former was smallest(LSD,P＜0.01).especially in the affected hemisphere.It might mean the disrupted functional connectivity between the M1 area of unaffected hemisphere in patient group and motor area located in the collateral side.Conclusion The increased connectivity between the M1 area of the affected hemisphere and the other motor cortex might indicate that the reorganization in the motor pathway and the formation of the potential compensatory network second to the impairment of the normal motor pathway resulted in the functional reorganization of the motor cortex.The fcMRI technique might be a valuable approach to reveal the pathophysiological changes of nerve network caused by brain tumor.

Recent Advances in Research on Reading and Processing of Chinese Characters with Functional Magnetic Resonance Imaging / 国际脑血管病杂志

Understanding the basic mechanism of reading is the foundation for studying the pathogenesis of alexia and its rehabilitation care. Functional magnetic resonance imaging is one of imaging methods that can display the neurological activities in brain in vivo. It has been used in the studies of linguistics in recent years, particularly in the mechanisms of reading and processing. The article reviews the lateralization of Chinese single word processing and whether or not the specific brain region for cognitive processing of Chinese characters exists.

Magnetic resonance imaging characteristics of visuospatial location defect in patients with mild cognitive impairment / 中国组织工程研究

BACKGROUND: Patients with Alzheimer disease (AD) usually have visuospatial dysfunction at an early stage and most patients with AD were evolved from mild cognitive impairment (MCI).OBJECTIVE: To detect whether a patient with MCI has a visuospatial dysfunction similar to AD. To compare the cerebral activation with ferromagnetic resonance between the healthy people and the patients with mild cognitive disorder.DESIGN: A case controlled observationSETTING: The Department of Neurology of the First Hospital of Peking University.PARTICIPANTS: Nine inpatients with mild cognitive disorder hospitalized at the Department of Neurology of the First Hospital of Peking University from April 2000 to March 2003 were involved and other 9 healthy people matching in age, gender and the educational level were also involved.METHODS: The subjects had the task of discriminating the different finger positions on the clockface. They could see the mission clearly showed on the cloth through refractor, and they were supposed to give the corresponding reaction to different cognitive tasks with left and right hands pressing the keys according to visual sign generated by the computer.Block design was adopted in the cognitive task. Stimulus block and baseline block appeared in turn. Baseline block displayed "+" mapped in the center of the image and was kept for 21s. Stimulus block displayed 10 pictures successively. The finger position of the two clockfaces among three clockfaces was the same in one picture. The absolute value of the rotated angles of the different clockfaces in each image on the same stimulus block was the same. The angles formed by six stimulus block fingers arranged randomly were 300, 450, 1800. The two clockfaces had the same finger positions, and the subjects were requested to discriminate the finger position of these two clockfaces. It was carried out on a 1.5 T GEMRTWIN magnetic resonance scanning apparatus. Then t test was performed to work out the right reaction time and proper rate with Excel software between the patients with mild Alzheimer's disease and the healthy persons. Pretreatment and statistical analyses were performed with analysis of functional neuroimages software used internationally.MAIN OUTCOME MEASURES: Comparison of the reaction time and proper rate between the two groups.parison of the reaction time between the two groups: The reaction time for distinguishing the change of 300, 450, 1800 was longer than that in the control group, and there was significant difference in distinguishing the change of 300, 450, 1800 for the patients [(1 776.7±570.2), (1 646.3±432.7)ms;of the proper rate between the two groups: The proper rate for distinguishing the change of 300, 450, 1800 was significantly lower than that in the control group (62.8±21.4)%, (82.8±15.8)% ;(76.7±17.0)%, (95.0±8.7)%; (69.4vation: the activation density at the bilateral parietal lobe, bilateral temporooccipital borderline and bilateral lateral striate cortex in patients was weaker than that in the control group (P ＜ 0.05).CONCLUSION: Neural network activation related with visual space in patients with MCI was weaker than that in the healthy people indicating that visuospatial impairment exists in the patients with mild cognitive impairment.

Calculation ability in mild cognitive impairment: A functional magnetic resonance imaging study / 中国康复理论与实践

@#ObjectiveTo explore the early diagnosis of Alzheimer's disease (AD),the arithmetic calculation ability in the patients with mild cognitive impairment (MCI) was detected under the functional magnetic resonance imaging (fMRI),combined with the neuropsychological test.Methods8 patients with MCI and 9 controls matched for the age, gender, level of education and handedness performed the subtraction of two digits presented visually while the MR machine was scanning. The raw data of the fMRI were processed with the software AFNI. The reaction time and correct ratio were analyzed with the statistical software Excel.ResultsCompared with the controls, the patients manifested longer reaction time and lower correct ratio. The patients' brain activation showed significant decrease in the inferior frontal lobe,temporal neocortex and inferior parietal area mainly in the left hemisphere. On the contrary, the activation intensity and extension in the right inferior frontal lobe were increased as compensation.ConclusionsThe patients with MCI have the deficit in calculation ability. The examination of the calculation by means of the cognitive neuropsychology and fMRI test can offer a powerful reference for the early diagnosis of AD.

Mapping cortical areas associated with Chinese word processing using functional magnetic resonance imaging / 中华医学杂志(英文版)

<p><b>OBJECTIVES</b>To identify the cortical areas engaged during Chinese word processing using functional magnetic resonance imaging (fMRI) and to examine the reliability and reproducibility of fMRI for localization of functional areas in the human brain.</p><p><b>METHODS</b>FMRI data were collected on 8 young, right-handed, native Chinese speakers during performance of Chinese synonym and homophone judgment tasks on two different clinical MRI systems (1.5 T GE Signa Horizon and 1.5 T Siemens Vision). A cross correlation analysis was used to statistically generate the activation map.</p><p><b>RESULTS</b>Broca's area, Wernicke's area, bilateral extrastriate, and ventral temporal cortex were significantly activated during both the synonym and homophone activities. There was essentially no difference between results acquired on two different MRI systems.</p><p><b>CONCLUSIONS</b>FMRI can be used for localizing cortical areas critical to Chinese language processing in the human brain. The results are reliable and well reproducible across different clinical MRI systems.</p>

Preliminary study on the mechanism of reading recovery in a pure alexia by using functional MRI / 中华放射学杂志

Objective To observe the changes of the brain function during reading recovery by using functional MRI (fMRI),and to provide the experimental data in elucidating the mechanism on the recovery of reading and language function.Methods fMRI was performed in a native Chinese patient with pure alexia on the 45 th and 130 th day after the onset,respectively.Three kinds of Chinese characters were presented during the scan and the patient was asked to make the judgement weather he could recognize the characters or not.The brain activation maps were acquired after postprocessing,and the activated location and volume were compared between the first and second experiments.Results In both experiments,Broca area,Wernicke area,and the right extrastriate were significantly activated,while the left extrastriate around the lesion was markedly activated only in the second experiment,and the volume of activation in the right extrastriate in the second experiment was about 3 times as large as that in the first experiment.Conclusion The left extrastriate cortex is one of the key areas responsible for reading function in the brain.The recovery of reading function can be compensated in contralateral corresponding cortical area,or it can be the result of reorganization in ipsilateral peri-lesion cortex.Both mechanisms may simultaneously play important roles in reading recovery.