Multimodal encoding in a simplified model of intracellular calcium signaling

Many cells use calcium signaling to carry information from the extracellular side of the plasma membrane to targets in their interior. Since virtually all cells employ a network of biochemical reactions for Ca²⁺ signaling, much effort has been devoted to understand the functional role of Ca²⁺ responses and to decipher how their complex dynamics is regulated by the biochemical network of Ca²⁺-related signal transduction pathways. Experimental observations show that Ca²⁺ signals in response to external stimuli encode information via frequency modulation (FM) or alternatively via amplitude modulation (AM). Although minimal models can capture separately both types of dynamics, they fail to exhibit different and more advanced encoding modes. By arguments of bifurcation theory, we propose instead that under some biophysical conditions more complex modes of information encoding can also be manifested by minimal models. We consider the minimal model of Li and Rinzel and show that information encoding can occur by AM of Ca²⁺ oscillations, by FM or by both modes (AFM). Our work is motivated by calcium signaling in astrocytes, the predominant type of cortical glial cells that is nowadays recognized to play a crucial role in the regulation of neuronal activity and information processing of the brain. We explain that our results can be crucial for a better understanding of synaptic information transfer. Furthermore, our results might also be important for better insight on other examples of physiological processes regulated by Ca²⁺ signaling.     

Multimodal encoding in a simplified model of intracellular calcium signaling

Many cells use calcium signaling to carry information from the extracellular side of the plasma membrane to targets in their interior. Since virtually all cells employ a network of biochemical reactions for Ca²⁺ signaling, much effort has been devoted to understand the functional role of Ca²⁺ responses and to decipher how their complex dynamics is regulated by the biochemical network of Ca²⁺-related signal transduction pathways. Experimental observations show that Ca²⁺ signals in response to external stimuli encode information via frequency modulation (FM) or alternatively via amplitude modulation (AM). Although minimal models can capture separately both types of dynamics, they fail to exhibit different and more advanced encoding modes. By arguments of bifurcation theory, we propose instead that under some biophysical conditions more complex modes of information encoding can also be manifested by minimal models. We consider the minimal model of Li and Rinzel and show that information encoding can occur by AM of Ca²⁺ oscillations, by FM or by both modes (AFM). Our work is motivated by calcium signaling in astrocytes, the predominant type of cortical glial cells that is nowadays recognized to play a crucial role in the regulation of neuronal activity and information processing of the brain. We explain that our results can be crucial for a better understanding of synaptic information transfer. Furthermore, our results might also be important for better insight on other examples of physiological processes regulated by Ca²⁺ signaling.     

The Conception of Synthetic Entities from a Personalist Perspective

Science and Engineering Ethics - Synthetic biology opens up the possibility of producing new entities not found in nature, whose classification as organisms or machines has been debated. In this...     

Size of the attentional focus and efficiency of processing

By following Eriksen and St. James (1986) the experiments reported in this study focused upon three questions: (a) Can the spatial extent of the attentional focus be made to vary in response to precues? (b) As the area of the attentional focus increases, is there a decrease in processing efficiency for stimuli within the focus? (c) Is the boundary of the focus sharply demarked from the residual field or does it show a gradual dropoff? The results seem to provide answers to these questions: (a) the size of the attentional focus can be adjusted so that it covers areas of the visual field of different size; (b) there is a decrease in processing efficiency when the area of the attentional focus increases; and (c) there is a gradual dropoff in processing efficiency around the attentional focus.     

Activity measures in stress-attenuated novelty tests as possible analogues for extraversion in rats: Some experimental results

In an attempt to extend and validate Garcia-Sevilla's (1974) hypothesis proposing ambulation in a non-stressful open field (OF) as an animal analogue of human extraversion, ambulatory behaviour and rearing behaviour were studied and compared in several experiments with genetically-unselected rats. The effects of variation of OF auditory stimulation level, the correlation with a two-way avoidance-learning situation and the effects of a stimulant dose of d-amphetamine and an anxiolytic one of diazepam upon rearing and ambulatory behaviours were studied. All in all, our results support some of the requirements of the hypothesis, but also generate some additional problems. The results show that the number of rearings could be a better and more sensitive measure of variations in the level of arousal and a better predictor of shuttle-avoidance conditioning than ambulation. However, all activity measures are at least moderately intercorrelated, and they become grouped when results are factor analysed. All the results are discussed with reference to Eysenck's personality theory and Gray's anxiety theory, and it is concluded that these measures are too multidetermined and too poorly controlled to represent correctly and in a direct form a personality dimension such as Extraversion. Anyway, this attempt could be a good point of departure for discovering more efficient animal behavioural measures of arousability.     

Optimism as a mediator between resilience and affective states in older adults / El optimismo como mediador entre la resiliencia y estados afectivos en adultos mayores

Abstract

The purpose of this study was to explore whether resilience is associated with and a predictor of depression, anxiety, negative and positive affect, life satisfaction and subjective happiness in older adults, and whether these relationships are mediated by optimism. To analyse this, different scales were administered to a sample of 240 elderly people and correlational and mediational analysis was carried out. The results showed relationships between all the variables. Similarly, we found that optimism is a partial mediator of the relationship between resilience and the aforementioned variables. Our results evidenced that increasing resilience and optimism in elderly people could be favourable to successful ageing.