Hideaki Tanaka

Assessing interactions in the brain with exact low-resolution electromagnetic tomography

Scalp electric potentials (electroencephalogram; EEG) are contingent to the impressed current density unleashed by cortical pyramidal neurons undergoing post-synaptic processes. EEG neuroimaging consists of estimating the cortical current density from scalp recordings. We report a solution to this inverse problem that attains exact localization: exact low-resolution brain electromagnetic tomography (eLORETA). This non-invasive method yields high time-resolution intracranial signals that can be used for assessing functional dynamic connectivity in the brain, quantified by coherence and phase synchronization. However, these measures are non-physiologically high because of volume conduction and low spatial resolution. We present a new method to solve this problem by decomposing them into instantaneous and lagged components, with the lagged part having almost pure physiological origin.

Cognitive deficits in amyotrophic lateral sclerosis evaluated by event-related potentials

OBJECTIVEnTo determine the cognitive profiles in non-demented, relatively less handicapped patients with early-stage sporadic amyotrophic lateral sclerosis (ALS) by using neuropsychological tests, event-related potentials (ERPs) and clinical scale.nnnMETHODSnWe recruited 19 patients with sporadic ALS (eight with limb-onset, 11 with bulbar-onset) and 19 controls. In addition to the mini-mental state examination and the Wechsler adult intelligence scale-revised, we assessed the frontal lobe function with Wisconsin card sorting test, Stroop test and trail making test. We used auditory oddball counting paradigm for the ERPs under 20-channel electroencephalogram (EEG) recording. Global field power (GFP) was computed, and its peak amplitudes and latencies of N1/N2/P3 were determined. The results of ERP and neuropsychological tests were correlated with respiratory function and clinical scale.nnnRESULTSnNo global cognitive impairment except for subtle frontal dysfunction was detected, although N1/N2/P3 GFP latencies were significantly prolonged in ALS patients than in the controls. Vital capacity correlated with P3 GFP amplitude, and the relative bulbar functional rating scale correlated with P3 GFP latency.nnnCONCLUSIONSnOur findings indicated the presence of sub-clinical cognitive deficits in non-demented, sporadic ALS patients. In addition, clinical sub-types and respiratory function dependently influenced cognitive function in patients with sporadic ALS.nnnSIGNIFICANCEnERP confirmed cognitive impairment in patients with sporadic ALS.

Monitoring cortical hemodynamic changes after sumatriptan injection during migraine attack by near-infrared spectroscopy

The aim of the present study is to provide effective tools for monitoring hemodynamic changes in the cortical and scalp surface during migraine attack and treatment. Using near-infrared spectroscopy system (NIRS) and laser Doppler skin blood flow (SkBF) devices in combination, we monitored changes in extra- and intra-cranial vasculature states upon sumatriptan injection during spontaneous migraine attack. We examined 4 control subjects and 4 migraine patients. Multi-channel NIRS probes were placed over the temporoparietal area bilaterally and oxygenated hemoglobin (oxy-Hb) was analyzed. Laser Doppler SkBF was simultaneously recorded to measure scalp surface blood flow changes. All patients were treated with a sumatriptan injection (3 mg), and all control subjects received a saline injection as a control for oxy-Hb/SkBF signals caused by injection pain over the monitoring period. There was a marked reduction of oxy-Hb/SkBF in all patients after sumatriptan injection, consistent with pain relief. Moreover, the changes in oxy-Hb/SkBF were significantly correlated. By contrast, saline injection did not cause any significant changes. These data suggest that sumatriptan induces blood vessel contraction at both cortical and scalp surfaces. Simultaneous oxy-Hb/SkBF recording enables real-time continuous monitoring of the effects of sumatriptan treatment in clinical situations.

Cognition and event-related potentials in adult-onset non-demented myotonic dystrophy type 1.

OBJECTIVEnTo clarify the cognitive and event-related potentials (ERPs) profiles of adult-onset genetically-proven non-demented myotonic dystrophy type 1 (DM1).nnnMETHODSnFourteen DM1 patients and matched 14 normal controls were enrolled. DM1 patients were compared with normal controls, using a variety of neuropsychological tests; an auditory oddball counting paradigm for the ERPs, and low-resolution brain electromagnetic tomography (LORETA). For patients, ERPs and neuropsychological parameters were correlated with CTG repeat size, duration of illness, grip strength, and arterial blood gas analysis.nnnRESULTSnFrontal lobe dysfunction, prolonged N1 latency, and attenuated N2/P3 amplitudes were observed in DM1. Longer CTG repeat size was associated with fewer categories achieved on Wisconsin Card Sorting Test. Greater grip strength was associated with better scores on color-word interference of Stroop test. P3 latency was negatively correlated with PaO(2). LORETA revealed significant hypoactivities at the orbitofrontal and medial temporal lobe, cingulate, and insula. There was no correlation between ERPs and CTG expansion.nnnCONCLUSIONSnAdult-onset non-demented DM1 presented frontal lobe dysfunction. Absence of correlations between CTG repeat size and objective ERP parameters suggested CTG expansion in lymphocytes does not directly contribute to cognitive dysfunction.nnnSIGNIFICANCEnCTG expansion in lymphocytes does not directly contribute to cognitive dysfunction of adult-onset non-demented DM1.

PHANTOM ARM AND LEG AFTER PONTINE HEMORRHAGE

The phantom limb appears not only after limb amputation1 but also after brain damage (known as supernumerary phantom limb [SPL]).2 A previous review1 on phantom limb following limb amputation proposed the remapping hypothesis of topographic reorganization of somatosensory cortex in which the referred sensation from the neighboring receptive field to phantoms is one of at least five possible sources for phantom sensation. On the other hand, the current theories of SPL emphasize the dissociation between established sensorimotor limb representation and marked changes in afferent and efferent signals in brain–limb communication.3,4nnThere is little information about SPL in patients with brainstem damage,5 which has somewhat different characteristics from phantom sensations following supratentorial cerebral lesions, as well as from phantoms following limb amputation. Here we address the contribution of the brainstem to SPL.nn### Case reports.nnA 47-year-old woman (Case 1) and a 55-year-old man (Case 2) developed acute pontine hemorrhage (figure, A [a, b] and B [a, b]). They survived a locked-in period with complete paralysis except for vertical eye movements. The neurologic examination …

Acceleration time ratio for the assessment of extracranial internal carotid artery stenosis.

PurposeTo apply the acceleration time (AcT) ratio as an additional marker for diagnosing internal carotid artery (ICA) stenosis.MethodsCarotid artery sonography was performed in 140 patients, and the AcT ratio was calculated as the AcT of the ICA divided by the AcT of the ipsilateral common carotid artery, and compared with diameter stenosis.ResultsThere was a significant correlation between diameter stenosis and the AcT ratio. The receiver operating characteristic curve revealed a cutoff level of 1.5, with 90.0xa0% sensitivity and 93.5xa0% specificity for stenosis >65xa0%.ConclusionOur results indicate that applying the AcT ratio can help in the diagnosis of ICA stenosis.

The photic driving response in electroencephalogram in migraine patients

It is well known that the migraine patients indicate abnormal information processing such as photic supersensitivity. And it is high incidence and an aggravation factor of migraine attack. In addition, it is included in the diagnostic criteria of ICHD-II. However, the underlining mechanism is still open for discussion. Our study aimed to investigate the photic driving responses of the electroencephalogram (EEG) with source localizing method. We recorded spontaneous eyes-closed resting EEG from 20 electrodes on the scalp during their inter-ictal phase. Stroboscope flashes consisting of 3-5-8-10-13-15-18-20 Hz were used. After recording, each photic stimulation was selected respectively. And we examined the relation between clinical backgrounds and the prophylaxis. In addition, we analyzed EEG by FFT and observed the frequency peaks and its topographies responded for photic stimulation. The photic driving response could be observed in higher flashing rate than 15 Hz in addition to lower flashing rate. And the case as having photic supersensitivity tended to show a lot of photic driving regardless of migraine subtypes. Moreover, in topographies, their activated areas were shifted anterior from fundamental driving to harmonic driving for each photic frequency. This anterior shift was more evident for longer duration of illness, although no significant differences between subgroups. And the global field power (GFP) value had a positive correlation between the duration of the illness. We conclude that high incidences of photic hypersensitivity and photic driving response in migraineurs were confirmed. The underlying mechanism of photic hypersensitivity might result in sensitization of limbic system.

The Value of Quantitative EEG Measures in the Early Diagnosis of Alzheimer’s Disease

There is growing interest in the discovery of clinically useful, robust biomarkers for Alzheimer’s disease (AD) and pre-AD; the ability to accurately diagnose AD or to predict conversion from a preclinical state to AD would aid in both prevention and early intervention. This study aimed to evaluate the usefulness of a statistical assessment of cortical activity using electroencephalograms (EEGs) with normative data and the ability of such an assessment to contribute to the diagnosis of AD. 15 patients with AD and 8 patients with mild cognitive impairment (MCI) were studied. Eyes-closed resting EEGs were digitally recorded at 200 Hz from 20 electrodes placed according to the international 10/20 system on the scalp, and 20 artifact-free EEG epochs lasting 2.56 ms were selected. Each EEG epoch was down-sampled to 100 Hz and matched to the normal data sets. The selected EEGs from each subject were analyzed by standardized Low Resolution Electromagnetic Tomography (sLORETA) and statistically compared with the age-matched normal data sets at all frequencies. This procedure resulted in cortical z values for each EEG frequency with 0.39 Hz frequency resolution for each subject. Some of the AD and MCI patients presented a peak of negative z value around 20 Hz, revealing hypoactivity of the parahippocampal gyrus and the insula in the sLORETA cortical image. In addition, severe cases of AD showed decreased parietal activation. These results were in agreement with evidence from statistical neuroimaging using MRI/SPECT. Submission of normal EEG data sets to sLORETA might be useful for the detection of diagnostic and predictive markers of AD and MCI in individual patients. The Value of Quantitative EEG Measures in the Early Diagnosis of Alzheimer’s Disease

51. Evaluation of cognitive function in migraine patients – A study using sLORETA

The aim of this study is to clarify the neurophysiological mechanism of cognitive impairments in migraine patients. We evaluated the relationships between event-related potentials (ERPs) and clinical parameters. Thirty-one migraine patients diagnosed by ICHD-II were submitted for this study. They were enrolled in headache-free periods. Clinical subtype (with/without aura), severity, duration, and preventative medicine use were evaluated as clinical parameters. We used 2 tones counting oddball paradigm to elicit P3 activities. EEG was recorded from 20 electrodes on the scalp according to international 10/20 system. We assessed the distribution of generator activity in the cortex by standardized low-resolution brain electromagnetic tomography (sLORETA). Regression analyzes of these clinical parameters and ERP source activities for the entire time frame was computed using sLORETA. sLORETA revealed a significant negative correlation in both attack frequency per a month and preventative medicine use in the cingulate gyrus and superior frontal gyrus 280 ms after the onset of target stimuli. Therefore, migraine patients might have impairment of cognitive function, such as executive dysfunction. The dysfunction is reflected by the attenuated activity of the frontal gyrus in sLORETA.

Evaluation of cognitive function in migraine patients-a study using event-related potential

It is known that cognitive impairments can be observed in some patients with migraine. To clarify the neurophysiological mechanism of cognitive impairments in migraine patients, we evaluated the relationships between event-related potentials (ERPs) and various behavioral data such as performance, subtype, severity, duration, and usage of preventive medicine. Thirty one patients suffering from migraine without and with aura were enrolled in headache-free periods. Severity of the headache was assessed by headache impact test-6(HIT-6). Two tones counting auditory oddball paradigm was used for the ERPs. EEG was recorded from 20 channels on the scalp and recomputed global field power (GFP) from the all channel. We assessed counting performance and the P3 GFP peak amplitude and latency. Forty four percent of patients (n=15) were classified into the good performance group. There were no differences in age, usage of prophylactic drug, the presence or absence of aura, score of HIT-6, and P3 parameters between the good and poor performance groups. The group of long duration showed decreased P3 GFP peak amplitude and HIT-6 score. The group with preventive treatment significantly had more attacks of the month than the non-medication group. In addition, this group showed prolonged P3 GFP peak latency and decreased P3 GFP peak amplitude. These findings suggest that ERPs abnormalities may reflect abnormal information-processing for the attention preceding target recognition in migraine patients regarding with preventive treatment.