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Biomedical subjects

J E Moran

Publications and source records attributed to J E Moran.

At least 19 recordsLinked to original sources
PubMed2006

Retrospective review of MEG visual evoked hemifield responses prior to resection of temporo-parieto-occipital lesions.

Visual evoked cortical magnetic field (VEF) waveforms were recorded from both hemifields in 21 patients with temporo-parieto-occipital mass lesions to identify preserved visual pathways. Fifteen patients had visual symptoms pre-operatively. Magnetoencephalographic (MEG) VEF responses were detected, using single equivalent current dipole (ECD), in 17/21 patients studied. Displaced or abnormal responses were seen in 15 patients with disruption of pathway in one patient. Three of 21 patients had alterations in the surgical approach or the planned resection based on the MEG findings. The surgical outcome for these three patients suggests that the MEG study may have played a useful role in pre-surgical planning.

Adult↗
PubMed2005

Multi-Resolution FOCUSS: a source imaging technique applied to MEG data.

A variety of techniques are available for imaging magnetoencephalographic (MEG) data to the corresponding cortical structures. Each performs a functional optimization that includes mathematical and physical restrictions on source activity. Unlike other imaging techniques, MR-FOCUSS (Multi-Resolution FOCal Underdetermined System Solution) utilizes a wavelet statistical operator that allows spatial resolution to be chosen appropriately for focal or extended sources. Control of focal imaging properties is achieved by specifying P in an l(P) norm distribution template used to construct the wavelets. In addition, incorporation of a multi-resolution wavelet operator desensitizes the mathematical algorithm to noise, (regularization). Like the FOCUSS imaging technique, an initial estimate of cortical activity is recursively enhanced to obtain the final high resolution imaging results. Studies of model MEG data representing all regions of a realistic cortical model are performed to quantify MR-FOCUSS imaging properties. These modeled data studies included single and multiple dipole sources as well as an extended source model. Thus, MR-FOCUSS is found to be very effective for imaging language processing for pre-surgical planning and provides a high-resolution method to image sequential activation of multiple correlated sources involved in language processing.

Algorithms↗
PubMed2004

ICA methods for MEG imaging.

Activity of individual cortical sources cannot be uniquely imaged when MEG data is a sequence of complex spatial patterns of multiple cortical sources. Auxiliary constraints integrated into the imaging equations are required to remove the mathematical ambiguity. Therefore, it is important to adapt source separation techniques to MEG imaging. It is much easier to accurately image field patterns of isolated brain electric sources. We demonstrate how a combination of second and fourth order Independent Component Analysis (ICA) methods can be used to remove noise and isolate source activity for improved MEG imaging accuracy. A second order ICA technique was used to extract respiratory and eye movement artifact by exploiting cross-correlation differences over time between cortical sources and artifact. For brain electric source separation, a fourth order ICA technique that quantified probabilities of simultaneous source activity was used to separate brain electric sources characterized by bursts of oscillatory circuit activity.

Humans↗
PubMed2004

MEG localization of language-specific cortex utilizing MR-FOCUSS.

OBJECTIVE: To demonstrate noninvasive localization of cognitive cortical areas involved in language processing with magnetoencephalography (MEG) interpreted by multiresolution FOCUSS (MR-FOCUSS), a current density imaging technique. METHOD: MEG data were collected during verb-generation and picture-naming tasks from 18 right-handed control subjects and 24 right-handed patients with epilepsy. RESULTS: The averaged epic data from the verb-generation task, analyzed by MR-FOCUSS, showed initial activation in the left supramarginal gyrus, superior temporal gyrus, and angular gyrus at 239 +/- 31 ms in all subjects, consistent with other language mapping studies. Average amplitude of underlying cortical sources was approximately 452 pAm. The averaged epic data from the picture-naming task, analyzed by MR-FOCUSS, showed activation in the left inferior frontal gyrus (IFG) area starting at 436 +/- 40 ms in all subjects. Average amplitudes of underlying cortical sources were approximately 380 pAm. CONCLUSION: The time course of neuronal language processing can be imaged noninvasively with millisecond resolution by magnetoencephalography using the multiresolution FOCUSS technique.

Cerebral Cortex↗
PubMed2001

129I and 127I transport in the Mississippi River.

The watershed processes which control 129I/127I ratios, 129I and 127I concentrations, and speciation of iodine isotopes were studied through an investigation into the variability of these parameters in the Mississippi River near New Orleans, undertaken in 1996-1998. Analyses of suspended particulate matter (SPM) revealed a greater percent association of 127I than of 129I, resulting in lower 129I/127I ratios in SPM than in surrounding water. Furthermore, crossflow ultrafiltration showed that organo-iodine was the dominant form for both isotopes, with 70-85% of these isotopes found in the 0.45 microm filter-passing fraction associated with colloidal macromolecular organic matter. 129I showed a weak correlation, 127I no correlation, and 129I/127I ratios a strong inverse correlation with river flow rate. Inverse correlations between 129I/127I ratios and river flow rates can be best explained by rainwater and evapotranspiration dominated ratios at base flow and a lowering of the isotope ratios during higher flow due to extra inputs of 127I from soil weathering. We postulate that different equilibration times for 127I and 129I as well as for bomb-produced 129I and reprocessing-produced 129I are responsible for these fractionation effects and the differential mobilities of these isotopes in the Mississippi River watershed.

Colloids↗
PubMed2001

Magnetoencephalographic fields from patients with spontaneous and induced migraine aura.

We investigate and characterize the magnetoencephalographic waveforms from patients during spontaneous and visually induced migraine aura. Direct current neuromagnetic fields were measured during spontaneous onset of migraine auras in 4 migraine patients, and compared with recordings from 8 migraine-with-aura patients and 6 normal controls during visual stimulation of the occipital cortex. Complex direct current magnetoencephalographic shifts, similar in waveform, were observed in spontaneous and visually induced migraine patients, but not in controls. Two-dimensional inverse imaging showed multiple cortical areas activated in spontaneous and visually induced migraine aura patients. In normal subjects, activation was only observed in the primary visual cortex. Results support a spreading, depression-like neuroelectric event occurring during migraine aura that can arise spontaneously or be visually triggered in widespread regions of hyperexcitable occipital cortex.

Adult↗
PubMed2000

Two dimensional inverse imaging (2DII) of current sources in magnetoencephalography.

A new magnetoencephalographic (MEG) technique for imaging the cortical distribution of neuronal activity is described. An iterative algorithm is employed, which successively alters an initial estimate of cortical source structure until it corresponds to the measured magnetic field data. In this new technique, the continuum of electrical activity across the cortical surface is modeled as a dense grid of thousands of single equivalent current dipoles. MEG imaging of both compact and extended sources is facilitated by a wavelet-like transformation of the source space into a sequence of successively smaller composite source structures. Two of these composite source structures are combined during each iterative step to generate an improved estimate of the cortical source structure. Thus, inversion of the complete gain matrix corresponding to thousands of cortical sources is not performed. The technique requires only moderate PC based resources even for very large source grids. In contrast to minimum norm MEG imaging methods, this new algorithm is insensitive to random noise in the data. If available, prior knowledge of source structure from other imaging techniques, such as PET, MRI and fMRI, is easily incorporated as additional constraints on the source structure solution. Source images solutions corresponding to simulated data are presented. In addition, the technique is applied to source imaging of real MEG data incorporating cortical structure from volumetric MRI data. These results demonstrate the capability of our new technique for imaging combinations of compact and extended source structures.

Algorithms↗
PubMed1999

Analysis of MEG signals of spreading cortical depression with propagation constrained to a rectangular cortical strip. I. Lissencephalic rabbit model.

Magnetic fields arising from the rabbit cortex during spreading cortical depression (SCD) were measured in order to study the currents in the neocortex during SCD. SCD was constrained to propagate in a rectangular cortical strip perpendicular to the midline. This simplified in vivo cortical preparation enabled us to correlate magnetoencephalographic (MEG) signals to their underlying currents within the cortical strip. The propagation of SCD was monitored with an array of electrodes placed along the strip. The propagation speed for SCD in the lissencephalic rabbit brain was 3. 5+/-0.3 mm/min (mean+/-S.E.M., n=14). Slow, quasi-dc, MEG signals were observed as the SCD entered into the longitudinal fissure. The currents giving rise to the MEG signals were perpendicular to the cortical surface and directed from the surface to deeper layers of the cortex. A distributed dipolar source model was used to relate the data to the underlying cortical current. The moment of the single equivalent current dipole source was 38+/-9 nA-m (n=17). This study clarified the nature of the cortical currents during SCD in a lissencephalic in vivo preparation.

Animals↗
PubMed1998

Elevation of whole-blood glutathione in peritoneal dialysis patients by L-2-oxothiazolidine-4-carboxylate, a cysteine prodrug (Procysteine).

Glutathione is a major cellular antioxidant that protects protein thiols and inhibits cellular damage due to oxygen free radicals. It has been reported previously that patients undergoing dialysis have low levels of blood glutathione, which may lead to increased susceptibility to oxidant stress. L-2-oxothiazolidine-4-carboxylic acid (OTZ) is a cysteine prodrug that raises cellular glutathione levels by increasing delivery of cysteine, the rate-limiting substrate for glutathione synthesis. This study investigates the effect of OTZ on blood glutathione in a blinded, placebo-controlled study of patients with chronic renal failure treated by peritoneal dialysis. Twenty patients were randomly selected to receive OTZ (0.5 g three times a day orally with meals) or placebo for 14 d. Patients visited the clinic for predose blood collection and safety evaluation at baseline (days 3, 7, and 14 and again at 14 d from the last dose [follow-up]). Glutathione concentrations were determined in whole blood by HPLC. OTZ resulted in a significant rise in whole-blood glutathione at days 7 (594 +/- 129 mumol/L) and 14 (620 +/- 108 mumol/L) compared with baseline (544 +/- 139 mumol/L) (P < 0.01 and P < 0.05, respectively). Glutathione was also significantly increased at days 7 and 14 when normalized by hematocrit (Hct) or hemoglobin to correct for anemic status (e.g., 20.7 +/- 5.7 mumol/L per % Hct [day 7] and 20.9 +/- 4.0 mumol/L per % Hct [day 14] versus 18.0 +/- 4.2 mumol/L per % Hct [baseline]; P < 0.05). Glutathione levels did not change in the placebo group at any patient visit, and levels in the OTZ-treated group returned to baseline at follow-up. There were no serious adverse events attributable to OTZ, and the drug appeared to be well tolerated by patients with renal failure treated by continuous ambulatory peritoneal dialysis. Our results show that OTZ increases blood glutathione levels, which may improve antioxidant status in dialysis patients.

Administration, Oral↗
PubMed1998

The ethics of farming-out: ideology, the state, and the asylum in nineteenth-century Quebec.

This article traces the development of the farming-out system of asylum provision which emerged in Quebec for the treatment and care of those who were considered to be insane. The kind of asylum provision that developed in Quebec was met with strong criticism by alienists elsewhere in Ontario, Britain and the United States who considered farming-out to be highly unethical. These criticisms were not lost on the state which tried to exercise increased control over the daily affairs of the asylum. But for much of the nineteenth century the state largely failed in these efforts. The community response to the rise of the farming-out system further complicated the role of the state in the management and control of insanity. I argue that the farming-out system is best considered as the product of complex relations between the state officials, alienists, and community members. This understanding of asylum development in Quebec has important implications for the study of the nineteenth-century state formation.

Canada↗
PubMed1993

Evidence for multiple generators in evoked responses using finite difference field mapping: auditory evoked fields.

Electric potential maps and magnetic field maps have been used to study brain electrical activity. During the temporal course of an evoked cortical response, the electrical activity of specific neuronal subpopulations change in a sequential manner giving rise to measurable electrical potentials and magnetic fields. For these potentials and fields, both the amplitude and rate of amplitude change have characteristic, time-dependent waveforms. Presently, amplitude waveforms from multiple locations are used to generate magnetic field and electric potential maps which have been found to be useful in understanding the activity of the neurons which give rise to these maps (Romani 1990). This paper introduces a data transformation technique which results in a derived map that we have termed a "finite difference field map" (FDFM). This mapping technique provides information associated with the rate at which the amplitude of the neuronal electric activity changes. In this paper, some advantage of FDFM analysis are illustrated by application of this technique to the study of the auditory evoked cortical field (AECF) N1m waveform. Using data obtained from normal subjects it will be demonstrated that application of the FDFM technique allows the localization of the primary N1m source at an earlier latency than is possible using the conventional waveform data. The source location determined at an early latency by FDFM analysis was identical to that obtained at later from the conventional field data. These data suggest that the primary N1m source is stationary. In addition, analysis of the time sequence of FDFM field maps contains evidence of a second spatially separate source which is co-active with primary N1m source.

Adult↗
PubMed1991

Magnetic fields associated with anoxic depolarization in anesthetized rats.

We have performed simultaneous measurements of the DC-magnetoencephalogram (DC-MEG) and DC-electrocorticogram (DC-ECoG) in rats (n = 6) subjected to 90 s of reversible anoxia. The onset of major shifts of electric and magnetic signals occurred at 52 +/- 18 (S.D.) and 68 +/- 14 (S.D.), respectively, and reached a peak at 83 +/- 27 and 102 +/- 19 (S.D.) s, respectively, after termination of mechanical ventilation. DC-ECoG signal deflections were always associated with DC-MEG deflections. The time of onset and peak signals in both DC-MEG and DC-ECoG changes caused by asphyxia were highly correlated (r + 0.83, 0.94; P less than 0.05, 0.001; respectively). Our observations suggest that the non-invasive technique of DC-MEG is reliable and may provide insight into the mechanisms of anoxic cerebral depolarization.

Anesthesia, General↗
PubMed1991

Beta 2-microglobulin kinetics in end-stage renal failure.

The kinetics of beta 2-microglobulin (beta 2m) were studied in five anephric or anuric hemodialysis patients. Human beta 2m was isolated from peritoneal dialysate using ion-exchange and gel chromatography and radiolabeled with 125I. Patients were injected with 10 microCi labeled beta 2m. In one study (N = 4), plasma activity was measured over 72 hours. In a second study (N = 4), patients received low-flux dialysis 24 hours after injection and high-clearance dialysis (Bellco BL655) at 48 hours. Plasma activities were fitted to a three-compartment, variable volume model. Endogenous beta 2m levels (radioimmunoassay) were 56 +/- 6 mg/liter. The beta 2m distribution volume was 12.7 +/- 2.0 liter (0.20 +/- 0.03 liter/kg) and the non-renal clearance was 3.0 +/- 0.4 ml/min. The generation rate, 9.9 +/- 1.7 mg/hr (0.16 +/- 0.04 mg/kg/hr), was similar to that measured in subjects with normal renal function. The three compartment model derived from the turnover data gave an adequate fit of the arterial concentrations of endogenous and exogenous beta 2m during low-flux (nil beta 2m clearance) and high-clearance (beta 2m clearance of 19 ml/min) dialysis. Simulations based on this model indicate that extracorporeal treatment can at best remove about 50% of weekly production. These results suggest that beta 2m production is not increased in dialysis patients, that there is substantial non-renal beta 2m clearance, and that the amount of beta 2m that can be removed by extracorporeal therapy is therefore limited.

Adult↗
PubMed1991

Techniques for DC magnetoencephalography.

DC shifts are known to occur in association with a number of physiologic phenomena including spreading depression, hypoxia, epilepsy, and hypercapnia and possibly in migraine, closed head injury, and ischemia. Magnetoencephalography (MEG) makes it possible to record these shifts by prolonged DC monitoring of brain activity and offers several advantages over DC EEG and DC electrocorticography. Among the advantages of MEG is its non-invasive nature and the lack of impedance changes at the electrode-tissue interface that produce baseline shifts in DC EEG. In DC MEG measurements, great care must be taken in dealing with a variety of artifactual signals. Environmental noise can be reduced by magnetic shielding and recognized by use of reference magnetometers. Patient-generated artifacts are numerous and can be recognized and limited by a variety of methods.

Humans↗
PubMed1991

Beta 2 microglobulin-related amyloidosis causing atlantoaxial spondylarthropathy with spinal-cord compression in haemodialysis patients: detection by MRI.

Bone destruction due to beta-2 microglobulin (beta 2-M)-related amyloid deposition is becoming more frequently observed in long-term haemodialysis patients. We report five cases in an unusual site, the upper cervical spine. All patients had been on haemodialysis for more than 13 years and presented with progressive spinal-cord involvement in the region of the first and second cervical nerves. While conventional X-rays and CT scans showed only minor vertebral destruction, MRI disclosed a tumour-like mass within the upper spinal canal, best seen with long TR gradient recalled images. One patient required urgent surgical intervention because of severe spinal-cord compression, and the material was shown to be typically beta 2-M-related amyloid.

Adult↗