Visual attention deficits in Alzheimer's disease: an fMRI study

Cognitive and neuroscience studies indicate that attentional operations are impaired in Alzheimer's disease (AD). Our goal was to define the anatomical areas of activation associated with visual attention processing and to define deficits or changes that may occur in AD patients compared with control group. Thirteen AD patients and 13 age- and education-matched normal controls were tested in two visual search tasks (one was a conjunction task, where feature binding is required. The other was a subset task, where group stimuli is needed without feature binding) using fMRI techniques. After stereotactical normalization, voxel-by-voxel t statistics was used to compare activated brain areas between patients and control subjects. Our findings suggest that both search tasks are controlled by partially overlapping cerebral networks, including parietal, frontal and occipital-temporal cortical regions and primary visual cortex. The AD patient group showed less activation in both parietal lobes and the left frontal regions, while increased activation was found in the right frontal lobes and the right occipito-temporal cortical regions with the conjunction task. In the subset task, decreased activation in AD patients was seen in the left parietal lobe and bilateral frontal lobes, while increased activation was seen in both medial temporal lobes. In addition, for the comparison between tasks, The difference is very small for AD patients. Control group showed a higher amplitude in the right prefrontal region, temporal cortical regions and parietal lobe. These results indicate that attention deficits in AD patients may be attributed to both binding problem and grouping inefficiency.     

An fMRI Investigation of the Cortical Network Underlying Detection and Categorization Abilities in Hemianopic Patients

The current study aims to investigate visual scene perception and its neuro-anatomical correlates for stimuli presented in the central visual field of patients with homonymous hemianopia, and thereby to assess the effect of a right or a left occipital lesion on brain reorganization. Fourteen healthy participants, three left brain damaged (LBD) patients with right homonymous hemianopia and five right brain damaged (RBD) patients with left homonymous hemianopia performed a visual detection task (i.e. “Is there an image on the screen?”) and a categorization task (i.e. “Is it an image of a highway or a city?”) during a block-designed functional magnetic resonance imaging recording session. Cerebral activity analyses of the posterior areas—the occipital lobe in particular—highlighted bi-hemispheric activation during the detection task but more lateralized, left occipital lobe activation during the categorization task in healthy participants. Conversely, in patients, the same network of activity was observed in both tasks. However, LBD patients showed a predominant activation in their right hemisphere (occipital lobe and posterior temporal areas) whereas RBD patients showed a more bilateral activation (in the occipital lobes). Overall, our preliminary findings suggest a specific pattern of cerebral activation depending on the task instruction in healthy participants and cerebral reorganization of the posterior areas following brain injury in hemianopic patients which could depend upon the side of the occipital lesion.     

正常中老年人词语联想任务功能磁共振成像研究

目的 采用功能磁共振成像(fMRI)技术对正常中老年人进行研究,检测与词语联想功能相关脑区的激活特点.方法 采用GE 1.5 T磁共振扫描仪对23例(男12例,女11例)正常中老年人行组块设计的词语联想任务fMRI研究.采用SPM 2软件进行数据处理和统计分析,通过组分析获得平均脑激活图,观察脑激活区的部位和激活强度.结果 12例符合入组条件,激活脑区为运动前区(PMC)、双侧额下回后部(Broca区及Broca镜像区)、双侧辅助运动区(SMA)、左侧顶后皮层、双侧岛叶、双侧扣带回前部、双侧基底节、左侧丘脑以及右侧小脑半球.全脑以左侧PMC激活强度最大.激活强度左侧大于右侧的脑区为额下回后部、背侧PMC及SMA;右侧大于左侧的脑区为腹侧PMC、岛叶、扣带回前部、基底节.结论 中老年人参与运动性语言表达的脑区,由包括Broca区在内的多个脑区组成复杂的神经网络,且相关脑区存在偏侧化现象,以左侧大脑半球和右侧小脑半球激活为主.     

Where language meets meaningful action: a combined behavior and lesion analysis of aphasia and apraxia

It is debated how language and praxis are co-represented in the left hemisphere (LH). As voxel-based lesion-symptom mapping in LH stroke patients with aphasia and/or apraxia may contribute to this debate, we here investigated the relationship between language and praxis deficits at the behavioral and lesion levels in 50 sub-acute stroke patients. We hypothesized that language and (meaningful) action are linked via semantic processing in Broca’s region. Behaviorally, half of the patients suffered from co-morbid aphasia and apraxia. While 24 % (n = 12) of all patients exhibited aphasia without apraxia, apraxia without aphasia was rare (n = 2, 4 %). Left inferior frontal, insular, inferior parietal, and superior temporal lesions were specifically associated with deficits in naming, reading, writing, or auditory comprehension. In contrast, lesions affecting the left inferior frontal gyrus, premotor cortex, and the central region as well as the inferior parietal lobe were associated with apraxic deficits (i.e., pantomime, imitation of meaningful and meaningless gestures). Thus, contrary to the predictions of the embodied cognition theory, lesions to sensorimotor and premotor areas were associated with the severity of praxis but not language deficits. Lesions of Brodmann area (BA) 44 led to combined apraxic and aphasic deficits. Data suggest that BA 44 acts as an interface between language and (meaningful) action thereby supporting parcellation schemes (based on connectivity and receptor mapping) which revealed a BA 44 sub-area involved in semantic processing.     

Severity of Post-stroke Aphasia According to Aphasia Type and Lesion Location in Koreans

To determine the relations between post-stroke aphasia severity and aphasia type and lesion location, a retrospective review was undertaken using the medical records of 97 Korean patients, treated within 90 days of onset, for aphasia caused by unilateral left hemispheric stroke. Types of aphasia were classified according to the validated Korean version of the Western Aphasia Battery (K-WAB), and severities of aphasia were quantified using WAB Aphasia Quotients (AQ). Lesion locations were classified as cortical or subcortical, and were determined by magnetic resonance imaging. Two-step cluster analysis was performed using AQ values to classify aphasia severity by aphasia type and lesion location. Cluster analysis resulted in four severity clusters: 1) mild; anomic type, 2) moderate; Wernicke''s, transcortical motor, transcortical sensory, conduction, and mixed transcortical types, 3) moderately severe; Broca''s aphasia, and 4) severe; global aphasia, and also in three lesion location clusters: 1) mild; subcortical 2) moderate; cortical lesions involving Broca''s and/or Wernicke''s areas, and 3) severe; insular and cortical lesions not in Broca''s or Wernicke''s areas. These results revealed that within 3 months of stroke, global aphasia was the more severely affected type and cortical lesions were more likely to affect language function than subcortical lesions.     

Reorganization after pre- and perinatal brain lesions

The developing human brain can compensate for pre‐ and perinatally acquired focal lesions more effectively than the adult brain. The mechanisms by which this effective reorganization is achieved vary considerably between different functional systems, reflecting differences in the normal maturation of these systems. In the motor system, descending cortico‐spinal motor projections have already reached their spinal target zones at the beginning of the third trimester of pregnancy, with initially bilateral projections from each hemisphere. During normal development, the ipsilateral projections are gradually withdrawn, whereas the contralateral projections persist. When, during this period, a unilateral brain lesion disrupts the cortico‐spinal projections of one hemisphere, the ipsilateral projections from the contralesional hemisphere will persist. This allows the contralesional hemisphere to take over motor control over the paretic extremities. Although this mechanism of reorganization is available throughout the pre‐ and perinatal period, the efficacy of this ipsilateral takeover of motor functions decreases with increasing age at the time of the insult. In the somatosensory system, ascending thalamo‐cortical somatosensory projections have not yet reached their cortical target zones at the beginning of the third trimester of pregnancy. Therefore, these projections can still ‘react’ to brain lesions acquired during this period, and can form ‘axonal bypasses’ around periventricular white matter lesions to reach their original cortical target areas in the postcentral gyrus. Thus, somatosensory functions can be well preserved even in cases of large periventricular lesions. In contrast, when the postcentral gyrus itself is affected, no signs for reorganization have been observed. Accordingly, somatosensory functions are often poor in these patients. Language functions can be normal even in patients with extensive early left‐hemispheric brain lesions. This is achieved by language organization in the right hemisphere, which takes place in brain regions homotopic to the classical left‐hemispheric language areas in normal subjects. In patients with periventricular lesions, the degree of right‐hemispheric takeover of language functions correlates with the severity of structural damage to facial (and, thus, articulatory) motor projections.     

Neurophysiological correlates of word and pseudo-word processing in well-recovered aphasics and patients with right-hemispheric stroke

Neurophysiological correlates of language recovery after stroke were investigated. Neurological patients with single focal lesions in their left or right hemisphere and healthy control subjects made lexical decisions on written words and pseudo-words while EEG responses were recorded. At the time of testing, patients did not show clinically apparent language dysfunction, although those with left-hemisphere lesions had suffered from aphasia in the first months after their stroke. A P3-like positive deflection of the event-related potential (ERP) was reduced in the patients relative to healthy controls, this reduction being most pronounced over the hemisphere affected by stroke. Consistent with earlier research, healthy control subjects showed more positive ERPs to words than to pseudo-words. This pattern was reversed in both patient groups, where words elicited more negative-going ERPs than pseudo-words already 160-320 ms after stimulus onset. Because ERPs showed between-group differences only for words, these word-specific neurophysiological signatures altered in stroke patients with well-recovered language functions may be a correlate of cortical lesions or an index of reorganization of language after stroke.     

Inhibition of ongoing responses following frontal,nonfrontal, and basal ganglia lesions

The authors investigated the role of the frontal lobes and the basal ganglia in the inhibition of ongoing responses. Seventeen patients with frontal lesions (FG), 20 patients with lesions outside the frontal cortex (NFG), 8 patients with lesions to the basal ganglia (BG), and 20 orthopedic controls (OG) performed the stop-signal task that allows the estimation of the time it takes to inhibit an ongoing reaction (stop signal reaction time [SSRT]). The FG and the BG showed significantly longer SSRTs than the OG. Within the FG, patients with right and bilateral lesions showed significantly longer SSRTs than patients with left lesions. Results provide evidence for a role of the frontal lobes and the basal ganglia in the inhibition of ongoing responses.     

Lateralization of cognitive functions in aphasia after right brain damage

Purpose

The lateralization of cognitive functions in crossed aphasia in dextrals (CAD) has been explored and compared mainly with cases of aphasia with left hemisphere damage. However, comparing the neuropsychological aspects of CAD and aphasia after right brain damage in left-handers (ARL) could potentially provide more insights into the effect of a shift in the laterality of handedness or language on other cognitive organization. Thus, this case study compared two cases of CAD and one case of ARL.

Materials and Methods

The following neuropsychological measures were obtained from three aphasic patients with right brain damage (two cases of CAD and one case of ARL); language, oral and limb praxis, and nonverbal cognitive functions (visuospatial neglect and visuospatial construction).

Results

All three patients showed impaired visuoconstructional abilities, whereas each patient showed a different level of performances for oral and limb praxis, and visuospatial neglect.

Conclusion

Based on the analysis of these three aphasic patients'' performances, we highlighted the lateralization of language, handedness, oral and limb praxis, visuospatial neglect and visuospatial constructive ability in aphasic patients with right brain damage.     

Verbal dichotic listening and manual performance in children with congenital unilateral brain lesions

The authors assessed manual performance and verbal dichotic listening performance in 16 epilepsy-free children with congenital unilateral brain lesions and normal IQ to investigate cerebral reorganization. In all children, the paretic hand had fair grip function, but reaction times were impaired, and cerebral reorganization of hand function in those with right hemiplegia was shown by the high incidence of pathological left-handedness. The dichotic listening results showed that most children with left lesions had a left ear advantage significantly related to the extent of brain damage. This finding suggests that extent of cortical damage and presence of thalamic involvement, irrespective of neuropathology, are the primary factors inducing rightward cerebral language reorganization in children with unilateral congenital brain lesions.     

Amusia and aphasia of Bolero's creator--influence of the right hemisphere on music

OBJECTIVES: The experience with cortical localization (BA 44, 45, 22) of language (Broca, Wernicke and others) in the left hemisphere has been repeatedly tested over the last 150 years and is now generally accepted. A single case report with autopsy findings (Leborgne, Tan tan), has enabled to localize the seat of spoken language in the left third frontal convolution. As music and language have a lot in common and even share the same hearing system, it is logical to try to localize the cognitive centers for music too. METHODS: The disabling neurological disease illness of Maurice Ravel (1875-1937), a French impressionist composer, is not the right example to localize music center as that of Broca's language center, but it demonstrates the role of the right hemisphere in music production. In the last five years of his life, Ravel suffered from an unknown disease that affected the left hemisphere causing aphasia, apraxia, alexia, agraphia and amusia. It was the reason why Ravel could not compose during the last years of his life. In contrast to Ravel, Shebalin and Britten continued writing music works of their own although aphasic after having sustained two strokes to the left hemisphere. While lacking clinical cases with selective ablative brain lesions, research into the music localization can be done using modern imaging technologies such as fMRI and PET. RESULTS: Exercising music (professionally) develops analytical process in the left hemisphere whereas other individuals process music in their right hemisphere. There is right ear (left hemisphere) predominance in musicians and vice versa in musical amateurs. Music lateralization towards the right hemisphere is seen in women and in inattentive listeners. It can be subject to cultural influence, so the Japanese process their traditional popular music in the left hemisphere, whereas Westerners process the same music in the right hemisphere. Music and language are processed separately; they are localized in homologous regions of the opposite hemispheres. In 1937, Ravel underwent neurosurgical procedure performed by Vincent; autopsy was not done. It is believed that the cause of hi disease was primary progressive aphasia associated with Pick's disease. CONCLUSION: Boléro and Concerto for the Left Hand were the last Ravel's works (the onset of his disease), so it is possible that the projected the influence of the healthy right hemisphere onto his music (and on the creative process) because Ravel's left hemispher was damaged. Indeed, in these last music works one can feel the predominance of changes in pitch (timbre), i. e. right hemisphere, in comparison to only few changes of melody (left hemisphere).     

Altered Structure and Intrinsic Functional Connectivity in Post-stroke Aphasia

Previous studies have demonstrated that alterations of gray matter exist in post-stroke aphasia (PSA) patients. However, so far, few studies combined structural alterations of gray matter volume (GMV) and intrinsic functional connectivity (iFC) imbalances of resting-state functional MRI to investigate the mechanism underlying PSA. The present study investigated specific regions with GMV abnormality in patients with PSA (n?=?17) and age- and sex- matched healthy controls (HCs, n?=?20) using voxel-based morphometry. In addition, we examined whether there is a link between abnormal gray matter and altered iFC. Furthermore, we explored the correlations between abnormal iFC and clinical scores in aphasic patients. We found significantly increased GMV in the right superior temporal gyrus, right inferior parietal lobule (IPL)/supramarginal gyrus (SMG), and left middle occipital gyrus. Decreased GMV was found in the right caudate gyrus, bilateral thalami in PSA patients. Patients showed increased remote interregional FC between the right IPL/SMG and right precuneus, right angular gyrus, right superior occipital gyrus; while reduced FC in the right caudate gyrus and supplementary motor area, dorsolateral superior frontal gyrus. Moreover, iFC strength between the left middle occipital gyrus and the left orbital middle frontal gyrus was positively correlated with the performance quotient. We suggest that GMV abnormality contributes to interregional FC in PSA. These results may provide useful information to understand the pathogenesis of post-stroke aphasia.     

性相关视觉刺激对右脑Broca区不对称性兴奋的功能核磁共振研究

目的:了解与视觉性刺激相关的脑功能定位。方法:用张贴广告的形式征集到13例正常女性,通过功能核磁共振比较其观看普通影片和含有性内容图片时的大脑兴奋差异,确定差异有统计学意义的脑区。结果:与中性图片相比,涉性图片激发了广泛的大脑区域,包括侧枕叶皮质、中央后回、顶上小叶、枕叶梭状回、海马等。大部分脑区的兴奋都是左右半球对称的,只有额下回岛盖部(Z=3.64,P0.0001)和三角部(Z=3.42,P=0.003)为右脑优势。讨论:本文通过功能核磁共振方法发现,当女性受试在被呈示以与性相关的图片时,大脑右半球额下回岛盖部和三角部有显著的不对称兴奋。该脑区可能对性心理调控有重要意义。     

Metabolic and electric brain patterns during pleasant and unpleasant emotions induced by music masterpieces.

Brain correlates comparing pleasant and unpleasant states induced by three dissimilar masterpiece excerpts were obtained. Related emotional reactions to the music were studied using Principal Component Analysis of validated reports, fMRI, and EEG coherent activity. A piano selection by Bach and a symphonic passage from Mahler widely differing in musical features were used as pleasing pieces. A segment by Prodromidès was used as an unpleasing stimulus. Ten consecutive 30 s segments of each piece alternating with random static noise were played to 19 non-musician volunteers for a total of 30 min of auditory stimulation. Both brain approaches identified a left cortical network involved with pleasant feelings (Bach and Mahler vs. Prodromidès) including the left primary auditory area, posterior temporal, inferior parietal and prefrontal regions. While the primary auditory zone may provide an early affective quality, left cognitive areas may contribute to pleasant feelings when melodic sequences follow expected rules. In contrast, unpleasant emotions (Prodromidès vs. Bach and Mahler) involved the activation of the right frontopolar and paralimbic areas. Left activation with pleasant and right with unpleasant musical feelings is consistent with right supremacy in novel situations and left in predictable processes. When all musical excerpts were jointly compared to noise, in addition to bilateral auditory activation, the left temporal pole, inferior frontal gyrus, and frontopolar area were activated suggesting that cognitive and language processes were recruited in general responses to music. Sensory and cognitive integration seems required for musical emotion.     

Localization of cerebral lesions in aphasia – a computer aided comparison between men and women

It is still a matter of debate whether there are differences between men and women concerning the localization of higher cerebral functions. To further elucidate this problem we conjointly evaluated the aphasia protocols and corresponding computer-assisted tomography (CT) scans of 49 men and 35 women who presented with unilateral ischemic cerebral lesions. Both, the aphasia tests and CT scans, were fed into computer programs warranting a high degree of objectivity. Comparing the four main aphasic syndromes we found differences for each of them displaying a more posterior extension of lesions with global and amnestic aphasia in men and larger lesions with Broca and Wernicke aphasia in women. When all templates were compared, men displayed a wider extension within the left hemisphere than women whose lesions were more focused in the perisylvian area. This study confirms earlier findings claiming that aphasic men and women differ regarding the anterior-posterior extension and the frequency of lesions within the classical language zones. However, while the predominance of men's lesions in the posterior areas was in accordance with previous findings, the greater overall scatter within the left hemisphere contradicts published studies.     

The cortical modulation from the external cues during gait observation and imagination

The cortical involvement of gait observation and imagination under the modulation of external cues was studied in human using fMRI. Fourteen healthy volunteers were scanned using visual stimuli, which showed an actor walking in different background. The defined relevant cue was a background of evenly spaced stripes orthogonal to the walking direction, which was rhythmic presented as the actor proceeded. The irrelevant cue was two parallel lines within which the actor was confined. When viewing the relevant cue, the subject showed activation, noticeably in dorsal premotor areas, posterior parietal lobes, bilateral parahippocampal lobes, and visual related areas. The relevant external cue leads to the modulation of cortical activation related to gait, which could initialize the processing of the input information and lead to a different motor strategy from the native automatic gait. The understanding of the cortical involvement of gait under different cues might lead to a new clinical impact on the therapeutic intervention of patients with Parkinson's disease.     

Distributed cortical networks for focused auditory attention and distraction

We used behavioral measures and functional magnetic resonance imaging (fMRI) to study the effects of parametrically varied task-irrelevant pitch changes in attended sounds on loudness-discrimination performance and brain activity in cortical surface maps. Ten subjects discriminated tone loudness in sequences that also included infrequent task-irrelevant pitch changes. Consistent with results of previous studies, the task-irrelevant pitch changes impaired performance in the loudness discrimination task. Auditory stimulation, attention-enhanced processing of sounds and motor responding during the loudness discrimination task activated supratemporal (auditory cortex) and inferior parietal areas bilaterally and left-hemisphere (contralateral to the hand used for responding) motor areas. Large pitch changes were associated with right hemisphere supratemporal activations as well as widespread bilateral activations in the frontal lobe and along the intraparietal sulcus. Loudness discrimination and distracting pitch changes activated common areas in the right supratemporal gyrus, left medial frontal cortex, left precentral gyrus, and left inferior parietal cortex.     

遭受多重侵害高职高专女生静息态脑功能局部一致性的研究

目的:探讨遭受多重侵害的高职高专女生静息态脑功能磁共振特点。方法:15名遭受多重侵害无创伤后应激症状被试(PV无PTSS组)、15名多重侵害有创伤后应激症状被试(PV有PTSS组)和15名正常对照接受静息态脑功能扫描。采用SPM8和静息态功能磁共振数据处理工具包分别进行数据预处理和ReHo分析。结果:静息状态下,与对照组相比,PV无PTSS组左侧额下回、左右额内侧回、右侧中央后回、左侧梭状回、左右海马旁回、右侧扣带回、左右豆状核和右侧岛叶的ReHo值降低;左右额上回、左右额中回、左右额下回、左右顶下小叶、左右楔前叶、左右颞上回、左侧颞横回、左右颞中回、右侧舌回和右侧扣带后回的ReHo值升高。与PV有PTSS组相比,PV无PTSS组在右侧额中回和额下回、左侧楔前叶、左侧舌回、左右海马旁回、左侧扣带回和左侧豆状核ReHo值降低;在左右额上回、左右额中回、左侧额内侧回、右侧中央后回、左侧缘上回、左右顶下小叶、左侧梭状回和左侧尾状核ReHo值升高。结论:遭受多重侵害但无创伤后应激症状的高职高专女生在静息状态下脑默认网络以及岛叶、基底神经节、海马旁回存在局部一致性信号异常,这些脑区异常可能为遭受多重侵害导致精神障碍的发病机制提供重要线索。     

Alzheimer's pathology in primary progressive aphasia

Primary progressive aphasia (PPA) is a neurodegenerative disorder with language impairment as the primary feature. Different subtypes have been described and the 3 best characterized are progressive nonfluent aphasia (PNFA), semantic dementia (SD) and logopenic/phonological aphasia (LPA). Of these subtypes, LPA is most commonly associated with Alzheimer's disease (AD) pathology. However, the features of PPA associated with AD have not been fully defined. Here we retrospectively identified 14 patients with PPA and either pathologically confirmed AD or cerebrospinal fluid (CSF) biomarkers consistent with AD. Analysis of neurological and neuropsychological features revealed that all patients had a syndrome of LPA with relatively nonfluent spontaneous speech, phonemic errors, and reduced digit span; most patients also had impaired verbal episodic memory. Analysis of the pattern of cortical thinning in these patients revealed left posterior superior temporal, inferior parietal, medial temporal, and posterior cingulate involvement and in patients with more severe disease, increasing involvement of left anterior temporal and frontal cortices and right hemisphere areas in the temporo-parietal junction, posterior cingulate, and medial temporal lobe. We propose that LPA may be a “unihemispheric” presentation of AD, and discuss this concept in relation to accumulating evidence concerning language dysfunction in AD.     

Beyond the Arcuate Fasciculus: Damage to Ventral and Dorsal Language Pathways in Aphasia

Previous regional-based diffusion tensor imaging (DTI) studies focused on impairment of the arcuate fasciculus in aphasia; little is known about the extent to which aphasia severity is affected by damage to both ventral and dorsal language white matter (WM) pathways. To understand whether disconnection of these pathways contributes to clinical symptoms, we assessed the relationship between the alterations of WM integrity and clinical characteristics in acute aphasia after stroke. Eighteen patients with acute aphasia and age-, gender-, and education-matched healthy controls underwent language assessment and DTI scanning. The whole brain unbiased tract-based spatial statistics method was employed to quantitate WM integrity (fractional anisotropy) for both groups. Linear correlation analyses were performed to evaluate the relationship between WM integrity and clinical features. The aphasic patients showed decreased WM integrity in the left inferior fronto-occipital fasciculus/inferior longitudinal fasciculus (IFOF/ILF) and the left uncinate fasciculus, which represents components of ventral language pathway, and the left superior longitudinal fasciculus (SLF), which relates to dorsal language pathway. In addition, WM integrity of the left IFOF and SLF showed a positive correlation with aphasia quotient, performance quotient, and cortical quotient, respectively. These findings suggested that impaired WM integrity in both language pathways not only contributed to language performance, but also to general cognitive status. We suggest that aphasia involves a breakdown of multiple connections of dorsal and ventral streams that directly contributes to language deficits. Damage to these dual-streams may serve as a neuromarker for aphasias after stroke.