EEG-Based Functional Brain Networks: Does the Network Size Matter?

Functional connectivity in human brain can be represented as a network using electroencephalography (EEG) signals. These networks – whose nodes can vary from tens to hundreds – are characterized by neurobiologically meaningful graph theory metrics. This study investigates the degree to which various graph metrics depend upon the network size. To this end, EEGs from 32 normal subjects were recorded and functional networks of three different sizes were extracted. A state-space based method was used to calculate cross-correlation matrices between different brain regions. These correlation matrices were used to construct binary adjacency connectomes, which were assessed with regards to a number of graph metrics such as clustering coefficient, modularity, efficiency, economic efficiency, and assortativity. We showed that the estimates of these metrics significantly differ depending on the network size. Larger networks had higher efficiency, higher assortativity and lower modularity compared to those with smaller size and the same density. These findings indicate that the network size should be considered in any comparison of networks across studies

Identification of TAAR5 Agonist Activity of Alpha-NETA and Its Effect on Mismatch Negativity Amplitude in Awake Rats

Mismatch negativity (MMN) is a well-defined component of human event-related potentials that reflects the pre-attentive, stimulus-discrimination process and is associated with involuntary switching of attention. MMN-like responses detected in animal models provide an opportunity to investigate the neural mechanisms of this process that involves several neurotransmitter and neuromodulator systems. Trace amines are believed to play a significant role in neuromodulation of synaptic transmission. The present study aimed to determine the role of trace amine-associated receptor 5 (TAAR5) in the MMN-like response in rats. First, using a bioluminescence resonance energy transfer (BRET) cAMP biosensor, we performed unbiased screening of TAAR5 ligands from a commercially available compound library (661 compounds) and identified 2-(alpha-naphthoyl)ethyltrimethylammonium iodide (alpha-NETA) as a potent (EC50 150 nM) TAAR5 agonist. Then, we recorded auditory event-related potentials during an oddball paradigm in awake freely moving rats that were intraperitoneally injected with a vehicle or two doses of the putative TAAR5 agonist alpha-NETA. The MMN-like response was increased by alpha-NETA 3 mg/kg dose, but not by 1 mg/kg dose or 0.9% saline solution. These results suggest that the MMN-like response in rats may be modulated, at least in part, through TAAR5-dependent processes

Сurrent problems in energetic materials ignition studies

Several problems of ignition of energetic materials (EMs), which are able to burn in the absence of an external oxidizer, are discussed in this chapter. Scientific investigation of the EMs ignition has started at the end 1930th when the first field missiles (Katyusha) were developed in the USSR. Later the investigations were actively performed in USA and Europe but despite rather long history there still remain unsolved problems related to complete description of nonstationary transition to self-sustaining combustion, correct determination of the ignition moment, determination of the EM high-temperature reaction kinetics, etc. In the early studies, the limiting cases of the EM ignition solely due to exothermic reactions either in the condensed or gas phase were investigated but later it was revealed that formany EMs such reactions can proceed simultaneously in both phases. This implies the necessity of analyzing the ignition mechanisms involving reactions in the condensed as well as in the gas phase. In this chapter, the attention is paid to theoretical description of transient burning rate behavior of the EMs exothermically reacting in both phases, to the formulation of ignition criterion and to the experimental methods of measuring transient burning rate. In addition, the problems of correct determination of the EMs high-temperature kinetics are discussed as well as the problems of ignition of EMs with shielded reacting surface (opaque and semitransparent substances). Obviously, due to restricted volume, the chapter could not answer all questions but its content may become useful for researchers working in this field in order to better understand state of the art of EMs ignition studies and better plan some future researches in this direction