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Results for “Brain Mapping”

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PubMed1993

Effect of handedness on the middle latency auditory evoked potential.

The effect of handedness on the middle latency response of the auditory evoked potential was investigated by testing 16 right-handed and 16 left-handed young adults with normal hearing. Each handedness group contained eight males and eight females. Peaks PO, N(a),P(a),Nb,and Pb showed a progressive, statistically significant latency increase in left-handed subjects when compared with right-handed subjects. The latency difference was 1.1 ms at peak P(a) and 3.6 ms at peak Pb. There was no significant latency difference between males and females. Topographic brain mapping showed that the distribution of positivity of wave Pb was similar to the distribution for wave P(a) in both right- and left-handed subjects.

Acoustic Stimulation↗

PubMed1998

Imaging and cochlear implant.

The auditory pathway imaging may be morphologic and/or functional. The high resolution computed tomography and the magnetic resonance imaging (MRI) provide an evaluation of the anatomical and structural landmarks useful for a safe and successful cochlear implantation. The electrical stimulations supplied by the cochlear implant give rise to ascending electrochemical activities reaching the cortex. These activities can be recorded with scalp electrodes by Evoked Potentials (EP) or fields techniques and eventually translated in isochronic or isopotential brain mapping. These techniques provide a very sharp temporal resolution with an imprecise spatial resolution. The late auditory EP of implantees are closely comparable to the responses of normal hearing people. The neuronal metabolism's increase is associated with a cerebral blood flow increase. Comparing regional cerebral blood flow (rCBF) between two or more conditions allows the localisation of brain areas involved in a fixed task. Single photon or positron emission tomography and functional MRI (fMRI) demonstrate cBF changes associated with an auditory stimulation. (f)MRI is contraindicated in cochlear implantees.

Brain↗

PubMed1995

Specific tonotopic organizations of different areas of the human auditory cortex revealed by simultaneous magnetic and electric recordings.

This paper presents data concerning auditory evoked responses in the middle latency range (wave Pam/Pa) and slow latency range (wave N1m/N1) recorded from 12 subjects. It is the first group study to report multi-channel data of both MEG and EEG recordings from the human auditory cortex. The experimental procedure involved potential and current density topographical brain mapping as well as magnetic and electric source analysis. Responses were compared for the following 3 stimulus frequencies: 500, 1000 and 4000 Hz. It was found that two areas of the auditory cortex showed mirrored tonotopic organization; one area, the source of N1m/N1 wave, exhibited higher frequencies at progressively deeper locations, while the second area, the source of the Pam/Pa wave, exhibited higher frequencies at progressively more superficial locations. The Pa tonotopic map was located in the primary auditory cortex anterior to the N1m/N1 mirror map. It is likely that N1m/N1 results from activation of secondary auditory areas. The location of the Pa map in A1, and its N1 mirror image in secondary auditory areas is in agreement with observations from animal studies.

Acoustic Stimulation↗

PubMed1996

Acoustic trauma caused by lightning.

Lesions produced by exposure to noise are frequent in everyday life. Injuries may be found in all systems of the human body, from the digestive to the endocrine, from the cardiovascular to the nervous system. Many organs may be damaged, the ear being one of them. It is known that noise produced by factories, airports, musical instruments and even toys can cause auditory loss. Noises in nature can also cause acoustic trauma. This report is the case history of acoustic trauma caused by lightning. The patient was studied with CAT scan, electroencephalogram, and brain mapping, impedance audiometry with tympanogram and acoustic reflex, audiometry and evoked otoacoustics emissions: distortion products and transients.

Acoustic Impedance Tests↗

PubMed1993

Small sets of putative interneurons are octopamine-immunoreactive in the central nervous system of the pond snail, Lymnaea stagnalis.

An antibody raised against conjugated octopamine was applied to map octopamine-containing neurons in the central nervous system of the pond snail Lymnaea stagnalis. A small number of octopamine-like immunoreactive neurones occurs in all ganglia, but the pleural ones. The neurons are located either in small clusters or occur individually. Major concentrations of octopamine-immunoreactive neurons can first of all be found in the buccal, cerebral and pedal ganglia. Varicose arborizations were observed in the neuropiles, but peripheral projections of labelled elements could not be traced. We suggest that a set of octopaminergic interneurons would exist in the Lymnaea brain. Mapping of octopamine-immunoreactive neurons given may also facilitate physiological investigations on octopaminergic neurotransmission in the gastropod nervous system.

Animals↗

PubMed2005

Compartment-resolved imaging of activity-dependent dynamics of cortical blood volume and oximetry.

Optical imaging, positron emission tomography, and functional magnetic resonance imaging (fMRI) all rely on vascular responses to image neuronal activity. Although these imaging techniques are used successfully for functional brain mapping, the detailed spatiotemporal dynamics of hemodynamic events in the various microvascular compartments have remained unknown. Here we used high-resolution optical imaging in area 18 of anesthetized cats to selectively explore sensory-evoked cerebral blood-volume (CBV) changes in the various cortical microvascular compartments. To avoid the confounding effects of hematocrit and oximetry changes, we developed and used a new fluorescent blood plasma tracer and combined these measurements with optical imaging of intrinsic signals at a near-isosbestic wavelength for hemoglobin (565 nm). The vascular response began at the arteriolar level, rapidly spreading toward capillaries and venules. Larger veins lagged behind. Capillaries exhibited clear blood-volume changes. Arterioles and arteries had the largest response, whereas the venous response was smallest. Information about compartment-specific oxygen tension dynamics was obtained in imaging sessions using 605 nm illumination, a wavelength known to reflect primarily oximetric changes, thus being more directly related to electrical activity than CBV changes. Those images were radically different: the response began at the parenchyma level, followed only later by the other microvascular compartments. These results have implications for the modeling of fMRI responses (e.g., the balloon model). Furthermore, functional maps obtained by imaging the capillary CBV response were similar but not identical to those obtained using the early oximetric signal, suggesting the presence of different regulatory mechanisms underlying these two hemodynamic processes.

Animals↗

PubMed2006

Structural analysis of the basal ganglia in schizophrenia.

Increases in the total volume of basal ganglia structures have been reported in schizophrenia. However, patterns of basal ganglia shape change, which can reveal localized changes in substructure volumes, have not been investigated. In this study, the total volume and shape of several basal ganglia structures were compared in subjects with and without schizophrenia. T(1)-weighted magnetic resonance scans were collected in 54 schizophrenia and 70 comparison subjects. High-dimensional (large-deformation) brain mapping was used to assess the shape and volume of several basal ganglia structures. The relationships of shape and volume measures with psychopathology, cognition and motor function were also assessed. Left and right volumes of the caudate and putamen, as well as the right globus pallidus volume, were significantly increased in subjects with schizophrenia as compared to comparison subjects after total brain volume was included as a covariate. Significant differences in shape accompanied these volume changes in the caudate, putamen and globus pallidus, after their total volumes were included as covariates. There were few significant correlations between volume or shape measures and either cognitive function or clinical symptoms, other than a positive correlation between an attention/vigilance cognitive dimension and the volume of the caudate and putamen, and a negative correlation between nucleus accumbens volume and delusions. In conclusion, basal ganglia volumes relative to total brain volume were larger in schizophrenia subjects than healthy comparison subjects. Specific patterns of shape change accompanied these volume differences.

Adult↗

PubMed1995

Blood flow in human anterior temporal cortex decreases with stimulus familiarity.

In this positron emission tomography investigation of human nonverbal visual memory, we determined the anatomical distribution of changes in regional cerebral blood flow (rCBF) reflecting familiarity of visual shapes. All stimuli consisted of relatively simple, abstract outlines generated by Fourier expansions. Subjects performed the same task twice, once using unfamiliar and once using familiar stimuli. The task was a modified version of delayed nonmatching-to-sample, consisting of one sample presentation prior to tracer injection and a sequence of test trials during which images were acquired. When this task was performed with familiar instead of unfamiliar stimuli, only decreases in rCBF were observed, which were localized to the left lateral anterior temporal neocortex, the left medial temporal pole, and the rostral anterior cingulate. The correlates of familiarity measured in this human brain mapping experiment may correspond with what has been measured in single neurons in monkeys. This correspondence holds both for the type and for the localization of changes.

Adolescent↗

PubMed1989

Inter- versus intra-subject variance in topographic mapping of the electroencephalogram.

The variability of the normal topographic EEG distribution between a quiet, eyes closed, resting state and the performance of cognitive tasks (listening to a story or music) was studied in 20 normal (10 male) right-handed college students or graduates ages 18-40 yrs. Amplitude changes in the topographic frequency distribution (2.5-7 SD) of alpha frequency band (8-13 Hz) were noted between tasks and resting state in individual subjects. When group data for the resting versus listening states were compared, no statistical differences could be demonstrated. The group variability was 50% of the power of the resting record. Repeat studies in 10 subjects demonstrated a test-retest variance of 10% of the mean individual power. The data suggest that inter-subject differences in the alpha frequency and individual topographic differences will require careful normalization for development of baseline "brain maps" to serve as a standard for investigation of disease states.

Adult↗

PubMed2007

Observer-independent analysis of high-resolution MR images of the human cerebral cortex: in vivo delineation of cortical areas.

Using high-resolution MRI, it is now possible to examine the living human cortex down to a resolution of less than 300 mum. Thus, in vivo imaging is now approaching the resolution that has been successfully used in histological analysis of the cerebral cortex for many years, e.g., low-magnification light microscopy. This allows unprecedented views of cortical microstructure that reflect defined histological features, specifically, individual cortical layers. As in histological brain mapping, it is possible to use the changes in the cortical lamination patterns to define individual cortical areas. This allows in vivo neuroanatomical maps to be generated for individual subjects and precise correlation of the results from functional imaging studies in these subjects with their own microanatomical information. To this end, we adapted the well-established observer-independent cytoarchitectonic mapping techniques for defining cortical borders based on changes in cortical lamination for in vivo parcellation of high-resolution structural MR images.

Brain Mapping↗

PubMed1993

Dynamic multichannel near-infrared optical imaging of human brain activity.

The present paper demonstrates functional brain mapping with an optical imaging technique by using tissue-transparent near-infrared light. With a maximal five-channel optical monitoring system, we succeeded in detecting region-specific changes in both the hemoglobin oxygenation state and blood volume during various mental tasks, in addition to visual and auditory stimulation. The time course of increases in blood supply varied with each brain region and depended on the type of internal operations occurring during the mental tasks. Changes in the hemoglobin oxygenation state were also different from region to region. This showed that there were regional variations of the oxygen delivery-oxygen utilization relationship during activation of brain activity. The usefulness of multichannel near-infrared functional imaging was well documented.

Acoustic Stimulation↗

PubMedDate not supplied

[Parameters of the spatial of organization of EEG in persons with various individual characteristics].

The relationships between some characteristics of EEG topographic maps and personality traits (extraversion-introversion, sensation-intuition, thinking-feeling, judging-impulsiveness) by the Keirsey's Type Inventory were studied in 46 17-20-year-old men). The most considerable distinctions in the spatial organization of the EEG were observed between the functions sensation and intuition. The high-sensation responders were characterized by higher EEG power in the theta 1, 2 and alpha 1-bands in all derivations and higher coherence (especially in the theta 1, 2 bands most expressed in the frontoparietal areas) as compared with the high-intuition responders. The expression of extraversion was positively correlated with coherence values in the theta 1, 2 and negatively correlated with coherence in the alpha 1, 2 bands. Characteristic EEG patterns for other types of personality traits were also described. The results suggest that some characteristics of brain maps reflect the individual psychological features determined on the basis of Jung's typology.

Adolescent↗

PubMed2005

Simultaneous recording of task-induced changes in blood oxygenation, volume, and flow using diffuse optical imaging and arterial spin-labeling MRI.

Increased neural activity in brain tissue is accompanied by an array of supporting physiological processes, including increases in blood flow and the rates at which glucose and oxygen are consumed. These responses lead to secondary effects such as alterations in blood oxygenation and blood volume, and are ultimately the primary determinants of the amplitude and temporal signature of the blood oxygenation level-dependent (BOLD) signal used prevalently to map brain function. We have performed experiments using a combination of optical and MRI-based imaging methods to develop a more comprehensive picture of the physiological events accompanying activation of primary motor cortex during a finger apposition task. Temporal profiles for changes in tissue hemoglobin concentrations were qualitatively similar to those observed for MRI-based flow and oxygenation signals. Quantitative analysis of these signals revealed peak changes of +16 +/- 2% for HbO, -13 +/- 2% for HbR, +8 +/- 3% for total Hb, +83 +/- 9% for cerebral blood flow, and +1.4 +/- 0.1% for the BOLD MRI signal. A mass balance model was used to estimate the change in rate of oxidative metabolism implied by the optical and flow measurements, leading to a computed value of +47 +/- 5%. It should be noted that the optical and MRI observations may in general reflect changes over different volumes of tissue. The ratio of fractional changes in oxidative metabolism to fractional change in blood flow was found to be 0.56 +/- 0.08, in general agreement with previous studies of flow-metabolism coupling.

Arousal↗

PubMed2003

The LONI Pipeline Processing Environment.

The analysis of raw data in neuroimaging has become a computationally entrenched process with many intricate steps run on increasingly larger datasets. Many software packages exist that provide either complete analyses or specific steps in an analysis. These packages often possess diverse input and output requirements, utilize different file formats, run in particular environments, and have limited abilities with certain types of data. The combination of these packages to achieve more sensitive and accurate results has become a common tactic in brain mapping studies but requires much work to ensure valid interoperation between programs. The handling, organization, and storage of intermediate data can prove difficult as well. The LONI Pipeline Processing Environment is a simple, efficient, and distributed computing solution to these problems enabling software inclusion from different laboratories in different environments. It is used here to derive a T1-weighted MRI atlas of the human brain from 452 normal young adult subjects with fully automated processing. The LONI Pipeline Processing Environment's parallel processing efficiency using an integrated client/server dataflow model was 80.9% when running the atlas generation pipeline from a PC client (Acer TravelMate 340T) on 48 dedicated server processors (Silicon Graphics Inc. Origin 3000). The environment was 97.5% efficient when the same analysis was run on eight dedicated processors.

Brain Mapping↗

PubMed1988

Probability mapping: power and coherence analyses of cognitive processes.

In recent years different mapping techniques have proved to be an efficient means in studying cognitive processes. Our approach is based on recordings with 19 EEG channels and the computation of spectral parameters. Power and coherence values are obtained from the EEG of control recordings and recordings during the performance of cognitive tasks and are compared for significant differences. The statistical procedures used yield descriptive error probabilities for the rejection of the null hypothesis which are mapped either colour coded or by black and white squares. The usefulness of this method is demonstrated on a mental cube rotation study involving 31 students, 13 males and 18 females. One essential result during the performance of this test is an increase of theta power only in females. As far as local coherence and the theta band are concerned, males show increased values right parietally and right temporo-occipitally; opposed to this, in females the left hemisphere is more affected. In the beta bands, local coherence increases in males right parietally and left temporo-occipitally. Contrary to this, in females the parietal increase of local coherence is more accentuated in the left hemisphere but temporo- occipital coherence is increased in the right hemisphere. In both sexes interhemispheric parietal coherence increases during cube rotation suggesting increased functional couplings between the hemispheres. This study demonstrates that the inclusion of the coherence parameter in brain mapping furthers the detection of sex and hemispheric differences during the performance of cognitive tasks.

Adult↗

PubMed1999

[Guidelines for recording/analyzing quantitative EEG and evoked potentials. Part II: Clinical aspects].

Digital EEG (DEEG) and quantitative EEG (QEEG) are recently developed tools present in many clinical situations. Besides showing didactic and research utility, they may also have a clinical role. Although a considerable amount of scientific literature has been published related to QEEG, many controversies still subsist regarding its clinical utilization. Clinical applications are: 1. DEEG is already an established substitute for conventional EEG, representing a clear technical advance. 2. Certain QEEG techniques are an established addition to DEEG for: 2a) screening for epileptic spikes or seizures in long-term recordings; 2b) Operation room and intensive care unit EEG monitoring. 3. Certain QEEG techniques are considered possible useful additions to DEEG: 3a) topographic voltage and dipole analysis in epilepsy evaluations; 3b) frequency analysis in cerebrovascular disease and dementia, mostly when other tests have been inconclusive. 4. QEEG remains investigational for clinical use in postconcussion syndrome, learning disability, attention disorders, schizophrenia, depression, alcoholism and drug abuse. EEG brain mapping and other QEEG techniques should be clinically used only by physicians highly skilled in clinical EEG interpretation and as an adjunct to traditional EEG work.

Brain Mapping↗

PubMed2007

Brain imaging correlates of depressive symptom severity and predictors of symptom improvement after antidepressant treatment.

BACKGROUND: It would be therapeutically useful to predict clinical response to antidepressant drugs. We evaluated structural magnetic resonance imaging (MRI) and functional MRI (fMRI) data as predictors of symptom change in people with depression. METHODS: Brain structure and function were measured with MRI in 17 patients with major depression immediately before 8 weeks treatment with fluoxetine 20 mg/day. For fMRI, patients were scanned during visual presentation of faces representing different intensities of sadness. Clinical response was measured by change in serial scores on the Hamilton Rating Scale for Depression. Symptom change scores (and baseline symptom severity) were regressed on structural and functional MRI data to map brain regions where grey matter volume, or activation by sad facial affect processing, was significantly associated with symptom change (or baseline severity). RESULTS: Faster rates of symptom improvement were strongly associated with greater grey matter volume in anterior cingulate cortex, insula, and right temporo-parietal cortex. Patients with greater than median grey matter volume in this system had faster rates of improvement and significantly lower residual symptom scores after 8 weeks' treatment. Faster improvement was also predicted by greater functional activation of anterior cingulate cortex. Baseline symptom severity was negatively correlated with greater grey matter volume in dorsal prefrontal and anterior midcingulate regions anatomically distinct from the pregenual and subgenual cingulate regions predicting treatment response. CONCLUSIONS: Structural MRI measurements of anterior cingulate cortex could provide a useful predictor of antidepressant treatment response.

Adult↗

PubMed1994

Multichannel recording of cerebral potentials evoked by esophageal balloon distension in humans.

In order to obtain insight in the generator localization of esophageal evoked potentials, cerebral responses were recorded from 32 scalp electrodes in five healthy volunteers (two male; three female; age 20-30 years), using series of 50 balloon inflations with 15 ml of air. Sequential topographical mapping of waveforms was performed in each subject. Biphasic waveforms were recorded. At Fpz, a positive deflection at 300 and a negative deflection at 465 msec (P300 and N465) were recorded and at Pz, N300 and P465. At Cz the first peak (N270) was slightly earlier than 300 msec. Waveforms were left to right symmetrical. At distal electrodes, biphasic waveforms were recorded (P300 and N465). In four subjects, a gradual phase shift occurred in between the waveforms at midline electrode Cz and the left and right mastoids. Brain mapping showed phase reversals between central negativity and surrounding positivity at about 300 msec, and between central positivity and surrounding negativity at 400-500 msec. Our data suggest the presence of more than one generator in the anterior and dorsal part of the insula and/or dorsal periinsular cortex.

Adult↗