fMRI评估癫痫患者记忆及语言功能研究

目的探讨fMRI对癫痫患者记忆及语言功能的评估价值。方法 58例癫痫患者分为观察组,50例正常人分为对照组,分别采用fMRI及韦氏量表对2组进行记忆、语言功能评估,对比2组韦氏量表评分,以韦氏量表评价结果作为标准计算fMRI对癫痫患者记忆、语言功能评估的符合率、灵敏度。结果治疗前观察组语言功能VIQ评分显著低于对照组(P0.01),治疗后评分显著增高(P0.01),且与正常人群比较差异无统计学意义(P0.05);2组语言功能FIQ及记忆功能MQ评分比较均差异无统计学意义(P0.05)。治疗前fMRI与韦氏量表对语言功能评价符合率为65%,对记忆功能评价符合率为50%;治疗后分别为80%与50%。治疗前fMRI对语言功能评价灵敏度为78.9%,对记忆功能评价灵敏度为66.7%;治疗后分别为75.0%与55.6%。结论 fMRI对癫痫患者记忆、语言功能有一定的评估意义,对于术前脑功能区的定位、手术方案的指导、疗效监测等方面均具有重要意义。     

Mechanical flutter stimulation induces a lasting response in the sensorimotor cortex as revealed with BOLD fMRI

It has been recently shown that 20 min of mechanical flutter stimulation induces lasting motor cortical excitability changes, as assessed by transcranial magnetic stimulation in relaxed hand muscles. The present functional magnetic resonance imaging (fMRI) study aims to examine if such neuromodulatory changes are reflected in the BOLD signal during a motor test. Therefore, two groups were recruited: one group receiving whole‐hand flutter stimulation with a frequency of 25 Hz (FSTIM group, n = 22) and a second group receiving no stimulation (NOSTIM group, n = 22). As motor test finger‐to‐thumb tapping was performed to activate a wide sensorimotor network during the fMRI measurements. Three fMRI measurements were obtained with this test: before stimulation (PRE), after stimulation (POST1), and 1 h after stimulation (POST2). Three regions of interest (ROIs) were defined: primary motor area (M1), primary somatosensory area (S1), and supplementary motor area. In the absence of baseline differences between both groups, the FSTIM group showed increased movement‐related brain activations compared with the NOSTIM group, both at POST1 and POST2. ROI analysis revealed increased blood‐oxygenation‐level‐dependent (BOLD) responses within contralateral S1 (+20%) and M1 (+25%) at POST1, which lasted until POST2. These poststimulatory effects within S1 and M1 obviously reflect neuroplastic changes associated with augmented cortical excitability. These findings are of high clinical relevance, for example, to improve the treatment of stroke patients. Hum Brain Mapp 34:2767–2774, 2013. © 2012 Wiley Periodicals, Inc.     

Simultaneous EEG and fMRI recordings (EEG‐fMRI) in children with epilepsy

By combining electroencephalography (EEG) with functional magnetic resonance imaging (fMRI) it is possible to describe blood oxygenation level–dependent (BOLD) signal changes related to EEG patterns. This way, EEG‐pattern–associated networks of hemodynamic changes can be detected anywhere in the brain with good spatial resolution. This review summarizes EEG‐fMRI studies that have been performed in children with epilepsy. EEG‐fMRI studies in focal epilepsy (structural and nonlesional cases, benign epilepsy with centrotemporal spikes), generalized epilepsy (especially absence epilepsy), and epileptic encephalopathies (West syndrome, Lennox‐Gastaut syndrome, continuous spike and waves during slow sleep, and Dravet syndrome) are presented. Although EEG‐fMRI was applied mainly to localize the region presumably generating focal interictal discharges in focal epilepsies, EEG‐fMRI identified underlying networks in patients with generalized epilepsies and thereby contributed to a better understanding of these epilepsies. In epileptic encephalopathies a specific fingerprint of hemodynamic changes associated with the particular syndrome was detected. The value of the EEG‐fMRI technique for diagnosis and investigation of pathogenetic mechanisms of different forms of epilepsy is discussed.     

Cognitive fMRI and neuropsychological assessment in patients with secondarily generalized seizures

OBJECTIVES: Cognitive dysfunction is a frequent comorbid disorder in epilepsy which has been associated with high seizure frequency. We examined the effect of secondarily generalized tonic-clonic seizures (SGTCS) on cognitive dysfunction using neuropsychological assessment and fMRI. PATIENTS AND METHODS: Sixteen patients with localization-related epilepsy of varying etiologies and SGTCS underwent extensive neuropsychological assessment. Functional MRI was performed probing the frontal and temporal lobes with two paradigms aimed at investigating speed of mental processing and working memory. RESULTS: A high number of total lifetime SGTCS was associated with lower intelligence scores. Moreover, a trend towards cognitive decline related to the number of SGTCS was observed. A relatively increased prefrontal activation related to the number of SGTCS was demonstrated, plus a trend towards a decreased activation in the frontotemporal areas. CONCLUSION: High numbers of SGTCS are associated with a drop in intelligence scores and altered prefrontal brain activation. A shift from frontotemporal to prefrontal activation seems to have occurred, suggesting that a functional reorganization of working memory is induced by a high number of SGTCS. It remains uncertain if this reorganization reflects a compensation mechanism, or the underlying pathological processes of cognitive dysfunction.     

Presurgical language fMRI in patients with drug-resistant epilepsy: effects of task performance

PURPOSE: To determine whether language functional magnetic resonance imaging (fMRI) before epilepsy surgery can be similarly interpreted in patients with greatly different performance levels. METHODS: An fMRI paradigm using a semantic decision task with performance control and a perceptual control task was applied to 226 consecutive patients with drug-resistant localization-related epilepsy during their presurgical evaluations. The volume of activation and lateralization in an inferior frontal and a temporoparietal area was assessed in correlation with individual performance levels. RESULTS: We observed differential effects of task performance on the volume of activation in the inferior frontal and the temporoparietal region of interest, but performance measures did not correlate with the lateralization of activation. CONCLUSIONS: fMRI, as applied here, in patients with a wide range of cognitive abilities, can be interpreted regarding language lateralization in a similar way.     

Longitudinal fMRI study of reading in a patient with letter-by-letter reading

The present study provides a longitudinal fMRI study of reading 7 days after a hemorrhage in the left basal occipito-temporal region when the patient showed letter-by-letter (LBL) reading, and repeated again 50 days after onset, when his LBL reading had resolved. Direct comparison of the two sessions showed that right homologue of the so called visual word form area (VWFA), as well as a network related to language and verbal working memory, such as the bilateral premotor areas, Broca's area and its right homologue, and the left supplementary motor area were more strongly activated when his LBL reading persisted than when he recovered, whereas perilesional activity around the VWFA and the activity of superior part of the left superior parietal lobule were more strongly activated when he recovered than when his LBL reading persisted. These results suggest that dynamic functional reorganization of the brain was caused in the acute phase and that the increased activation of certain areas in the left superior parietal lobule in addition to the VWFA may be related to recovery from LBL reading.     

Cerebellar activation and lateralization during verbal and visuospatial tasks as revealed by fMRI

BACKGROUND: Many studies concerning cerebral activation and lateralization of cognitive functions are being conducted. Cerebellar function has been much researched with reference to high-level cognitive processing, but has been barely researched in systematization and diversification. In particular, cerebellar lateralization has never been researched, in comparison to cerebral lateralization for which reliable results have been reported. OBJECTIVE: This study ascertains cerebellar activation and its lateralization in relation to verbal and visuospatial tasks, using functional magnetic resonance imaging (fMRI). DESIGN, TIME, AND SETTING: A block design for functional Magnetic Resonance Imaging (fMRI) observation. This study was performed at the fMRI Laboratory, Brain Science Research Center, Korea Advanced Institute of Science and Technology from May 2006 to September 2008. PARTICIPANTS: Sixteen healthy male college students (23.3 ± 0.5 years) and another sixteen healthy male college students (21.5 ± 2.3 years) participated in this fMRI study of verbal and visuospatial tasks, respectively. METHODS: The verbal and visuospatial tasks were presented while functional brain images were acquired using a 3T fMRI system (ISOL Technology, Korea). The verbal analogy testing required the subject to select the word which had the same relationship as one of the given words. The verbal antonym testing required the subject to select the word which had a different meaning among 4 words. The visuospatial tasks involved selecting a shape that corresponded to a given figure using four examples, as well as selecting a development figure of a diagram. MAIN OUTCOME MEASURE: The double subtraction method was used to analyze the differences of the cerebellar activation between the two cognition tasks. The numbers of activated voxels were calculated in bilateral cerebellums for the two tasks. The lateralization index of the cerebellum was calculated for each task. RESULTS: The bilateral hemisphere lobule VI and IX, the right hemisphere lobule VIII, the bilateral hemisphere lobule crus I, and the vermis lobule IV, V and VI are closely related to verbal tasks in comparison to visuospatial tasks. Conversely, the bilateral hemisphere lobule IV and V, and the right hemisphere lobule VI were closely related to visuospatial tasks compared to verbal tasks. There was no great difference between the bilateral cerebellums in the numbers of activated voxels for the tasks and cerebellar lateralization was not observed. CONCLUSION: In the case of the cerebellum, the activation region was different between the verbal and visuospatial tasks, but lateralization was not different.     

Eye position-dependent activity in the primary visual area as revealed by fMRI

Internal senses of the position of the eye in the orbit may influence the cognitive processes that take into account gaze and limb positioning for movement or guiding actions. Neuroimaging studies have revealed eye position-dependent activity in the extrastriate visual, parietal, and frontal areas, but, at the earliest vision stage, the role of the primary visual area (V1) in these processes remains unclear. Functional MRI (fMRI) was used to investigate the effect of eye position on V1 activity evoked by a quarter-field stimulation using a visual checkerboard. We showed that the amplitude of V1 activity was modulated by the position of the eye, the activity being maximal when both the eye and head positions were aligned. Previous studies gave impetus to the emerging view that V1 activity is a cortical area in which contextual influences take place. The present study suggests that eye position may affect an early stage of visual processing.     

Reduced somatosensory hand representation in thalidomide-induced dysmelia as revealed by fMRI

The concept of cerebral plasticity suggests that the hand representation in somatosensory cortex is abnormal in congenital malformation disorders. To investigate this issue we studied 11 subjects with different degrees of upper extremity dysmelia due to thalidomide embryopathy in comparison to 10 control subjects. In the affected subjects fingers are typically missing in radio-ulnar order beginning with the thumb. Haemodynamic responses to electrical stimulation of the radial-most and ulnar-most fingers were measured in each subject using functional magnetic resonance tomography. The size of the hand area in the primary somatosensory cortex was estimated by calculating the Euclidian distance between corresponding activation peaks on the lateral postcentral gyrus. The cortical somatosensory hand representation was found to be significantly smaller in dysmelic subjects as compared with the control subjects (P <0.001). The shrinkage of the hand area was not proportional to the number of missing fingers. Furthermore, the cortical representation of the ulnar fingers in the dysmelic subjects was shifted towards the cortical thumb representation of the control group. We suggest that the unproportional reduction of the hand area together with the observed shift may reflect use-dependent rather than malformation-induced reorganization of the somatosensory hand area.     

FMRI lateralization of expressive language in children with cerebral lesions

PURPOSE: Lateralization of language function is crucial to the planning of surgery in children with frontal or temporal lobe lesions. We examined the utility of functional magnetic resonance imaging (fMRI) as a determinant of lateralization of expressive language in children with cerebral lesions. METHODS: fMRI language lateralization was attempted in 35 children (29 with epilepsy) aged 8-18 years with frontal or temporal lobe lesions (28 left hemisphere, five right hemisphere, two bilateral). Axial and coronal fMRI scans through the frontal and temporal lobes were acquired at 1.5 Tesla by using a block-design, covert word-generation paradigm. Activation maps were lateralized by blinded visual inspection and quantitative asymmetry indices (hemispheric and inferior frontal regions of interest, at p<0.001 uncorrected and p<0.05 Bonferroni corrected). RESULTS: Thirty children showed significant activation in the inferior frontal gyrus. Lateralization by visual inspection was left in 21, right in six, and bilateral in three, and concordant with hemispheric and inferior frontal quantitative lateralization in 93% of cases. Developmental tumors and dysplasias involving the inferior left frontal lobe had activation overlying or abutting the lesion in five of six cases. fMRI language lateralization was corroborated in six children by frontal cortex stimulation or intracarotid amytal testing and indirectly supported by aphasiology in a further six cases. In two children, fMRI language lateralization was bilateral, and corroborative methods of language lateralization were left. Neither lesion lateralization, patient handedness, nor developmental versus acquired nature of the lesion was associated with language lateralization. Involvement of the left inferior or middle frontal gyri increased the likelihood of atypical language lateralization. CONCLUSIONS: fMRI lateralizes language in children with cerebral lesions, although caution is needed in interpretation of individual results.     

Changes in singing performance and fMRI activation following right temporal lobe surgery

Introduction

This study arose in the context of having to estimate risk to the musical abilities of a trained singer (patient A.M.) recommended for right anterior temporal lobectomy (RATL) to ameliorate medically intractable seizures. To date there has been no systematic investigation of reorganisation of musical functions in the presence of epileptogenic lesions, although it is well established that RATL can impair pitch processing in nonmusicians.

Methods

Using fMRI, we compared the network activated by covert singing with lyrics in A.M. before and after surgery, while taking language activation and singing expertise into consideration. Before surgery, A.M. showed lower pitch accuracy of singing relative to individuals of similar experience (experts), thus we compared her to 12 healthy controls matched for singing pitch accuracy.

Results

We found atypical organisation of A.M.'s singing network before surgery in the presence of a malformation of cortical development, including partial activation of the singing network of pitch-matched controls, and diffuse activation along the midline spreading laterally into association cortex, typical of generalised cortical hyperexcitability in intractable epilepsy. After tailored RATL, A.M. showed striking behavioural and neuroimaging changes, including significant improvement in pitch accuracy of singing relative to controls (p = .026) and the subjective experience of being a more technically proficient singer. This was accompanied by a significant reduction in cortical activation (p < .05, corrected), with a more focal, expert-like pattern of singing activation emerging, including decreased involvement of frontal language regions. These changes were largely specific to singing, with A.M. showing language activation and performance similar to controls.

Conclusions

This case provides evidence for selective disruption of the singing network that reorganised after successful resection of an epileptogenic lesion and likely occurred through decoupling of the singing and language networks.     

High frequency functional brain networks in neonates revealed by rapid acquisition resting state fMRI

Understanding how spatially remote brain regions interact to form functional brain networks, and how these develop during the neonatal period, provides fundamental insights into normal brain development, and how mechanisms of brain disorder and recovery may function in the immature brain. A key imaging tool in characterising functional brain networks is examination of T2*‐weighted fMRI signal during rest (resting state fMRI, rs‐fMRI). The majority of rs‐fMRI studies have concentrated on slow signal fluctuations occurring at <0.1 Hz, even though neuronal rhythms, and haemodynamic responses to these fluctuate more rapidly, and there is emerging evidence for crucial information about functional brain connectivity occurring more rapidly than these limits. The characterisation of higher frequency components has been limited by the sampling frequency achievable with standard T2* echoplanar imaging (EPI) sequences. We describe patterns of neonatal functional brain network connectivity derived using accelerated T2*‐weighted EPI MRI. We acquired whole brain rs‐fMRI data, at subsecond sampling frequency, from preterm infants at term equivalent age and compared this to rs‐fMRI data acquired with standard EPI acquisition protocol. We provide the first evidence that rapid rs‐fMRI acquisition in neonates, and adoption of an extended frequency range for analysis, allows identification of a substantial proportion of signal power residing above 0.2 Hz. We thereby describe changes in brain connectivity associated with increasing maturity which are not evident using standard rs‐fMRI protocols. Development of optimised neonatal fMRI protocols, including use of high speed acquisition sequences, is crucial for understanding the physiology and pathophysiology of the developing brain. Hum Brain Mapp 36:2483–2494, 2015. © 2015 Wiley Periodicals, Inc .     

Linking generalized spike-and-wave discharges and resting state brain activity by using EEG/fMRI in a patient with absence seizures

PURPOSE: To illustrate a functional interpretation of blood oxygen level-dependent (BOLD) signal changes associated with generalized spike-and-wave discharges in patients with absence seizures and to demonstrate the reproducibility of these findings in one case. METHODS: In a 47 year-old patient with frequent absence seizures, BOLD signal changes during generalized spike-and-wave discharges (GSWD) were mapped by using simultaneous and continuous electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) at 1.5 T and 6 months later at 3 T. GSWDs were modeled as individual events and as blocks. RESULTS: The patient studied exhibited frequent generalized spike-wave activity with temporal properties ideal for study with EEG/fMRI. Highly reproducible GSWD-associated fMRI signal decreases (deactivations) were seen in bilateral frontal and temporoparietal cortices and the precuneus, in addition to activations in occipital cortex and, at 3 T, the posterior thalamus. CONCLUSIONS: The GSWD-associated changes seen here involve cortical regions that have been shown to be more active at conscious rest compared with sleep and with various types of extroverted perception and action. These regions have been proposed to constitute the core of a functional "default mode" system. We propose that the findings of deactivation of this distributed brain system during GSWDs mirrors the clinical manifestation of GSWDs (i.e., absence seizures). Furthermore, we suggest that these deactivations may reflect the functional consequences of GSWDs on physiologic brain activity at rest rather than direct hemodynamic correlates of epileptic discharges.     

Functional Reorganization Associated with Semantic Language Processing in Temporal Lobe Epilepsy Patients after Anterior Temporal Lobectomy : A Longitudinal Functional Magnetic Resonance Image Study

Objective

The focus of this study is brain plasticity associated with semantic aspects of language function in patients with medial temporal lobe epilepsy (mTLE).

Methods

Using longitudinal functional magnetic resonance imaging (fMRI), patterns of brain activation were observed in twelve left and seven right unilateral mTLE patients during a word-generation task relative to a pseudo-word reading task before and after anterior temporal section surgery.

Results

No differences were observed in precentral activations in patients relative to normal controls (n = 12), and surgery did not alter the phonological-associated activations. The two mTLE patient groups showed left inferior prefrontal activations associated with semantic processing (word-generation > pseudo-word reading), as did control subjects. The amount of semantic-associated activation in the left inferior prefrontal region was negatively correlated with epilepsy duration in both patient groups. Following temporal resection, semantic-specific activations in inferior prefrontal region became more bilateral in left mTLE patients, but more left-lateralized in right mTLE patients. The longer the duration of epilepsy in the patients, the larger the increase in the left inferior prefrontal semantic-associated activation after surgery in both patient groups. Semantic activation of the intact hippocampus, which had been negatively correlated with seizure frequency, normalized after the epileptic side was removed.

Conclusion

These results indicate alternation of semantic language network related to recruitment of left inferior prefrontal cortex and functional recovery of the hippocampus contralateral to the epileptogenic side, suggesting an intra- and inter-hemispheric reorganization following surgery.     

Identification of attention and cognitive control networks in a parametric auditory fMRI study

In the competition for limited processing resources, top-down attention and cognitive control processes are needed to separate relevant from irrelevant sensory information and to interact with the environment in a meaningful way. The demands for the recruitment of top-down control processes depend on the relative salience of the competing stimuli. In the present event-related functional magnetic resonance imaging (fMRI) study we investigated the dynamics of neuronal networks during varying degrees of top-down control demands. We tested 20 participants with a dichotic auditory discrimination task in which the relative perceptual salience of two simultaneously presented syllables was parametrically varied by manipulating the inter-aural intensity differences (IIDs) and instructing the subjects to selectively attend to either the louder or weaker of the two stimuli. A significant interaction of IID manipulation and attentional instruction was detected bilaterally in the inferior parietal lobe and pre-supplementary motor area, and in the precentral gyrus, anterior cingulate cortex, and inferior frontal gyrus of the right hemisphere. The post hoc analysis of the interaction pattern allowed for an assignment of these regions to either of two sets of regions which can be interpreted to constitute two different brain networks: a fronto-parietal attention control network, involved in the integration of saliency-based and instruction-based processing preferences, and a medial-lateral frontal cognitive control network, involved in the processing of the conflicts arising in the attempt to follow the attentional instruction in face of the varying inter-aural stimulus salience.     

Movement-dependent stroke recovery: a systematic review and meta-analysis of TMS and fMRI evidence

Evidence indicates that experience-dependent cortical plasticity underlies post-stroke motor recovery of the impaired upper extremity. Motor skill learning in neurologically intact individuals is thought to involve the primary motor cortex, and the majority of studies in the animal literature have studied changes in the primary sensorimotor cortex with motor rehabilitation. Whether changes in engagement in the sensorimotor cortex occur in humans after stroke currently is an area of much interest. The present study conducted a meta-analysis on stroke studies examining changes in neural representations following therapy specifically targeting the upper extremity to determine if rehabilitation-related motor recovery is associated with neural plasticity in the sensorimotor cortex of the lesioned hemisphere. Twenty-eight studies investigating upper extremity neural representations (e.g., TMS, fMRI, PET, or SPECT) were identified, and 13 met inclusion criteria as upper extremity intervention training studies. Common outcome variables representing changes in the primary motor and sensorimotor cortices were used in calculating standardized effect sizes for each study. The primary fixed effects model meta-analysis revealed a large overall effect size (ES=0.84, S.D.=0.15, 95% CI=0.76-0.93). Moreover, a fail-safe analysis indicated that 42 null effect studies would be necessary to lower the overall effect size to an insignificant level. These results indicate that neural changes in the sensorimotor cortex of the lesioned hemisphere accompany functional paretic upper extremity motor gains achieved with targeted rehabilitation interventions.     

Response inhibition results in the emotional devaluation of faces: neural correlates as revealed by fMRI

Although it is well established that prior experience with faces determines their subsequent social-emotional evaluation, recent work shows that top-down inhibitory mechanisms, including response inhibition, can lead to social devaluation after even a single, brief exposure. These rapidly induced effects indicate interplay among perceptual, attentional, response-selection and social-emotional networks; yet, the brain mechanisms underlying this are not well understood. This study used functional magnetic resonance imaging (fMRI) to investigate the neural mechanism mediating the relationship between inhibitory control and emotional devaluation. Participants performed two tasks: (i) a Go/No-Go task in response to faces and (ii) a trustworthiness rating task involving the previously seen faces. No-Go faces were rated as significantly less trustworthy than Go faces. By examining brain activations during Task 1, behavioral measures and brain activations obtained in Task 2 could be predicted. Specifically, activity in brain areas during Task 1 associated with (i) executive control and response suppression (i.e. lateral prefrontal cortex) and (ii) affective responses and value representation (i.e. orbitofrontal cortex), systematically covaried with behavioral ratings and amygdala activity obtained during Task 2. The present findings offer insights into the neural mechanisms linking inhibitory processes to affective responses.