A modified oddball paradigm for investigation of neural correlates of attention: a simultaneous ERP–fMRI study

Introduction

The objective of the presented study was to develop and evaluate a P300 experimental protocol for simultaneous registration of event-related potentials (ERPs) and functional MRI (fMRI) data with continuous imaging. It may be useful for investigating attention and working memory processes in specific populations, such as children and neuropsychiatric patients.

Materials and methods

Eleven children were investigated with simultaneous ERP–fMRI. To fulfill requirements of both BOLD and electroencephalographic signal registration, a modified oddball task was used. To verify the ERP–fMRI protocol we also performed a study outside the scanner using a typical two-stimuli oddball paradigm.

Results

Localization of the P300 component of ERPs partially corresponded with fMRI results in the frontal and parietal brain regions. FMRI activations were found in: middle frontal gyrus, insula, SMA, parietal lobule, thalamus, and cerebellum. Our modified oddball task provided ERP–fMRI results with high level of significance (EEG SNR = 35, fMRI p < 0.05–Bonf.). ERPs obtained in the scanner were comparable with those registered outside the scanner, although some differences in the amplitude were noticed, mainly in the N100 component.

Conclusion

In our opinion the presented paradigm may be successfully applied for simultaneous ERP–fMRI registration of neural correlates of attention in vulnerable populations.     

Detection of ATP by “in line” 31P magnetic resonance spectroscopy during oxygenated hypothermic pulsatile perfusion of pigs’ kidneys

Object

To demonstrate that adenosine triphosphate (ATP), which provides a valuable biomarker for kidney viability in the context of donation after cardiac death (DCD) transplantation, can be detected by means of ³¹P magnetic resonance spectroscopy (MRS) if kidneys are perfused with oxygenated hypothermic pulsatile perfusion (O₂+HPP).

Materials and methods

Porcine kidney perfusion was carried out using a home made, MR-compatible HPP-machine. Consequently, kidney perfusion could be performed continuously during magnetic resonance imaging and magnetic resonance spectroscopy recording. ³¹P MR spectroscopy consisted of 3-dimensional chemical shift imaging (CSI), which allowed for the detection of ATP level in line. ³¹P CSI was performed at 3?tesla in 44?min with a nominal voxel size of 6.1?cc.

Results

³¹P CSI enabled the detection of renal ATP when pO₂ was equal to 100?kPa. With pO₂ of 20?kPa, only phosphomonoester, inorganic phosphate and nicotinamide adenine dinucleotide could be found. Semi-quantitative analysis showed that ATP level was 1.3?mM in normal kidney perfused with pO₂ of 100?kPa.

Conclusions

This combined technology may constitute a new advance in DCD organ diagnostics prior to transplantation, as it allows direct assessment of ATP concentration, which provides a reliable indicator for organ bioenergetics and viability. In this study, kidneys presenting no warm ischemia were tested in order to establish values in normal organs. The test could be easily integrated into the clinical environment and would not generate any additional delay into the transplantation clinical workflow.     

Quantitative T 2 * assessment of acute and chronic myocardial ischemia/reperfusion injury in mice

Object

Imaging of myocardial infarct composition is essential to assess efficacy of emerging therapeutics. T ₂ ^* mapping has the potential to image myocardial hemorrhage and fibrosis by virtue of its short T ₂ ^* . We aimed to quantify T ₂ ^* in acute and chronic myocardial ischemia/reperfusion (I/R) injury in mice.

Materials and methods

I/R-injury was induced in C57BL/6 mice (n?=?9). Sham-operated mice (n?=?8) served as controls. MRI was performed at baseline, and 1, 7 and 28?days after surgery. MRI at 9.4?T consisted of Cine, T ₂ ^* mapping and late-gadolinium-enhancement (LGE). Mice (n?=?6) were histologically assessed for hemorrhage and collagen in the fibrotic scar.

Results

Baseline T ₂ ^* values were 17.1?±?2.0?ms. At day 1, LGE displayed a homogeneous infarct enhancement. T ₂ ^* in infarct (12.0?±?1.1?ms) and remote myocardium (13.9?±?0.8?ms) was lower than at baseline. On days 7 and 28, LGE was heterogeneous. T ₂ ^* in the infarct decreased to 7.9?±?0.7 and 6.4?±?0.7?ms, whereas T ₂ ^* values in the remote myocardium were 14.2?±?1.1 and 15.6?±?1.0?ms. Histology revealed deposition of iron and collagen in parallel with decreased T ₂ ^* .

Conclusion

T ₂ ^* values are dynamic during infarct development and decrease significantly during scar maturation. In the acute phase, T ₂ ^* values in infarcted myocardium differ significantly from those in the chronic phase. T ₂ ^* mapping was able to confirm the presence of a chronic infarction in cases where LGE was inconclusive. Hence, T ₂ ^* may be used to discriminate between acute and chronic infarctions.     

Measurement of anesthetic uptake kinetics in the brain using 19F MRI and cross-correlation analysis after pulsed application

Object

We present a pilot study based on ¹⁹F-MRI to measure fast and slow wash-in and wash-out kinetics of volatile anesthetics in pig brain.

Method

The periodic administration of anesthetics in pulsed mode is used to enhance the sensitivity of the anesthetic concentration detection by ¹⁹F-MRI signal. Temporal correlation analysis allows mapping the kinetics time constants.

Results

The clear correlation response to anesthetics concentration changes was found in the brain region in comparison with fatty tissues.

Conclusion

The methodology may yield important pharmacological findings on regional effect of the anesthetics in brain and be a step towards human studies.     

Iterative separation of transmit and receive phase contributions and B 1 + -based estimation of the specific absorption rate for transmit arrays

Object

The specific absorption rate (SAR) can be determined from radiofrequency transmit fields measured via magnetic resonance imaging.

Materials and methods

The proposed method estimates the SAR solely from the complex transmit field (B ₁ ⁺ ) by taking into account the particular properties of the electromagnetic field generated by an 8-channel transmit array. It is further based on an iterative consistency check between the measured B ₁ ⁺ magnitude and an appropriate field estimate fulfilling Maxwell’s equations. For testing the method, simulations and phantom experiments were performed for a multi-transmit array at 3T using a cylindrical phantom.

Results

The method’s robustness with respect to the assumptions made about electric tissue properties as well as its stability under different initial conditions regarding the signal phase was shown. A high sensitivity to signal noise was found. Robust reconstruction results were achieved including information from more than two transmit elements. The validity of the experimental results was confirmed by a qualitative comparison to simulated electromagnetic fields.

Conclusions

The method allows the determination of the SAR as well as the transmit phase of the individual channels of a multi-transmit array. With additional B₀ inhomogeneity measurements, a reconstruction of the receive phase is feasible independent of the receive coil type in use.     

Pulsed arterial spin labelling at ultra-high field with a <Emphasis Type="Italic">B</Emphasis><Stack><Subscript>1</Subscript><Superscript>+</Superscript></Stack>-optimised adiabatic labelling pulse

Objective

Arterial spin labelling (ASL) techniques benefit from the increased signal-to-noise ratio and the longer T ₁ relaxation times available at ultra-high field. Previous pulsed ASL studies at 7 T concentrated on the superior regions of the brain because of the larger transmit radiofrequency inhomogeneity experienced at ultra-high field that hinders an adequate inversion of the blood bolus when labelling in the neck. Recently, researchers have proposed to overcome this problem with either the use of dielectric pads, through dedicated transmit labelling coils, or special adiabatic inversion pulses.

Materials and methods

We investigate the performance of an optimised time-resampled frequency-offset corrected inversion (TR-FOCI) pulse designed to cause inversion at much lower peak B ₁ ⁺ . In combination with a PICORE labelling, the perfusion signal obtained with this pulse is compared against that obtained with a FOCI pulse, with and without dielectric pads.

Results

Mean grey matter perfusion with the TR-FOCI was 52.5 ± 10.3 mL/100 g/min, being significantly higher than the 34.6 ± 2.6 mL/100 g/min obtained with the FOCI pulse. No significant effect of the dielectric pads was observed.

Conclusion

The usage of the B ₁ ⁺ -optimised TR-FOCI pulse results in a significantly higher perfusion signal. PICORE–ASL is feasible at ultra-high field with no changes to operating conditions.

     

Delayed hepatic signal recovery on ferucarbotran-enhanced magnetic resonance images: an experimental study in rat livers with gadolinium chloride-induced Kupffer cell damage

Objective

Hepatic signal recovery, rather than reduction, in ferucarbotran-enhanced magnetic resonance imaging (MRI) is a potential diagnostic marker of liver damage. We investigated hepatic signal recovery in rats with gadolinium chloride (GdCl₃)-induced Kupffer cell (KC) damage.

Materials and methods

Twelve rats received 8 μmol iron/kg of ferucarbotran 1 day after 0–7.5 mg/kg GdCl₃ injection (experiment A). Another 12 rats received ferucarbotran followed by GdCl₃ injection 6 h later (experiment B). In each experiment, three rats without GdCl₃ (“no injury group”) served as control. Another six rats received GdCl₃ alone without ferucarbotran. Hepatic signals were assessed on T ₂ ^* -weighted images for up to 29 days. Iron deposits were histologically examined on day 29.

Results

Hepatic signal recovery was delayed in a GdCl₃ dose-dependent manner in experiment A. Gadolinium chloride alone reduced hepatic signal 15 % during this experiment. Hepatic signal recovery was delayed only in rats that received 7.5 mg/kg GdCl₃ in experiment B. Hepatic signals negatively correlated with iron deposits in KCs and hepatocytes.

Conclusion

Hepatic signal recovery on ferucarbotran-enhanced MRI was delayed in the context of GdCl₃-induced KC damage due to increased hepatic iron deposits. Hepatic signal recovery may be used as a clinical marker of KC damage in liver disorders, including radiation-induced hepatitis.     

Evaluating metabolites in patients with major depressive disorder who received mindfulness-based cognitive therapy and healthy controls using short echo MRSI at 7 Tesla

Objectives

Our aim was to evaluate differences in metabolite levels between unmedicated patients with major depressive disorder (MDD) and healthy controls, to assess changes in metabolites in patients after they completed an 8-week course of mindfulness-based cognitive therapy (MBCT), and to exam the correlation between metabolites and depression severity.

Materials and methods

Sixteen patients with MDD and ten age- and gender-matched healthy controls were studied using 3D short echo-time (20 ms) magnetic resonance spectroscopic imaging (MRSI) at 7 Tesla. Relative metabolite ratios were estimated in five regions of interest corresponding to insula, anterior cingulate cortex (ACC), caudate, putamen, and thalamus.

Results

In all cases, MBCT reduced severity of depression. The ratio of total choline-containing compounds/total creatine (tCr) in the right caudate was significantly increased compared to that in healthy controls, while ratios of N-acetyl aspartate (NAA)/tCr in the left ACC, myo-inositol/tCr in the right insula, and glutathione/tCr in the left putamen were significantly decreased. At baseline, the severity of depression was negatively correlated with my-inositol/tCr in the left insula and putamen. The improvement in depression severity was significantly associated with changes in NAA/tCr in the left ACC.

Conclusions

This study has successfully evaluated regional differences in metabolites for patients with MDD who received MBCT treatment and in controls using 7 Tesla MRSI.

     

Possibilities and limitations for high resolution small animal MRI on a clinical whole-body 3T scanner

Object

To investigate the potential of a clinical 3 T scanner to perform MRI of small rodents.

Materials and methods

Different dedicated small animal coils and several imaging sequences were evaluated to optimize image quality with respect to SNR, contrast and spatial resolution. As an application, optimal grey-white-matter contrast and resolution were investigated for rats. Furthermore, manganese-enhanced MRI was applied in mice with unilateral crush injury of the optic nerve to investigate coil performance on topographic mapping of the visual projection.

Results

Differences in SNR and CNR up to factor 3 and more were observed between the investigated coils. The best grey-white matter contrast was achieved with a high resolution 3D T ₂-weighted TSE (SPACE) sequence. Delineation of the retino-tectal projection and detection of defined visual pathway damage on the level of the optic nerve could be achieved by using a T ₁-weighted, 3D gradient echo sequence with isotropic resolution of (0.2?mm)³.

Conclusions

Experimental studies in small rodents requiring high spatial resolution can be performed by using a clinical 3 T scanner with appropriate dedicated coils.     

In vivo chlorine and sodium MRI of rat brain at 21.1 T

Object

MR imaging of low-gamma nuclei at the ultrahigh magnetic field of 21.1 T provides a new opportunity for understanding a variety of biological processes. Among these, chlorine and sodium are attracting attention for their involvement in brain function and cancer development.

Materials and methods

MRI of ³⁵Cl and ²³Na were performed and relaxation times were measured in vivo in normal rat (n = 3) and in rat with glioma (n = 3) at 21.1 T. The concentrations of both nuclei were evaluated using the center-out back-projection method.

Results

T ₁ relaxation curve of chlorine in normal rat head was fitted by bi-exponential function (T _1a = 4.8 ms (0.7) T _1b = 24.4 ± 7 ms (0.3) and compared with sodium (T ₁ = 41.4 ms). Free induction decays (FID) of chlorine and sodium in vivo were bi-exponential with similar rapidly decaying components of $ T_{{2{\text{a}}}}^{*} = 0.4 $  ms and $ T_{{2{\text{a}}}}^{*} = 0.53 $  ms, respectively. Effects of small acquisition matrix and bi-exponential FIDs were assessed for quantification of chlorine (33.2 mM) and sodium (44.4 mM) in rat brain.

Conclusion

The study modeled a dramatic effect of the bi-exponential decay on MRI results. The revealed increased chlorine concentration in glioma (~1.5 times) relative to a normal brain correlates with the hypothesis asserting the importance of chlorine for tumor progression.     

Detection of vascular alterations by in vivo magnetic resonance angiography and histology in APP/PS1 mouse model of Alzheimer’s disease

Object

The brain of patients with Alzheimer’s disease (AD) is characterized by the presence of amyloid plaques and neurofibrillary tangles. Vascular alterations such as amyloid angiopathy are also commonly reported in patients with AD and participate in mechanisms involved in disease onset and progression. Transgenic mouse models of AD have been engineered to evaluate the pathophysiology and new treatments of the disease. Our study evaluated vascular alterations in APP_SweLon/PS1_M146L mouse model of AD.

Materials and methods

Histological analysis and in vivo magnetic resonance angiography protocols based on time of flight (TOF) and contrast-enhanced (CE) angiography were applied to evaluate cerebrovascular alterations.

Results

Histological analysis showed that cerebrovascular amyloid deposition starts by the same time as extracellular amyloid plaques. However, unlike plaques deposition, severity of cerebrovascular alterations is stabilized in older animals. Alteration of the middle cerebral artery was detected in old APP_SweLon/PS1_M146L mice with respect to adult ones by evaluating the severity of vessel voids and the reduction of vessel length on TOF- and CE-angiograms. Age-related alterations in control PS1 mice were only detected as a reduced vessel length on CE-angiograms.

Conclusion

These results show that macroscopic vascular abnormalities are part of the pathological alterations developed by APP_SweLon/PS1_M146L mouse models of AD.     

Ultra-high field MRI for primate imaging using the travelling-wave concept

Object

Ultra-high field (UHF) neuroimaging is usually conducted with volume transmit (Tx) and phased array receive (Rx) coils, both tightly enclosing the object. The travelling-wave (TW) concept allows a remote excitation offering more flexible experimental setups. To investigate the feasibility of primate MRI in horizontal UHF MRI, we first compared the distribution of the electromagnetic fields in an oil phantom and then verified the concept with an in vivo experiment.

Materials and methods

In the phantom experiments an in-house circularly polarized hybrid birdcage coil and a self-developed patch antenna were used for Tx and an eight-element phased array antenna for Rx. B ₁ ⁺ fields were calculated and measured for both approaches. For in vivo experiments the Rx part was replaced with an optimized three-element phased array head coil. The SAR was calculated using field simulation.

Results

In the phantom the field distribution was homogenous in a central volume of interest of about 10 cm diameter. The TW concept showed a slightly better homogeneity. Examination of a female crab-eating macaque led to homogeneous high-contrast images with a good delineation of anatomical details.

Conclusion

The TW concept opens up a new approach for MRI of medium-sized animals in horizontal UHF scanners.     

Direct cerebral and cardiac 17O-MRI at 3 Tesla: initial results at natural abundance

Purpose

To establish direct ¹⁷O-magnetic resonance imaging (MRI) for metabolic imaging at a clinical field strength of 3 T.

Methods

An experimental setup including a surface coil and transmit/receive switch was constructed. Natural abundance in vivo brain images of a volunteer were acquired with a radial three-dimensional (3D) sequence in the visual cortex and in the heart with electrocardiogram (ECG)-gating.

Results

In the brain, a signal-to-noise ratio of 36 was found at a nominal resolution of (5.6 mm)³, and a transverse relaxation time of T₂* = (1.9 ± 0.2) ms was obtained. In the heart ¹⁷O images were acquired with a temporal resolution of 200 ms.

Conclusion

Cerebral and cardiac ¹⁷O-MRI at natural abundance is feasible at 3 T.     

Morphologic and functional changes in the unilateral 6-hydroxydopamine lesion rat model for Parkinson’s disease discerned with μSPECT and quantitative MRI

Object

In the present study, we aimed to evaluate the impact of neurodegeneration of the nigrostriatal tract in a rodent model of Parkinson’s disease on the different MR contrasts (T₂, T₁, CBF and CBV) measured in the striatum.

Material and methods

Animals were injected with 6-hydroxydopamine (6OHDA) in the substantia nigra resulting in massive loss of nigrostriatal neurons and hence dopamine depletion in the ipsilateral striatum. Using 7T MRI imaging, we have quantified T₂, T₁, CBF and CBV in the striata of 6OHDA and control rats. To validate the lesion size, behavioral testing, dopamine transporter μSPECT and tyrosine hydroxylase staining were performed.

Results

No significant differences were demonstrated in the absolute MRI values between 6OHDA animals and controls; however, 6OHDA animals showed significant striatal asymmetry for all MRI parameters in contrast to controls.

Conclusions

These PD-related asymmetry ratios might be the result of counteracting changes in both intact and affected striatum and allowed us to diagnose PD lesions. As lateralization is known to occur also in PD patients and might be expected in transgenic PD models as well, we propose that MR-derived asymmetry ratios in the striatum might be a useful tool for in vivo phenotyping of animal models of PD.     

Water exchange-minimizing DCE-MRI protocol to detect changes in tumor vascular parameters: effect of bevacizumab/paclitaxel combination therapy

Objective

The purpose of this study was to assess changes in the tumor microvasculature induced by combination antiangiogenic therapy in MCF-7 breast tumor mouse models, using a noninvasive DCE-MRI method that minimizes the effect of water exchange.

Materials and methods

3D quantitative DCE-MRI images were acquired with a heavily T ₁-weighted saturation recovery gradient echo sequence with a recovery delay of 20 ms. Tumor vascular volume (VV) and vascular permeability-surface area product (PS) were obtained through a linear regression of the albumin-Gd-DTPA-enhanced dynamic image intensity on MCF-7 breast tumor mouse models treated with combination bevacizumab/paclitaxel therapy.

Results

Measured tumor VV values were significantly higher than the values that have been reported previously using quantitative T ₁ mapping, and are in good agreement with micro-CT (computed tomography) results reported earlier from other tumor models. A trend of decreasing tumor PS was detected in the group of MCF-7 tumor bearing mice treated with the bevacizumab/paclitaxel combination regimen.

Conclusion

VV and PS maps obtained by a heavily T ₁-weighted acquisition protocol revealed the large peripheral blood vessels as well as the permeable areas within the tumor. A 12-day/three-dose combination treatment of bevacizumab and paclitaxel resulted in delayed tumor growth and a trend of decreasing tumor vascular permeability surface area product.     

Two-dimensional accelerated MP-RAGE imaging with flexible linear reordering

Object

Implementation of an accelerated Magnetization Prepared RApid Gradient Echo (MP-RAGE) sequence for T1 weighted neuroimaging; exploiting modern MRI technologies to minimize scan time while preserving the image quality.

Materials and methods

A custom MP-RAGE sequence was implemented on a state-of-the-art 3T MR scanner equipped with a 32-channel receiver array head coil. The sequence utilized a shifted CAIPIRINHA k _y –k _z under-sampling pattern combined with elliptical scanning and a two-dimensional view ordering scheme to achieve high parallel imaging acceleration factors at maintained image contrast.

Results

It could be shown that MP-RAGE accelerated in two k-space directions outperforms single direction acceleration, which is the common practice with standard view ordering. Applying the CAIPIRINHA technique in conjunction with elliptical scanning further increased this benefit.

Conclusion

By combining MP-RAGE with CAIPIRINHA sampling and elliptical scanning, the scan time can be reduced from 4–5 min to 2–3 min with insignificant reduction in image quality.     

Chlorine and sodium chemical shift imaging during acute stroke in a rat model at 9.4 Tesla

Object

A triple-resonant coil setup with an ¹H linear resonator and a double-tuned ²³Na/³⁵Cl surface coil was used to study the evolution of T ₂ ^* and M ₀ for ³⁵Cl and ²³Na in a rat stroke model during the acute phase at 9.4 Tesla.

Materials and methods

In vivo measurements were performed 1.5–7 h after onset of stroke (n = 2), ten days after onset (n = 1) and on a healthy control rat by a chemical shift imaging sequence. Measurement times were 15 min (²³Na) and 57 min (³⁵Cl).

Results

The relaxation times ten days after onset [T ₂ ^*  = 14.3 ± 1.8 ms (²³Na) and 6.0 ± 1.3 ms (³⁵Cl)] are clearly prolonged in comparison to a healthy rat [T ₂ ^*  = 4.8 ± 0.6 ms (²³Na) and 2.1 ± 0.3 ms (³⁵Cl)] and the acute phase [T ₂ ^*  = 5.6 ± 0.2 ms (²³Na) and 1.9 ± 0.1 ms (³⁵Cl)].

Conclusion

M ₀ in the infarcted region clearly rises later and slower for chlorine than for sodium. To the best of our knowledge, these are the first combined proton, sodium, and chlorine measurements in an animal stroke model during the acute phase.     

Numerical and experimental evaluation of RF shimming in the human brain at 9.4 T using a dual-row transmit array

Objective

To provide a numerical and experimental investigation of the static RF shimming capabilities in the human brain at 9.4 T using a dual-row transmit array.

Materials and methods

A detailed numerical model of an existing 16-channel, inductively decoupled dual-row array was constructed using time-domain software together with circuit co-simulation. Experiments were conducted on a 9.4 T scanner. Investigation of RF shimming focused on B₁ ⁺ homogeneity, efficiency and local specific absorption rate (SAR) when applied to large brain volumes and on a slice-by-slice basis.

Results

Numerical results were consistent with experiments regarding component values, S-parameters and B₁ ⁺ pattern, though the B₁ ⁺ field was about 25 % weaker in measurements than simulations. Global shim settings were able to prevent B₁ ⁺ field voids across the entire brain but the capability to simultaneously reduce inhomogeneities was limited. On a slice-by-slice basis, B₁ ⁺ standard deviations of below 10 % without field dropouts could be achieved in axial, sagittal and coronal orientations across the brain, even with phase-only shimming, but decreased B₁ ⁺ efficiency and SAR limitations must be considered.

Conclusion

Dual-row transmit arrays facilitate flexible 3D RF management across the entire brain at 9.4 T in order to trade off B₁ ⁺ homogeneity against power-efficiency and local SAR.     

Quantification and localization of contrast agents using delta relaxation enhanced magnetic resonance at 1.5?T

Object

Delta relaxation enhanced magnetic resonance (dreMR) is a new imaging technique based on the idea of cycling the magnetic field B ₀ during an imaging sequence. The method determines the field dependency of the relaxation rate (relaxation dispersion dR ₁/dB). This quantity is of particular interest in contrast agent imaging because the parameter can be used to determine contrast agent concentrations and increases the ability to localize the contrast agent.

Materials and methods

In this paper dreMR imaging was implemented on a clinical 1.5?T MR scanner combining conventional MR imaging with fast field-cycling. Two improvements to dreMR theory are presented describing the quantification of contrast agent concentrations from dreMR data and a correction for field-cycling with finite ramp times.

Results

Experiments demonstrate the use of the extended theory and show the measurement of contrast agent concentrations with the dreMR method. A second experiment performs localization of a contrast agent with a significant improvement in comparison to conventional imaging.

Conclusion

dreMR imaging has been extended by a method to quantify contrast agent concentrations and improved for field-cycling with finite ramp times. Robust localization of contrast agents using dreMR imaging has been performed in a sample where conventional imaging delivers inconclusive results.     

Motor cortical reorganization is present after a single attack of multiple sclerosis devoid of cortico-spinal dysfunction

Object

While occurrence of motor cortical reorganization has been clearly demonstrated in patients with multiple sclerosis (MS), it is not yet clear whether this cortical reorganization constitutes a response to cortico-spinal lesions or to more diffuse damage affecting the neuronal network involved in motor act preparation, or both. We proposed to investigate the changes in the activation pattern during a simple motor task devoid of cortico-spinal dysfunction occurring in patients with clinically isolated syndrome (CIS) suggestive of MS.

Materials and methods

Among 15 right-handed CIS patients, we selected eight patients with a preserved central motor pathway established by motor evoked potentials. Ten healthy right-handed gender- and age-matched volunteers were also included. After morphological MRI, subjects performed calibrated conjugated finger flexion and extension movements during fMRI acquision.

Results

In CIS patients, simple movements of the non-dominant hand induced recruitment of the anterior cingulate cortex (BA32) usually involved in complex motor movements. This reorganization was correlated with the diffuse brain tissue damage (brain T ₂ lesion load).

Conclusion

These results suggest that at least part of the cortical reorganization observed during very simple tasks in the earliest stage of MS occurs whether or not the efferent pathways are intact.