Dry phantom for magnetoencephalography -Configuration, calibration, and contribution.

Background: An artificial object that imitates human brain activity is called "phantom" and is used for evaluation of magnetoencephalography (MEG) systems. The accuracy of the phantom itself had not been guaranteed in the previous studies, although role of the phantom is to evaluate the accuracy of MEG measurement. The purposes of this paper are to develop a novel MEG phantom that can be calibrated and to demonstrate the advantages of the calibrated phantoms.

Publication criteria for evoked magnetic fields of the human brain: a proposal.

Magnetoencephalography (MEG) is a record of the magnetic fields produced by the electrical activities of the brain using MEG systems. There are three types of sensors for MEG systems: magnetometer and two types of gradiometer. Among them, two types of gradiometer, axial and planar, have been used worldwide.

Diversity of neural-hemodynamic relationships associated with differences in cortical processing during bilateral somatosensory activation in rats.

The neural-hemodynamic relationships may vary depending on cortical processing patterns. To investigate how cortical hemodynamics reflects neural activity involving different cortical processing patterns, we delivered electrical stimulation pulses to rat hindpaws, unilaterally or bilaterally, and simultaneously measured electrophysiological (local field potential, LFP < 100 Hz; multiunit activity, MUA>300 Hz) and optical intrinsic signals associated with changes in cerebral blood volume (CBV). Unilateral stimulation evoked neural and optical signals in bilateral primary somatosensory cortices.

Exploring the physiology and function of high-frequency oscillations (HFOs) from the somatosensory cortex.

A brief review of previous studies is presented on high frequency oscillations (HFOs)>300 Hz overlying the cortical response in the somatosensory evoked potential (SEP) or magnetic field (SEF) in humans as well as other mammals. The characteristics of somatosensory HFOs are described about reproducibility and origin (area 3b and 1) of the HFOs, changes during a wake-sleep cycle, effects of stimulus rate or tactile interference, and pharmacological effects. Also, several hypotheses on the neural mechanisms of the HFOs are reconsidered; the early HFO burst is probably generated from action potentials of thalamocortical fibers at the time when they arrive at the area 3b (and 1), since this component is resistant to higher stimulus rate >10 Hz, general anesthesia, or application of glutamatergic receptor antagonist: by contrast, the late HFO burst is sensitive to higher stimulus rate and eliminated after application of glutamatergic receptor antagonist, reflecting activities of a postsynaptic neural network in areas 3b and 1 of the somatosensory cortex.

High-frequency transcutaneous electrical nerve stimulation (TENS) differentially modulates sensorimotor cortices: an MEG study.

Objective: Transcutaneous electrical nerve stimulation (TENS) affects excitability of the central motor system as well as the somatosensory system. To determine whether TENS has influence on excitability in the sensorimotor cortices of TENS-treated finger muscle, we investigated magnetoencephalogram associated with voluntary, self-paced finger movement before and after TENS.

Methods: High-frequency TENS was applied on the extensor digitorum muscle for 15 min.

Impulse propagation along thalamocortical fibers can be detected magnetically outside the human brain.

Orchestrating cortical network activity with synchronous oscillations of neurons across distant regions of the brain underlies information processing in humans (Knight, 2007) and monkeys (Saalmann et al., 2007; Womelsdorf et al., 2007).

Dynamic movement of N100m current sources in auditory evoked fields: comparison of ipsilateral versus contralateral responses in human auditory cortex.

We recorded auditory evoked magnetic fields (AEFs) to monaural 400Hz tone bursts and investigated spatio-temporal features of the N100m current sources in the both hemispheres during the time before the N100m reaches at the peak strength and 5ms after the peak. A hemispheric asymmetry was evaluated as the asymmetry index based on the ratio of N100m peak dipole strength between right and left hemispheres for either ear stimulation. The results of asymmetry indices showed right-hemispheric dominance for left ear stimulation but no hemispheric dominance for right ear stimulation.

High-frequency oscillations change in parallel with short-interval intracortical inhibition after theta burst magnetic stimulation.

Objective: Theta burst transcranial magnetic stimulation (TBS) causes changes in motor cortical excitability. In the present study, somatosensory-evoked potentials (SEPs) and high-frequency oscillations (HFOs) were recorded before and after TBS over the motor cortex to examine how TBS influenced the somatosensory cortex.

Methods: SEPs following electric median nerve stimulation were recorded, and amplitudes for the P14, N20, P25, and N33 components were measured and analyzed.

Changes in somatosensory-evoked potentials and high-frequency oscillations after paired-associative stimulation.

Paired-associative stimulation (PAS), combining electrical median nerve stimulation with transcranial magnetic stimulation (TMS) with a variable delay, causes long-term potentiation or depression (LTP/LTD)-like cortical plasticity. In the present study, we examined how PAS over the motor cortex affected a distant site, the somatosensory cortex. Furthermore, the influences of PAS on high-frequency oscillations (HFOs) were investigated to clarify the origin of HFOs.

Co-activation of the secondary somatosensory and auditory cortices facilitates frequency discrimination of vibrotactile stimuli.

The contribution of the auditory cortex to tactile information processing was studied by measuring somatosensory evoked magnetic fields (SEFs). Three kinds of vibrotactile stimuli with frequencies of 180, 280 and 380 Hz were randomly delivered on the right index finger with a probability of 40, 20 and 40%, respectively. Twenty normal subjects participated in four kinds of tasks: a control condition to ignore these stimuli, a simple task to discriminate the 280-Hz stimulus from the other two stimuli (discrimination task for the vibrotactile stimuli, Ts task), a feedback task modified from the Ts task by adding acoustic feedback of the vibratory frequency at 1300 ms poststimulus (tactile discrimination with auditory clues, TA), and an easy version of the TA task (TA-easy) to discriminate the 280-Hz stimulus (20% target) from the 180- or 380-Hz stimuli (80% nontarget).

Human tonotopic maps and their rapid task-related changes studied by magnetic source imaging.

A brief review of previous studies is presented on tonotopic organization of primary auditory cortex (AI) in humans. Based on the place theory for pitch perception, in which place information from the cochlea is used to derive pitch, a well-organized layout of tonotopic map is likely in human AI. The conventional view of tonotopy in human AI is a layout inwhich the medial-to-lateral portion of Heschl's gyrus represents high-to-low frequency tones.

Interferon-gamma down-regulates expression of the 230-kDa bullous pemphigoid antigen gene (BPAG1) in epidermal keratinocytes via novel chimeric sequences of ISRE and GAS.

The 230-kDa bullous pemphigoid antigen (BPAG1) is an integral component of hemidesmosomes. We have previously reported that interferon-gamma (IFNgamma) inhibits the transcription of the BPAG1 gene (1). Here we investigated the target sequences of IFNgamma-signal transduction pathway in the BPAG1 promoter in epidermal keratinocytes.

Neural mechanisms of the ultrafast activities.

A brief review of previous studies is presented on ultra-fast activities > 300 Hz (high frequency oscillations, HFOs) overlying the cortical response in the somatosensory evoked potential (SEP) or magnetic field (SEF). The characteristics of somatosensory HFOs are described in terms of reproducibility and origin (area 3b and 1) of the HFOs, changes during a wake-sleep cycle, effects of higher stimulus rate or tactile interference, etc. Also, several hypotheses on the neural mechanisms of the HFOs are introduced; the early HFO burst is probably generated from action potentials of thalamocortical fibers at the time when they arrive at the area 3b (and 1), since this component is resistant to higher stimulus rate > 10Hz or general anesthesia: by contrast, the late HFO burst is sensitive to higher stimulus rate, reflecting activities of a postsynaptic neural network in the somatosensory cortices, area 3b and 1.

Attention induces reciprocal activity in the human somatosensory cortex enhancing relevant- and suppressing irrelevant inputs from fingers.

Objective: We studied whether attention regulates information processing in the human primary somatosensory cortex (SI) by selective enhancement of relevant- and suppression of irrelevant information.

Methods: Under successive and simultaneous electric stimuli to both the right index and middle fingers, tactile stimuli were randomly (20%) presented on one of the two fingers in separate two runs exchanging the finger. Subjects were requested to discriminate the tactile stimuli in an attention task to induce attention to one finger and to ignore the stimuli in a control task to avoid such an attention focus.

Keratinocyte-specific modulation of type VII collagen gene expression by pro-inflammatory cytokines (tumor necrosis factor-alpha and interleukin-1beta).

Previous studies have shown that pro-inflammatory cytokines such as tumor necrosis factor (TNF)-alpha and interleukin (IL)-1beta up-regulate type VII collagen gene (COL7A1) expression in cultured dermal fibroblasts. The present study was designed to investigate the effects of TNF-alpha and IL-1beta on COL7A1 expression in epidermal keratinocytes. We demonstrated that both TNF-alpha and IL-1beta reduced COL7A1 expression in epidermal keratinocytes in an additive manner, whereas they increased COL7A1 expression in dermal fibroblasts.

Functional connectivity between forearm and digits representations in human somatosensory area 3b.

Objective: We compared the effects of tactile interference to the forearm on magnetic responses evoked by electric stimulation of the little finger (D5) and the thumb (D1).

Methods: Electric stimulation was delivered to D5 or D1 individually. In each stimulus session, magnetic recordings were conducted with or without concurrent tactile interference to the radial side of the anterior forearm.

Disinhibition of the somatosensory cortex in cervical dystonia-decreased amplitudes of high-frequency oscillations.

Objective: To determine whether patients with cervical dystonia have electrophysiological signs of disinhibition in the somatosensory cortex by recording high-frequency oscillations (HFOs) in somatosensory evoked potentials (SEPs).

Methods: HFOs were recorded in 13 patients and 10 age-matched control subjects, and the data were analyzed statistically by paired comparison and by Pearson's correlation.

Results: In patients with cervical dystonia, the early part of HFOs showed a significant decrease in amplitude, and the amplitude ratios of both early and late parts of HFOs/N20 potential were also significantly decreased.

Rapid change of tonotopic maps in the human auditory cortex during pitch discrimination.

Objective: To study early cognitive processes and hemispheric differences in the primary auditory cortex during selective attention.

Methods: We measured auditory evoked magnetic fields (AEFs) to 400 and 4000 Hz tone pips that were randomly presented at the right or left ear. Subjects paid attention to target stimuli during pitch (high or low) or laterality (left or right) discrimination tasks.

Serial N20m dipoles in somatosensory evoked magnetic fields move along the distal-proximal representation of the digit area 3b of the human cortex.

We studied the relationship between the distal-proximal representation of the digit in area 3b and moving dipoles of the primary magnetic response (N20m). By the use of ring electrodes, a distal or proximal portion of the middle finger was stimulated to elicit N20m. The dipole locations were sequentially analyzed around the N20m peak.

Is there training-dependent reorganization of digit representations in area 3b of string players?

Objective: The digit representations in area 3b were studied to examine whether there is training-dependent reorganization in string players.

Methods: Somatosensory evoked magnetic fields were recorded following electrical stimulation of digits 1 (D1), 2 (D2) and 5 (D5) of both hands in 8 string players and of the left hand in 12 control subjects. The N20m and P30m responses, and high-frequency oscillations (HFOs) were separated by 3-300 Hz and 300-900 Hz bandpass filtering.

Tactile interference to the face affects magnetic responses elicited by electric thumb stimulation.

Objective: We examined the effect of tactile interference to the face on somatosensory evoked magnetic fields (SEFs) following electric thumb stimulation.

Methods: SEFs were elicited by electric stimulation of the right thumb in a control and two interference conditions. In the interference conditions, continuous tactile stimuli were delivered to the skin surface over the right upper face or the right thumb.

Muscle afferent inputs from the hand activate human cerebellum sequentially through parallel and climbing fiber systems.

Objective: Spatio-temporal response characteristics of the human cerebellum to median nerve stimulation (MNS) were studied with the use of a whole-head magnetoencephalographic (MEG) system covering the cerebellum and upper cervical spine.

Methods: Neuromagnetic responses from the cerebellum were recorded following electric stimulation of the right median nerve in 12 subjects. In 6 out of 12 subjects, the responses to the left median nerve and to the right index or middle finger stimulation were also recorded.

Dynamic movement of N100m dipoles in evoked magnetic field reflects sequential activation of isofrequency bands in human auditory cortex.

Objective: To investigate spatiotemporal features of the isofrequency bands for 400 and 4000 Hz tones in human auditory cortex and on the hemispheric differences in the arrangement of isofrequency bands.

Methods: We recorded auditory evoked magnetic fields (AEFs) to 400 or 4000 Hz tone pips presented at right or left ear from 31 normal subjects. The dipole location for the N100m sources was successively calculated from the AEFs obtained from the hemisphere contralateral to the stimulated ear.