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.     

Simultaneous classification and multidimensional scaling with external information

For the exploratory analysis of a matrix of proximities or (dis)similarities between objects, one often uses cluster analysis (CA) or multidimensional scaling (MDS). Solutions resulting from such analyses are sometimes interpreted using external information on the objects. Usually the procedures of CA, MDS and using external information are carried out independently and sequentially, although combinations of two of the three procedures (CA and MDS, or multidimensional scaling and using external information) have been proposed in the literature. The present paper offers a procedure that combines all three procedures in one analysis, using a model that describes a partition of objects with cluster centroids represented in a low-dimensional space, which in turn is related to the information in the external variables. A simulation study is carried out to demonstrate that the method works satisfactorily for data with a known underlying structure. Also, to illustrate the method, it is applied to two empirical data sets.     

Respiration and postural sway: detection of phase synchronizations and interactions

The aim of the central nervous system in upright stance is to control an intrinsically unstable plant. Internal disturbances, such as haemodynamics and respiration, constitute an endogenous threat to equilibrium. The way CNS reacts to those perturbations was studied in this work, through the analysis of summary scores taken from posturographic and pneumographic data. Signals were recorded simultaneously during trials administered on a sample population of healthy young adults, while sitting and standing and at paced and spontaneous uncontrolled breathing. The extraction of posturographic and pneumographic parameters was accompanied by the utilization of techniques for the detection of phase synchronization in bivariate data, and the extraction of an interaction index, the mutual information MI. The effects of the biomechanical condition and respiratory amplitude on MI and summary measures were tested with a two-way ANOVA. Summary scores clearly depend on posture condition. Synchronization between breath and postural sway is always present, depends on both biomechanical condition and respiratory threat, and cannot be reduced to a simple linear relation.     

Conflict of interest in biomedical research: a view from Europe

In this paper I address the conflict of interest (CoI) issue from a legal point of view at a European level. We will see that the regulatory framework that exists in Europe does state the need for the independence of ethics committee involved in authorisation of research and clinical trials. We will see that CoI is an element that has to be closely monitored at National and International level. Therefore, Member States and Newly Associated States do have to address CoI in the authorisation process of research and clinical protocols of biomedicine. The opinions here expressed are personal and do not commit the European Commission. An earlier version of this paper was delivered at a Conference on Conflict of Interest and Its Significance in Science and Medicine, 5–6 April, 2002, Warsaw, Poland. The author is a Scientific Officer in the Programme Science and Society dealing with ethics and science (Unit C.3).     

Depression, self-esteem, and complex attributions for life problems

Past research has suggested that mild and moderate depression are associated with increased attributional processing and a tendency to make complex attributions involving two or more causes. The present research tested the hypothesis that depression and low self-esteem are associated with a tendency to make attributions to multiple causes when faced with life problems. The results were used to demonstrate that the tendency to make multiple attributions for specific life problems accounts for unique variance in depression and self-esteem scores, even after removing variance due to general attributional style. The findings are discussed with reference to the need for multidimensional models of attribution in depression and attributional retraining efforts to include an emphasis on individual differences in the number of multiple attributions made by people.     

Customer experience in coffee stores: A multidisciplinary Neuromarketing approach

Companies in the service retailing industry are constantly looking for strategies to provide a customer experience that improves brand perception and increases customer loyalty. This study provides a deeper understanding of customer experience in two coffee stores in Vietnam by providing a multidisciplinary approach, including a quantitative and a neuromarketing approach. Two-hundred participants participated in the study, combining mystery shopping visits with the Brand Association Reaction Time Test (BARTT). Results from the mystery shopping visits confirm the holistic concept of customer experience. Store atmosphere, employee service, drink quality, price, and previous visits significantly impact customer experience. Empirical results also confirm the impact of customer experience on loyalty. Furthermore, the BARTT analysis shows that in-store customer experience can influence customers' short-term brand perceptions. The national brand is associated with friendly, expensive, globalized, and unique, whereas the local brand revealed significant associations with clean, smells good, welcoming, and unique. From the mystery shopping results and the BARTT, we can infer that customer experience needs multi-methodological capturing of its multifaceted aspects. Our findings are relevant to researchers and practitioners seeking to understand and bolster customer experiences, justifying a multidisciplinary approach and the application of new insightful tools.