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Results for “Brain Mapping”

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PubMed1998

Experimentation with a transcranial magnetic stimulation system for functional brain mapping.

We describe functional brain mapping experiments using a transcranial magnetic stimulation (TMS) device. This device, when placed on a subject's scalp, stimulates the underlying neurons by generating focused magnetic field pulses. A brain mapping is then generated by measuring responses of different motor and sensory functions to this stimulation. The key process in generating this mapping is the association of the 3-D positions and orientations of the TMS probe on the scalp to a 3-D brain reconstruction such as is feasible with a magnetic resonance image (MRI). We have developed a registration system which not only generates functional brain maps using such a device, but also provides real-time feedback to guide the technician in placing the probe at appropriate points on the head to achieve the desired map resolution. Functional areas we have mapped are the motor and visual cortex. Validation experiments focus on repeatability tests for mapping the same subjects several times. Applications of the technique include neuroanatomy research, surgical planning and guidance, treatment and disease monitoring, and therapeutic procedures.

Brain Mapping↗

PubMed1988

Clinical utility of topographic EEG brain mapping.

Topographic EEG brain mapping was performed on 100 patients referred for both EEG and neuroimaging procedures. Topographic maps were abnormal in 78% of patients with stroke, 50% with head trauma and 100% of those with space occupying lesions (tumor, abscess or intracerebral hematoma). Of the patients with abnormal EEG maps 30% had either sole or better localization with mapping than routine EEG or neuroimaging procedures. In no cases were there false localizing abnormalities by EEG mapping. Topographic mapping appears to provide better detection of low amplitude slow activity not easily discernible by routine EEG. It also provides faithful correspondence with localization of many lesions on neuroimaging procedures, and at times distinguishes abnormalities not immediately definable by CT/MRI. Topographic EEG mapping is a valuable adjunct to routine EEG.

Adolescent↗

PubMed1998

Effects of contralateral speech competition on auditory event-related potentials recorded from elderly listeners: brain map study.

Topographic brain mapping was used to investigate the ability of young and elderly female listeners to attend to tones at one ear in the presence of speech competition at the opposite ear. An oddball stimulus presentation paradigm was used to record the N1, P2, and P300 components of the late auditory evoked potential from 19 scalp locations. With speech competition, elderly listeners exhibited significantly larger reductions in N1 amplitude than did young listeners. This suggests that N1 may provide an electrophysiologic index of age-related breakdowns in processing sounds in the presence of background competition. An unexpected difference was also found between young and elderly listeners in P300 scalp topography. While the young listeners' P300 response was centered at midline for both left and right ear stimulation, the elderly participants had P300 maxima centered in the parietal area of the hemisphere located contralateral to the test ear. This suggests that some of the functional properties (e.g., timing, strength, orientation) of the P300 neural generators may change with age or, alternatively, that different generators may be operative in elderly listeners.

Adult↗

PubMed1990

Computerized topographic brain mapping during carotid endarterectomy.

Computerized topographic brain mapping processes standard electroencephalographic data and displays it in a color map, thus simplifying interpretation. During a 2-year period, 65 carotid endarterectomies were performed with the use of brain mapping as the sole criterion for shunt replacement. Forty-three patients (66%) were found to have abnormal brain maps preoperatively. Ten patients (15%) developed ischemic changes after cross-clamping (all resolved after shunt placement). Postoperative brain maps were unchanged in 54 patients (83%) and improved in 7 patients (11%). A new, small focal abnormality was identified in 4 patients without shunts (6%), none of whom had a change in neurologic status. The overall major morbidity and mortality was 1.5%. Computerized brain mapping is a sensitive and readily interpretable means of monitoring cerebral perfusion during carotid surgery. We found the computerized electroencephalographic data to be a dependable criterion for selective shunting and for confirmation of shunt patency during carotid endarterectomy.

Adult↗

PubMed1991

Stable bimodal response to cholinomimetic drugs in Alzheimer's disease. Brain mapping correlates.

We investigated quantitative EEG brain mapping as a physiologic marker of drug response while studying the stability of intersubject variability in patients with Alzheimer's disease (AD) who were receiving bethanechol through intracerebroventricular (ICV) shunts. Two of the patients had previously demonstrated cognitive and behavioral improvements on medication; the third had cognitive deterioration complicated by agitated depression. All three patients were reexamined in a dose-response paradigm. Serial brain mapping examinations were performed along with brief cognitive testing. All patients showed drug responses that were comparable with responses during their initial dose-response phase. There were strong linear correlations between global decreases in 2 to 6 Hz slow-wave activity and cognitive improvement. Brain mapping demonstrated that slowing decreased in magnitude and field with increasing dose until optimal dose was reached; with supra-optimal doses, the magnitude and field of the slowing increased dramatically. These results suggest that the quality of cholinomimetic drug responses are stable over time in individual patients, and that magnitude and pattern of slow-wave activity as measured by brain mapping may be useful in monitoring treatment with cholinomimetic agents.

Alzheimer Disease↗

PubMed1991

EEG brain mapping in diagnostic and therapeutic assessment of dementia.

EEG brain mapping has been proven to be a valuable method in diagnostic and therapeutic assessment in dementia trials, because it is a readily available, inexpensive, high time-resolution method for objective and quantitative evaluation of the neurophysiological aspects of dementias. In 111 mildly to moderately demented patients diagnosed according to DSM-III as both degenerative [senile dementia of the Alzheimer type (SDAT)] and vascular [multi-infarct dementia (MID) type], we were interested in showing not only differences between SDAT and MID patients and normal controls but also the relationship between CT scans, EEG maps, clinical ratings and psychometric tests. CT measures included 10 cerebrospinal fluid (CSF) space variables as well as 17 cortical density measures (1.7 mm3 cubes, Hounsfield units). Clinical investigations consisted of the SCAG score/factors, the digit symbol substitution test, the trailmaking test and the digit span forward test. In brain maps, SDAT patients showed slightly to moderately more slow and less alpha and beta activity as well as a slowing of the dominant frequency (DF) and the centroid (C) than did normal controls. These findings were most prominent in parietal and temporal regions. MID patients exhibited markedly augmented delta/theta and attenuated alpha and beta activity and a slowing of the DF and C. These neurophysiological findings suggest a deterioration of vigilance. Differences between SDAT and MID patients were found mostly in measures concerning differences in the maps. Brain maps of correlation coefficients between CT and EEG variables demonstrated: the greater the anterior horn distance, lateral ventricle distance, and Evan's index, as well as the less cortical density, the more delta/theta and the less alpha and beta activity in the EEG. Moreover, the higher the delta/theta, the less alpha and beta activity, the higher the SCAG scores, and the worse the psychometric performance. From the pharmacological point of view, we observed a significant improvement in vigilance after administration of several nootropic drugs both in normal and pathologically aging subjects, which was associated also with improvement of psychopathometric scores. Based on multi-variante analysis of variance (MANOVA)/Hotlelling T2 we observed a drug's effect in different brain regions of MID and SDAT patients. Thus, pharmaco-EEG mapping mediates valuable information regarding if, how, when, in which dosage, and where a nootropic drug acts on its target organ--the aging human brain.

Aged↗

PubMed2002

A space for measuring mind and brain: interdisciplinarity and digital tools in the development of brain mapping and functional imaging, 1980-1990.

Brain mapping is said to have opened up the possibility of a new collaboration between the sciences of mind and the sciences of the brain, potentially leading to a new kind of scientist, sometimes called "cognitive neuroscientist." This article traces the recent history of brain mapping and analyzes the processes that have led to a new "close working relationship" between the sciences of mind and brain. A key part of the working relationship is shown to be constituted through the development of the Talairach system, a digital space in which to measure structure and function. The development of meaningful brain mapping data involves the creation of measurement spaces that allow interdisciplinary collaboration and is not the result solely of theoretical developments or of the application of a technology.

Brain↗

PubMed1990

On the controversies about clinical use of EEG brain mapping.

Quantitative EEG analysis, often called EEG Brain Mapping, consists of a large variety of separate techniques. Most of these techniques have demonstrated research uses, but few have been shown to have clinical applications that actually impact patient care. Substantial problems exist that can interfere with routine clinical applications. These include a variety of artifacts, confounding clinical problems, diversity of techniques and statistical issues. Existing medical literature suggests several areas where there are clinical uses at this time. EEG Brain Mapping can be used as a testing technique to determine abnormality and perhaps as a monitoring tool, too. It should be viewed as complementary to neuroimaging techniques, rather than a competitor. Those who introduce costly new technology bear the burden of proof for demonstrating its usefulness and cost-effectiveness. Evaluation of new tests should be based on several principles outlined here. EEG Brain Mapping, when used for clinical purposes, should be read together with the accompanying traditional polygraph EEG record. Reproducibility of results should be demonstrated, and artifacts, normal variants and other problems must be identified or avoided. The reader must recognize that features noted on statistical tests do not necessarily imply that pathology exists. Reporting results and clinical implications should be done carefully, thoroughly and with appropriate caution. Results are often quite nonspecific. The user must have skills, knowledge and abilities for reading polygraph EEG as well as additional experience and knowledge about quantitative EEG techniques and problems. Experts must remain careful and responsible about introducing EEG Brain Mapping into routine clinical practice.

Brain↗

PubMed1999

Functional brain mapping using positron emission tomography scanning in preoperative neurosurgical planning for pediatric brain tumors.

OBJECT: The purpose of this report is to demonstrate the value of functional brain mapping using the positron emission tomography (PET) method for preoperative neurosurgical planning in children with brain tumors. Brain maps were used to characterize the relationship between potentially resectable tumors and functionally eloquent brain areas. METHODS: Five children, ranging in age from 3 to 13 years, with hemispheric brain tumors adjacent to eloquent cortex were studied. Magnetic resonance (MR) imaging was used to identify the brain tumors; PET imaging after injection of [18F] fluorodeoxyglucose (FDG), [11C]L-methionine (CMET), or a combination of the two was performed to grade the tumors; and a [15O] H2O uptake study was used to characterize the anatomical relationships of the tumors to functional cortex. The cortical activation maps were obtained during control periods and during behavioral tasks and were used to document motor, visual, and speech and language organizational areas. Wada tests were performed in two patients. Language and speech activation was concordant with the results of Wada testing. CONCLUSIONS: Functional brain mapping using PET scans and coregistered MR images provided the neurosurgeon with precise definitions of structural and functional cortical areas; this altered surgical management in some cases and/or was used to predict outcome. The combination of PET imaging with FDG and/or CMET and measurements of [15O] water uptake was useful in characterizing and grading tumors and instrumental in achieving effective neurosurgical planning. Postoperative results in the five cases suggest that preoperative functional brain mapping has the potential to improve outcome by defining a surgical plan to maximize resection and minimize the risk of neurological sequelae.

Adolescent↗

PubMed2003

Relevance of computerized electroencephalographic topography (brain mapping) in ischemic stroke.

BACKGROUND AND AIMS: Computerized electroencephalographic topography (CET) (brain mapping) is a non-invasive, spatially oriented procedure for depicting amplitude and frequency patterns by two-dimensional color-coded frequency and amplitude display of the electroencephalograph (EEG). MATERIAL AND METHODS: We prospectively studied the relationship between CT scan lesions, conventional EEG and brain mapping in 40 patients with ischemic stroke within 1 week of onset. EEG and brain mapping was done within 24 hours of doing CT scan. RESULTS: There were 32 males and 8 females and the mean age was 56 years (range 27-75 years). CET/EEG was normal in 2 patients with capsular infarct. Brain mapping showed abnormalities (most commonly low-frequency high-amplitude changes) in 95% of patients, whereas EEG abnormalities were seen in only 40%. Brain mapping abnormalities were appropriate to the side of the CT scan lesion in 20 (52.63%) patients and were present bilaterally n 18 (47.37%) patients. Brain mapping abnormalities were ipsilateral to the side of the CT lesion when the lesion was < 2 cm in diameter and they were bi-hemispherical when the CT lesion was > 2 cm in diameter. CONCLUSIONS: There was no correlation between motor deficits and brain map abnormalities.

Adult↗

PubMed1988

Auditory brain map, effects of age.

Brain maps of late auditory evoked cortical potentials were obtained with the Brain Atlas III system in school-aged children and adults. All subjects were judged as neurologically normal, right-handed, and having normal hearing. The stimulus was a 100 ms burst of 500 Hz pure tone at 75 dB HL presented separately to the left and right ear. The results showed a frontoparietal maximum of negative activity corresponding to N1 and designated as the focus of N1 (FN1). FN1 had latencies of 108 ms (left stimulation (stim] and 113 ms (right stim) and amplitudes of -6.0 microV (left stim) and -4.8 microV (right stim) in children and a latency of 90 ms and an amplitude of -6.5 microV in adults. Among the children, more had ipsilateral than contralateral FN1, usually on the right side. The distance between the centers of gravity of FN1s obtained on stimulation of the two ears was significantly smaller in the maps of children than adults (p less than 0.01). The present findings indicated that the topography of the electrical activity changes during adolescence.

Adult↗

PubMed1997

A sensory brain map for each behavior?

Multiple brain maps are commonly found in virtually every vertebrate sensory system. Although their functional significance is generally relatively little understood, they seem to specialize in processing distinct sensory parameters. Nevertheless, to yield the stimulus features that ultimately elicit the adaptive behavior, it appears that information streams have to be combined across maps. Results from current lesion experiments in the electrosensory system, however, suggest an alternative possibility. Inactivations of different maps of the first-order electrosensory nucleus in electric fish, the electrosensory lateral line lobe, resulted in markedly different behavioral deficits. The centromedial map is both necessary and sufficient for a particular electrolocation behavior, the jamming avoidance response, whereas it does not affect the communicative response to external electric signals. Conversely, the lateral map does not affect the jamming avoidance response but is necessary and sufficient to evoke communication behavior. Because the premotor pathways controlling the two behaviors in these fish appear to be separated as well, this system illustrates that sensory-motor control of different behaviors can occur in strictly segregated channels from the sensory input of the brain all through to its motor output. This might reflect an early evolutionary stage where multiplication of brain maps can satisfy the demand on processing a wider range of sensory signals ensuing from an enlarged behavioral repertoire, and bridging across maps is not yet required.

Animals↗

PubMed1988

Computed electroencephalographic topographic brain mapping. A new and accurate monitor of cerebral circulation and function for patients having carotid endarterectomy.

To determine the usefulness of computed electroencephalographic (EEG) topographic (CET) brain mapping to monitor neurologic function during carotid endarterectomy (CEA), 46 consecutive patients having CEA were monitored preoperatively, intraoperatively, and immediately postoperatively by CET brain mapping and simultaneous 16-lead EEG. Preoperative studies revealed that 7 of 16 asymptomatic patients, 5 of 11 patients with amaurosis fugax, and 8 of 12 patients with transient ischemic attacks (TIAs) had abnormal CET brain mapping suggestive of previous subclinical stroke. EEG was abnormal in only 8 of the 20 patients with abnormal CET brain mapping. Intraoperatively during carotid cross-clamping, ischemic changes were seen on CET brain mapping in 23 patients whereas EEG detected these changes in only 13 patients. Ischemic changes detected by intraoperative CET brain mapping were more likely to occur in patients with previous stroke (six of seven) than in patients without previous stroke (17 of 39), p less than 0.05. Patients with changes detected by intraoperative CET brain mapping had an average carotid back-pressure of 38 mm Hg, in contrast to 57 mm Hg for patients without CET brain mapping changes, p less than 0.05. After endarterectomy, CET brain mapping revealed new ischemic changes in one patient who awoke with a mild stroke and in one patient who had TIAs and amaurosis fugax within 6 hours of surgery. We conclude that CET brain mapping is a sensitive, accurate, and useful noninvasive monitor of cerebral circulation and function for patients having CEA.(ABSTRACT TRUNCATED AT 250 WORDS)

Blindness↗

PubMed2001

Introducing navigated transcranial magnetic stimulation as a refined brain mapping methodology.

A major intrinsic limitation of transcranial magnetic stimulation (TMS) to map the human brain lies in the unclear relationship between the position of the stimulating coil on the scalp and the underlying stimulated cortex. The relationship between structure and function as the major feature constituting a brain mapping modality can therefore not be established. Recent advances in image processing allowed us to refine TMS by combining magnetic resonance imaging (MRI) modalities with TMS using a neuronavigation system to measure the position of the stimulating coil and map this position onto a MRI data set. This technique has several advantages over recent TMS mapping strategies. The position of the coil on the scalp can be held constant as verified by real time visual guidance. When evaluating higher cortical functions, the relationship between underlying cortical anatomy and the scalp stimulation site can be accurately assessed. Cortical motor output maps can be easily obtained for preoperative planning and decision making for mass lesions near rolandic cortex in patients. In conclusion, navigated TMS is a reliable alternative for localizing cortical functions and therefore may be a useful adjunct or in selected patients even a helpful alternative to other functional neuroimaging methods.

Brain↗

PubMedDate not supplied

[Brain mapping studies in dyslexia].

Brain EEG mapping has been recorded during three different conditions, rest closed eyes, rest open eyes, and reading task, in a group of 22 dyslexic children, age mean 9.3 years, range 8-11, and control group of normal readers of the same age. All the subjects were right-handed, and laterality was assessed through the Edinburgh test. The individual maps in dyslexic and controls were averaged, and mean maps of both groups were obtained for a very different experimental condition. Rest closed eyes maps of dyslexics and controls disclose a powerful and symmetric alpha over occipital areas, with higher energy peak at 8.5-9.5 Hz., without significant differences in both groups. Brain maps centered in the fast beta band, 18-25 Hz., disclose significant differences in control group versus dyslexics, with more power in control group over all areas. Our findings suggest less adequate brain activation in dyslexics during reading tasks.

Brain Mapping↗

PubMed1990

[Diagnosis of focal epilepsy using electroencephalographic brain mapping].

By means of the EEG brain mapping method we analyzed electroencephalograms of patients who presented focal abnormalities in standard EEG. A total of 15 patients with various epileptic manifestations was investigated. According to the etiology of the disease, they were divided into 3 groups: microfactor, stationary macrofactor, and non-stationary macrofactor. The brain mapping technique proved to be very useful as imaging method of focal abnormalities, useful for registering asymmetries in reaction to following of intermittent photostimulation. The method is especially suitable for storing findings and chronological comparison of findings during pharmacological therapy. The specificity of the method regarding the etiological factor and type of epileptic manifestation could not be verified in such a small number of patients.

Brain Mapping↗

PubMed1996

Electrophysiological alterations in hepatic encephalopathy detected by brain mapping.

Analogical electroencephalogram has been used to study electric alterations in the brain during liver encephalopathy. We adopted digital technique brain mapping to study the electric background activity in the brain and to evaluate the diagnostic and prognosis usefulness of this technique compared with the methods routinely used in this disease. We studied 18 patients with liver cirrhosis and varying degrees of liver encephalopathy and 7 healthy control subjects to assess correlation between the severity of encephalopathy and abnormal electric activity in the brain, and to detect the main differences between the brain mapping findings obtained in the two groups. The findings revealed an overall reduction in the rhythm, increased amplitude and anomalous distribution of the waveforms in the cirrhotic patients. Although similar results have already been reported, brain mapping furnished prompt and more easily visualised findings. Moreover, brain mapping facilitated detailed analysis of wave amplitude, frequency and topographic location indicating that this technique is a valid tool in diagnosing brain disorders.

Brain Mapping↗

PubMed1993

Systematic comparisons of interpolation techniques in topographic brain mapping.

The performance of one local interpolation technique, the nearest neighbors, and two global spline techniques, one planar and the other spherical, commonly used for topographic mapping of brain potential data has been quantitatively evaluated. The method of evaluation was one of cross-validation where the potential at each site in a 31-electrode full scalp recording montage is predicted by interpolation from the other sites. Errors between the measured potentials and those predicted by interpolation were quantified using 4 measures defined as inaccuracy, precision, bias and tolerance. The evaluation was applied to the background EEGs from 5 normal volunteers and from 4 patients with epilepsy, tumor or stroke. The results indicate that none of the interpolation techniques performed well and that for localized components in the EEG, the errors can increase almost without limit. Further, the global techniques performed significantly better than the local technique with 2 being the best order for the nearest-neighbor technique and 3 for the spline techniques. It is concluded that interpolation should not be used with electrode densities of the order of that provided by the international 10-20 system neither to increase the spatial resolution of the electroencephalogram nor in more sophisticated analysis techniques in quantitative EEG for estimates such as the radial-current density.

Brain↗