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PubMed1999

[Importance and limitations of the validation of functional MRI of motor function and language using preoperative cortical stimulation].

UNLABELLED: This chapter describes and discusses the value of the localization of functional areas obtained from functional MRI in brain tumor cases. Correlation method is cortical brain mapping by intraoperative stimulation. The experience reported here is focused on the study of motricity and language. METHODS: Twenty two patients with tumors of the rolandic region (n = 16) or in the temporal lobe (n = 6) underwent functional MR mapping and subsequently cortical mapping before tumor resection. The tasks chosen were a flexion and extension of the fingers or a naming task. We used 3D reconstructed images of the surface of the brain to assess intra and post operatively the functional MRI and stimulation data. RESULTS: For the motor correlation, in each case, the results of direct cortical mapping matched those obtained with functional MRI, both positively and negatively, although the extent of the functional activations was larger than the area required to elicit the corresponding movement during intraoperative brain mapping. For the language correlation and for the task chosen, only the results of the precentral areas matched those of functional MRI. CONCLUSIONS: Functional MRI can be used preoperatively to assess motor functional area in patients with rolandic tumors. More studies are needed to validate intraoperatively the language areas and the real extent of functional MRI activations. Finally, the observed discrepancy between functional MRI and cortical stimulation is likely due to the rather profound differences between both techniques, in terms of neurophysiology, practical applications and statistical analysis.

Adult↗

PubMed2005

Functional correlations of spatial quantitative EEG and intelligences in a nonalphabetical language group.

This study investigated any functional correlations between intelligences and spatially recorded quantitative electroencephalograms (QEEGs) in a nonalphabetical language group. Participants, between 6 and 8 years old, were sampled in a teaching hospital located at the central Taiwan region. The Chinese Wechsler Intelligence Scale for Children-III (WISC-III) intelligence test and quantitative electroencephalograph recording procedures were both administrated to collect data. Intelligences were divided into two categories, verbal and performance intelligences, for statistical investigations. Statistical analyses of the noncontaminated QEEG dataset investigated the differentiability of each frequency on a single cortical region and coherence between cortical regions. Low QEEG frequencies were found to have a significant correlation with intelligences on some cortical regions. Coherence between symmetric cortical regions was found to be an important factor in predicting intelligences. Results showed the feasibility of functional brain mapping in the particular language population.

Brain Mapping↗

PubMed1988

Clinico-experimental studies on auditory evoked middle latency response (AEMLR) with specific reference to generation and auditory dominancy.

The present study was carried out on animals and humans in order to clarify auditory dominancy or lateralization and the contribution site of auditory evoked middle latency responses (AEMLRs). Normal AEMLRs on guinea pigs and humans were quite similar and consisted of two negative and two positive peaks between 8 and 50 msec following the start of an auditory stimulus. In normal human subjects, the component Pa (peak to baseline measurement) or Na-Pa (trough to peak measurement) was significantly greater in the temporal area contralateral to the stimulated ear than in the ipsilateral temporal area. In guinea pigs, however, AEMLRs were attenuated only by stimulation contralateral to the side, on which a lesion was made by unilateral aspiration of the lemniscus or the inferior colliculus. This auditory lateralization and contralateral dominancy were also verified by the direct cortical recording of AEMLRs in humans and also by analysis of auditory evoked brain mapping. In clinical studies, AEMLRs have been obtained even in a premature infant born after a 44-week pregnancy. In patients with well localized lesions of the brain stem, all components of the AEMLR to stimulation contralateral to the lesion side were affected. However, component Pa of the response to stimulation contralateral to the lesion was mainly abolished in patients with unilateral thalamic or temporal lesions. The following results were obtained: 1) component Pa (or Na-Pa) of AEMLR has significant lateralization, 2) the generation site of Pa may be in the subcortical thalamic projection of the contralateral lobe, 3) component Po (or No-Po) is a true neurogenic response but is frequently enhanced by the post-auricular reflex, 4) the contralateral inferior colliculus is very important for the generation of Po, 5) the auditory system (hearing) may have contralateral AEMLR dominancy.

Adolescent↗

PubMed2000

Cranio-orbital missile wound and bullet migration. Case report.

An unusual case of craniocerebral missile injury, with orbital roof perforation and spontaneous bullet migration into the maxillary sinus, is reported. Emergency treatment consisted in wide craniectomy around the bullet entry point, blood and foreign bodies debridement. Subsequent procedures were necessary for abscess evacuation, transmaxillary bullet removal and later cranial vault reconstruction. Challenging aspects were the treatment of the infectious complications, following cerebrospinal fluid fistula through the wound, and the onset of post-traumatic epilepsy, scarcely responsive to common antiepileptic drugs. The treatment of the abscess by combined systemic and intracavitary antibiotic therapy and of the chronic seizures by progressive adjustment with new protocols of antiepileptic drugs under EEG and brain mapping revealed successful.

Adult↗

PubMed2005

In vivo flow territory mapping of major brain feeding arteries.

The ability to visualize the perfusion territories of major feeding arteries to the brain is important for many clinical applications. Since the work of Duret in 1874 on vascularization of the brain, many textbooks and atlases have shown schematic drawings of the supply areas of the major cerebral arteries. Recent postmortem studies demonstrated that the variability of the cerebral vascular territories is significantly greater than previously assumed. The aim of the present study was to investigate in vivo, the variability of flow territories of major brain feeding arteries. Flow territory mapping of the anterior (internal carotid arteries) and posterior (basilar artery) circulation was performed in 115 (58 +/- 9 years of age) subjects with selective arterial spin labeling MRI. Flow territory maps for the entire population indicated significant variation in flow territories. However, when the subjects are further categorized into groups with a complete circle of Willis, with a missing A1 segment and with a unilateral or bilateral fetal-type posterior cerebral artery, the results showed considerably lower variation within groups. It is therefore concluded that, the variation observed from the entire population is mainly caused by anatomical variants of the circle of Willis. To relate focal brain lesions to underlying flow territories in individual cases, knowledge of the anatomy of the circle of Willis is essential.

Aged↗

PubMed1997

MRI and PET coregistration--a cross validation of statistical parametric mapping and automated image registration.

Coregistration of functional PET and T1-weighted MR images is a necessary step for combining functional information from PET images with anatomical information in MR images. Several coregistration algorithms have been published and are used in functional brain imaging studies. In this paper, we present a comparison and cross validation of the two most widely used coregistration routines (Friston et al., 1995, Hum. Brain Map. 2: 165-189; Woods et al., 1993, J. Comput. Assisted Tomogr: 17: 536-546). Several transformations were applied to high-resolution anatomical MR images to generate simulated PET images so that the exact (rigid body) transformations between each MR image and its associated simulated PET images were known. The estimation error of a coregistration in relation to the known transformation allows a comparison of the performance of different coregistration routines. Under the assumption that the simulated PET images embody the salient features of real PET images with respect to coregistration, this study shows that the routines examined reliably solve the MRI to PET coregistration problem.

Algorithms↗

PubMed1990

Dynamic infrared functional mapping of the cerebral cortex.

Although many neuroimaging methods (computer tomography, H+ and isotope clearance, [14C]deoxyglucose utilization, potential-sensitive dyes, electroencephalogram and magnetoencephalogram-mapping, nuclear magnetic resonance tomography, single photon emission computer tomography, and positron emission tomography) are now being used to map brain structure and function, there still exists a need for a new approach that is functional, dynamic, remote, and noninvasive, and that also has reasonable sensitivity and spatial and temporal resolution. Such a method is described here. Thermoencephaloscopy (TES), based on thermovision and digital image processing techniques, is a method of neuroimaging consisting of recording through the intact skull the very weak changes in infrared radiation that are connected with brain activity. The parameters of the method are: temperature sensitivity of 0.002 degrees C, instrumental spatial resolution of 70 microns pixel-1, and instrumental temporal resolution of 40 ms (enabling up to twenty-five maps to be produced per second). The distribution over the rat cerebral cortex of local, multiple, and modally and regionally specific thermoresponses to various sensory stimuli, direct cortical stimulation, and associative learning (conditioning), have been studied, as well as the spreading of thermowaves over the brain cortex. The underlying mechanisms which form the basis of the technique of TES, such as joule heating, local changes in brain metabolism and local cerebral blood flow, as well as the formation of thermodipoles, are discussed.

Animals↗

PubMed2004

Changes in effective connectivity models in the presence of task-correlated motion: an fMRI study.

We investigated the effects of motion-correction strategy and time course selection method when structural equation modeling is applied to fMRI data in the presence of task-correlated motion. Three motion-correction methods were employed for a group of 12 subjects performing an orthographic lexical retrieval task: (1) a rigid body realignment as implemented in SPM99, (2) a rigid body realignment combined with the inclusion of motion parameters in the statistical model, and (3) the FLIRT motion correction followed by an ICA analysis aiming to identify and remove the motion-related components and the ghosting artifacts. For each motion correction, the time courses of the activated regions were selected in three ways: (1) using the voxels with the highest Z scores, (2) using the average across all the statistically significant voxels in the region of interest, and (3) using a within-region, across-subjects, singular value decomposition. The resulting models of effective connectivity were markedly different, although the activation pattern was not substantially altered by the motion-correction method. Higher values for the path coefficients were obtained for the models fitted to the covariance matrices based on the average time courses than for the covariance matrices based on a single voxel time course. Our results suggest caution with the interpretation of task-induced changes in effective connectivity since, for higher-order cognitive brain functions, multiple models can be fitted to a given data set and these models cannot be rejected on an anatomical or cognitive basis. Hum. Brain Mapping 21:49-63, 2004.

Brain Mapping↗

PubMed1988

Conscious-sedation analgesia during craniotomy for intractable epilepsy: a review of 354 consecutive cases.

The perioperative records of 354 consecutive patients undergoing craniotomy for surgical treatment of intractable epilepsy performed with conscious-sedation analgesia were reviewed retrospectively. There was no perioperative morbidity or mortality identified which could be attributed to the anaesthetic technique. The technique was not suitable for seven patients, in whom general anaesthesia was induced. The most frequent intraoperative problems were convulsions (16 per cent) and nausea and vomiting (eight per cent). Less frequent problems included excessive sedation (three per cent), "tight brain" (1.4 per cent) and local anaesthetic toxicity (two per cent). This study confirms that conscious-sedation analgesia provides suitable conditions for craniotomies when brain mapping is required.

Adolescent↗

PubMed2003

Dynamics of gray matter loss in Alzheimer's disease.

We detected and mapped a dynamically spreading wave of gray matter loss in the brains of patients with Alzheimer's disease (AD). The loss pattern was visualized in four dimensions as it spread over time from temporal and limbic cortices into frontal and occipital brain regions, sparing sensorimotor cortices. The shifting deficits were asymmetric (left hemisphere > right hemisphere) and correlated with progressively declining cognitive status (p < 0.0006). Novel brain mapping methods allowed us to visualize dynamic patterns of atrophy in 52 high-resolution magnetic resonance image scans of 12 patients with AD (age 68.4 +/- 1.9 years) and 14 elderly matched controls (age 71.4 +/- 0.9 years) scanned longitudinally (two scans; interscan interval 2.1 +/- 0.4 years). A cortical pattern matching technique encoded changes in brain shape and tissue distribution across subjects and time. Cortical atrophy occurred in a well defined sequence as the disease progressed, mirroring the sequence of neurofibrillary tangle accumulation observed in cross sections at autopsy. Advancing deficits were visualized as dynamic maps that change over time. Frontal regions, spared early in the disease, showed pervasive deficits later (>15% loss). The maps distinguished different phases of AD and differentiated AD from normal aging. Local gray matter loss rates (5.3 +/- 2.3% per year in AD v 0.9 +/- 0.9% per year in controls) were faster in the left hemisphere (p < 0.029) than the right. Transient barriers to disease progression appeared at limbic/frontal boundaries. This degenerative sequence, observed in vivo as it developed, provides the first quantitative, dynamic visualization of cortical atrophic rates in normal elderly populations and in those with dementia.

Aged↗

PubMed2003

Detecting low-frequency functional connectivity in fMRI using a self-organizing map (SOM) algorithm.

Low-frequency oscillations (<0.08 Hz) have been detected in functional MRI studies, and appear to be synchronized between functionally related areas. A current challenge is to detect these patterns without using an external reference. Self-organizing maps (SOMs) offer a way to automatically group data without requiring a user-biased reference function or region of interest. Resting state functional MRI data was classified using a self-organizing map (SOM). Functional connectivity between the left and right motor cortices was detected in five subjects, and was comparable to results from a reference-based approach. SOMs are shown to be an attractive option in detecting functional connectivity using a model-free approach. Hum. Brain Mapping 20:220-226, 2003.

Algorithms↗

PubMed1989

Digital rat brain: a computerized atlas.

Digital brain mapping provides the techniques required for 3 dimensional (3D) reconstruction and display. This paper describes work which extends the data published in the Paxinos and Watson (1982) atlas of the rat brain to a computerized form. The product of these experiments is a 3D digital neuroanatomic atlas. The data were transformed from 2D outlines to 3D volumes each associated with a specific neuroanatomic structure. The system which manages this transformation also provides tools to manipulate the composition, orientation and appearance of the displays interactively.

Animals↗

PubMed2001

[Functional recuperation following lesions of the primary somatosensory fields. Study of compensatory mechanisms].

During a long time, lesions of the primary somatosensory area (S I) were considered as generating severe and definitive neurological sequelae. However, recent reports described a recovery following stroke and resective surgeries (for epilepsy or tumor). On the basis of these observations, of experimentations in animals, and of studies of the (re)organization of eloquent areas in man using new methods of functional mapping, brain plasticity phenomena underlying the recovery were analyzed. They seems to implicate the recruitment of local areas (sensory redundancies within S I), regional areas (primary motor area, secondary somatosensory area, posterior parietal cortex, insula), controlateral eloquent regions, and even learning of new compensatory strategies. Such data could allow us to extend surgical indications of resection of lesions located within S I. An improvement of our knowledge of these functional reshaping phenomena (unmasking of latent networks and/or participation of eloquent homologous and/or sprouting) and then their prediction remains mandatory, with the goal to optimize the surgical preplanning in functional regions, taking account of the individual dynamic spatiotemporal cortical organization. This better knowledge seems to be obtained by studying the correlations between pre- and post-operative functional neuroimaging (fMRI, MEG) data, and the intraoperative functional mapping results.

Animals↗

PubMed2002

Multiecho segmented EPI with z-shimmed background gradient compensation (MESBAC) pulse sequence for fMRI.

A MultiEcho Segmented EPI with z-shimmed BAckground gradient Compensation (MESBAC) pulse sequence is proposed and validated for functional MRI (fMRI) study in regions suffering from severe susceptibility artifacts. This sequence provides an effective tradeoff between spatial and temporal resolution and reduces image distortion and signal dropout. The blood oxygenation level-dependent (BOLD)-weighted fMRI signal can be reliably obtained in the region of the orbitofrontal cortex (OFC). To overcome physiological motion artifacts during prolonged multisegment EPI acquisition, two sets of navigator echoes were acquired in both the readout and phase-encoding directions. Ghost artifacts generally produced by single-shot EPI acquisition were eliminated by separately placing the even and odd echoes in different k-space trajectories. Unlike most z-shim methods that focus on increasing temporal resolution for event-related functional brain mapping, the MESBAC sequence simultaneously addresses problems of image distortion and signal dropout while maintaining sufficient temporal resolution. The MESBAC sequence will be particularly useful for pharmacological and affective fMRI studies in brain regions such as the OFC, nucleus accumbens, amygdala, parahippocampus, etc.

Adult↗

PubMed2000

Functional magnetic resonance imaging aided radiation treatment planning.

Functional MRI (magnetic resonance imaging) allows one to noninvasively identify various eloquent cortices in the brain. The integration of cortical activation information into radiosurgical treatment planning may provide an alternative to prevent or minimize radiation damage to eloquent cortex. A novel approach of directly integrating the fMRI (functional magnetic resonance imaging) brain map into treatment planning is proposed. Three brain tumor patients have been studied using this method with motor and/or visual paradigms. Brain activation was demonstrated in eloquent cortex at the precentral gyrus (motor area) and medial occipital lobe (visual area). The activation maps were transferred to a treatment planning workstation, (XKnife), and 3D (three-dimensional) activation maps were generated and co-registered to a 3D CT (computed tomography) anatomical data set, which provided the calibration localizer, for treatment planning. Radiosurgery was designed based on both functional and structural information by the medical team consisting of a radiation oncologist, a neurosurgeon and a physicist. The average maximum dose for the tumor was 2113 cGy. The average maximum dose for tissue surrounding the tumor was 1600 cGy. The average dose with fMRI information to the eloquent cortex was 163.4 cGy over three patients, while without fMRI information it was 240.5 cGy. The average percentage dose reduction over three patients is 32%. The results suggest that using this method can reduce the dose to the eloquent cortex. This approach provides the physician with additional information for treatment planning and may spare the patient unnecessary radiation exposure to adjacent eloquent cortices.

Adult↗

PubMed2004

Detection of abnormal cerebral excitability by coincident stimulation and recording.

OBJECTIVE: A method for mapping brain excitability and detecting abnormalities, by concurrently stimulating and recording 'focal' compound responses through one microelectrode, was evaluated in three rat epilepsy models in comparison with distal stimulation of perforant path afferents. METHODS: A fixed trajectory from neocortex to dentate gyrus was mapped under halothane anesthesia. Several weeks earlier, tetanus toxin or vehicle was microinjected into the dentate polymorphic layer, or else rats were genetically epilepsy-prone (GEPR-9) or epilepsy-resistant (GERR-0). Other (unmapped) rats received acute penicillin microinjections within the dentate granular layer. RESULTS: Focal responses, although widespread, proved largest in the dentate (>+/-0.5 mV). Tetanus toxin diminished focal responses near the microinjection site versus vehicle-microinjected (66%) or contralateral controls (55%), but enhanced them elsewhere in the dentate. It enhanced distal responses at all hippocampal locations. Focal but not distal responses were higher in GEPR-9 than in GERR-0 rats at widespread forebrain locations (mean 233%). Penicillin facilitated both focal and distal dentate responses, but the focal facilitation peaked sooner (about 75 versus 180 min). CONCLUSIONS: Focal responses better uncover pervasive or discrete excitability differences. SIGNIFICANCE: Focal mapping may aid in diagnostic imaging and intraoperative targeting, offering high resolution, rapid performance, low stimulus currents and minimal invasion.

Animals↗

PubMed1996

Non-invasive functional mapping with multi-channel near infra-red spectroscopic topography in humans.

Near-infrared spectroscopy (NIRS) is a new technique for non-invasive monitoring of tissue oxygenation and its kinetics. Up to this date, it has been used solely in research for the global hemodynamic change of the brain and for rough regional activation after stimulating the brain physiologically. This paper describes functional brain mapping using multi channel (ten channel) NIRS by applying the motor stimulation in humans. Our results demonstrate that the regional hemodynamic change was detected in a small area around the motor cortex with a time resolution of 1-2 s. NIRS technique offers considerable potential for research and clinical applications with no invasion.

Adult↗

PubMed2003

Neural correlates of segmental and tonal information in speech perception.

The Chinese language provides an optimal window for investigating both segmental and suprasegmental units. The aim of this cross-linguistic fMRI study is to elucidate neural mechanisms involved in extraction of Chinese consonants, rhymes, and tones from syllable pairs that are distinguished by only one phonetic feature (minimal) vs. those that are distinguished by two or more phonetic features (non-minimal). Triplets of Chinese monosyllables were constructed for three tasks comparing consonants, rhymes, and tones. Each triplet consisted of two target syllables with an intervening distracter. Ten Chinese and English subjects were asked to selectively attend to targeted sub-syllabic components and make same-different judgments. Direct between-group comparisons in both minimal and non-minimal pairs reveal increased activation for the Chinese group in predominantly left-sided frontal, parietal, and temporal regions. Within-group comparisons of non-minimal and minimal pairs show that frontal and parietal activity varies for each sub-syllabic component. In the frontal lobe, the Chinese group shows bilateral activation of the anterior middle frontal gyrus (MFG) for rhymes and tones only. Within-group comparisons of consonants, rhymes, and tones show that rhymes induce greater activation in the left posterior MFG for the Chinese group when compared to consonants and tones in non-minimal pairs. These findings collectively support the notion of a widely distributed cortical network underlying different aspects of phonological processing. This neural network is sensitive to the phonological structure of a listener's native language. Hum. Brain Mapping 20:185-200, 2003.

Adult↗