Impulse Propagation along Thalamocortical Fibers Can Be Detected Magnetically outside the Human Brain

Kimura, Tomoaki; Ozaki, Isamu; Hashimoto, Isao

doi:10.1523/jneurosci.3022-08.2008

Cited by 37 publications

(33 citation statements)

References 14 publications

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“…The sensors (axial gradiometers) of this child-MEG system originally had the potential to record brain oscillation even from deep brain structures (Kimura et al, 2008), and the combination of young children (i.e., thin skull) and custom-sized MEG system (i.e., close sensors) achieved a shorter distance between sensors and deeper brain structures, such as the hippocampal formation. Before this research, using MRI brain images in three young children, we estimated the distance between the sensors selected for the temporal lobes and hippocampus.…”

Section: Discussionmentioning

confidence: 99%

Lateralized Theta Wave Connectivity and Language Performance in 2- to 5-Year-Old Children

Kikuchi¹,

Shitamichi²,

Yoshimura³

et al. 2011

J. Neurosci.

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Recent neuroimaging studies support the view that a left-lateralized brain network is crucial for language development in children. However, no previous studies have demonstrated a clear link between lateralized brain functional network and language performance in preschool children. Magnetoencephalography (MEG) is a noninvasive brain imaging technique and is a practical neuroimaging method for use in young children. MEG produces a reference-free signal, and is therefore an ideal tool to compute coherence between two distant cortical rhythms. In the present study, using a custom child-sized MEG system, we investigated brain networks while 78 right-handed preschool human children (32-64 months; 96% were 3-4 years old) listened to stories with moving images. The results indicated that left dominance of parietotemporal coherence in theta band activity (6-8 Hz) was specifically correlated with higher performance of languagerelated tasks, whereas this laterality was not correlated with nonverbal cognitive performance, chronological age, or head circumference. Power analyses did not reveal any specific frequencies that contributed to higher language performance. Our results suggest that it is not the left dominance in theta oscillation per se, but the left-dominant phase-locked connectivity via theta oscillation that contributes to the development of language ability in young children.

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Section: Discussionmentioning

confidence: 99%

Lateralized Theta Wave Connectivity and Language Performance in 2- to 5-Year-Old Children

Kikuchi¹,

Shitamichi²,

Yoshimura³

et al. 2011

J. Neurosci.

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“…10). This early cortical activity is likely to overlap with activity in deep subcortical areas along thalamocortical fibers (Kimura et al, 2008), and this might be why it was not identified in some subjects.…”

Section: Discussionmentioning

confidence: 99%

BA3b and BA1 activate in a serial fashion after median nerve stimulation: Direct evidence from combining source analysis of evoked fields and cytoarchitectonic probabilistic maps

et al. 2011

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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.

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“…As described in the literature, we expect magnetic moments of an equivalent current dipole originating from the cortex in the range between 10 nAm and 15 nAm. Equivalent current dipoles originating from the brain stem are expected to show an electric dipole moment between 25 nAm and 150 nAm [19,26,32,41]. Hence, the applied electric dipole moment ranged from 5 nAm up to 150 nAm in steps of 5 nAm, and the orientation was tangential ( Table 1).…”

Section: Simulationmentioning

confidence: 99%

“…Gradiometers measure the gradient of the magnetic field, which leads to an amplitude reduction of the signal from distant, i.e., deep sources. Our results will be compared to those of published work on in vitro data [19,24,29] and phantom data [2,4,10,16,30], and are relevant to emerging new MEG devices based on atomic magnetometers [18,33].…”

Section: Introductionmentioning

confidence: 97%

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Magnetoencephalographic accuracy profiles for the detection of auditory pathway sources

Bauer

Trahms

Sander

2015

Biomedical Engineering / Biomedizinische Technik

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The detection limits for cortical and brain stem sources associated with the auditory pathway are examined in order to analyse brain responses at the limits of the audible frequency range. The results obtained from this study are also relevant to other issues of auditory brain research. A complementary approach consisting of recordings of magnetoencephalographic (MEG) data and simulations of magnetic field distributions is presented in this work. A biomagnetic phantom consisting of a spherical volume filled with a saline solution and four current dipoles is built. The magnetic fields outside of the phantom generated by the current dipoles are then measured for a range of applied electric dipole moments with a planar multichannel SQUID magnetometer device and a helmet MEG gradiometer device. The inclusion of a magnetometer system is expected to be more sensitive to brain stem sources compared with a gradiometer system. The same electrical and geometrical configuration is simulated in a forward calculation. From both the measured and the simulated data, the dipole positions are estimated using an inverse calculation. Results are obtained for the reconstruction accuracy as a function of applied electric dipole moment and depth of the current dipole. We found that both systems can localize cortical and subcortical sources at physiological dipole strength even for brain stem sources. Further, we found that a planar magnetometer system is more suitable if the position of the brain source can be restricted in a limited region of the brain. If this is not the case, a helmet-shaped sensor system offers more accurate source estimation.

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Impulse Propagation along Thalamocortical Fibers Can Be Detected Magnetically outside the Human Brain

Cited by 37 publications

References 14 publications

Lateralized Theta Wave Connectivity and Language Performance in 2- to 5-Year-Old Children

Lateralized Theta Wave Connectivity and Language Performance in 2- to 5-Year-Old Children

BA3b and BA1 activate in a serial fashion after median nerve stimulation: Direct evidence from combining source analysis of evoked fields and cytoarchitectonic probabilistic maps

Magnetoencephalographic accuracy profiles for the detection of auditory pathway sources

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