Stimulus-specific adaptation, habituation and change detection in the gaze control system

This prospect article addresses the neurobiology of detecting and responding to changes or unexpected events. Change detection is an ongoing computational task performed by the brain as part of the broader process of saliency mapping and selection of the next target for attention. In the optic tectum (OT) of the barn owl, the probability of the stimulus has a dramatic influence on the neural response to that stimulus; rare or deviant stimuli induce stronger responses compared to common stimuli. This phenomenon, known as stimulus-specific adaptation, has recently attracted scientific interest because of its possible role in change detection. In the barn owl??s OT, it may underlie the ability to orient specifically to unexpected events and is therefore opening new directions for research on the neurobiology of fundamental psychological phenomena such as habituation, attention, and surprise.     

Demonic explanations of disease among Moroccan Jews in Israel

Demonic explanations of disease preserved among Moroccan Jews living in two Israeli moshavim are described and analyzed. Applied most often to sira, a traditional ailment involving somatic and anxiety symptoms, these explanations are construed as a two-level ordered sequence of steps including elements from both ordinary reality and the demonic world. Traditional patients are usually more aware of the manifest chain of precipitating events centering around emotional consequences of a real trauma. Their rabbi-healers, however, are predisposed towards molding these events into a covert-demonic pattern, the core of which involves a human injuring a jinn and the latter's retaliation. In the explanatory scheme the real-traumatic and the demonic plots are intermingled and this fusion lends the etiological sequence a meaningful rationale as exemplified by two case illustrations. Nevertheless, our analysis renders the demonic substratum quite vulnerable, since the manifest-traumatic plot may be singled out as an autonomous explanation under the impact of the mainstream of modern Israeli society. Reasons for the hitherto tenacious preservation of the demonic component among traditional segments in Israel are presented by comparing the explanatory status of demons and psychoanalytic concepts. Certain vulnerabilities of the demonic explanation which throw doubt upon its long-term survival in modern context are discussed as well.     

Early traces of life investigations in drilling Archean hydrothermal and sedimentary rocks of the Pilbara Craton,Western Australia and Barberton Greenstone Belt,South Africa

The Pilbara Craton of Western Australia and the Barberton Greenstone Belt of the Kaapvaal Craton, South Africa, contain some of the oldest and best preserved Archaean rocks and microfossils in the world. Two stratigraphic horizons in the Pilbara Craton were drilled as part of a collaborative effort between France and Australia (the Pilbara Drilling Project) during August 2004, including the 3481 Ma Dresser Formation (Warrawoona Group) and 2724 Ma Tumbiana Formation (Fortescue Group). A new diamond drill hole was cored in August 2008 through part of the ～3250 Ma Fig Tree Group in the Barberton Greenstone Belt as part of a joint project between France and South Africa. These pristine diamond drill cores present a unique opportunity to constrain the chemistry of the earliest ocean, the composition of the atmosphere, and the settings and types of microbial ecosystems spanning the Archean Eon. These drill core samples can also provide new clues on the earliest metabolic pathways.     

U.v.-induced blackening of rose petals

Blackening of petals is common in roses cv. Mercedes during the winter in unheated greenhouses clad with polyethylene films which are transparent to solar radiation of 300 nm wavelength and longer. Petal blackening was prevented when the rose plants were kept at 18°C or a higher temperature. Blackening was also prevented when the flower buds were covered with aluminum foil from dawn to dusk, or when flower buds were covered with polyethylene or PVC films, opaque to solar radiation in a u.v. range shorter than 350 nm even when they were exposed to outdoor conditions with minimum temperatures as low as 5°C. Blackening was not prevented when the flower buds were covered with aluminum foil only during the night, or when covered with polyethylene film transparent to u.v. radiation. Measurements of the spectral transmission of the various plastic materials showed that PVC film and the IR/VR-type of polyethylene were opaque to u.v. radiation. High levels of u.v. transmission were measured in the IR-type polyethylene and low levels of u.v. transmission were present under horticultural glass. The involvement of u.v.-B radiation in the phenomenon of rose petal blackening and its interaction with low temperature is discussed.     

Prolonged Intracellular Na+ Dynamics Govern Electrical Activity in Accessory Olfactory Bulb Mitral Cells

Persistent activity has been reported in many brain areas and is hypothesized to mediate working memory and emotional brain states and to rely upon network or biophysical feedback. Here, we demonstrate a novel mechanism by which persistent neuronal activity can be generated without feedback, relying instead on the slow removal of Na⁺ from neurons following bursts of activity. We show that mitral cells in the accessory olfactory bulb (AOB), which plays a major role in mammalian social behavior, may respond to a brief sensory stimulation with persistent firing. By combining electrical recordings, Ca²⁺ and Na⁺ imaging, and realistic computational modeling, we explored the mechanisms underlying the persistent activity in AOB mitral cells. We found that the exceptionally slow inward current that underlies this activity is governed by prolonged dynamics of intracellular Na⁺ ([Na⁺]_i), which affects neuronal electrical activity via several pathways. Specifically, elevated dendritic [Na⁺]_i reverses the Na⁺-Ca²⁺ exchanger activity, thus modifying the [Ca²⁺]_i set-point. This process, which relies on ubiquitous membrane mechanisms, is likely to play a role in other neuronal types in various brain regions.     

Primal-size neural circuits in meta-periodic interaction

Experimental observations of simultaneous activity in large cortical areas have seemed to justify a large network approach in early studies of neural information codes and memory capacity. This approach has overlooked, however, the segregated nature of cortical structure and functionality. Employing graph-theoretic results, we show that, given the estimated number of neurons in the human brain, there are only a few primal sizes that can be attributed to neural circuits under probabilistically sparse connectivity. The significance of this finding is that neural circuits of relatively small primal sizes in cyclic interaction, implied by inhibitory interneuron potentiation and excitatory inter-circuit potentiation, generate relatively long non-repetitious sequences of asynchronous primal-length periods. The meta-periodic nature of such circuit interaction translates into meta-periodic firing-rate dynamics, representing cortical information. It is finally shown that interacting neural circuits of primal sizes 7 or less exhaust most of the capacity of the human brain, with relatively little room to spare for circuits of larger primal sizes. This also appears to ratify experimental findings on the human working memory capacity.     

Pathological factors underlying hyperthermia

Hyperthermia is the result of an imbalance between total heat (metabolic heat and environmental heat) accumulated in the body and heat loss from the body, and is defined as a condition when core temperature rises above its normal range. This article will present an overview of syndromes associated with hyperthermia, through discussion of the etiology and pathophysiologic mechanisms that underlie those disorders. Emphasis will also be placed on the therapeutic measures to be taken in order to avert the complications of these disorders.     

Effect of Vaccination in Environmentally Induced Diseases

Along with the constant improvement in hygiene in the last few decades there has been a continuous increase in the incidence of particular diseases, mainly of autoimmune or allergic etiology, but also of diseases caused by infectious agents, such as listeriosis. We here present a model for the effect of exposure to agents causing or inducing the disease on the incidence of morbidity. The proposed model is an expansion of the SIR model to non-contagious diseases and aims to estimate the balance between immunization and disease probability. The model results indicate that, paradoxically in a wide range of parameters, a decrease in exposure to the disease inducing agent results in an increase in disease incidence. This can occur if: (a) the probability of developing disease, given an exposure to the agent increases with age, (b) immunity to the agent is long. The inverse relation between exposure and disease incidence results from a decrease in the adult immunized population following a previous decrease in the exposure rate. Therefore, a lower exposure can lead to lower incidence in the short term but to higher incidence in the long term.     

Sex specificity in the anal gland secretion of the Egyptian mongoose Herpestes ichneumon

The Egyptian mongoose, Herpestes ichneumon , uses its anal gland secretion to mark objects in its home range, presumably to communicate with members of its own or other groups. Chemical analysis (gas chromatography-mass spectrometry) of the secretion showed that it contained a complex mixture of long-chain (C₁₀-C₂₂) carboxylic acids with varying degrees of methyl branching. All the branched acids found in females were 4 methyl substituted. Males possess an additional component that seems to be a sex specific compound 2, 4, 6, 10 tetramethylundecanoic acid, which is a major component of the secretion.