Detection of Intrinsic Optical Signals in the Somatosensory Cortex of Neonatal Rats by Principal Components Analysis

© 2018, Springer Science+Business Media, LLC, part of Springer Nature. Recording of the intrinsic optical signal (IOS) is widely used or functional studies of the cerebral cortex in vivo. Despite the fact that IOS provides for detection of active areas, regardless of the age of the object, it is widely used in studies of the developing brain. However, in immature brains IOS has low amplitude, which hinders its use and requires other recording and analysis methods. We report here our assessment of the use of the principal components analysis (PCA) method for the automatic detection of IOS at the early stages of development of the rat brain. Recording of IOS in infrared light and use of PCA was found to provide reliable detection of IOS in rats in the first three weeks after birth. Addition of artificial noise to IOS showed that detection using PCA was effective in half of cases despite increases in the noise level to four times baseline. These results provide evidence that the PCA method has potential to be used for detecting IOS at the early stages of development and that the PCA method is very robust for detection of IOS

Developmental changes in sensory-evoked optical intrinsic signals in the rat barrel cortex

© 2017 Sintsov, Suchkov, Khazipov and Minlebaev. Optical Intrinsic Signal imaging (OISi) is a powerful technique for optical brain studies. OIS mainly reflects the hemodynamic response (HR) and metabolism, but it may also involve changes in tissue light scattering (LS) caused by transient cellular swelling in the active tiss ue. Here, we explored the developmental features of sensory-evoked OIS in the rat barrel cortex during the first 3 months after birth. Multispectral OISi revealed that two temporally distinct components contribute to the neonatal OIS: an early phase of LS followed by a late phase of HR. The contribution of LS to the early response was also evidenced by an increase in light transmission through the active barrel. The early OIS phase correlated in time and amplitude with the sensory-evoked electrophysiological response. Application of the Modified Beer-Lambert Law (MBLL) to the OIS data revealed that HR during the early phase involved only a slight decrease in blood oxygenation without any change in blood volume. In contrast, HR during the late phase manifested an adult-like increase in blood volume and oxygenation. During development, the peak time of the delayed HR progressively shortened with age, nearly reaching the stimulus onset and overlapping with the early LS phase by the fourth postnatal week. Thus, LS contributes to the sensory-evoked OIS in the barrel cortex of rats at all ages, and it dominates the early OIS phase in neonatal rats due to delayed HR. Our results are also consistent with the delayed blood oxygen level dependent (BOLD) signal in human preterm infants

Improved Recordings of the Optical Intrinsic Signals in the Neonatal Rat Barrel Cortex

© 2016, Springer Science+Business Media New York.Optical imaging of intrinsic signals (OIS) is widely used for the functional cortical mapping in vivo. Recently, OIS is also implemented for the functional mapping in the neonatal rat barrel cortex. However, the OIS is characterized by relatively low signal to noise ratio (SNR). Here, we determined parameters for post hoc data analysis that allowed improving OIS mapping and analysis in the developing rat barrel cortex in vivo. We found that application of spatial Gaussian filtering with sigma of 1 px increases the OIS SNR almost twofold. Additional light correction and low-pass temporal filtering with 1 s window size resulted in further improvement of the OIS SNR. Thus, the proposed digital filtering can substantially improve quality of the OIS recordings in the developing somatosensory cortex

Attenuation of the Early Gamma Oscillations During the Sensory-Evoked Response in the Neonatal Rat Barrel Cortex

© 2016, Springer Science+Business Media New York.Whisker stimulation evokes bursts of activity organized in gamma frequency band oscillations in the corresponding barrel of the neonatal rat barrel cortex, so called early gamma oscillations (EGOs). Here, we show that EGO properties dynamically change during the sensory-evoked response, including (i) a progressive decrease in the EGOs’ dominant frequency, (ii) a decrease in the gamma trough amplitudes, and (iii) a reduction in the multiple unit firings in association with each consecutive EGOs’ trough. Circular statistics of the multiple unit activity in relation to EGOs revealed a progressive decrease in the Rayleigh vector amplitude yet without any significant change in its angle. Thus, EGO properties and synchronization of the cortical barrel units dynamically change through the time course of the sensory-evoked response in the neonatal rat barrel cortex

Somatosensory-Evoked Early Sharp Waves in the Neonatal Rat Hippocampus

The developing entorhinal–hippocampal system is embedded within a large-scale bottom-up network, where spontaneous myoclonic movements, presumably via somatosensory feedback, trigger hippocampal early sharp waves (eSPWs). The hypothesis, that somatosensory feedback links myoclonic movements with eSPWs, implies that direct somatosensory stimulation should also be capable of evoking eSPWs. In this study, we examined hippocampal responses to electrical stimulation of the somatosensory periphery in urethane-anesthetized, immobilized neonatal rat pups using silicone probe recordings. We found that somatosensory stimulation in ~33% of the trials evoked local field potential (LFP) and multiple unit activity (MUA) responses identical to spontaneous eSPWs. The somatosensory-evoked eSPWs were delayed from the stimulus, on average, by 188 ms. Both spontaneous and somatosensory-evoked eSPWs (i) had similar amplitude of ~0.5 mV and half-duration of ~40 ms, (ii) had similar current-source density (CSD) profiles, with current sinks in CA1 strata radiatum, lacunosum-moleculare and DG molecular layer and (iii) were associated with MUA increase in CA1 and DG. Our results indicate that eSPWs can be triggered by direct somatosensory stimulations and support the hypothesis that sensory feedback from movements is involved in the association of eSPWs with myoclonic movements in neonatal rats

Enhancement of CO2 conversion by counterflow gas quenching of the post-discharge region in microwave plasma sustained by gyrotron radiation

A threefold increase in the CO2 conversion and energy efficiency due to the cooling of the post-discharge region by the counter gas flow has been achieved in the plasma of an atmospheric pressure discharge supported by microwave radiation of a gyrotron with a frequency of 24 GHz in a carbon dioxide gas flow. The role of convective heat transfer in the process of gas mixture cooling in the post-discharge region has been experimentally demonstrated. At nitrogen quench gas flow of 4.5 l/min, the CO2 conversion was 23.8 % and energy efficiency was 19.7 %. The possibility of using the flow of cooled gas mixture (CO2,CO,O2) taken from the reactor as quenching gas has been experimentally demonstrated, which made it possible to achieve a CO2 conversion degree of 23.4 % and to eliminate the problem of dilution of reaction products by third-party gases. Based on numerical modeling, it is shown that the increase in the conversion degree upon the destruction of the plasma torch structure is due to the increase in heat exchange with the surrounding atmosphere, and the efficiency of this destruction is determined by the velocity and density of quenching gas.Comment: 20 pages, 14 pages, submitted to the Journal of Energy Chemistry 28.11.202

Preferential initiation and spread of anoxic depolarization in layer 4 of rat barrel cortex

© 2017 Juzekaeva, Nasretdinov, Gainutdinov, Sintsov, Mukhtarov and Khazipov. Anoxic depolarization (AD) is a hallmark of ischemic brain damage. AD is associated with a spreading wave of neuronal depolarization and an increase in light transmittance. However, initiation and spread of AD across the layers of the somatosensory cortex, which is one of the most frequently affected brain regions in ischemic stroke, remains largely unknown. Here, we explored the initiation and propagation of AD in slices of the rat barrel cortex using extracellular local field potential (LFP) recordings and optical intrinsic signal (OIS) recordings. We found that ischemia-like conditions induced by oxygen-glucose deprivation (OGD) evoked AD, which manifested as a large negative LFP shift and an increase in light transmittance. AD typically initiated in one or more barrels and further spread across the entire slice with a preferential propagation through L4. Elevated extracellular potassium concentration accelerated the AD onset without affecting proneness of L4 to AD. In live slices, barrels were most heavily labeled by the metabolic level marker 2,3,5-triphenyltetrazolium chloride, suggesting that the highest metabolic demand is in L4 when compared to the other layers. Thus, L4 is the layer of the barrel cortex most prone to AD, which may be due to the highest metabolic demand and cell density in this layer

Hybrid subterahertz atmospheric pressure plasmatron for plasma chemical applications

This paper presents the results of an experimental study of a new hybrid plasmatron scheme, which was used to realize a gas discharge at atmospheric pressure supported by continuous focused submillimeter radiation with a frequency of 263 GHz. The implemented design allowed organizing a self-consistent interaction between submillimeter radiation and the supercritical plasma in a localized area both in terms of gas flow and electrodynamic. It is experimentally shown that the gas discharge absorbs up to 80% of the introduced submillimeter radiation power. The hybrid subterahertz plasmatron as an effective reactor for non-equilibrium plasma chemical processes was tested for the atmospheric nitrogen fixation

Differentiation of the Pre-Caspian Sandy Plague Foci on the Basis of the Frequency of Epizootic Manifestations

Displayed are the results of epizootiological differentiation of the Pre-Caspian sandy plague focus in the territory supervised by Astrakhan and Elista plague control stations (Volga-Kumsk Interfleuve). This differentiation is significant for further development of epizootiological monitoring practice in the enzootic regions. Using circular extrapolation method, designed is the map of the persistent epizootic region within the last period of the focus activation since 1979 till 2010. Depicted is the dislocation of focus activity nucleuses and areas where short-term epizootic process is registered. Identified are their qualitative characteristics. Determined is the fact that density of plague-positive samples in the nucleuses is much higher, than in the areas with non-recurring manifestations. This cartographic differentiation model can be used for justified and substantiated planning of epidemiological control measures and further investigation of problems related to plague epizootiology