Different coding characteristics between flight and freezing in dorsal periaqueductal gray of mice during exposure to innate threats.

BACKGROUND: Flight and freezing are two vital defensive behaviors that mice display to avoid natural enemies. When they are exposed to innate threats, visual cues are processed and transmitted by the visual system into the emotional nuclei and finally transmitted to the periaqueductal gray (PAG) to induce defensive behaviors. However, how the dorsal PAG (dPAG) encodes the two defensive behaviors is unclear. METHODS: Multi-array electrodes were implanted in the dPAG nuclei of C57BL/6 mice. Two kinds of visual stimuli (looming and sweeping) were used to induce defensive behaviors in mice. Neural signals under different defense behaviors were recorded, and the encoding characteristics of the two behaviors were extracted and analyzed from spike firing and frequency oscillations. Finally, synchronization of neural activity during the defense process was analyzed. RESULTS: The neural activity between flight and freezing behaviors showed different firing patterns, and the differences in the inter-spike interval distribution were mainly reflected in the 2-10 ms period. The frequency band activities under both defensive behaviors were concentrated in the theta band; the active frequency of flight was ~8 to 10 Hz, whereas that of freezing behavior was ~6 to 8 Hz. The network connection density under both defense behaviors was significantly higher than the period before and after defensive behavior occurred, indicating that there was a high synchronization of neural activity during the defense process. CONCLUSIONS: The dPAG nuclei of mice have different coding features between flight and freezing behaviors; during strong looming stimulation, fast neuro-instinctive decision making is required while encountering weak sweeping stimulation, and computable planning late behavior is predicted in the early stage. The frequency band activities under both defensive behaviors were concentrated in the theta band. There was a high synchronization of neural activity during the defense process, which may be a key factor triggering different defensive behaviors.

The Superior Colliculus/Lateral Posterior Thalamic Nuclei in Mice Rapidly Transmit Fear Visual Information Through the Theta Frequency Band.

Animals perceive threat information mainly from vision, and the subcortical visual pathway plays a critical role in the rapid processing of fear visual information. The superior colliculus (SC) and lateral posterior (LP) nuclei of the thalamus are key components of the subcortical visual pathway; however, how animals encode and transmit fear visual information is unclear. To evaluate the response characteristics of neurons in SC and LP thalamic nuclei under fear visual stimuli, extracellular action potentials (spikes) and local field potential (LFP) signals were recorded under looming and dimming visual stimuli. The results showed that both SC and LP thalamic nuclei were strongly responsive to looming visual stimuli but not sensitive to dimming visual stimuli. Under the looming visual stimulus, the theta (θ) frequency bands of both nuclei showed obvious oscillations, which markedly enhanced the synchronization between neurons. The functional network characteristics also indicated that the network connection density and information transmission efficiency were higher under fear visual stimuli. These findings suggest that both SC and LP thalamic nuclei can effectively identify threatening fear visual information and rapidly transmit it between nuclei through the θ frequency band. This discovery can provide a basis for subsequent coding and decoding studies in the subcortical visual pathways.

The adaptive market hypothesis and high frequency trading.

This paper uses NASDAQ order book data for the S&P 500 exchange traded fund (SPY) to examine the relationship between one-minute, informational market efficiency and high frequency trading (HFT). We find that the level of efficiency varies widely over time and appears to cluster. Periods of high efficiency are followed by periods of low efficiency and vice versa. Further, we find that HFT activity is higher during periods of low efficiency. This supports the argument that HFTs seek profits and risk reduction by actively processing information, through limit order additions and cancellations, during periods of lower efficiency and revert to more passive market-making and rebate-generation during periods of higher efficiency. These findings support the argument that the adaptive market hypothesis (AMH) is an appropriate description of how prices evolve to incorporate information.

Effects of fitness qigong and tai chi on middle-aged and elderly patients with type 2 diabetes mellitus.

Currently, qigong and tai chi exercises are the two most common preventive as well as therapeutic interventions for chronic metabolic diseases such as type 2 diabetes mellitus (T2DM). However, the quantitative evaluation of these interventions is limited. This study aimed to evaluate the therapeutic efficacy of qigong and tai chi intervention in middle-aged and older adults with T2DM. The study included 103 eligible participants, who were randomized to participate for 12 weeks, in one of the following intervention groups for the treatment of T2DM: fitness qigong, tai chi, and control group. Three biochemical measures, including fasting plasma glucose (FPG), glycated hemoglobin (HbA1C), and C-peptide (C-P) levels, assessed at baseline and 12 weeks, served as the primary outcome measures. During the training process, 16 of the 103 participants dropped out. After the 12-week intervention, there were significant influences on HbA1C (F2,83 = 4.88, p = 0.010) and C-P levels (F2,83 = 3.64, p = 0.031). Moreover, significant reduction in C-P levels was observed after 12-week tai chi practice (p = 0.004). Furthermore, there was a significant negative correlation between the duration of T2DM and the relative changes in FPG levels after qigong intervention, and the relative changes in HbA1C levels were positively correlated with waist-to-height ratio after tai chi practice. Our study suggests that targeted qigong exercise might have a better interventional effect on patients with a longer duration of T2DM, while tai chi might be risky for people with central obesity. Trial registration: This trial was registered in Chinese Clinical Trial Registry. The registration number is ChiCTR180020069. The public title is "Health-care qigong · study for the prescription of chronic diabetes intervention."

Tunable wideband slot antennas based on printable graphene inks.

Nano-materials could endow electronics with some new functionalities. A slot antenna with a tunable bandwidth, consisting of a planar slot antenna with graphene at the end and a gap located between the ground and a small patch, is proposed in this study. The printed graphene inks deposited onto the antenna are made of graphene powder and graphene oxide aqueous dispersion. Graphene oxide sheets function as effective surfactants providing assistance to form uniform inks; meanwhile, the tailored blending proportions endow the graphene inks with optimized original resistances. Dried graphene inks display alterable electrical resistance under DC voltages and the variation in the resistance affects the radiation of the antenna. The slot antenna realizes an operating bandwidth (reflection coefficient |S11| < -10 dB) from 2.83 GHz to 6 GHz and a maximum frequency shift of 0.54 GHz after applying a DC voltage of less than 15 V. The graphene inks reported in this work integrate the dual advantages of graphene and graphene oxide. They not only provide stable and tunable graphene solution to antennas, but also could expand their applications in many other fields of electronic devices.