Recent functional imaging and electrical stimulation studies have localized in humans two frontal regions critical for the production of saccadic and anti-saccadic eye movements: the frontal and supplementary eye fields (FEF and SEF, respectively). We investigated the time course of their activations during the generation of pro- and anti-saccades from direct intracranial EEG recordings of three human epileptic patients. We found the preparation and the production of the saccades to be coincident with focal and transient increases of EEG power above 60 Hz. Those were produced in very specific brain sites distributed in the FEF and the SEF (as identified by previous human studies at a coarser time resolution). Furthermore, the spatio-temporal resolution of those recordings turned out to be sufficient to discriminate anatomically between several types of neural responses, determined either by the visual or by the motor components of the saccade tasks, and within this second category of responses, between some associated with the preparation of the saccades and others associated with their execution. Altogether, this study provides the first evidence of high-frequency neural responses in the generation of saccades in humans, and provides a firm basis for other studies detailing further the functional organization of the human oculomotor system at this level of spatial and temporal resolution.

Sef (similar expression to fgf genes) is a member of the fibroblast growth factor (FGF) synexpression group that negatively regulates FGF receptor (FGFR) signaling in zebrafish during early embryonic development and in mammalian cell culture systems. The mechanism by which Sef exerts its inhibitory effect remains controversial. It has been reported that Sef functions either through binding to and inhibiting FGFR1 activation or by acting downstream of FGF receptors at the level of MEK/ERK kinases. In both cases, the intracellular domain of Sef was found to play a role in the inhibitory function of Sef. Here we demonstrated that both extracellular and transmembrane domains of Sef contributed to Sef-mediated negative regulation of FGF signaling. In fact, over-expression studies in NIH3T3 cells showed that a truncated mutant of Sef, which lacks the intracellular domain (SefECTM), exerted the inhibitory activity on FGF signaling by inhibiting FGFR1 tyrosine phosphorylation and subsequent activation of the Raf/MEK/ERK signaling cascade. We also showed that SefECTM associated with FGFR1, and inhibited FGF-induced ERK activation in HEK293T cells. Furthermore, we demonstrated that the over-expression of SefECTM was able to inhibit the function of a constitutively activated form of FGFR1, FGFR1-C289R, but not FGFR1-K562E. Finally, we found that SefECTM reduced cell viability when over-expressed in human umbilical vein endothelial cells (HUVEC). These data provide additional insight into the structure-activity relationship in the mechanism of inhibitory action of Sef on FGFR1-mediated signaling.

OBJECTIVE

Sclerosing epithelioid fibrosarcoma (SEF) is a rare mesenchymal neoplasm composed of rounded, vimentin-immunoreactive tumor cells disposed in nests and cords within a hyalinized collagenous matrix. Most examples arise in the deep skeletal muscles of adults. The cases recorded to date have been characterized by protracted clinical evolutions with a tendency for stubborn local recurrence, followed by late metastasis. Accordingly, SEF has been regarded as a low-grade sarcoma. A single instance of brain and vertebral metastasis has been described. We report three examples of SEF distinguished by primary involvement of the neuraxis at initial presentation.

METHODS

Two tumors had intracranial, calvarial and extracalvarial, soft-tissue components, whereas the third tumor manifested as a paraspinal mass with extension into the T12-L1 neural foramen and invasion of the T12 nerve root.

METHODS

All three affected patients experienced local recurrence and distant metastasis after resection of the primary site. These complications appeared early in the disease course in two cases. In no case was there a response to adjuvant chemotherapy or radiotherapy.

CONCLUSIONS

Our experience indicates that SEFs arising along the neuraxis may demonstrate unexpectedly aggressive clinical behavior, compared with those arising in the more typical location of deep skeletal muscles.

OBJECTIVE

To evaluate the maturation of tactile processing by recording somatosensory evoked magnetic fields (SEFs) from healthy human subjects.

METHODS

SEFs to tactile stimulation of the left index finger were measured from the contralateral somatosensory cortex with magnetoencephalography (MEG) in five age groups: newborns, 6- and 12-18-month-olds, 1.6-6-year-olds, and adults. The waveforms of the measured signals and equivalent current dipoles (ECDs) were analyzed in awake and sleep states in order to separate the effects of age and vigilance state on SEFs.

RESULTS

There was an orderly, systematic change in the measured and ECD source waveforms of the initial cortical responses with age. The broad U-shaped response in newborns (M60) shifted to a W-shaped response with emergence of a notch by 6 months of age. The adult-type response with M30 and M50 components was present by 2 years. The ECDs of M60 and M30 were oriented anteriorly and that of M50 posteriorly. These maturational changes were independent of vigilance state.

CONCLUSIONS

The most significant maturation of short latency cortical responses to tactile stimulation takes place during the first 2 years of life.

CONCLUSIONS

The maturational changes of somatosensory processing can noninvasively be evaluated with MEG already in infancy.

To determine threshold values, sensitivity and specificity of the spectral edge frequency (SEF) of the electroencephalogram (EEG) that indicate intraoperative movements, we studied 49 patients undergoing, elective laparotomy. Extradural analgesia was used in all patients. To maintain general anaesthesia, patients in group 1 (n = 23) received 0.4-1.2 vol% isoflurane and patients in group 2 (n = 24) propofol 3-5 mg kg-1 h-1 i.v. During operation and emergence from anaesthesia, spontaneous purposeful movements were documented. The EEG was recorded continuously in the awake state until the end of anaesthesia. Power spectral analysis calculated the SEF and power in the delta, theta, alpha and beta bands and the delta ratio. Adequate anaesthesia caused a statistically significant decrease in SEF from 16 to 12 Hz. Power in the beta band decreased and power in the theta band and total power increased compared with the awake state. Before and during movements observed in the intraoperative period or during emergence from general anaesthesia, SEF increased from 12 to 18 Hz, the power in beta band increased and theta power decreased compared with the state of adequate anaesthesia. A threshold value of SEF 14 Hz to predict movements during anaesthesia had a sensitivity of 72% and specificity of 82%.

Salivary gland scintigraphy with technetium-99m pertechnetate was used to follow changes in the excretion and uptake function of the major salivary glands until 1 year after irradiation. Twenty-five patients who received radiotherapy for head and neck tumours were included in the study. Seventy-nine salivary glands (39 parotid and 40 submandibular) were evaluated in relation to the average received radiation dose. Salivary gland scintigraphy was performed before and 1, 6 and 12 months after radiotherapy. For each gland the excretion response to carbachol, evaluated by calculation of the salivary excretion fraction (SEF), the cumulative gland uptake (CGU) and the absolute excreted activity (AEA) at various intervals after radiotherapy were compared with the baseline values. The excretion response decreased in 20 of 25 patients at 1 month after radiotherapy. One month after radiotherapy both SEF and AEA decreased significantly in relation to the radiation dose. These decreases in excretion parameters persisted during the follow-up period. Parotid excretion was affected significantly more than submandibular excretion. CGU values did not change significantly until 6 months after radiotherapy, but at 12 months a significant decrease related to radiation dose was observed. Xerostomia was assessed during radiotherapy and on the days of the scintigraphic tests. The incidence of xerostomia did not correspond to the effects observed in the scintigraphic studies. It is concluded that radiotherapy induces early and persistent impairment of salivary gland excretion, related to the radiation dose. This impairment is stronger in parotid glands than in submandibular glands.

OBJECTIVE

Our aim was to assess the effectiveness and reliability of spatiotemporal signal space separation (tSSS) and movement correction (MC) in magnetoencephalography (MEG) recordings disturbed by head movements and magnetized material on the head.

METHODS

We recorded MEG from 20 healthy adults in stationary (reference) head position and during controlled head movements. Nearby magnetic interference sources were simulated by attaching magnetized particles on the subject's head. Auditory and somatosensory stimuli were presented. MC, tSSS and averaging were performed to obtain auditory (AEF) and somatosensory (SEF) evoked fields. Neuronal sources were modeled as equivalent current dipoles. MC was also validated by reconstructing signals generated by current dipoles in a phantom.

RESULTS

After MC, the AEF and SEF responses recorded during intermittent head movements were similar in amplitude to the reference recordings and differed by 5-7mm in source location. The tSSS method removed artifacts due to the attached magnetized particles but did not affect the reference data.

CONCLUSIONS

The methods are able to reliably recover MEG responses contaminated by movements and magnetic artifacts on the head.

CONCLUSIONS

The combination of tSSS and MC methods is especially useful in clinical measurements, where movements and magnetic disturbances are commonly present.

The promoter region of two sunflower (Helianthus annuus L. HA89 genotype) seed specifically expressed genes, coding for an oleate desaturase (HaFAD2-1) and a lipid transfer protein (HaAP10), were cloned and in silico characterized. The isolated fragments are 867 and 964 bp long, respectively, and contain several seed-specific motifs, such as AACA motif, ACGT element, E-Boxes, SEF binding sites and GCN4 motif. Functional analysis of these promoters in transgenic Arabidopsis plants was investigated after fusing them with the beta-glucuronidase (GUS) reporter gene. None of the promoters triggered GUS activity in any vegetative tissue, with the exception of early seedling cotyledons. HaFAD2-1 and HaAP10 promoters were tested along seed development from globular stage to mature seeds. GUS staining was restricted to embryonic tissue and quantitative fluorometric assays showed high activity values at the later stages of development. In this work we demonstrate that HaFAD2-1 promoter is as strong as 35S promoter even though it is a tissue-specific promoter and its activity derived just from the embryo, thus confirming that it can be considered a strong highly specific seed promoter useful for biotechnology applications.

Reperfusion injury is believed to contribute to the pathophysiology of ischemic cell death, but the precipitating factors have yet to be completely elucidated. The goal of this study was to examine if reflow-induced secondary energy failure is a component in the events that lead to cell death following increasing periods of middle cerebral artery (MCA) occlusion in Wistar rats. Discrete sections within the MCA distribution were dissected and analyzed for high-energy phosphates and glucose. Regional cerebral blood flow was determined by [14C]-iodoantipyrine technique in representative groups. The levels of ATP + P-creatine were initially depressed at the end of the focal ischemia and the concentrations in the penumbra were unchanged for up to 8 h after 2 h of ischemia which contrasts with response in the ischemic core, striatum, and penumbra where the HEP generally recovered to values near those of control only to decrease with increasing periods of reflow. The possibility of a rebound ischemia in secondary energy failure (SEF) was precluded by regional CBF values and concentrations of glucose that were significantly higher than the threshold for an ischemic effect. The depletion of cellular energy stores following SEF strongly indicates that the evolution of infarct during reflow results from loss of ATP and its synthesis.

The effects of somatostatin hormones are mediated by a family of five different seven-helix transmembrane spanning receptors (SSTR1-5). The expression of the five different SSTR subtypes displays a complex temporal- and tissue-specific pattern. To investigate the molecular mechanisms controlling the different expression patterns of the SSTRs, we cloned the 5'-flanking region of the human SSTR2 gene. Characterization of the SSTR2 promoter resulted in the identification of a novel initiator element (SSTR2inr). Transcriptional activity of the SSTR2inr is dependent on the presence of a binding site (E-box) for basic helix-loop-helix (bHLH) transcription factors. By screening a mouse brain cDNA expression library we isolated a cDNA coding for the bHLH transcription factor SEF-2. SEF-2 binds to the E-box present in the SSTR2inr, both in vitro and in vivo and activates transcription from the SSTR2inr. A single point mutation within the E-box eliminates binding of SEF-2 and results in a complete loss of transcriptional activity of the SSTR2inr. Furthermore, DNA binding studies demonstrate that the basal transcription factor TFIIB can be tethered to the SSTR2inr through physical interaction with SEF-2. In summary, the SSTR2inr represents a novel type of initiator element that confers gene expression in the absence of a TATA-box or binding sites for other known initiator factors, like YY-1 or USF.

We examined recently neuronal substrates for predictive pursuit using a memory-based smooth pursuit task that distinguishes the discharge related to memory of visual motion-direction from that related to movement preparation. We found that the supplementary eye fields (SEF) contain separate signals coding memory and assessment of visual motion-direction, decision not-to-pursue, and preparation for pursuit. Since medial superior temporal area (MST) is essential for visual motion processing and projects to SEF, we examined whether MST carried similar signals. We analyzed the discharge of 108 MSTd neurons responding to visual motion stimuli. The majority (69/108 = 64%) were also modulated during smooth pursuit. However, in nearly all (104/108 = 96%) of the MSTd neurons tested, there was no significant discharge modulation during the delay periods that required memory of visual motion-direction or preparation for smooth pursuit or not-to-pursue. Only 4 neurons of the 108 (4%) exhibited significantly higher discharge rates during the delay periods; however, their responses were non-directional and not instruction specific. Representative signals in the MSTd clearly differed from those in the SEF during memory-based smooth pursuit. MSTd neurons are unlikely to provide signals for memory of visual motion-direction or preparation for smooth pursuit eye movements.

Although the supplementary eye field (SEF) has been implicated in the control of head movements associated with gaze shifts, there is no direct evidence that SEF plays a role in the generation of head movements independent of gaze. If the SEF does, varying the duration of stimulation should selectively alter the head-movement kinematics during the postgaze-shift period. The duration of the stimulation was manipulated while head-unrestrained monkeys maintained stable head forward postures. The initial positions of the eyes in the orbits were systematically varied. Although combined movements of the eyes and head were produced in the majority of the trials, head movements were sometimes evoked in the absence of gaze shifts. These head-alone movements were most frequent when the initial eye position was contralateral to the stimulated side. When the stimulation produced eye and head movements, gaze onset was sometimes preceded by a relatively low-velocity phase of the head movement. Evoked head movements were primarily horizontal, unlike the gaze shifts, which typically had vertical components that varied according to the initial positions of the eyes in the orbits. The postgaze-shift head movements tended to be of low velocity and in many cases persisted until stimulation offset. In general, prolonging the stimulation resulted in improved centering of the eyes in the orbits. These findings suggest that, in addition to its previously described role in the generation of coordinated eye-head gaze shifts, the SEF is also involved in the control of head movements in the absence of a change of gaze.

The GP64 and F proteins were previously identified as the sole functional envelope fusion proteins in Baculoviridae. F-like proteins, present only in group I nucleopolyhedroviruses (NPVs), are remnant, nonfunctional F proteins. In this report, we describe the effect of the presence or absence of the F-like protein Ac23 in a gp64-null Autographa californica multinucleocapsid NPV pseudotyped with the F protein from Spodoptera exigua multicapsid NPV (SeF). We found that the presence of Ac23 elevates the infectivity of the pseudotyped virus. This is in contrast to the results of Lung et al. (J. Virol. 76:5729-5736, 2002), who found no such effect. The possible reasons for the differing results are discussed.

The functional organization of the low-threshold supplementary eye field (SEF) was studied by analyzing presaccadic activity, electrically elicited saccades, and the relationship between them. Response-field optimal vectors, defined as the visual field coordinates or saccadic eye-movement dimensions evoking the highest neural discharge, were quantitatively estimated for 160 SEF neurons by systematically varying peripheral target location relative to a central fixation point and then fitting the responses to Gaussian functions. Saccades were electrically elicited at 109 SEF sites by microstimulation (70 ms, 10-100 microA) during central fixation. The distribution of response fields and elicited saccades indicated a complete representation of all contralateral saccades in SEF. Elicited saccade polar directions ranged between 97 and 262 degrees (data from left hemispheres were transformed to a right-hemisphere convention), and amplitudes ranged between 1.8 and 26.9 degrees. Response-field optimal vectors (right hemisphere transformed) were nearly all contralateral as well; the directions of 115/119 visual response fields and 80/84 movement response fields ranged between 90 and 279 degrees, and response-field eccentricities ranged between 5 and 50 degrees. Response-field directions for the visual and movement activity of visuomovement neurons were strongly correlated (r = 0.95). When neural activity and elicited saccades obtained at exactly the same sites were compared, response fields were highly predictive of elicited saccade dimensions. Response-field direction was highly correlated with the direction of saccades elicited at the recording site (r = 0.92, n = 77). Similarly, response-field eccentricity predicted the size of subsequent electrically elicited saccades (r = 0.49, n = 60). However, elicited saccades were generally smaller than response-field eccentricities and consistently more horizontal when response fields were nearly vertical. The polar direction of response fields and elicited saccades remained constant perpendicular to the cortical surface, indicating a columnar organization of saccade direction. Saccade direction progressively shifted across SEF; however, these orderly shifts were more indicative of a hypercolumnar organization rather than a single global topography. No systematic organization for saccade amplitude was evident. We conclude that saccades are represented in SEF by congruent visual receptive fields, presaccadic movement fields, and efferent mappings. Thus SEF specifies saccade vectors as bursts of activity by local groups of neurons with appropriate projections to downstream oculomotor structures. In this respect, SEF is organized like the superior colliculus and the frontal eye field even though SEF lacks an overall global saccade topography. We contend that all specialized oculomotor functions of SEF must operate within the context of this fundamental organization.

Hypertension-induced arterial remodeling has been previously modeled using stress-driven remodeling rate equations in terms of global geometrical adaptation (Rachev A, Stergiopulos N, Meister JJ. Theoretical study of dynamics of arterial wall remodeling in response to changes in blood pressure. J Biomech 29: 635-642, 1996) and was extended later to include adaptation of material properties (Rachev A, Stergiopulos N, Meister JJ. A model for geometric and mechanical adaptation of arteries to sustained hypertension. J Biomech Eng 120: 9-17, 1998). These models, however, used a phenomenological strain energy function (SEF), the parameters of which do not bear a clear physiological meaning. Here, we extend the work of Rachev et al. (1998) by applying similar remodeling rate equations to a constituent-based SEF. The new SEF includes a statistical description for collagen engagement, and remodeling now affects material properties only through changes in the collagen engagement probability density function. The model predicts asymptotic wall thickening and unchanged deformed inner radius as to conserve hoop stress and intimal shear stress, respectively, at the final adapted hypertensive state. Mechanical adaptation serves to restore arterial compliance to control levels. Average circumferential stress-strain curves show that the material at the final adapted hypertensive state is softer than its normotensive counterpart. These findings as well as the predicted pressure-diameter curves are in good qualitative agreement with experimental data. The novelty in our findings is that biomechanical adaptation leading to maintenance of compliance at the hypertensive state can be perfectly achieved by appropriate readjustment of the collagen engagement profile alone.

Human arteries with non-atherosclerotic intimal thickening consist of three distinct layers: adventitia, media and intima. From a series of axial extension and inflation tests on intact and layer-dissected human carotid arteries (adventitia and media-intima composite), a 3D structurally-based strain-energy function (SEF) is calibrated, and a set of five material parameters is identified which is not yet available in the literature. The zero-stress states of the artery tubes investigated are considered in the calibration process, and the related kinematics for the finite deformation of the individual continuum are described in detail. The SEF employed is capable of describing the different mechanical properties of the intact and layer-dissected tissue tubes (arterial segments) investigated at different pressure domains and axial stretches. The correlation coefficients and error measures determined indicate good correlation between the model and the experimental data for all tested tubes. Mean values of each individual material parameter provide a kind of 'master model' that characterizes the mean response of all mechanical data obtained from the human carotid arteries. The material parameters and the 3D constitutive model serve as a foundation for finite element simulations, and hence the analysis of more complex patient-specific boundary-value problems in the human carotid physiology and pathology.

We evoked both ear and eye movements in area 8b, the rostral area of frontal cortex, in two monkeys. In some sites it was possible to evoke only ear movements or only eye movements; in other locations we evoked both ear and eye movements by varying the intensity of electrical stimulation. The electrically evoked ear movements were forward, or backward, or oblique (upward-forward; upward-backward). In two penetrations the ear movements were bilateral, in the other penetrations they were contralateral. Ipsilateral ear movements were not observed. The evoked eye movements were mainly fixed-vector saccades, contralateral and with an upward orientation of about 45 degrees. If we considered only the sites where the threshold was equal to or lower than 50 microA, the stimulation of this area evoked mainly ear movements. In addition we recorded the electrical activity of 195 neurons. Of these neurons: 74% (145/195) discharged before ear movements (ear cells); 20% (40/195) discharged before ear and eye movements (ear-eye cells); 5% (10/195) discharged only before eye movements (eye cells). Ninety-one percent (132/145) of ear cells presented a preferred direction; 90% (36/40) of ear-eye cells presented a preferred direction for ear movements, and 15% (6/40) presented a preferred direction for eye movements. Eighty-five percent (34/40) of cells did not present a preferred direction for visually guided saccades and were active when the monkey made saccades toward the unlit targets (checking saccades). Our results show that a field of area 8b is related to ear movements and to eye-ear movements. The findings that it is possible to obtain both ear and eye movements with low-intensity currents and that there are cells firing for the two types of movements suggest that area 8b may be involved in the orientation and coordination of both ear and eye. This area might be considered a rostral extension of supplementary eye field (SEF) or a different region. However, based on its distinct functional characteristics and connectivity, it is probably better regarded as a separate field. Regardless, the combination of 8b and SEF may constitute a cortical center for orienting processes.

BACKGROUND

The aim of this study was to investigate the accuracy of frontal spontaneous electromyography (SEMG) and EEG spectral edge frequency (SEF 95%), median frequency (MF), relative delta power (RDELTA) and bispectral index (BIS) in monitoring loss of and return of consciousness and hypnotic drug effect during propofol administration at different calculated plasma target concentrations.

METHODS

Propofol was administered by using a target-controlled infusion at different propofol steady-state concentrations. All variables were measured simultaneously at specific calculated concentrations and endpoints.

RESULTS

Loss of consciousness was accurately monitored by BIS, SEMG and SEF 95%, and propofol drug effect by BIS only. Return of consciousness was predicted by BIS, MF and SEF 95%. Due to the biphasic EEG pattern of propofol and the lack of reproducible data at specific propofol concentrations, the clinical usefulness of SEF 95%, MF and RDELTA was very limited. SEMG was useful to detect loss and return of consciousness, but without predictive value.

CONCLUSIONS

The BIS might be an accurate measure to monitor depth of anaesthesia and hypnotic drug effect. Other neurophysiologic measures have limited value to monitor depth of anaesthesia and hypnotic drug effect.

OBJECTIVE

In order to study the interaction between left- and right-sided stimuli on the activation of cortical somatosensory areas, we recorded somatosensory evoked magnetic fields (SEFs) from 8 healthy subjects with a 122 channel whole-scalp SQUID gradiometer.

METHODS

Right and left median nerves were stimulated either alternately within the same run, with interstimulus intervals (ISIs) of 1.5 and 3 s, or separately in different runs with a 3 s ISI. In all conditions 4 cortical source areas were activated: the contralateral primary somatosensory cortex (SI), the contra- and ipsilateral secondary somatosensory cortices (SII) and the contralateral posterior parietal cortex (PPC).

RESULTS

The earliest activity starting at 20 ms was generated solely in the SI cortex, whereas longer-latency activity was detected from all 4 source areas. The mean peak latencies for SII responses were 86-96 ms for contralateral and 94-97 ms for ipsilateral stimuli. However, the activation of right and left SII areas started at 61+/-3 and 62+/-3 ms to contralateral stimuli and at 66+/-2 and 63+/-2 ms to ipsilateral stimuli, suggesting a simultaneous commencing of activation of the SII areas. PPC sources were activated between 70 and 110 ms in different subjects. The 1.5 s ISI alternating stimuli elicited smaller SII responses than the 3 s ISI non-alternating stimuli, suggesting that a considerable part of the neural population in SII responds both to contra- and ipsilateral stimuli. The earliest SI responses did not differ between the two conditions. There were no significant differences in source locations of SII responses to ipsi- and contralateral stimuli in either hemisphere. Subaverages of the responses in sets of 30 responses revealed that amplitudes of the SII responses gradually attenuated during repetitive stimulation, whereas the amplitudes of the SI responses were not changed.

CONCLUSIONS

The present results implicate that ipsi- and contralateral SII receive simultaneous input, and that a large part of SII neurons responds both to contra- and ipsilateral stimulation. The present data also highlight the different behavior of SI and SII cortices to repetitive stimuli.

How does working memory store multiple spatial positions to control sequences of eye movements, particularly when the same items repeat at multiple list positions, or ranks, during the sequence? An Item-Order-Rank model of working memory shows how rank-selective representations enable storage and recall of items that repeat at arbitrary list positions. Rank-related activity has been observed in many areas including the posterior parietal cortices (PPC), prefrontal cortices (PFC) and supplementary eye fields (SEF). The model shows how rank information, originating in PPC, may support rank-sensitive PFC working memory representations and how SEF may select saccades stored in working memory. It also proposes how SEF may interact with downstream regions such as the frontal eye fields (FEF) during memory-guided sequential saccade tasks, and how the basal ganglia (BG) may control the flow of information. Model simulations reproduce behavioral, anatomical and electrophysiological data under multiple experimental paradigms, including visually- and memory-guided single and sequential saccade tasks. Simulations reproduce behavioral data during two SEF microstimulation paradigms, showing that their seemingly inconsistent findings about saccade latency can be reconciled.

The vascular wall exhibits nonlinear anisotropic mechanical properties. The identification of a strain energy function (SEF) is the preferred method to describe its complex nonlinear elastic properties. Earlier constituent-based SEF models, where elastin is modeled as an isotropic material, failed in describing accurately the tissue response to inflation-extension loading. We hypothesized that these shortcomings are partly due to unaccounted anisotropic properties of elastin. We performed inflation-extension tests on common carotid of rabbits before and after enzymatic degradation of elastin and applied constituent-based SEFs, with both an isotropic and an anisotropic elastin part, on the experimental data. We used transmission electron microscopy (TEM) and serial block-face scanning electron microscopy (SBFSEM) to provide direct structural evidence of the assumed anisotropy. In intact arteries, the SEF including anisotropic elastin with one family of fibers in the circumferential direction fitted better the inflation-extension data than the isotropic SEF. This was supported by TEM and SBFSEM imaging, which showed interlamellar elastin fibers in the circumferential direction. In elastin-degraded arteries, both SEFs succeeded equally well in predicting anisotropic wall behavior. In elastase-treated arteries fitted with the anisotropic SEF for elastin, collagen engaged later than in intact arteries. We conclude that constituent-based models with an anisotropic elastin part characterize more accurately the mechanical properties of the arterial wall when compared to models with simply an isotropic elastin. Microstructural imaging based on electron microscopy techniques provided evidence for elastin anisotropy. Finally, the model suggests a later and less abrupt collagen engagement after elastase treatment.

At the current state of technology, multichannel simultaneous recording of combined electric potentials and magnetic fields should constitute the most powerful tool for separation and localization of focal brain activity. We performed an explorative study of multichannel simultaneous electric SEPs and magnetically recorded SEFs. MEG only sees tangentially oriented sources, while EEG signals include the entire activity of the brain. These characteristics were found to be very useful in separating multiple sources with overlap of activity in time. The electrically recorded SEPs were adequately modelled by three equivalent dipoles located: (1) in the region of the brainstem, modelling the P14 peak at the scalp, (2) a tangentially oriented dipole, modelling the N20-P20 and N30-P30 peaks, and part of the P45, and (3) a radially oriented dipole, modelling the P22 peak and part of the P45, both located in the region of the somatosensory cortex. Magnetically recorded SEFs were adequately modelled by a single equivalent dipole, modelling the N20-P20 and N30-P30 peaks, located close to the posterior bank of the central sulcus, in area 3b (mean deviation: 3 mm). The tangential sources in the electrical data were located 6 mm on average from the area 3b. MEG and EEG was able to locate the sources of finger stimulated SEFs in accordance with the somatotopic arrangement along the central fissure. A combined analysis demonstrated that MEG can provide constraints to the orientation and location of sources and helps to stabilize the inverse solution in a multiple-source model of the EEG.

This study combines source analysis imaging data for early somatosensory processing and the probabilistic cytoarchitectonic maps (PCMs). Human somatosensory evoked fields (SEFs) were recorded by stimulating left and right median nerves. Filtering the recorded responses in different frequency ranges identified the most responsive frequency band. The short-latency averaged SEFs were analyzed using a single equivalent current dipole (ECD) model and magnetic field tomography (MFT). The identified foci of activity were superimposed with PCMs. Two major components of opposite polarity were prominent around 21 and 31 ms. A weak component around 25 ms was also identified. For the most responsive frequency band (50-150 Hz) ECD and MFT revealed one focal source at the contralateral Brodmann area 3b (BA3b) at the peak of N20. The component ~25 ms was localised in Brodmann area 1 (BA1) in 50-150 Hz. By using ECD, focal generators around 28-30 ms located initially in BA3b and 2 ms later to BA1. MFT also revealed two focal sources - one in BA3b and one in BA1 for these latencies. Our results provide direct evidence that the earliest cortical response after median nerve stimulation is generated within the contralateral BA3b. BA1 activation few milliseconds later indicates a serial mode of somatosensory processing within cytoarchitectonic SI subdivisions. Analysis of non-invasive magnetoencephalography (MEG) data and the use of PCMs allow unambiguous and quantitative (probabilistic) interpretation of cytoarchitectonic identity of activated areas following median nerve stimulation, even with the simple ECD model, but only when the model fits the data extremely well.

OBJECTIVE

To evaluate the viability of MEG source reconstruction in the presence of large interference due to orthodontic material.

METHODS

We recorded the magnetic fields following a simple hand movement and following electrical stimulation of the median nerve (somatosensory evoked field -SEF). These two tasks were performed twice, once with and once without artificial dental artefacts. Temporal Signal Space Separation (tSSS) was applied to spatially filter the data and source reconstruction was performed according to standard procedures for pre-surgical mapping of eloquent cortex, applying dipole fitting to the SEF data and beamforming to the hand movement data.

RESULTS

Comparing the data with braces to the data without braces, the observed distances between the activations following hand movement in the two conditions were on average 6.4 and 4.5 mm for the left and right hand, respectively, whereas the dipole localisation errors for the SEF were 4.1 and 5.4 mm, respectively. Without tSSS it was generally not possible to obtain reliable dipole fit or beamforming results when wearing braces.

CONCLUSIONS

We confirm that tSSS is a required and effective pre-processing step for data recorded with the Elekta-MEG system. Moreover, we have shown that even the presence of large interference from orthodontic material does not significantly alter the results from dipole localisation or beamformer analysis, provided the data are spatially filtered by tSSS.

CONCLUSIONS

State-of-the-art signal processing techniques enable the use of MEG for pre-surgical evaluation in a much larger clinical population than previously thought possible.