Cortical and subcortical contributions to absence seizure onset examined with EEG/fMRI

In patients with idiopathic generalized epilepsies (IGEs), bursts of generalized spike and wave discharges (GSWDs) lasting > or =2 seconds are considered absence seizures. The location of the absence seizures generators in IGEs is thought to involve interplay between various components of thalamocortical circuits; we have recently postulated that medication resistance may, in part, be related to the location of the GSWD generators [Szaflarski JP, Lindsell CJ, Zakaria T, Banks C, Privitera MD. Epilepsy Behav. 2010;17:525-30]. In the present study we hypothesized that patients with medication-refractory IGE (R-IGE) and continued absence seizures may have GSWD generators in locations other than the thalamus, as typically seen in patients with IGE. Hence, the objective of this study was to determine the location of the GSWD generators in patients with R-IGE using EEG/fMRI. Eighty-three patients with IGE received concurrent EEG/fMRI at 4 T. Nine of them (aged 15-55) experienced absence seizures during EEG/fMRI and were included; all were diagnosed with R-IGE. Subjects participated in up to three 20-minute EEG/fMRI sessions (400 volumes, TR=3 seconds) performed at 4 T. After removal of fMRI and ballistocardiographic artifacts, 36 absence seizures were identified. Statistical parametric maps were generated for each of these sessions correlating seizures to BOLD response. Timing differences between brain regions were tested using statistical parametric maps generated by modeling seizures with onset times shifted relative to the GSWD onsets. Although thalamic BOLD responses peaked approximately 6 seconds after the onset of absence seizures, other areas including the prefrontal and dorsolateral cortices showed brief and nonsustained peaks occurring approximately 2 seconds prior to the maximum of the thalamic peak. Temporal lobe peaks occurred at the same time as the thalamic peak, with a cerebellar peak occurring approximately 1 second later. Confirmatory analysis averaging cross-correlation between cortical and thalamic regions of interest across seizures corroborated these findings. Finally, Granger causality analysis showed effective connectivity directed from frontal lobe to thalamus, supporting the notion of earlier frontal than thalamic involvement. The results of this study support our original hypothesis and indicate that in the patients with R-IGE studied, absence seizures may be initiated by widespread cortical (frontal and parietal) areas and sustained in subcortical (thalamic) regions, suggesting that the examined patients have cortical onset epilepsy with propagation to thalamus.

Longitudinal comparison of pre- and postoperative diffusion tensor imaging parameters in young children with hydrocephalus

OBJECT

The goal in this study was to compare the integrity of white matter before and after ventriculoperitoneal (VP) shunt insertion by evaluating the anisotropic diffusion properties with the aid of diffusion tensor (DT) imaging in young children with hydrocephalus.

METHODS

The authors retrospectively identified 10 children with hydrocephalus who underwent both pre- and postoperative DT imaging studies. The DT imaging parameters (fractional anisotropy [FA], mean diffusivity, axial diffusivity, and radial diffusivity) were computed and compared longitudinally in the splenium and genu of the corpus callosum (gCC) and in the anterior and posterior limbs of the internal capsule (PLIC). The patients' values on DT imaging at the pre- and postshunt stages were compared with the corresponding age-matched controls as well as with a large cohort of healthy children in the database.

RESULTS

In the gCC, 7 of 10 children had abnormally low preoperative FA values, 6 of which normalized postoperatively. All 3 of the 10 children who had normal preoperative FA values had normal FA values postoperatively as well. In the PLIC, 7 of 10 children had abnormally high FA values, 6 of which normalized postoperatively, whereas the other one had abnormally low postoperative FA. Of the remaining 3 children, 2 had abnormally low preoperative FA values in the PLIC; this normalized in 1 patient after surgery. The other child had a normal preoperative FA value that became abnormally low postoperatively. When comparing the presurgery frequency of abnormally low, normal, and abnormally high FA values to those postsurgery, there was a statistically significant longitudinal difference in both gCC (p = 0.02) and PLIC (p = 0.002).

CONCLUSIONS

In this first longitudinal DT imaging study of young children with hydrocephalus, DT imaging anisotropy yielded abnormal results in several white matter regions of the brain, and trended toward normalization following VP shunt placement.

A group independent component analysis of covert verb generation in children: a functional magnetic resonance imaging study

Semantic language skills are an integral part of early childhood language development. The semantic association between verbs and nouns constitutes an important building block for the construction of sentences. In this large-scale functional magnetic resonance imaging (fMRI) study, involving 336 subjects between the ages of 5 and 18 years, we investigated the neural correlates of covert verb generation in children. Using group independent component analysis (ICA), seven task-related components were identified including the mid-superior temporal gyrus, the most posterior aspect of the superior temporal gyrus, the parahippocampal gyrus, the inferior frontal gyrus, the angular gyrus, and medial aspect of the parietal lobule (precuneus/posterior cingulate). A highly left-lateralized component was found including the medial temporal gyrus, the frontal gyrus, the inferior frontal gyrus, and the angular gyrus. The associated independent component (IC) time courses were analyzed to investigate developmental changes in the neural elements supporting covert verb generation. Observed age effects may either reflect specific local neuroplastic changes in the neural substrates supporting language or a more global transformation of neuroplasticity in the developing brain. The results are analyzed and presented in the framework of two theoretical models for neurocognitive brain development. In this context, group ICA of fMRI data from our large sample of children aged 5-18 years provides strong evidence in support of the regionally weighted model for cognitive neurodevelopment of language networks.

Anisotropic diffusion properties in infants with hydrocephalus: a diffusion tensor imaging study

BACKGROUND AND PURPOSE

Diffusion tensor imaging (DTI) can noninvasively detect in vivo white matter (WM) abnormalities on the basis of anisotropic diffusion properties. We analyzed DTI data retrospectively to quantify the abnormalities in different WM regions in children with hydrocephalus during early infancy.

MATERIALS AND METHODS

Seventeen infants diagnosed with hydrocephalus (age range, 0.13-16.14 months) were evaluated with DTI and compared with 17 closely age-matched healthy children (age range, 0.20-16.11 months). Fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity, and radial diffusivity values in 5 regions of interest (ROIs) in the corpus callosum and internal capsule were measured and compared. The correlation between FA and age was also studied and compared by ROI between the 2 study groups.

RESULTS

Infants with hydrocephalus had significantly lower FA, higher MD, and higher radial diffusivity values for all 3 ROIs in the corpus callosum, but not for the 2 ROIs in the internal capsule. In infants with hydrocephalus, the increase of FA with age during normal development was absent in the corpus callosum but was still preserved in the internal capsule. There was also a significant difference in the frequency of occurrence of abnormal FA values in the corpus callosum and internal capsule.

CONCLUSIONS

This retrospective DTI study demonstrated significant WM abnormalities in infants with hydrocephalus in both the corpus callosum and internal capsule. The results also showed evidence that the impact of hydrocephalus on WM was different in the corpus callosum and internal capsule.

Quantification of head motion in children during various fMRI language tasks

PURPOSE

Head motion during functional MRI scanning can lead to signal artifact, a problem often more severe with children. However, the documentation for the characteristics of head motion in children during various language functional tasks is very limited in the current literature. This report characterizes head motion in children during fMRI as a function of age, sex, and task.

METHODS

Head motion during four different fMRI language tasks was investigated in a group of 323 healthy children between the age of 5 and 18 years. A repeated measures ANOVA analysis was used to study the impact of age, sex, task, and the interaction of these factors on the motion.

RESULTS

Pediatric subjects demonstrated significantly different amounts of head motion during fMRI when different language tasks were used. Word-Picture Matching, the only task that involved visual engagement, suffered the least amount of motion, which was significantly less than in any of the other three tasks; the latter were not significantly different from each other. Further examination revealed that the main effect of language task on motion was significantly affected by age, sex, and their interaction.

CONCLUSION

Our results suggest that age, sex, and task are all associated with the degree of head motion in children during fMRI experiments. Investigators working with pediatric patients may increase their success by using task components associated with less motion (e.g., visual stimuli), or by using this large scale dataset to estimate the effects of sex and age on motion for planning purposes.

Comparison of fMRI data from passive listening and active-response story processing tasks in children

PURPOSE

To use functional MRI (fMRI) methods to visualize a network of auditory and language-processing brain regions associated with processing an aurally-presented story. We compare a passive listening (PL) story paradigm to an active-response (AR) version including online performance monitoring and a sparse acquisition technique.

MATERIALS AND METHODS

Twenty children (ages 11-13 years) completed PL and AR story processing tasks. The PL version presented alternating 30-second blocks of stories and tones; the AR version presented story segments, comprehension questions, and 5-second tone sequences, with fMRI acquisitions between stimuli. fMRI data was analyzed using a general linear model approach and paired t-test identifying significant group activation.

RESULTS

Both tasks showed activation in the primary auditory cortex, superior temporal gyrus bilaterally, and left inferior frontal gyrus (IFG). The AR task demonstrated more extensive activation, including the dorsolateral prefrontal cortex and anterior/posterior cingulate cortex. Comparison of effect size in each paradigm showed a larger effect for the AR paradigm in a left inferior frontal region-of-interest (ROI).

CONCLUSION

Activation patterns for story processing in children are similar in PL and AR tasks. Increases in extent and magnitude of activation in the AR task are likely associated with memory and attention resources engaged across acquisition intervals.

Language networks in children: evidence from functional MRI studies

OBJECTIVE

The purpose of our study was to review functional MRI and other neuroimaging studies of language skills in children from infancy to adulthood.

CONCLUSION

Functional MRI (fMRI) and other neuroimaging studies show developmental changes in the networks of brain regions supporting language, which can be affected by brain injuries or neurologic disorders. Particular aspects of language rely on networks that lateralize to the dominant hemisphere; others rely on bilateral or nondominant mechanisms. Multiple fMRI tasks for pediatric patients characterize functional brain reorganization that may accompany language deficits.

Preliminary fMRI findings in experimentally sleep-restricted adolescents engaged in a working memory task

Here we report preliminary findings from a small-sample functional magnetic resonance imaging (fMRI) study of healthy adolescents who completed a working memory task in the context of a chronic sleep restriction experiment. Findings were consistent with those previously obtained on acutely sleep-deprived adults. Our data suggest that, when asked to maintain attention and burdened by chronic sleep restriction, the adolescent brain responds via compensatory mechanisms that accentuate the typical activation patterns of attention-relevant brain regions. Specifically, it appeared that regions that are normally active during an attention-demanding working memory task in the well-rested brain became even more active to maintain performance after chronic sleep restriction. In contrast, regions in which activity is normally suppressed during such a task in the well-rested brain showed even greater suppression to maintain performance after chronic sleep restriction. Although limited by the small sample, study results provide important evidence of feasibility, as well as guidance for future research into the functional neurological effects of chronic sleep restriction in general, the effects of sleep restriction in children and adolescents, and the neuroscience of attention and its disorders in children.

Correlation of diffusion tensor imaging with executive function measures after early childhood traumatic brain injury

OBJECTIVE

Examine relationships of diffusion tensor imaging (DTI) fractional anisotropy (FA) to executive function (EF) and attention measures following early childhood (3-7 years) traumatic brain injury (TBI).

DESIGN

Exploratory correlation and comparison study.

SETTING

Children's hospital outpatient facilities.

PARTICIPANTS

9 children with a history of TBI (age = 7.89 ± 1.00 years; Glasgow Coma Scale (GCS) = 10.11 ± 4.68) were compared to 12 children with OI (age = 7.51 ± 0.95). All children were at least 12 months post injury at time of evaluation.

MAIN OUTCOME MEASURES

FA in various regions of interest (ROI), EF and attention measures.

RESULTS

FA values primarily in the frontal white matter tracks correlated with EF measures. Separate tasks of inhibition and switching correlated significantly with FA in bilateral frontal lobes. Tasks combining both inhibition and switching correlated significantly with FA values in the left frontal lobe. Tasks of attention negatively correlated with FA values in the right frontal white matter and the superior longitudinal fasciculus.

CONCLUSIONS

Associations between late measurement of FA and EF measures following early childhood TBI suggest that persistent white matter changes, especially in the frontal white matter, may provide an index of EF deficits.

Comparison of SNR and CNR for in vivo mouse brain imaging at 3 and 7 T using well matched scanner configurations

Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) for magnetic resonance microimaging were measured using two nearly identical magnetic resonance imaging (MRI) scanners operating at field strengths of 3 and 7 T. Six mice were scanned using two imaging protocols commonly applied for in vivo imaging of small animal brain: RARE and FLASH. An accounting was made of the field dependence of relaxation times as well as a small number of hardware disparities between scanner systems. Standard methods for relaxometry were utilized to measure T1 and T2 for two white matter (WM) and two gray matter (GM) regions in the mouse brain. An average increase in T1 between 3 and 7 T of 28% was observed in the brain. T2 was found to decrease by 27% at 7 T in agreement with theoretical models. The SNR was found to be uniform throughout the mouse brain, increasing at higher field by a factor statistically indistinguishable from the ratio of Larmor frequencies when imaging with either method. The CNR between GM and WM structures was found to adhere to the expected field dependence for the RARE imaging sequence. Improvement in the CNR for the FLASH imaging sequence between 3 and 7 T was observed to be greater than the Larmor ratio, reflecting a greater susceptibility to partial volume effects at the lower SNR values at 3 T. Imaging at 7 T versus 3 T in small animals clearly provides advantages with respect to the CNR, even beyond the Larmor ratio, especially in lower SNR regimes. This careful multifaceted assessment of the benefits of higher static field is instructive for those newly embarking on small animal imaging. Currently the number of 7 T MRI scanners in use for research in human subjects is increasing at a rapid pace with approximately 30 systems deployed worldwide in 2008. The data presented in this article verify that if system performance and radio frequency uniformity is optimized at 7 T, it should be possible to realize the expected improvements in the CNR and SNR compared with MRI at 3 T.

Partially adaptive STAP algorithm approaches to functional MRI

In this paper, the architectures of three partially adaptive space-time adaptive processing (STAP) algorithms are introduced, one of which is explored in detail, that reduce dimensionality and improve tractability over fully adaptive STAP when used in the construction of brain activation maps in functional magnetic resonance imaging (fMRI). Computer simulations incorporating actual MRI noise and human data analysis indicate that element space partially adaptive STAP can attain close to the performance of fully adaptive STAP while significantly decreasing processing time and maximum memory requirements, and thus demonstrates potential in fMRI analysis.

Compensatory brain activation for recognition memory in patients with medication-resistant epilepsy

Progressive decline of memory functions has been observed in patients with chronic medication-resistant epilepsy. The progression likely relates to the effects of epileptiform discharges, seizures, and medications on the processes of encoding and retrieval. The goal of the study described here was to use functional MRI (fMRI) to examine the effects of chronic epilepsy on verbal recognition memory. We enrolled 12 patients with medication-resistant epilepsy (5 with right and 7 with left hemispheric seizure onset) and 18 healthy controls matched for age, gender, and handedness. Subjects underwent fMRI at 3T using a word recognition task during which they had to recall if words presented during scanning were words they had learned prior to scanning. Although we noted many similarities in the fMRI activation patterns between the subjects with epilepsy and the healthy subjects in areas typically involved in memory processing, testing of the interaction effects for target-foil differences between groups revealed several differences in activation including the right insula, the left cuneus, and the bilateral subgenual anterior cingulate cortex (ACC). In patients with epilepsy, these regions exhibited greater activation for targets than foils, but in healthy subjects the difference was reversed (right insula), absent (left cuneus), or included deactivation to target words (pregenual ACC). These differences were seen despite similar performance during the memory task, suggesting that activations observed in these additional regions may represent compensatory processes for verbal recognition memory that are induced by chronic brain injury related to recurrent seizures.

Reprint of "Cortical reorganization of language functioning following perinatal left MCA stroke" [Brain and Language 105 (2008) 99-111]

OBJECTIVE

Functional MRI was used to determine differences in patterns of cortical activation between children who suffered perinatal left middle cerebral artery (MCA) stroke and healthy children performing a silent verb generation task.

METHODS

Ten children with prior perinatal left MCA stroke (age 6-16 years) and ten healthy age matched controls completed an executive language activation task. fMRI scans were acquired on a 3T scanner using T2* weighted gradient echo, echo-planar imaging (EPI) sequence. Random effects analysis and independent component analysis (ICA) were used to compute activation maps.

RESULTS

Both analysis methods demonstrated alternative activation of cortical areas in children with perinatal stroke. Following perinatal stroke, typical left dominant productive language areas in the inferior frontal gyrus were displaced to anatomical identical areas in the right hemisphere (p=.001). In addition, stroke patients showed more bilateral activation in superior temporal and anterior cingulate gyri and increased activation in primary visual cortex when compared to healthy controls. There was no relation between lesion size and the degree of right hemisphere activation. ICA showed that the healthy controls had a negative correlation with the time course in the right inferior frontal gyrus in the same region that was activated in stroke subjects.

INTERPRETATION

This functional MRI study in children revealed novel patterns of cortical language reorganization following perinatal stroke. The addition of ICA is complementary to Random Effects Analysis, allowing for the exploration of potential subtle differences in pathways in functional MRI data obtained from both healthy and pathological groups.

Developmental differences in white matter architecture between boys and girls

Previous studies have found developmental differences between males and females in brain structure. During childhood and adolescence, relative white matter volume increases faster in boys than in girls. Sex differences in the development of white matter microstructure were investigated in a cohort of normal children ages 5-18 in a cross-sectional diffusion tensor imaging (DTI) study. Greater fractional anisotropy (FA) in boys was shown in associative white matter regions (including the frontal lobes), while greater FA in girls was shown in the splenium of the corpus callosum. Greater mean diffusivity (MD) in boys was shown in the corticospinal tract and in frontal white matter in the right hemisphere; greater MD in girls was shown in occipito-parietal regions and the most superior aspect of the corticospinal tract in the right hemisphere. Significant sex-age interactions on FA and MD were also shown. Girls displayed a greater rate of fiber density increase with age when compared with boys in associative regions (reflected in MD values). However, girls displayed a trend toward increased organization with age (reflected in FA values) only in the right hemisphere, while boys displayed this trend only in the left hemisphere. These results indicate differing developmental trajectories in white matter for boys and girls and the importance of taking sex into account in developmental DTI studies. The results also may have implications for the study of the relationship of brain architecture with intelligence.

Infant brain probability templates for MRI segmentation and normalization

Spatial normalization and segmentation of infant brain MRI data based on adult or pediatric reference data may not be appropriate due to the developmental differences between the infant input data and the reference data. In this study we have constructed infant templates and a priori brain tissue probability maps based on the MR brain image data from 76 infants ranging in age from 9 to 15 months. We employed two processing strategies to construct the infant template and a priori data: one processed with and one without using a priori data in the segmentation step. Using the templates we constructed, comparisons between the adult templates and the new infant templates are presented. Tissue distribution differences are apparent between the infant and adult template, particularly in the gray matter (GM) maps. The infant a priori information classifies brain tissue as GM with higher probability than adult data, at the cost of white matter (WM), which presents with lower probability when compared to adult data. The differences are more pronounced in the frontal regions and in the cingulate gyrus. Similar differences are also observed when the infant data is compared to a pediatric (age 5 to 18) template. The two-pass segmentation approach taken here for infant T1W brain images has provided high quality tissue probability maps for GM, WM, and CSF, in infant brain images. These templates may be used as prior probability distributions for segmentation and normalization; a key to improving the accuracy of these procedures in special populations.

Reliability of fMRI for studies of language in post-stroke aphasia subjects

Quantifying change in brain activation patterns associated with post-stroke recovery and reorganization of language function over time requires accurate understanding of inter-scan and inter-subject variability. Here we report inter-scan variability measures for fMRI activation patterns associated with verb generation (VG) and semantic decision/tone decision (SDTD) tasks in 4 healthy controls and 4 aphasic left middle cerebral artery (LMCA) stroke subjects. A series of 10 fMRI scans was completed on a 4T Varian scanner for each task for each subject, except for one stroke subject who completed 5 and 6 scans for SDTD and VG, thus yielding 35 and 36 total stroke subject scans for SDTD and VG, respectively. Group composite and intraclass correlation coefficient (ICC) maps were computed across all subjects and trials for each task. The patterns of reliable activation for the VG and SDTD tasks correspond well to those regions typically activated by these tasks in healthy and aphasic subjects. ICCs for activation were consistently high (R(0.05) approximately 0.8) for individual tasks among both control and aphasic subjects. These voxel-wise measures of reliability highlight regions of low inter-scan variability within language circuitry for control and post-recovery stroke subjects. ICCs computed from the combination of the SDTD/VG data were markedly reduced for both control and aphasic subjects as compared with the ICCs for the individual tasks. These quantitative measures of inter-scan variability support the proposed use of these fMRI paradigms for longitudinal mapping of neural reorganization of language processing following left hemispheric insult.

Cortical reorganization of language functioning following perinatal left MCA stroke

OBJECTIVE

Functional MRI was used to determine differences in patterns of cortical activation between children who suffered perinatal left middle cerebral artery (MCA) stroke and healthy children performing a silent verb generation task.

METHODS

Ten children with prior perinatal left MCA stroke (age 6-16 years) and ten healthy age matched controls completed an executive language activation task. fMRI scans were acquired on a 3T scanner using T2* weighted gradient echo, echo-planar imaging (EPI) sequence. Random effects analysis and independent component analysis (ICA) were used to compute activation maps.

RESULTS

Both analysis methods demonstrated alternative activation of cortical areas in children with perinatal stroke. Following perinatal stroke, typical left dominant productive language areas in the inferior frontal gyrus were displaced to anatomical identical areas in the right hemisphere (p=.001). In addition, stroke patients showed more bilateral activation in superior temporal and anterior cingulate gyri and increased activation in primary visual cortex when compared to healthy controls. There was no relation between lesion size and the degree of right hemisphere activation. ICA showed that the healthy controls had a negative correlation with the time course in the right inferior frontal gyrus in the same region that was activated in stroke subjects.

INTERPRETATION

This functional MRI study in children revealed novel patterns of cortical language reorganization following perinatal stroke. The addition of ICA is complementary to Random Effects Analysis, allowing for the exploration of potential subtle differences in pathways in functional MRI data obtained from both healthy and pathological groups.

Characterization of abnormal diffusion properties of supratentorial brain tumors: a preliminary diffusion tensor imaging study

OBJECT

Diffusion tensor (DT) imaging was used in children with supratentorial tumors to evaluate the anisotropic diffusion properties between different tumor grades and between tumors and adjacent and contralateral white matter.

METHODS

In this retrospective review, the authors review the cases of 16 children (age range 1-18 years) who presented to their institution with supratentorial tumors and were treated between 2004 and 2007. Eleven patients had low-grade and 5 had high-grade tumors. Fractional anisotropy (FA), mean diffusivity, and axial (lambda parallel) and radial (lambda perpendicular) eigenvalues within selected regions were studied. Mitotic index, necrosis, and vascularity of the tumors were compared with DT imaging parameters.

RESULTS

The mean diffusivity was significantly higher in low-grade than in high-grade tumors (p = 0.04); the 2 tumor grades also significantly differed for both lambda parallel (p < 0.05) and lambda perpendicular (p < 0.05). Mean diffusivity values in low-grade tumors were significantly higher than in adjacent normal-appearing white matter (NAWM; p = 0.0004) and contralateral NAWM (p = 0.0001). In both low- and high-grade tumors, the FA was significantly lower than in NAWM (p < 0.0001 and p < 0.03, respectively) and contralateral NAWM (p < 0.0001 and p < 0.003, respectively). Tumor cellularity highly correlated with mean diffusivity and lambda parallel and lambda perpendicular.

CONCLUSIONS

Diffusion tensor imaging is a useful tool in the evaluation of supratentorial tumors in children. The mean diffusivity appears to be a significant marker in differentiating tumors grades. Findings related to lambda parallel and lambda perpendicular within tumor groups and between tumors and NAWM may be an indirect manifestation of the combined effects of axonal injury, demyelination, and tumor mass within the cranial compartment.

Multiple sclerosis: pathogenesis and MR imaging features of T1 hypointensities in a [corrected] murine model

PURPOSE

To prospectively determine how T1 hypointensities (T1 black holes) on brain magnetic resonance (MR) images are generated by the immune system by using a Theiler murine encephalitis virus-induced model of multiple sclerosis and high-field-strength MR imaging.

MATERIALS AND METHODS

All animal protocols and experiments were approved by the institutional animal care and use committee. Volumetric MR imaging studies were conducted at 7 T in six C57BL/6 mice and in immune differentiation marker (recombination activation gene [RAG]-1)-, immune cell (CD4, CD8)-, and immune effector molecule (Fas ligand, perforin)-deficient mice (six mice in each group) to determine which immune cell types and effector molecules lead to T1 hypointensities. The main outcome measure was the total T1 black hole volume per animal, as determined with volumetric analysis, and was analyzed statistically by using software.

RESULTS

Compared with C57BL/6 mice, RAG-1-deficient mice showed a significant (P = .003) decrease in total T1 black hole volume, suggesting a clear role for the adaptive immune system. While CD4-deficient mice did not show a significant decrease in T1 black hole volume (P = .33), CD8-deficient mice did (P = .003). Perforin-deficient mice showed a significant reduction of T1 black hole volume (P = .002), whereas Fas ligand-deficient mice did not (P = .77).

CONCLUSION

The data suggest that CD8 T cells utilizing perforin effector molecules are responsible for T1 black hole formation.

Functional magnetic resonance imaging assessment of cognitive function in childhood-onset systemic lupus erythematosus: a pilot study

OBJECTIVE

To investigate changes in brain activation patterns detected by functional magnetic resonance imaging (FMRI), and the relationship between FMRI activation patterns and results of formal neuropsychological testing, in patients with childhood-onset systemic lupus erythematosus (SLE).

METHODS

Ten patients with childhood-onset SLE underwent formal neuropsychological testing and FMRI using 3 paradigms: a continuous performance task (CPT) to evaluate attention, an N-Back task to assess working memory, and verb generation to evaluate language processing. Composite Z maps were generated to summarize the brain activation patterns for each FMRI paradigm in patients with childhood-onset SLE and to compare these patterns with those observed in healthy controls. Between-group comparison Z maps showing differences in activation between childhood-onset SLE patients and controls were generated, using a significance level of P < 0.05 in a general linear model.

RESULTS

Compared with the control group, the childhood-onset SLE group showed statistically significant increased activation of brain areas involved in the CPT, N-Back, and verb generation tasks. In contrast, in the absence of active stimulus, e.g., during times of the paradigm control tasks, childhood-onset SLE patients consistently undersuppressed activity in the expected brain areas. Activation in selected cortical areas was found to correlate negatively with results of a subset of individual neuropsychological test scores.

CONCLUSION

FMRI abnormalities are present in childhood-onset SLE, manifesting as an imbalance between active and inhibitory responses to an array of stimuli. Differences in brain activation patterns compared with those observed in controls suggest that childhood-onset SLE may be associated with abnormalities in white matter connectivity resulting in neuronal network dysfunction, rather than injury of specific gray matter areas.

Comprehensive presurgical functional MRI language evaluation in adult patients with epilepsy

Functional magnetic resonance imaging (fMRI) has the potential to replace the intracarotid amobarbital procedure (IAP) in presurgical evaluation of patients with epilepsy. In this study, we compared fMRI verb generation (VG) and semantic decision/tone decision (SDTD) tasks and the IAP in their ability to localize language functions in patients with epilepsy undergoing presurgical evaluation. We enrolled 50 healthy controls to establish normal language activation patterns for VG and SDTD tasks at 3 or 4 T, and to design language regions of interest (ROIs) that were later applied to 38 patients with epilepsy (28 of 38 also underwent the IAP). We calculated laterality indices (LIs) for each task for each subject based on the ROIs, and we used general linear modeling to analyze the fMRI data. All healthy and epileptic subjects activated language areas with both fMRI tasks. We found significant correlations in language lateralization between the fMRI tasks (r=0.495, P<0.001) and between VG and IAP (r=0.652, P<0.001) and SDTD and IAP (r=0.735, P<0.001). The differences in LIs between SDTD and VG tasks were small and not affected by age, gender, epilepsy status, handedness, or performance. SDTD and VG tasks combined explained approximately 58.4% in the variability of the IAP/language. In the general linear modeling, only the SDTD task significantly contributed to the determination of language lateralization in patients with epilepsy undergoing presurgical evaluation. Results indicate a moderate convergent validity between both fMRI language tasks and between IAP and fMRI tasks. The results of this study indicate that either of these fMRI tasks can be used for language lateralization in patients with epilepsy undergoing presurgical evaluation, but that the SDTD task is likely to provide more information regarding language lateralization than the VG task.