The resting microstate networks (RMN): cortical distributions, dynamics, and frequency specific information flow

A brain microstate is characterized by a unique, fixed spatial distribution of electrically active neurons with time varying amplitude. It is hypothesized that a microstate implements a functional/physiological state of the brain during which specific neural computations are performed. Based on this hypothesis, brain electrical activity is modeled as a time sequence of non-overlapping microstates with variable, finite durations (Lehmann and Skrandies 1980, 1984; Lehmann et al 1987). In this study, EEG recordings from 109 participants during eyes closed resting condition are modeled with four microstates. In a first part, a new confirmatory statistics method is introduced for the determination of the cortical distributions of electric neuronal activity that generate each microstate. All microstates have common posterior cingulate generators, while three microstates additionally include activity in the left occipital/parietal, right occipital/parietal, and anterior cingulate cortices. This appears to be a fragmented version of the metabolically (PET/fMRI) computed default mode network (DMN), supporting the notion that these four regions activate sequentially at high time resolution, and that slow metabolic imaging corresponds to a low-pass filtered version. In the second part of this study, the microstate amplitude time series are used as the basis for estimating the strength, directionality, and spectral characteristics (i.e., which oscillations are preferentially transmitted) of the connections that are mediated by the microstate transitions. The results show that the posterior cingulate is an important hub, sending alpha and beta oscillatory information to all other microstate generator regions. Interestingly, beyond alpha, beta oscillations are essential in the maintenance of the brain during resting state.Comment: pre-print, technical report, The KEY Institute for Brain-Mind Research (Zurich), Kansai Medical University (Osaka

Innovations orthogonalization: a solution to the major pitfalls of EEG/MEG "leakage correction"

The problem of interest here is the study of brain functional and effective connectivity based on non-invasive EEG-MEG inverse solution time series. These signals generally have low spatial resolution, such that an estimated signal at any one site is an instantaneous linear mixture of the true, actual, unobserved signals across all cortical sites. False connectivity can result from analysis of these low-resolution signals. Recent efforts toward "unmixing" have been developed, under the name of "leakage correction". One recent noteworthy approach is that by Colclough et al (2015 NeuroImage, 117:439-448), which forces the inverse solution signals to have zero cross-correlation at lag zero. One goal is to show that Colclough's method produces false human connectomes under very broad conditions. The second major goal is to develop a new solution, that appropriately "unmixes" the inverse solution signals, based on innovations orthogonalization. The new method first fits a multivariate autoregression to the inverse solution signals, giving the mixed innovations. Second, the mixed innovations are orthogonalized. Third, the mixed and orthogonalized innovations allow the estimation of the "unmixing" matrix, which is then finally used to "unmix" the inverse solution signals. It is shown that under very broad conditions, the new method produces proper human connectomes, even when the signals are not generated by an autoregressive model.Comment: preprint, technical report, under license "Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0)", https://creativecommons.org/licenses/by-nc-nd/4.0

Outer retinal circular structures in patients with Bietti crystalline retinopathy.

[Background] : Bietti crystalline retinopathy (BCR) is a distinct retinal degenerative disease characterised by retinal degeneration with many yellow–white crystals located mainly at the posterior pole area. Using spectral domain-optical coherence tomography (SD-OCT), the structural change in retina was investigated. [Methods] : Patients diagnosed with BCR (n=12), retinitis pigmentosa (RP, n=292) and cone dystrophy (n=16) were included in this study. The authors mainly examined fundus photographs and SD-OCT, infrared and fundus autofluorescence images of these patients. [Results]: Crystalline deposits were detected in portions of the retinal pigment epithelium that lacked patchy degenerated lesions. SD-OCT revealed that most of the observed crystalline deposits were located adjacent to the inner side of retinal pigment epithelium layer. The change most frequently observed was circular hyper-refractive structures in the outer nuclear layer. Although the structures were considered to be previously reported “tubular formation” or “tubular degeneration”, we determined that many of these circular structures were slices of spherical structures and were typically noted in areas suspected of ongoing active degeneration. [Conclusion] : BCR has characteristic structures in the outer nuclear layer. Although the incidence of the structure varies, it may be characteristic of retinal degeneration and can be found in many retinal degenerative diseases

Concentric division of 10° visual field tests in retinitis pigmentosa.

The purpose of this study was to estimate the optimal size of visual field test for detecting longitudinal changes in retinitis pigmentosa (RP) by dividing the visual field

High intensity all-out exhaustive exercise enhances taste sensitivity to sour but not to sweet compounds.

Sensitivity of taste sensations following exercise has been the focus of several studies with the outcomes somewhat equivocal and seemingly dependent on the type, duration, and intensity of exercise. Very few studies have looked at the infl uence of high intensity all-out exhaustive exercise on taste sensitivities and the purpose of present study was to assess the infl uence of this high-level of exercise on sensitivity to sweet and sour compounds. Four healthy young adult males and one female (mean ± SD: 23.2 ± 5.5 yrs) served as subjects. The exercise load was set to 80% of the maximal workload. The exercise trials required the subject to pedal an ergometer at the prescribed load until exhaustion, rest for three minutes, and then repeat this load until exhaustion again. Taste sensitivities to six levels of concentrations of sweet (sucrose) and sour (citric acid) compounds were assessed by the triangle test method before and after (10 mins.) completing the exercise. Each subject repeated the exercise on five separate occasions. The distinction rate for each compound concentration for each subject was calculated using inverse sine transformation. The derived sensitivity values were then analyzed by two way repeated measures ANOVA. The sensitivity to sucrose was not affected by exercise (p>0.05), nor was any interaction evident between the sucrose concentrations and exercise (p>0.05). However, sensitivity to citric acid was affected by the exercise (F1,4=14.09, P<0.02) with a much higher level of sensitivity following exercise. We believe that these outcomes provide additional direction for further study on the impact of exercise on specifi c taste sensitivities

A pharmaco-EEG study on antipsychotic drugs in healthy volunteers

Rationale: Both psychotropic drugs and mental disorders have typical signatures in quantitative electroencephalography (EEG). Previous studies found that some psychotropic drugs had EEG effects opposite to the EEG effects of the mental disorders treated with these drugs (key-lock principle). Objectives: We performed a placebo-controlled pharmaco-EEG study on two conventional antipsychotics (chlorpromazine and haloperidol) and four atypical antipsychotics (olanzapine, perospirone, quetiapine, and risperidone) in healthy volunteers. We investigated differences between conventional and atypical drug effects and whether the drug effects were compatible with the key-lock principle. Methods: Fourteen subjects underwent seven EEG recording sessions, one for each drug (dosage equivalent of 1mg haloperidol). In a time-domain analysis, we quantified the EEG by identifying clusters of transiently stable EEG topographies (microstates). Frequency-domain analysis used absolute power across electrodes and the location of the center of gravity (centroid) of the spatial distribution of power in different frequency bands. Results: Perospirone increased duration of a microstate class typically shortened in schizophrenics. Haloperidol increased mean microstate duration of all classes, increased alpha 1 and beta 1 power, and tended to shift the beta 1 centroid posterior. Quetiapine decreased alpha 1 power and shifted the centroid anterior in both alpha bands. Olanzapine shifted the centroid anterior in alpha 2 and beta 1. Conclusions: The increased microstate duration under perospirone and haloperidol was opposite to effects previously reported in schizophrenic patients, suggesting a key-lock mechanism. The opposite centroid changes induced by olanzapine and quetiapine compared to haloperidol might characterize the difference between conventional and atypical antipsychotic

SYNTHESIS OF EVERNITROSE AND ITS ENANTIOMER

Evernitrose (1: 2,3,6-trideoxy-3-C,4-0-dimethyl-3-nitro-Larabino-hexopyranose) and its enantiomer (17) were synthesized frommethyl 2,6-dideoxy-4-o-methyl-a-L-erythro-hexopyranosid-3-ulose and methyl 4,6-o-benzylidene-2-deoxy-a-D-erythro-hexopyranosid-3-ulose, respectively. In both cases, the unique nitro group attached to thetertiary branching carbon was introduced by oxidation of the corresponding amino derivatives prepared by Bourgeois\u27s method

Wide-Field Fundus Autofluorescence Abnormalities and Visual Function in Patients With Cone and Cone-Rod Dystrophies

METHODS. Sixteen patients with cone dystrophy (CD) and 41 patients with cone-rod dystrophy (CRD) were recruited at one institution. The right eye of each patient was included for analysis. We obtained wide-field FAF images using a ultra-widefield retinal imaging device and measured the area of abnormal FAF. The association between the area of abnormal FAF and the results of visual acuity measurements, kinetic perimetry, and electroretinography (ERG) were investigated. RESULTS. The mean age of the participants was 51.4 6 17.4 years, and the mean logarithm of the minimum angle of resolution was 1.00 6 0.57. The area of abnormal FAF correlated with the scotoma measured by the Goldman perimetry I/4e isopter (q ¼ 0.79, P &lt; 0.001). The area also correlated with amplitudes of the rod ERG (q ¼ À0.63, P &lt; 0.001), combined ERG awave (q ¼ À0.72, P &lt; 0.001), combined ERG b-wave (q ¼ À0.66, P &lt; 0.001), cone ERG (q ¼ À0.44, P ¼ 0.001), and flicker ERG (q ¼ À0.47, P &lt; 0.001). CONCLUSIONS. The extent of abnormal FAF reflects the severity of functional impairment in patients with cone-dominant retinal dystrophies. Fundus autofluorescence measurements are useful for predicting retinal function in these patients

Branched-chain Sugars. XIX. On the Application of 13C NMR Spectroscopy to the Configurational Assignment of 3-C-Substituents of Aldohexopyranose Derivatives

It was found that 13C NMR spectroscopy is applicable to the unequivocal configurational assignment at the quarternary carbon in seven pairs of 3-C-substituted-hexopyranose derivatives. The configuration of methyl 4,6-O-benzylidene-3-C-nitromethyl-2-O-p-tolylsulfonyl-α-D-glucopyranoside reported by Jordaan et al. is revised to D-allo by a chemical method