Leaky integrate and fire models coupled through copulas: association properties of the interspike intervals

We propose a model able to describe the Interspike Intervals of two or more neurons subject to common inputs from the network. The single neuron dynamic is described through a classical Leaky Integrate and Fire model, but the model also catches the joint behavior of two neurons resorting to the use of copulas. Copulas are mathematical objects largely used to describe dependencies laws. Synchronous and delayed dependencies are considered by means of a set of examples. Results are discussed making use of crosscorrelograms.     

The dynamics of EEG entropy

The scaling properties of human EEG have so far been analyzed predominantly in the framework of detrended fluctuation analysis (DFA). In particular, these studies suggested the existence of power-law correlations in EEG. In DFA, EEG time series are tacitly assumed to be made up of fluctuations, whose scaling behavior reflects neurophysiologically important information and polynomial trends. Even though these trends are physiologically irrelevant, they must be eliminated (detrended) to reliably estimate such measures as Hurst exponent or fractal dimension. Here, we employ the diffusion entropy method to study the scaling behavior of EEG. Unlike DFA, this method does not rely on the assumption of trends superposed on EEG fluctuations. We find that the growth of diffusion entropy of EEG increments of awake subjects with closed eyes is arrested only after approximately 0.5 s. We demonstrate that the salient features of diffusion entropy dynamics of EEG, such as the existence of short-term scaling, asymptotic saturation, and alpha wave modulation, may be faithfully reproduced using a dissipative, first-order, stochastic differential equation—an extension of the Langevin equation. The structure of such a model is utterly different from the “noise+trend” paradigm of DFA. Consequently, we argue that the existence of scaling properties for EEG dynamics is an open question that necessitates further studies.     

Mechanical properties of zona pellucida hardening

We have investigated the changes in the mechanical properties of the zona pellucida (ZP), a multilayer glycoprotein coat that surrounds mammalian eggs, that occur after the maturation and fertilization process of the bovine oocyte by using atomic force spectroscopy. The response of the ZP to mechanical stress has been recovered according to a modified Hertz model. ZP of immature oocytes shows a pure elastic behavior. However, for ZPs of matured and fertilized oocyte, a transition from a purely elastic behavior, which occurs when low stress forces are applied, towards a plastic behavior has been observed. The high critical force necessary to induce deformations, which supports the noncovalent long interaction lifetimes of polymers, increases after the cortical reaction. Atomic force microscopy (AFM) images show that oocyte ZP surface appears to be composed mainly of a dense, random meshwork of nonuniformly arranged fibril bundles. More wrinkled surface characterizes matured oocytes compared with immature and fertilized oocytes. From a mechanical point of view, the transition of the matured ZP membrane toward fertilized ZP, through the hardening process, consists of the recovery of the elasticity of the immature ZP while maintaining a plastic transition that, however, occurs with a much higher force compared with that required in matured ZP.     

Population structure and dynamics of <Emphasis Type="Italic">Procambarus clarkii</Emphasis> (Girard, 1852) in a Mediterranean brackish wetland (Central Italy)

In 2006 an unusual find of Procambarus clarkii, today considered one of the most dangerous exotic crayfish, was made within the preserved brackish Mediterranean biotope “Palude di Torre Flavia” (Rome, Italy). Here the investigation on the population structure and dynamics of P. clarkii inhabiting this brackish wetland is presented in an attempt to describe the life history pattern in this type of habitat. The present study showed that this species has a lower growth rate and higher longevity than other studied European P. clarkii populations, and that it can damage brackish habitats and human livelihoods. The main results of this study chiefly concern the differences found between several life-history parameters of the studied population and those obtained in previous studies. These results showed the high ecological plasticity of P. clarkii, indicate the need to intervene before the species spreads further in brackish water, for the conservation of Mediterranean coastal habitats.     

Brain Response to a Humanoid Robot in Areas Implicated in the Perception of Human Emotional Gestures

Background

The humanoid robot WE4-RII was designed to express human emotions in order to improve human-robot interaction. We can read the emotions depicted in its gestures, yet might utilize different neural processes than those used for reading the emotions in human agents.

Methodology

Here, fMRI was used to assess how brain areas activated by the perception of human basic emotions (facial expression of Anger, Joy, Disgust) and silent speech respond to a humanoid robot impersonating the same emotions, while participants were instructed to attend either to the emotion or to the motion depicted.

Principal Findings

Increased responses to robot compared to human stimuli in the occipital and posterior temporal cortices suggest additional visual processing when perceiving a mechanical anthropomorphic agent. In contrast, activity in cortical areas endowed with mirror properties, like left Broca''s area for the perception of speech, and in the processing of emotions like the left anterior insula for the perception of disgust and the orbitofrontal cortex for the perception of anger, is reduced for robot stimuli, suggesting lesser resonance with the mechanical agent. Finally, instructions to explicitly attend to the emotion significantly increased response to robot, but not human facial expressions in the anterior part of the left inferior frontal gyrus, a neural marker of motor resonance.

Conclusions

Motor resonance towards a humanoid robot, but not a human, display of facial emotion is increased when attention is directed towards judging emotions.

Significance

Artificial agents can be used to assess how factors like anthropomorphism affect neural response to the perception of human actions.     

Interactions between yeasts, fungicides and apple fruit russeting

The effect of inoculations with yeasts occurring on apple surfaces and fungicide treatments on the russeting of Elstar apples was studied. Captan, dithianon and a water treatment were implemented to study the interaction between the fungicides, the inoculated yeast species and Aureobasidium pullulans, and the development of russet. All yeast inoculations aggravated russet, but Rhodotorula glutinis, Sporidiobolus pararoseus and A. pullulans did so to a greater extent than the other species. Both captan and dithianon significantly reduced russeting. Denaturing gradient gel electrophoresis analysis showed that inoculations with R. glutinis and S. pararoseus seemed to suppress other yeast species present on the apple surface.     

Timing the generation of distinct retinal cells by homeobox proteins

The reason why different types of vertebrate nerve cells are generated in a particular sequence is still poorly understood. In the vertebrate retina, homeobox genes play a crucial role in establishing different cell identities. Here we provide evidence of a cellular clock that sequentially activates distinct homeobox genes in embryonic retinal cells, linking the identity of a retinal cell to its time of generation. By in situ expression analysis, we found that the three Xenopus homeobox genes Xotx5b, Xvsx1, and Xotx2 are initially transcribed but not translated in early retinal progenitors. Their translation requires cell cycle progression and is sequentially activated in photoreceptors (Xotx5b) and bipolar cells (Xvsx1 and Xotx2). Furthermore, by in vivo lipofection of “sensors” in which green fluorescent protein translation is under control of the 3′ untranslated region (UTR), we found that the 3′ UTRs of Xotx5b, Xvsx1, and Xotx2 are sufficient to drive a spatiotemporal pattern of translation matching that of the corresponding proteins and consistent with the time of generation of photoreceptors (Xotx5b) and bipolar cells (Xvsx1 and Xotx2). The block of cell cycle progression of single early retinal progenitors impairs their differentiation as photoreceptors and bipolar cells, but is rescued by the lipofection of Xotx5b and Xvsx1 coding sequences, respectively. This is the first evidence to our knowledge that vertebrate homeobox proteins can work as effectors of a cellular clock to establish distinct cell identities.     

The decline of swimming performance with advancing age: a cross-sectional study

The aim of this cross-sectional study was to measure the swimming parameters-speed (V), stroke frequency (SF), and stroke length (SL)- in 162 male athletes aged 50-90 (divided into 7 age groups, from A to G) participating in the World Master Championships in the 200-m freestyle event, and to analyze the rates and magnitudes of their age-associated declines. The swimmers were video-recorded by 2 digital cameras during the competitions and the swimming parameters related to every 50-m section (lap) and to the entire race (average) subsequently measured or calculated. Lap V and SF decreased in the second and third quarter (11 and 4% on average) and increased (3% on average) in the fourth quarter of the race, whereas lap SL decreased from the first to the last 50-m section. Average V (m.s(-1)) decreased from 1.39 +/- 0.09 (group A) to 0.84 +/- 0.11 (group G); average SL (m) decreased from 2.10 +/- 0.20 (group A) to 1.78 +/- 0.19 (group G); and average SF (cycles.s(-1)) decreased from 0.67 +/- 0.06 (group A) to 0.47 +/- 0.04 (group G). One-way analysis of variance showed significant declines in average V, SL, and SF (p < 0.01) across the 7 groups. The swimming parameters were normalized to the highest values (set equal to 100); thereafter, a linear regression curve was fitted and the regression equations calculated. Decline of SF was about 2.5 times steeper than that of SL. It was highlighted that (a) among the swimming parameters, SL is less affected by the ageing process; (b) SL decreased from group A through group C and thereafter tended to keep steady, whereas the trend for SF was opposite. The results have the potential to give master swimmers and their coaches useful information for training program design.     

DNA methylation polymorphisms precede any histological sign of atherosclerosis in mice lacking apolipoprotein E

The present work investigates the occurrence and significance of aberrant DNA methylation patterns during early stages of atherosclerosis. To this end, we asked whether the genetically atherosclerosis-prone APOE-null mice show any changes in DNA methylation patterns before the appearance of histologically detectable vascular lesion. We exploited a combination of various techniques: DNA fingerprinting, in vitro methyl-accepting assay, 5-methylcytosine quantitation, histone post-translational modification analysis, Southern blotting, and PCR. Our results show that alterations in DNA methylation profiles, including both hyper- and hypomethylation, were present in aortas and PBMC of 4-week-old mutant mice with no detectable atherosclerotic lesion. Sequencing and expression analysis of 60 leukocytic polymorphisms revealed that epigenetic changes involve transcribed genic sequences, as well as repeated interspersed elements. Furthermore, we showed for the first time that atherogenic lipoproteins promote global DNA hypermethylation in a human monocyte cell line. Taken together, our results unequivocally show that alterations in DNA methylation profiles are early markers of atherosclerosis in a mouse model and may play a causative role in atherogenesis.