Specialization of phonological and semantic processing in Chinese word reading

The purpose of this study was to examine the neurocognitive network for processing visual word forms in native Chinese speakers using functional magnetic resonance imaging (fMRI). In order to compare the processing of phonological and semantic representations, we developed parallel rhyming and meaning association judgment tasks that required explicit access and manipulation of these representations. Subjects showed activation in left inferior/middle frontal gyri, bilateral medial frontal gyri, bilateral middle occipital/fusiform gyri, and bilateral cerebella for both the rhyming and meaning tasks. A direct comparison of the tasks revealed that the rhyming task showed more activation in the posterior dorsal region of the inferior/middle frontal gyrus (BA 9/44) and in the inferior parietal lobule (BA 40). The meaning task showed more activation in the anterior ventral region of the inferior/middle frontal gyrus (BA 47) and in the superior/middle temporal gyrus (BA 22,21). These findings are consistent with previous studies in English that suggest specialization of inferior frontal regions for the access and manipulation of phonological vs. semantic representations, but also suggest that this specialization extends to the middle frontal gyrus for Chinese. These findings are also consistent with the suggestion that the left middle temporal gyrus is involved in representing semantic information and the left inferior parietal lobule is involved in mapping between orthographic and phonological representations.     

Neural correlates of working memory performance in adolescents and young adults with dyslexia

Behavioral studies indicate deficits in phonological working memory (WM) and executive functioning in dyslexics. However, little is known about the underlying functional neuroanatomy. In the present study, neural correlates of WM in adolescents and young adults with dyslexia were investigated using event-related functional magnetic resonance imaging (fMRI) and a parametric verbal WM task which required the manipulation of verbal material. Dyslexics were not significantly slower than controls; however, they were less accurate with the highest WM demand. The functional analysis excluded incorrectly performed and omitted trials, thus controlling for potential activation confounds. Compared with control subjects, both increased and decreased activation of the prefrontal cortex were found in the dyslexic group. Dyslexics showed significantly more activation than controls with increasing WM demand in the left superior frontal gyrus (BA 8), as well as in the inferior frontal gyrus including Broca's area (BA 44) and its right homologue. Less activation was found in the middle frontal gyrus (BA 6) and in the superior parietal cortex (BA 7). A positive correlation between activation of prefrontal regions and verbal WM performance (as measured by digit span backwards) was found only in the dyslexic group. Accuracy deficits at the highest cognitive demand during the verbal WM task and the digit span backwards suggest that manipulation rather than maintenance is selectively impaired in dyslexics. The fMRI data provide further evidence for functional differences in cortical regions associated with language processing and executive function in subjects with dyslexia.     

Interconnected large-scale systems for three fundamental cognitive tasks revealed by functional MRI

The specific brain areas required to execute each of three fundamental cognitive tasks - object naming, same-different discrimination, and integer computation - are determined by whole-brain functional magnetic resonance imaging (fMRI) using a novel technique optimized for the isolation of neurocognitive systems. This technique (1) conjoins the activity associated with identical or nearly identical tasks performed in multiple sensory modalities (conjunction) and (2) isolates the activity conserved across multiple subjects (conservation). Cortical regions isolated by this technique are, thus, presumed associated with cognitive functions that are both distinguished from primary sensory processes and from individual differences. The object-naming system consisted of four brain areas: left inferior frontal gyrus, Brodmann's areas (BAs) 45 and 44; left superior temporal gyrus, BA 22; and left medial frontal gyrus, BA 6. The same-different discrimination system consisted of three brain areas: right inferior parietal lobule, BA 40; right precentral gyrus, BA 6; and left medial frontal gyrus, BA 6. The integer computation system consisted of five brain areas: right middle frontal gyrus, BA 6; right precentral gyrus, BA 6; left inferior parietal lobule, BA 40; left inferior frontal gyrus, BA 44; and left medial frontal gyrus, BA 6. All three neurocognitive systems shared one common cortical region, the left medial frontal gyrus, the object-naming and integer computation systems shared the left inferior frontal gyrus, and the integer computation and same-different discrimination systems shared the right precentral gyrus. These results are consistent with connectionist models of cognitive processes where specific sets of remote brain areas are assumed to be transiently bound together as functional units to enable these functions, and further suggest a superorganization of neurocognitive systems where single brain areas serve as elements of multiple functional systems.     

How are colors memorized in working memory? A functional magnetic resonance imaging study

The hypothesis that colors could be memorized either in verbal or visual working memory depending on the color category borders was tested using functional magnetic resonance imaging. We introduced a 2-back task to investigate the involvement of verbal and visual working memory in color memory. Colors across the categories, defined by basic color names, strongly activated the left inferior frontal gyrus and left inferior parietal lobule corresponding to the phonological loop as verbal working memory, whereas colors within the same category strongly activated the right inferior frontal gyrus corresponding to the visuospatial sketchpad as visual working memory. The choice of colors to memorize might modulate the cognitive load balance between the phonological loop and the visuospatial sketchpad.     

Developmental and skill effects on the neural correlates of semantic processing to visually presented words

Functional magnetic resonance imaging (fMRI) was used to explore the neural correlates of semantic judgments to visual words in a group of 9- to 15-year-old children. Subjects were asked to indicate if word pairs were related in meaning. Consistent with previous findings in adults, children showed activation in bilateral inferior frontal gyri (Brodmann area [BA] 47, 45) and left middle temporal gyrus (BA 21). Words with strong semantic association elicited significantly greater activation in bilateral inferior parietal lobules (BA 40), suggesting stronger integration of highly related semantic features. By contrast, words with weak semantic association elicited greater activation in left inferior frontal gyrus (BA 45) and middle temporal gyrus (BA 21), suggesting more difficult feature search and more extensive access to semantic representations. We also examined whether age and skill explained unique variance in the patterns of activation. Increasing age was correlated with greater activation in left middle temporal gyrus (BA 21) and inferior parietal lobule (BA 40), suggesting that older children have more elaborated semantic representations and more complete semantic integration processes, respectively. Decreasing age was correlated with activation in right superior temporal gyrus (BA 22) and decreasing accuracy was correlated with activation in right middle temporal gyrus (BA 21), suggesting the engagement of ancillary systems in the right hemisphere for younger and lower-skill children.     

Executive functions in obsessive–compulsive disorder: An activation likelihood estimate meta-analysis of fMRI studies

Objectives: To identify activation changes assessed in functional magnetic resonance imaging (fMRI) studies of obsessive–compulsive disorder (OCD) through Activation Likelihood Estimate meta-analysis. Methods: We included 28 peer-reviewed standard stereotactic space studies assessing adult OCD patients (OCDpts) vs. healthy controls (HCs) with fMRI during executive task performance. Results: In within-group analyses, HCs showed task-related activations in bilateral inferior frontal gyri, right middle frontal gyrus, right inferior parietal lobule, right claustrum, bilateral cingulate gyri, and left caudate body. OCDpts showed task-related left-sided activations in the superior, medial, and inferior frontal gyri, and thalamus, and bilateral activations in the middle frontal gyri, inferior parietal lobule, and insular cortices. Subtraction analysis showed increased left middle frontal gyrus activation in OCDpts. In between-groups analyses, OCDpts hypoactivated the right caudate body, left putamen, left ACC, and right medial and middle frontal gyri. Right caudate hypoactivation persisted also after applying Family‐wise error algorithms. Conclusions: This meta-analysis confirms that during executive functioning OCDpts show a functional deficit of the right caudate body, which could represent a major neural functional correlate of their illness.     

太溪和丘墟穴捻针时不同脑功能区的激活

A number of previous studies of acupuncture acupoint specificity have used sham acupoints,sham acupuncture or meridian acupoints at a great distance from each other as controls in functional MRI (fMRI) experiments.However,few studies have compared different meridian acupoints within the same segment,which are associated with similarly intense needle sensations.We performed fMRI on 12 healthy young volunteers and observed differences in brain activation elicited by acupuncture of the Taixi (KI 3) and Qiuxu (GB 40) acupoints.Acupuncture was applied at the Taixi and Qiuxu acupoints,using a multiple-block fMRI design with three blocks,involving three alternations of resting and task phases.After scanning,needle sensation was assessed.The behavioral results revealed that the subjective needle sensation was similar between the Taixi and Qiuxu acupoints.The fMRI results revealed that acupuncture at the right Taixi acupoint activated the right superior temporal gyrus (BA 22),left middle frontal gyrus (BA 46) and inferior frontal gyrus (BA 45),bilateral parietal lobe postcentral gyrus (BA 2),right parietal lobe (BA 3),and left parietal lobe (BA 40).Acupuncture at the right Qiuxu acupoint activated the left superior temporal gyrus (BA 42),right parietal lobe postcentral gyrus (BA 40,BA 43),right inferior frontal gyrus (BA 47),bilateral superior temporal gyrus (BA 22),and right insula BA13.These results suggest that the right Taixi and Qiuxu acupoints activated different brain areas.     

汉语单字词音、义加工的脑激活模式

目的：研究汉字音、义加工的脑机制。方法：采用汉字单字词为实验材料，通过功能磁共振成像扫描执行语音和语义两种认知任务的脑区。结果：语音任务激活的脑区有，左侧顶叶下部和颞上回(BA 40／39／22，BA：Brodmann Area，即布鲁德曼分区，下同)，左侧枕中回(BA18／19)，右侧枕下回(BA18／19)，以及左中央前回(BA6)。语义任务激活的脑区有，左侧顶叶下部(BA40／39)和左侧颞上回(BA22)，左侧额下回(BA10／47)，右侧额中回和额上回(BA10／11)，以及左侧额中回(BA11)。语义任务减去语音任务激活的脑区有，左侧额下回(BA47)，左侧海马(BA36)和右侧海马旁回(BA36)。语音任务减去语义任务没有发现任何脑区的显著激活。结论：在语义任务中与语音有关的脑区得到激活；而在语音任务中与语义有关的脑区没有激活。     

抑郁症患者对正性面部表情功能识别

目的：利用任务态功能核磁共振成像技术,初步探讨抗抑郁治疗对正性情绪识别脑区功能的影响。方法：检测19例抑郁症患者治疗前和治疗10周后在识别正性及中性面部表情视频时的激活脑区,并与19例匹配的健康者对照比较。结果：与正常对照组相比,治疗前抑郁症患者左右颞上回（BA39）、左后扣带回（BA23）、右后扣带回（BA30）、左丘脑、右岛叶（BA13）等脑区激活显著降低;治疗后患者左颞上回（BA39）、右颞上回（BA22）、左颞中回（BA37）、左右海马旁回（BA30）、右后扣带回（BA29）、右梭状回（BA36）、左额中回（BA8）、右额下回（BA47）、左顶下小叶（BA40）、右岛叶（BA13）等脑区激活较治疗前增强;但与正常组相比,左颞上回（BA22）、左额中回（BA10）、左梭状回（BA20）、左楔叶（BA19）、右顶上小叶（BA7）、右岛叶（BA13）等脑区激活仍存在一定程度的降低。结论：经抗抑郁治疗,抑郁症患者正性情绪识别脑区功能较治疗前有所改善,但与正常对照组相比,仍存在一定程度的功能损害。进一步证实了积极有效的抗抑郁治疗能够部分逆转正性情绪相关脑区损害。     

Relationships between years of education,regional grey matter volumes,and working memory-related brain activity in healthy older adults

The aim of this study was to examine the relationships between educational attainment, regional grey matter volume, and functional working memory-related brain activation in older adults. The final sample included 32 healthy older adults with 8 to 22 years of education. Structural magnetic resonance imaging (MRI) was used to measure regional volume and functional MRI was used to measure activation associated with performing an n-back task. A positive correlation was found between years of education and cortical grey matter volume in the right medial and middle frontal gyri, in the middle and posterior cingulate gyri, and in the right inferior parietal lobule. The education by age interaction was significant for cortical grey matter volume in the left middle frontal gyrus and in the right medial cingulate gyrus. In this region, the volume loss related to age was larger in the low than high-education group. The education by age interaction was also significant for task-related activity in the left superior, middle and medial frontal gyri due to the fact that activation increased with age in those with higher education. No correlation was found between regions that are structurally related with education and those that are functionally related with education and age. The data suggest a protective effect of education on cortical volume. Furthermore, the brain regions involved in the working memory network are getting more activated with age in those with higher educational attainment.     

注意缺陷/多动障碍工作记忆的bold-功能磁共振成像研究

目的应用bold-功能磁共振成像(bold-fMRI)技术来研究注意缺陷/多动障碍(AD/HD)患者的工作记忆。并探讨使用哌醋甲酯1个月治疗前后AD/HD患者的脑部激活的改变情况。方法利用倒数n刺激模式(n-back)对7例AD/HD(注意缺陷为主型)和7名正常人进行blod-fMRI检查,对照研究AD/HD患者在工作记忆时涉及的各脑区的激活情况。结果AD/HD组治疗后的1-back任务较治疗前1-back任务在右额下回和右额中回激活明显,二者有显著性差异(P<0.05);AD/HD组在治疗后的2-back任务较治疗前2-back任务在左额下回和左顶叶后下部激活明显(P<0.05)。正常组的1-back任务与患者组治疗前的1-back任务比较没有显著性差异,正常组的2-back任务与患者组治疗前2-back任务比较在左额下回和左顶叶后下部激活明显(P<0.05)。结论AD/HD障碍患者存在执行功能方面的缺陷,AD/HD患者的语义性工作记忆缺损可能与前额叶和顶叶的功能缺陷有关。     

Bilateral parieto-frontal network for verbal working memory: an interference approach using repetitive transcranial magnetic stimulation (rTMS)

Verbal working memory has been attributed to a left-dominant neuronal network, including parietal, temporal and prefrontal cortical areas. The current study was designed to evaluate the contribution of these brain regions to verbal working memory processes and to assess possible hemispheric asymmetry. The effect of repetitive transcranial stimulation (rTMS) on performance in a verbal working memory task both during, and after an rTMS train (110% of individual motor threshold, 4 Hz) over nine different scalp locations was studied [bilateral middle frontal gyrus (MFG), bilateral supramarginal gyrus (SMG), bilateral inferior parietal cortex (IP) and three different midline control sites]. Significant performance deterioration was observed during rTMS over the left and right MFG and left and right IP. There was no consistent interference effect across subjects over the left or right SMG and the three different midline control sites. The interference effect with the given stimulation parameters did not last beyond the rTMS train itself. The data provide evidence for a symmetrical, bilateral parieto-frontal verbal working memory network. The data are discussed with respect to the competing ideas of a parieto-frontal central executive network vs. a network that processes the inherent semantic and object features of the visually presented verbal stimuli in parallel.     

Activation of right fronto-temporal cortex characterizes the 'living' category in semantic processing.

It is a vital ability for humans to distinguish between living and non-living objects. Whether the semantic features of these two classes of objects are represented in distinct brain areas, is unknown. In our study, words belonging to the categories 'living' and 'non-living' were presented visually to twelve right-handed volunteers, while brain activation was measured with event-related fMRI. Subjects had to judge whether the item belonged to one of these categories. Common areas of activation (P<0.05, corrected) during processing of both categories include the inferior occipital gyri bilaterally (BA 17/18), left inferior frontal gyrus (BA 44/45) and left inferior parietal lobe (BA 40). During processing of 'living' minus 'non-living' items, signal changes (P<0.05, corrected) were present in the the right inferior frontal (BA 47), middle temporal (BA 21) and fusiform gyrus (BA 19). Our results are in line with findings from patients with a deficit in semantic processing of living things, who specifically suffer from right hemispheric lesions.     

Common and unique components of inhibition and working memory: an fMRI, within-subjects investigation

Behavioural findings indicate that the core executive functions of inhibition and working memory are closely linked, and neuroimaging studies indicate overlap between their neural correlates. There has not, however, been a comprehensive study, including several inhibition tasks and several working memory tasks, performed by the same subjects. In the present study, 11 healthy adult subjects completed separate blocks of 3 inhibition tasks (a stop task, a go/no-go task and a flanker task), and 2 working memory tasks (one spatial and one verbal). Activation common to all 5 tasks was identified in the right inferior frontal gyrus, and, at a lower threshold, also the right middle frontal gyrus and right parietal regions (BA 40 and BA 7). Left inferior frontal regions of interest (ROIs) showed a significant conjunction between all tasks except the flanker task. The present study could not pinpoint the specific function of each common region, but the parietal region identified here has previously been consistently related to working memory storage and the right inferior frontal gyrus has been associated with inhibition in both lesion and imaging studies. These results support the notion that inhibitory and working memory tasks involve common neural components, which may provide a neural basis for the interrelationship between the two systems.     

捻转和非捻转刺激太溪穴后脑激活状态的功能磁共振成像研究

目的：观察功能磁共振成像了解捻转刺激太溪穴和非捻转刺激所引起的脑激活区状态。 方法：纳入健康青年志愿者12名,选取右侧太溪穴,采用组块刺激模式,静息阶段与刺激阶段交替出现,重复3次,分为3个组块。刺激为手法捻转行针或非捻转,非捻转即手放在针柄,但不进行任何操作。扫描后图像使用SPM2进行后处理。 结果：捻转刺激太溪穴主要激活了右侧颞上回BA22,左侧的额中回BA46,其次为左右顶叶的中央后回BA2,BA3,左额叶的额下回BA45和左顶叶的顶下小叶BA40;而非捻转刺激则没有激活。 结论：捻转刺激太溪穴和非捻转刺激的激活不同,与本经相关的经络、脏腑联系密切相关。     

The neurodevelopmental differences of increasing verbal working memory demand in children and adults

Working memory (WM) – temporary storage and manipulation of information in the mind – is a key component of cognitive maturation, and structural brain changes throughout development are associated with refinements in WM. Recent functional neuroimaging studies have shown that there is greater activation in prefrontal and parietal brain regions with increasing age, with adults showing more refined, localized patterns of activations. However, few studies have investigated the neural basis of verbal WM development, as the majority of reports examine visuo-spatial WM.We used fMRI and a 1-back verbal WM task with six levels of difficulty to examine the neurodevelopmental changes in WM function in 40 participants, twenty-four children (ages 9–15 yr) and sixteen young adults (ages 20–25 yr). Children and adults both demonstrated an opposing system of cognitive processes with increasing cognitive demand, where areas related to WM (frontal and parietal regions) increased in activity, and areas associated with the default mode network decreased in activity. Although there were many similarities in the neural activation patterns associated with increasing verbal WM capacity in children and adults, significant changes in the fMRI responses were seen with age. Adults showed greater load-dependent changes than children in WM in the bilateral superior parietal gyri, inferior frontal and left middle frontal gyri and right cerebellum. Compared to children, adults also showed greater decreasing activation across WM load in the bilateral anterior cingulate, anterior medial prefrontal gyrus, right superior lateral temporal gyrus and left posterior cingulate. These results demonstrate that while children and adults activate similar neural networks in response to verbal WM tasks, the extent to which they rely on these areas in response to increasing cognitive load evolves between childhood and adulthood.     

Semantic association investigated with functional MRI and independent component analysis

Semantic association, an essential element of human language, enables discourse and inference. Neuroimaging studies have revealed localization and lateralization of semantic circuitry, making substantial contributions to cognitive neuroscience. However, because of methodological limitations, these investigations have only identified individual functional components rather than capturing the behavior of the entire network. To overcome these limitations, we have implemented group independent component analysis (ICA) to investigate the cognitive modules used by healthy adults performing the fMRI semantic decision task. When compared with the results of a standard general linear modeling (GLM) analysis, ICA detected several additional brain regions subserving semantic decision. Eight task-related group ICA maps were identified, including left inferior frontal gyrus (BA44/45), middle posterior temporal gyrus (BA39/22), angular gyrus/inferior parietal lobule (BA39/40), posterior cingulate (BA30), bilateral lingual gyrus (BA18/23), inferior frontal gyrus (L>R, BA47), hippocampus with parahippocampal gyrus (L>R, BA35/36), and anterior cingulate (BA32/24). Although most of the components were represented bilaterally, we found a single, highly left-lateralized component that included the inferior frontal gyrus and the medial and superior temporal gyri, the angular and supramarginal gyri, and the inferior parietal cortex. The presence of these spatially independent ICA components implies functional connectivity and can be equated with their modularity. These results are analyzed and presented in the framework of a biologically plausible theoretical model in preparation for similar analyses in patients with right- or left-hemispheric epilepsies.     

Default network connectivity during a working memory task

The default network exhibits correlated activity at rest and has shown decreased activation during performance of cognitive tasks. There has been little investigation of changes in connectivity of this network during task performance. In this study, we examined task‐related modulation of connectivity between two seed regions from the default network posterior cingulated cortex (PCC) and medial prefrontal cortex (mPFC) and the rest of the brain in 12 healthy adults. The purpose was to determine (1) whether connectivity within the default network differs between a resting state and performance of a cognitive (working memory) task and (2) whether connectivity differs between these nodes of the default network and other brain regions, particularly those implicated in cognitive tasks. There was little change in connectivity with the other main areas of the default network for either seed region, but moderate task‐related changes in connectivity occurred between seed regions and regions outside the default network. For example, connectivity of the mPFC with the right insula and the right superior frontal gyrus decreased during task performance. Increased connectivity during the working memory task occurred between the PCC and bilateral inferior frontal gyri, and between the mPFC and the left inferior frontal gyrus, cuneus, superior parietal lobule, middle temporal gyrus and cerebellum. Overall, the areas showing greater correlation with the default network seed regions during task than at rest have been previously implicated in working memory tasks. These changes may reflect a decrease in the negative correlations occurring between the default and task‐positive networks at rest. Hum Brain Mapp, 2011. © 2010 Wiley‐Liss, Inc.     

Depressive mood in pre-dialytic chronic kidney disease: Statistical parametric mapping analysis of Tc-99m ECD brain SPECT

The purpose of this study was to investigate depression-related regions in pre-dialytic patients with chronic kidney disease (CKD) patients. Participants comprised 33 patients with stage 4 and 5 CKD (age, 55 [42–63]) and 32 healthy volunteers (age, 53.5 [49.5–57]). Depressed mood was assessed in the patients, and both groups underwent Tc-99m-labeled ethylcysteinate dimer (Tc-99m ECD) single photon emission computed tomograpy (SPECT). Statistical parametric mapping identified 18 areas of hypoperfusion in the patients in comparison with the normal controls. The largest clusters were areas including left precentral gyrus, right superior and middle temporal gyrus, both cerebellar posterior lobes, both inferior frontal gyrus, right superior and middle frontal gyrus, right cuneus, right inferior parietal lobule, and right putamen. However, there were no specific hypoperfusion areas in CKD patients with depression compared with CKD patients without depression. Interestingly, several hypoperfusion areas in CKD patients (inferior frontal gyrus [BA46], superior temporal gyrus [BA42], anterior cingulate gyrus [BA24]) were concordant with hypoperfusion areas found in patients with major depression who were free of kidney disease. In conclusion, this study did not demonstrate specific depression-related cerebral hypoperfusion areas. However, the cerebral blood flow pattern in CKD patients was similar to that of patients with major depression in some areas. Although further investigations are needed in the future, we suggest that the causes of the higher prevalence of depression in CKD might be associated with this finding.     

The effects of listening comprehension of various genres of literature on response in the linguistic area: an fMRI study

Using fMRI at a static magnetic field strength of 1.5T, we investigated how comprehension and humor of sentences would correlate to activation of the language areas in listening comprehension of a native language. Sentences with a high comprehension score augmented activation in the left inferior parietal lobule and posterior part of the left superior temporal gyrus, which may be related to semantic processing. Sentences with a high humor score induced activation in Broca's area, which may be associated with syntactic processing and auditory working memory. Furthermore, sentences with a high humor factor and/or a low comprehension score activated the middle frontal gyrus, which may be attributed to auditory working memory.