Neuronal current distribution imaging using magnetic resonance

Kamei, Hiroyasu; Iramina, Keiji; Yoshikawa, Kiwamu; Ueno, Shinji

doi:10.1109/20.800771

Cited by 73 publications

(26 citation statements)

References 5 publications

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“…However, using a detection threshold (0.2%) smaller than these signal changes, no ncMRI activation was detected in the present study without the task-induced BOLD activation. This suggests that the signal changes observed in the previous ncMRI studies (2,3,7,8,10) cannot be confidently attributed to the direct effect of neuronal currents. They may result from the contamination of the task-induced BOLD background.…”

Section: Discussionmentioning

confidence: 82%

“…Therefore, both of these BOLD artifact-free human and animal studies indicate that the ncMRI signal evoked by the physiological (visual) stimulation is too weak to be detected. In the previous ncMRI studies on human subjects (2,3,7,8,10), fast signal changes of $0.3-1% were observed in the magnitude images using steady-state stimulation tasks. However, using a detection threshold (0.2%) smaller than these signal changes, no ncMRI activation was detected in the present study without the task-induced BOLD activation.…”

Section: Discussionmentioning

confidence: 87%

“…Nonetheless, up to date, a consensus has not been reached on the detectability of ncMRI on human subjects. Multiple groups have reported a successful detection of ncMRI signal in human brain (2)(3)(4)(5)(6)(7)(8)(9)(10), while a failure in ncMRI detection has been claimed in other studies (11)(12)(13)(14)(15). Due to these conflicting results, there is still no conclusion on the question whether ncMRI signal is detectable or not.…”

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confidence: 98%

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Detection of neuronal current MRI in human without BOLD contamination

Luo

Jiang

Gao

2011

Magnetic Resonance in Med

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Controversial results regarding the detectability of neuronal current magnetic resonance imaging (ncMRI) have been reported in different studies on human subjects. In all the previous studies, the ncMRI signal was detected under a continuous and paradigm task-induced blood oxygen level dependent (BOLD) signal background. The aim of this study is to investigate the possibility of detecting ncMRI signal in human brain in the situation that task-induced BOLD background is absent or minimum. In this study, by adopting an event-related visuomotor paradigm with long interstimulus interval (520 s), the ncMRI signal was detected when the BOLD signal fully returned to its baseline, and the potential BOLD background contamination was avoided effectively. The results showed that the visuomotor stimulation elicited BOLD activation in visual and motor cortices, but no significant ncMRI signal change (in magnitude) was detected in human brain. These experimental findings are consistent with theoretical predications. Magn Reson Med 66:492-497,

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Section: Discussionmentioning

confidence: 82%

Section: Discussionmentioning

confidence: 87%

mentioning

confidence: 98%

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Detection of neuronal current MRI in human without BOLD contamination

Luo

Jiang

Gao

2011

Magnetic Resonance in Med

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“…Several studies have explored the feasibility of using MRI for detecting the minute magnetic field changes induced by electrical currents in phantoms (1)(2)(3) or by neuronal currents in human subjects (4)(5)(6)(7)(8)(9)(10)(11)(12)(13), thereby combining the high temporal resolution of electrical and magnetic recording methods with the high spatial resolution and noninvasiveness inherent in MRI. Despite some encouraging results in phantoms, the direct imaging of neural activation in vivo has been challenging because of the small activation-induced magnetic field changes and because of multiple, synchronized, confounding signals in the brain reflecting cerebral blood oxygenation, blood volume, and blood flow changes or physiological noise (6,9).…”

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confidence: 99%

Finding neuroelectric activity under magnetic-field oscillations (NAMO) with magnetic resonance imaging in vivo

Truong

Song

2006

Proc. Natl. Acad. Sci. U.S.A.

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Neuroimaging techniques are among the most important tools for investigating the function of the human nervous system and for improving the clinical diagnosis of neurological disorders. However, most commonly used techniques are limited by their invasiveness or their inability to accurately localize neural activity in space or time. Previous attempts at using MRI to directly image neuroelectric activity in vivo through the detection of magnetic field changes induced by neuronal currents have been challenging because of the extremely small signal changes and confounding factors such as hemodynamic modulations. Here we describe an MRI technique that uses oscillating magnetic field gradients to significantly amplify and detect the Lorentz effect induced by neuroelectric activity, and we demonstrate its effectiveness in imaging sensory nerve activation in vivo in the human median nerve during electrical stimulation of the wrist. This direct, realtime, and noninvasive neuroimaging technique may potentially find broad applications in neurosciences.Lorentz effect ͉ median nerve ͉ neuroimaging ͉ MRI T he ongoing pursuit to better detect neural activity has led to many exciting technical advances over the past decades, including single-cell electrical recordings, electroencephalography (EEG), magnetoencephalography (MEG), positron emission tomography (PET), and, more recently, functional magnetic resonance imaging (fMRI). To date, neuroimaging techniques are invasive (single-cell recordings) and͞or limited in their ability to accurately localize neural activity in space (EEG, MEG) or in time (PET, fMRI). Even when information is combined across multiple modalities, there remain fundamental limitations that introduce sources of error and interpretative difficulties. It is therefore time to develop novel techniques that allow noninvasive imaging of neural activity with a high accuracy both spatially and temporally.Several studies have explored the feasibility of using MRI for detecting the minute magnetic field changes induced by electrical currents in phantoms (1-3) or by neuronal currents in human subjects (4-13), thereby combining the high temporal resolution of electrical and magnetic recording methods with the high spatial resolution and noninvasiveness inherent in MRI. Despite some encouraging results in phantoms, the direct imaging of neural activation in vivo has been challenging because of the small activation-induced magnetic field changes and because of multiple, synchronized, confounding signals in the brain reflecting cerebral blood oxygenation, blood volume, and blood flow changes or physiological noise (6, 9). Here we seek to address these two fundamental issues and to demonstrate the potential capability of MRI to directly image neuroelectric activity in vivo.First, to boost the signal detectability, we propose an acquisition strategy based on the Lorentz effect induced by neuroelectric activity. The contrast mechanism of Lorentz effect imaging was initially validated in phantoms with a proof-ofconcept puls...

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“…Kamei et al [1999] claimed the first human detection of magnitude changes due to neuronal activity, but reproducibility of these results remains to be demonstrated. Xiong et al [2003] also claimed the detection of magnitude changes due to dephasing produced by neural currents has been achieved.…”

Section: Introductionmentioning

confidence: 99%

Modeling direct effects of neural current on MRI

Heller

Barrowes

George

2007

Human Brain Mapping

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Abstract:We investigate the effect of the magnetic field generated by neural activity on the magnitude and phase of the MRI signal in terms of a phenomenological parameter with the dimensions of length; it involves the product of the strength and duration of these currents. We obtain an analytic approximation to the MRI signal when the neuromagnetically induced phase is small inside the MRI voxel. The phase shift is the average of the MRI phase over the voxel, and therefore first order in that phase; and the reduction in the signal magnitude is one half the square of the standard deviation of the MRI phase, which is second order. The analytic approximation is compared with numerical simulations. For weak currents the agreement is excellent, and the magnitude change is generally much smaller than the phase shift. Using MEG data as a weak constraint on the current strength we find that for a net dipole moment of 10 nAm, a typical value for an evoked response, the reduction in the magnitude of the MRI signal is two parts in 10 5 , and the maximum value of the overall phase shift is % 4 Á 10 À3 , obtained when the MRI voxel is displaced 2/3 the size of the neuronal activity. We also show signal changes over a large range of values of the net dipole moment. We compare these results with others in the literature.

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Neuronal current distribution imaging using magnetic resonance

Cited by 73 publications

References 5 publications

Detection of neuronal current MRI in human without BOLD contamination

Detection of neuronal current MRI in human without BOLD contamination

Finding neuroelectric activity under magnetic-field oscillations (NAMO) with magnetic resonance imaging in vivo

Modeling direct effects of neural current on MRI

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