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Objective To determine whether magnetoencephalography (MEG) can identify epileptiform discharges mimicking small sharp spikes (SSSs) on scalp electroencephalography (EEG) in patients with temporal lobe epilepsy (TLE). Methods We retrospectively reviewed simultaneous scalp EEG and MEG recordings of 83 consecutive patients with TLE and 49 with extra-TLE (ETLE). Results SSSs in scalp EEG were detected in 15 (18.1%) of 83 TLE patients compared to only two (4.1%) of 49 ETLE patients (p = 0.029). Five of the 15 TLE patients had MEG spikes with concurrent SSSs in EEG, but neither of the 2 ETLE patients. Three of these 5 TLE patients had additional interictal epileptiform discharges (IEDs) in EEG and MEG. Equivalent current dipoles (ECDs) of MEG spikes with concurrent SSSs and IEDs showed no difference in temporal lobe localization and horizontal orientation, whereas ECD moments were smaller in MEG spikes with concurrent SSSs than those with IEDs. Conclusions SSSs were more common in TLE than in ETLE. At least some morphologically diagnosed SSSs are true but low-amplitude epileptiform discharges in TLE which can be identified with simultaneous MEG. Significance Simultaneous MEG is useful to identify epileptiform discharges mimicking SSSs in patients with TLE.

Non-invasive human brain functional imaging with millisecond resolution can be achieved only with magnetoencephalography (MEG) and electroencephalography (EEG). MEG has better spatial resolution than EEG because signal distortion due to inhomogeneous head conductivity is negligible in MEG but serious in EEG. However, this advantage has been practically limited by the necessary setback distances between the sensors and scalp, because the Dewar vessel containing liquid helium for superconducting sensors requires a thick vacuum wall. Latest developments of high critical temperature (high-Tc) superconducting or optically pumped magnetometers have not allowed scalp-attached MEG due to cold or hot temperatures at the sensing point, respectively. Here we applied tunnel magneto-resistive (TMR) sensors that operate at room temperature. Improvement of TMR sensitivity with magnetic flux concentrators enabled scalp-attached and scalp-tangential MEG to target the largest signal component produced by the neural current below. In a healthy subject, our single-channel TMR-MEG system clearly demonstrated the N20m, the initial cortical component of the somatosensory evoked response after median nerve stimulation. Multisite measurement confirmed a spatially and temporally steep peak of N20m, immediately above the source at a latency around 20 ms, indicating a new approach to non-invasive functional brain imaging with millimeter and millisecond resolutions.

Palatal sensation is important for articulation, feeding, and swallowing. However, palatal sensation in patients with cleft palate (CP) after palatoplasty has been investigated only inadequately because of the complexity and high costs of objective evaluation. This study compared the somatosensory evoked magnetic fields (SEFs) induced by electrical stimulation of the palates of patients with CP after palatoplasty and the palatal sensory thresholds (PSTs) of the stimulation with those of healthy (control) subjects. The CP group comprised 12 patients with unilateral cleft lip and palate (UCLP). The control group comprised 31 control subjects. No significant difference in intensity was found between them. Nevertheless, the PSTs in the UCLP group were significantly higher than those in the control group at all sites (p 0.05). We infer that the electrical signals transmitted from palatal sensory receptors of patients with CP might be amplified by a compensation mechanism in the central nervous system. SEFs provide an effective method for objective evaluation of palatal sensation in patients with CP after palatoplasty. Evaluation of SEFs during palatal sensory stimulation in patients with CP after palatoplasty might lead to better corrective surgical methods that also preserve palatal sensation.

Background Cleft lip is the most common congenital anomaly worldwide. Nevertheless, lip somatosensory characteristics of patients with cleft lip after cheiloplasty have not yet been determined. The present study used magnetoencephalography to objectively evaluate the lip sensation in patients with unilateral cleft lip to establish a new objective evaluation method. Methods Participants were 15 patients with unilateral cleft lip after cheiloplasty (UCL group), and 30 healthy young subjects (control group). Five points of the upper and lower lips were stimulated electrically to measure somatosensory evoked magnetic fields (SEFs). The sources of the magnetic fields were modeled as single equivalent current dipoles (ECDs). ECDs located on the central sulcus by superimposition on magnetic resonance images were analyzed. Latency and intensity at 50–75 ms (cP60m) observed in the UCL group were compared with those in the control group. Thresholds of tactile stimuli in both groups were obtained using Semmes–Weinstein monofilaments for subjective sensory evaluation. Results No significant difference was found in the intensity of the cP60m or subjective evaluation between the groups. However, the latency of the cP60m was significantly longer in the upper lip of the UCL group than in the control group. Conclusions SEFs showed a difference in lip sensation between the UCL group and the control group, suggesting that longer latency might be caused by the effects of surgical scarring on the neurotransmission pathway. These results suggest SEFs as useful for the objective evaluation of lip sensations. This study might improve future surgical procedures and lip functions of patients with cleft lip.

The periodontal ligaments are very important sensory organ for our daily life such as perception of food size or hardness, determination of jaw position, and adjustment of masticatory strength. The sensory properties of the periodontal ligament, especially those of the maxillary and mandibular molars, have not yet been fully investigated. Somatosensory evoked magnetic fields (SEFs) can be measured and evaluated for latency and intensity to determine the sensory transmission characteristics of each body parts. However, previous reports on SEFs in the oral region have only reported differences in upper and lower gingival and lip sensations. In this study, the aim was to clarify these sensory characteristics by measuring SEFs during mechanical stimulation of the periodontal ligament in the maxillary and mandibular first molars. Somatosensory evoked magnetic fields were measured in the contralateral hemispheres of 33 healthy volunteers. Mechanical stimulation of the maxillary and mandibular right first molars, and the left wrist was performed with a specific handmade tool. The first peak latency for the mandibular first molars was 41.7 ± 5.70 ms (mean ± SD), significantly shorter than that for the maxillary first molars at 47.7 ± 7.36 ms. The peak intensity for the mandibular first molars was 13.9 ± 6.06 nAm, significantly larger than that for the maxillary first molars at 7.63 ± 3.55 nAm. The locations in the contralateral hemispheres showed no significant difference between the maxillary first molars and mandibular first molars. These locations were more anteroinferior and exterior than that of the wrist, as suggested by the brain homunculus. Neural signals from the mandibular periodontal ligaments pass faster and more intensely to the central nervous system than those from the maxillary periodontal ligaments, and may preferentially participate in adjustment of the occlusal force and the occlusal position.

Epilepsy is a network disease. The primary somatosensory cortex (S1) is usually considered to be intact, but could be subclinically disturbed based on abnormal functional connectivity in patients with temporal lobe epilepsy (TLE). We aimed to investigate if the S1 of TLE is abnormally modulated. Somatosensory evoked magnetic fields (SEFs) evoked by median nerve stimulation were recorded in each hemisphere of 15 TLE patients and 28 normal subjects. All responses were separately averaged in the awake state and light sleep using background magnetoencephalography. Latency and strength of the equivalent current dipole (ECD) was compared between the groups for the first (M1) and second peaks. Latencies showed no significant differences between the groups in either wakefulness or light sleep. ECD strengths were significantly lower in TLE patients than in controls only during wakefulness. The reduction of M1 ECD strength in the awake state is significantly correlated with duration of epilepsy. SEFs of TLE patients showed pure ECD strength reduction without latency delay. The phenomenon occurred exclusively during wakefulness, suggesting that a wakefulness-specific modulator of S1 is abnormal in TLE. Repetitive seizures may gradually insult the modulator of S1 distant from the epileptogenic network.

This chapter highlights the importance of the revised analysis of electroencephalography (EEG) and magnetoencephalography (MEG) spike source estimation based on comprehensive case conference discussion. It discusses two typical cases of localization-related epilepsy: case 1 as a simple situation and case 2 as a complicated situation. No “gold standard” for epileptic spike analysis in EEG or MEG has been established, so several methods must be adopted to achieve the most reasonable interpretation. However, such intense and revisional analyses may be too time-consuming in clinical settings and result in arbitrary conclusions. Therefore, the authors currently use a simple method first, that is, a single dipole model for the peak or preceding upward slope of unaveraged single spikes. In the following case conference, EEG and MEG data are reviewed with seizure semiology, anatomical magnetic resonance imaging (MRI), and 18F-fluorodeoxyglucose positron emission tomography (FDG-PET). If all the findings almost agree, the clinical decision can be easily made. If not, revisional analysis of EEG/MEG is recommended using averaged spikes and principal component analysis models as well as distributed source models. In addition to EEG/MEG, the authors often order revisional analysis and additional MRI and FDG-PET studies after the conference. Even further history taking will be recommended if necessary.

We developed tunnel magneto-resistive (TMR) sensors based on magnetic tunnel junctions (MTJs) that are able to detect a weak, sub-pT, magnetic field at a low frequency. Small detectivities of 0.94 pT/Hz1/2 at 1 Hz and 0.05 pT/Hz1/2 at 1 kHz were achieved by lowering the resistance of MTJs and enhancement of the signal using a thick CoFeSiB layer and magnetic flux concentrators. We demonstrated real-time measurement of magnetocardiography (MCG) and nuclear magnetic resonance (NMR) of protons using developed sensors. This result shows that both MCG and NMR can be measured by the same measurement system with ultra-sensitive TMR sensors.

To evaluate the localization of responses to stimulation of the periodontal mechanoreceptors in the primary somatosensory cortex, somatosensory evoked fields (SEFs) were measured for stimulation of the left mandibular canine and first molar using magnetoencephalography in 25 healthy subjects. Tactile stimulation used a handmade stimulus device which recorded the trigger at the moment of touching the teeth.SEFs for the canine and first molar were detected in 20 and 19 subjects, respectively. Both responses were detected in the bilateral hemispheres. The latency for the canine was 62.1 ± 12.9 ms in the ipsilateral hemisphere and 65.9 ± 14.8 ms in the contralateral hemisphere. The latency for the first molar was 47.4 ± 6.6 ms in the ipsilateral hemisphere and 47.8 ± 9.1 ms in the contralateral hemisphere. The latency for the first molar was significantly shorter than that for the canine. The equivalent current dipoles were estimated in the central sulcus and localized anteroinferiorly compared to the locations for the SEFs for the median nerve. No significant differences in three-dimensional coordinates were found between the canine and first molar. These findings demonstrate the precise location of the teeth within the orofacial representation area in the primary somatosensory cortex., Physiology; Nervous system; Dentistry; Medical imaging; Clinical research; Neuroscience; Neurology; Somatosensory evoked fields; Periodontal mechanoreceptor; Canine; First molar; Primary somatosensory cortex.

The N100m response to a specific same-sound stimulus may be altered by the degree of attention paid to the stimulus. When participants selectively pay attention to the stimulus, the N100m amplitude increases; however, minimal effects are observed on the N100m latency. In this study, we examined the effects of selective special attention (motivation) to extract the frequency (or pitch) information from a probe tone on the N100m response to the probe tone. We compared the N100m latencies and amplitudes using magnetoencephalography, with the following three experimental conditions: 1) vocalization task protocol (vocalize in tune with the pitch of the probe tone after the presentation of the probe tone), 2) hearing task protocol (just listen to the probe tone), and 3) imagining (just imagine the vocalization in tune with the probe tone). The results indicated that the N100m latency in response to the probe tone was significantly shortened in the vocalization and imagining tasks compared with the hearing task in the right hemisphere of the brain. The amplitude was significantly increased in the vocalization task compared with the imagining and hearing tasks in the right hemisphere, and in the vocalization task compared with the hearing task in the left hemisphere of the brain; that is, the attention and/or motivation required to extract the information from the stimulus tones may have caused N100m latency shortening. To our knowledge, this study is the first to demonstrate that the N100m latency may be shortened under particular attentional conditions in response to a simple tone.

An increasing number of biometeorological and psychological studies have demonstrated the importance and complexity of the processes involved in environmental thermal perception in humans. However, extant functional imaging data on thermal perception have yet to fully reveal the neural mechanisms underlying these processes because most studies were performed using local thermal stimulation and did not dissociate thermal sensation from comfort. Thus, for the first time, the present study employed functional magnetic resonance imaging (fMRI) and manipulated ambient temperature during brain measurement to independently explore the neural correlates of thermal sensation and comfort. There were significant correlations between the sensation of a lower temperature and activation in the left dorsal posterior insula, putamen, amygdala, and bilateral retrosplenial cortices but no significant correlations were observed between brain activation and thermal comfort. The dorsal posterior insula corresponds to the phylogenetically new thermosensory cortex whereas the limbic structures (i.e., amygdala and retrosplenial cortex) and dorsal striatum may be associated with supramodal emotional representations and the behavioral motivation to obtain heat, respectively. The co-involvement of these phylogenetically new and old systems may explain the psychological processes underlying the flexible psychological and behavioral thermo-environmental adaptations that are unique to humans.

Somatosensory evoked fields (SEFs) to electrical stimulation on the right and left sides of the lower lip were measured using magnetoencephalography and compared in the bilateral hemispheres of 31 healthy normal young and 29 healthy normal elderly subjects to evaluate age-related change in lip somatosensation. The initial peak of the response around 13 ms, designated as N13m, and the second peak of the response, designated as P21m, were investigated. The N13m response, which was detected in 22 of 62 hemispheres in young adults and 37 of 58 hemispheres in elderly adults, showed significantly prolonged latency and increased equivalent current dipole (ECD) moment in the elderly adults. The P21m response, which was detected in 56 of 62 hemispheres in young adults and in 52 of 58 hemispheres in elderly adults, showed longer peak latency in the elderly adults. No significant difference was found in the ECD moment for P21m, which suggests that aging affected the SEFs of the lip somatosensation, but the effects of aging on N13m and P21m differed. Prolonged latency and increased ECD moment of N13m might result from decreased peripheral conduction and increased cortical excitation system associated with aging. Therefore, the initial response component might be an objective parameter for investigating change in lip function with age.

We present a 28-year-old female patient whose epilepsy started at the age of 19. MRI showed right perisylvian polymicrogyria. She exhibited various seizure symptoms, such as somatosensory aura involving the left leg, dyscognitive seizures, and amnesic seizures. Her mother indicated that the patient sometimes had "sleep talking", which was associated with presence of epileptic seizures of the next day. Long-term video electroencephalography (EEG) revealed that her episodes of "sleep talking" were epileptic events, specifically ictal speech, originating in the right hemisphere. The present case demonstrates the importance of considering "sleep talk" as an epileptic symptom. Careful history taking is fundamental to carry patients with possibly pathological "sleep talk" to the long-term video EEG, which will contribute correct diagnosis and treatment. (Received August 16, 2016; Accepted September 9, 2016; Published February 1, 2017).

Objective Small focal cortical dysplasia (FCD) may be ambiguous or overlooked on magnetic resonance (MR) imaging. Source localization of EEG and magnetoencephalography (MEG) spikes was evaluated to confirm the diagnosis of small FCD. Methods This study included 6 epilepsy patients with a single small lesion on MR imaging suggesting FCD within a single gyrus among 181 consecutive epilepsy patients admitted to our epilepsy monitoring unit over 27months. Stereotypical interictal spikes were detected on simultaneous EEG and MEG recordings and the onset-related source of averaged spikes was estimated. Results All 6patients had unique clinical characteristics as follows: leg sensori-motor seizures in 5patients and eye version in 1patient; a small MR imaging lesion suggesting FCD in the dorsal peri-rolandic region, which had been overlooked until our evaluation; and both EEG and MEG dipoles were estimated adjacent to the MR imaging lesion. Conclusions Source localization of EEG and MEG spikes can confirm the diagnosis of FCD based on a single small MR imaging lesion, which was overlooked by previous examination of MR images. Significance Examination of MR images should be based on spike source localization as well as seizure semiology to identify subtle MR imaging abnormalities.

Objective To compare the detectability of the different auditory evoked responses in patients with retrocochlear lesion. Methods The 40-Hz auditory steady state response (ASSR) and the N1m auditory cortical response were examined by magnetoencephalography in 4 patients with vestibular schwannoma, in whom the auditory brainstem response (ABR) was absent. Results Apparent N1m responses were observed despite total absence of the ABR or absence except for small wave I in all patients, although the latency of N1m was delayed in most patients. On the other hand, clear ASSFs could be observed only in one patient. Very small 40-Hz ASSFs could be detected in 2 patients (amplitude less than 1 fT), but no apparent ASSFs were observed in one patient, in whom maximum speech intelligibility was extremely low and the latency of N1m was most prolonged. Conclusion The N1m response and 40-Hz ASSR could be detected in patients with absent ABR, but the N1m response appeared to be more detectable than the 40-Hz ASSR. Significance Combined assessment with several different evoked responses may be useful to evaluate the disease conditions of patients with retrocochlear lesions.

highlights abstract Objective: Corpus callosotomy limits the bilateral synchrony of epileptic discharges. However, the instan- taneous changes in bilateral synchrony during corpus callosotomy are unclear. The present study inves- tigated how and when bilateral synchrony is suppressed in the anterior and then posterior steps of corpus callosotomy. Methods: Intra-operative scalp electroencephalography (EEG) was recorded simultaneously with surgical video for six patients who underwent total corpus callosotomy for medically intractable drop attacks. The time-varying EEG inter-hemispheric coherence was quantified by wavelet transform coherence and trend analysis. Results: The 4-13 Hz coherence decreased after corpus callosotomy in five patients. Significant decrease in coherence was observed only during the posterior step of callosal sectioning in three patients, but throughout both steps in two patients. Conclusions: Decrease in inter-hemispheric coherence is not always correlated with the stages of callosal sectioning. Inter-hemispheric coherence is decreased during the final stage of corpus callosotomy and the effect is maximized after sectioning is completed. Significance: Various patterns of coherence decrease suggest individual variations in the participation of the corpus callosum in the genesis of bilateral synchrony. Time-varying inter-hemispheric EEG coherence is useful to monitor the physiological completeness of corpus callosotomy.

The effects of visual speech (the moving image of the speaker's face uttering speech sound) on early auditory evoked fields (AEFs) were examined using a helmet-shaped magnetoencephalography system in 12 healthy volunteers (9 males, mean age 35.5 years). AEFs (N100m) in response to the monosyllabic sound /be/ were recorded and analyzed under three different visual stimulus conditions, the moving image of the same speaker's face uttering /be/ (congruent visual stimuli) or uttering /ge/ (incongruent visual stimuli), and visual noise (still image processed from speaker's face using a strong Gaussian filter: control condition). On average, latency of N100m was significantly shortened in the bilateral hemispheres for both congruent and incongruent auditory/visual (A/V) stimuli, compared to the control A/V condition. However, the degree of N100m shortening was not significantly different between the congruent and incongruent A/V conditions, despite the significant differences in psychophysical responses between these two A/V conditions. Moreover, analysis of the magnitudes of these visual effects on AEFs in individuals showed that the lip-reading effects on AEFs tended to be well correlated between the two different audio-visual conditions (congruent vs. incongruent visual stimuli) in the bilateral hemispheres but were not significantly correlated between right and left hemisphere. On the other hand, no significant correlation was observed between the magnitudes of visual speech effects and psychophysical responses. These results may indicate that the auditory-visual interaction observed on the N100m is a fundamental process which does not depend on the congruency of the visual information.

This study examined behavioral changes in 15-day learning of word-picture (WP) and word-sound (WS) associations, using meaningless stimuli. Subjects performed a learning task and two recognition tasks under the WP and WS conditions every day for 15 days. Two main findings emerged from this study. First, behavioral data of recognition accuracy and response time were improved in both conditions of WP and WS by the 15-day learning of associations. Second, the performance in WP was better than that in WS for 15 days, but the correlation between accuracies in WP and WS was significant across subjects. These results suggest that even if meaningless stimuli are employed as an experimental stimulus, the long-term learning of associations between words and perceptual features could be formed in both visual and auditory modalities, between which the performance levels are highly correlated, but the learning effect could be dominant when words are associated with visual features, compared to auditory features.

Objective To examine whether auditory evoked fields (AEFs) can be used to objectively evaluate hearing in patients with absent auditory brainstem responses (ABRs) due to auditory neuropathy. Methods Subjects were 3 patients with auditory neuropathy, 1 male aged 29 years and 2 females aged 18 and 27 years, with absence of click evoked ABRs for bilateral ear stimuli at a level of 105 dB nHL. All patients also had optic atrophy. AEFs were measured with a helmet-shaped magnetoencephalography system for 2.0 kHz tone bursts of 60 ms duration to the unilateral ear. Results Bihemispherical AEF responses were clearly recorded in all three patients for either left or right ear stimulus. Although the latencies of N100m were severely prolonged and amplitudes were considerably decreased compared to the normal range of N100m responses in our facilities, N100m latency of AEF was shorter in the contralateral hemisphere to the stimulated ear, as usually found in normal subjects, despite the abnormal delay in N100m latency in all conditions. Conclusions Presence and abnormality of auditory cortical responses can be evaluated by AEFs in patients with auditory neuropathy even under null responses in ABRs. Significance AEFs are useful to evaluate residual hearing in patients with auditory neuropathy.

Introduction Benign epileptiform transients of sleep (BETS) is a finding on electroencephalography, defined as monophasic or diphasic transients with low amplitude ( μ V) and short duration ( Methods Patient 1, a 37-year-old right-handed male, was diagnosed with left TLE. Complex partial seizures started from age 15 years. Video-EEG (VEEG) showed interictal left anterior and posterior temporal sharp waves, and left temporal seizure onset was suggested. Magnetic resonance (MR) imaging revealed a mass lesion in the left lateral temporal lobe, suspected to be dysembryoplastic neuroepithelial tumor. Patient 2, a 38-year-old right-handed male, was diagnosed with left TLE. Complex partial seizures started from age 20 years. VEEG showed interictal bilateral independent temporal spikes, and left temporal seizure onset was suggested. MR imaging showed no abnormalities. Patient 3, a 33-year-old right-handed female, was diagnosed with right TLE. Complex partial seizures with oral automatism started from age 20 years. VEEG showed interictal right anterior temporal spikes, and right temporal seizure onset was suggested. MR imaging showed no abnormalities. All three patients underwent simultaneous EEG-MEG recording. EEG electrode placement used the 10–10 system with additional anterior temporal electrodes. MEG used a 200 channel whole-head system (MEGvision PQA160C, Ricoh Company, Ltd., Tokyo, Japan). The study investigated MEG activities correlated with EEG findings concordant with BETS. Results In Patient 1, MEG spikes correlated with BETS in the left temporal lobe had epileptic form, with high amplitude spike activity followed by slow wave activity. The source as evaluated with equivalent current dipoles was estimated around the left temporal lesion. In Patient 2, MEG spikes correlated with BETS in the right temporal lobe had epileptic form, with high amplitude spike activity followed by slow wave activity. No activity fulfilling the definition of BETS was detected in the left hemisphere. In Patient 3, no apparent MEG activity correlated with BETS was seen in the right temporal lobe. Conclusion The present study demonstrated variations in MEG findings correlated with EEG BETS in patients with TLE. These results may indicate heterogeneous background of BETS, so that only some BETS have an epileptic mechanism.

Magnetoencephalography (MEG) was used to measure the somatosensory evoked fields in six healthy males undergoing sacral surface therapeutic electrical stimulation, a recently introduced treatment for chronic urinary dysfunction. This study was performed to investigate the utility of MEG to optimize the stimulation parameters. Strong or weak electrical stimuli were applied to small or large surface electrodes placed over the bilateral sacral surfaces. The peak latency and strength of the equivalent current dipole were evaluated at the first peak originating from the primary somatosensory cortex (M30). There was no difference in M30 latency in response to stimulation intensity or electrode size. However, a larger equivalent current dipole strength was obtained in response to higher stimulus intensities, which indicated a more effective stimulus on the sacral surface. The present MEG study shows that stronger stimuli given through large electrodes evoke larger responses than small stimuli through small electrodes. The study also suggests that MEG can be used as an objective tool to monitor whether therapeutic stimulation parameters are appropriate.

Introduction Brain-imaging techniques have begun to be popular in evaluating the effectiveness of cognitive intervention training. Although gamma activities are rarely used as an index of training effects, they have several characteristics that suggest their potential suitability for this purpose. This pilot study examined whether cognitive training in elderly people affected the high-gamma activity associated with attentional processing and whether high-gamma power changes were related to changes in behavioral performance. Methods We analyzed (MEG) magnetoencephalography data obtained from 35 healthy elderly subjects (60–75 years old) who had participated in our previous intervention study in which the subjects were randomly assigned to one of the three types of intervention groups: Group V trained in a vehicle with a newly developed onboard cognitive training program, Group P trained with a similar program but on a personal computer, and Group C was trained to solve a crossword puzzle as an active control group. High-gamma (52–100 Hz) activity during a three-stimulus visual oddball task was measured before and after training. As a result of exclusion in the MEG data analysis stage, the final sample consisted of five subjects in Group V, nine subjects in Group P, and seven subjects in Group C. Results Results showed that high-gamma activities were differently altered between groups after cognitive intervention. In particular, members of Group V, who showed significant improvements in cognitive function after training, exhibited increased high-gamma power in the left middle frontal gyrus during top-down anticipatory target processing. High-gamma power changes in this region were also associated with changes in behavioral performance. Conclusions Our preliminary results suggest the usefulness of high-gamma activities as an index of the effectiveness of cognitive training in elderly subjects.

The effects of asynchrony between audio and visual (A/V) stimuli on the N100m responses of magnetoencephalography in the left hemisphere were compared with those on the psychophysical responses in 11 participants. The latency and amplitude of N100m were significantly shortened and reduced in the left hemisphere by the presentation of visual speech as long as the temporal asynchrony between A/V stimuli was within 100 ms, but were not significantly affected with audio lags of -500 and +500 ms. However, some small effects were still preserved on average with audio lags of 500 ms, suggesting similar asymmetry of the temporal window to that observed in psychophysical measurements, which tended to be more robust (wider) for audio lags; i.e., the pattern of visual-speech effects as a function of A/V lag observed in the N100m in the left hemisphere grossly resembled that in psychophysical measurements on average, although the individual responses were somewhat varied. The present results suggest that the basic configuration of the temporal window of visual effects on auditory-speech perception could be observed from the early auditory processing stage.

Summary Purpose: To assess neuromagnetic spike localization as an indication for extended lesionectomy of cavernoma. Methods: Electroencephalography (EEG) and magnetoencephalography (MEG) was simultaneously recorded in 17 patients (8 men, mean age 29.7 years) with single cavernoma. The location of the equivalent current dipole (ECD) of the interictal spikes was correlated with the lesion shown by magnetic resonance imaging. Results: Preoperative ECD localization was classified into four types: perilesional, adjacent to the cavernoma only (n = 6); mirror, adjacent to the lesion and at the contralateral homologous site (n = 5); remote, mainly at a remote site in the ipsilateral hemisphere (n = 3); and no spikes (n = 3). The spikes were detected by only MEG in two of five “mirror” and all three “remote” patients. In the mirror group, contralateral spikes were synchronized with the ipsilateral spikes, or also occurred independently. Two “perilesional” and two “mirror” patients became seizure-free and spike-free after extended lesionectomy. In contrast, the other two “mirror” patients had residual seizures and spikes after pure lesionectomy. Conclusion: The detectability of mirror and remote spikes was higher by MEG than by EEG, whereas the detectability of perilesional spikes was similar by MEG and EEG. Therefore, the use of both EEG and MEG will provide the maximum information about spike distribution and propagation. Residual seizures and spikes after pure lesionectomy, but not after extended lesionectomy, in the “mirror” patients suggest the importance of resection of the perilesional irritable zone. Extended resection of the irritable cortex surrounding cavernoma is recommended for better seizure control, particularly in “mirror” patients.

Objective To evaluate whether the orientation of interictal spikes, localized in major sulci by magnetoencephalography (MEG), predicts the epileptogenic side of the sulcal wall. Methods Sixteen epilepsy patients were analyzed in whom equivalent current dipoles (ECDs) of MEG spikes were localized on the central (four patients), interhemispheric (4), or sylvian fissure (8); and the epileptogenic side across the sulci had been confirmed by seizure semiology, structural lesions, or intracranial electroencephalography (EEG). ECD was classified as epileptogenic side or normal side oriented and correlated to the scalp EEG map. Results All central ( n =50) and interhemispheric ( n =83) spike ECDs were oriented toward the epileptogenic side at peak latency. In scalp EEG, 91% of the spikes showed radial pattern of broad negativity above the sulcus whereas 9% showed tangential pattern with positive maximum above the epileptogenic side. Sylvian spikes were only found in patients with temporal lobe epilepsy (TLE). In sylvian spikes ( n =220), 73% of ECDs were oriented toward the epileptogenic side, whereas 27% were oriented toward the normal side. Conclusions In central and interhemispheric spikes, epileptogenic side cortex may be gross surface negative through the sulcal wall to the adjacent gyrus. Inconsistent orientation of the sylvian spikes suggests a complex pattern of spike propagation in TLE. Significance ECD orientation of central and interhemispheric spikes in MEG may predict the epileptogenic side.

Interhemispheric time difference (ITD) measured by electroencephalography (EEG) and magnetoencephalography (MEG) was compared to seizure outcome after callosotomy. Two patients with frequent drop attacks underwent simultaneous EEG and MEG before and after total callosotomy. ITDs in 30 bilateral synchronized (BS) discharges were calculated independently by EEG and MEG. As minimum transcallosal conduction time was suggested to be approximately 20 msec, BS discharges were classified into five categories according to ITD and side: left- or right-leading long (300 to 80 msec), left- or right-leading moderate (80 to 20 msec), and negligible (

The somatotopic organization of the human primary somatosensory (SI) area in the cerebral cortex has been intensively studied for the hand, lip, and tongue, but little is known about the gingiva. Penfield concluded that the gingival SI area was above the tongue area, as shown in his famous homunculus map. However, our recent study suggested that the lingual gingiva area was not so different to the tongue area. To delineate the fine SI somatotopy of the gingiva area, evoked magnetic fields were measured in 6 healthy subjects for the stimulus of the anterior or posterior and upper or lower parts of the lip, buccal and lingual gingiva, and tongue. Source position was estimated by a current dipole model at the first peak of the posterior-oriented current in a total of 12 cerebral hemispheres contralateral to the stimulation side. No significant difference was found between the positions of anterior and posterior or upper and lower parts of each structure. Both buccal and lingual gingiva areas were localized adjacent to the tongue area, but significantly lower than the lip area. We believe that the fine SI somatotopy of the human oral structures should be reconsidered.