Discrimination learning and extinction in paramecia (P. caudatum).
ABSTRACT Prior attempts to condition a one-celled organism, paramecium, by either classical or instrumental procedures have yielded both positive and negative results. As the results of those studies may be subject to several interpretations other than one indicating learning, it was decided to use a more traditional technique for the present study. This experiment was designed to assess whether aversive electric shock could be used to train paramecia on a brightness discrimination task, a procedure that has been used in animal learning research. The results indicated that such learning may have occurred.
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ABSTRACT: Paramecium has long been a model eukaryote. The sequence of the Paramecium tetraurelia genome reveals a history of three successive whole-genome duplications (WGDs), and the sequence of Paramecium biaurelia and Paramecium sexaurelia suggests that these WGDs are shared by all members of the aurelia species complex. Here, we present the genome sequence of Paramecium caudatum, a species closely related to the Paramecium aurelia species group. P. caudatum shares only the most ancient of the three WGDs with the aurelia complex. We found that P. caudatum maintains twice as many paralogs from this early event as the P. aurelia species, suggesting that post-WGD gene retention is influenced by subsequent WGDs, and supporting the importance of selection for dosage in gene retention. The availability of P. caudatum as an outgroup allows an expanded analysis of the aurelia intermediate and recent WGD events. Both the GC content and the expression level of pre-duplication genes are significant predictors of duplicate retention. We find widespread asymmetrical evolution among aurelia paralogs, which is likely caused by gradual pseudogenization rather than by neofunctionalization. Finally, cases of divergent resolution of intermediate WGD duplicates between aurelia species implicate this process acts as an on-going reinforcement mechanism of reproductive isolation long after a WGD event.Genetics 05/2014; · 4.39 Impact Factor
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ABSTRACT: Extinction and its related phenomena are central to the study and development of associative learning theory. For a better understanding of the processes involved in extinction, it is important to know how general these phenomena are in different species. Extensive evidence of extinction in invertebrate species would be necessary in order to test the generality of its current theoretical and physiological accounts. We carried out three sets of experiments using terrestrial snails Helix aspersa. The repeated nonreinforced presentation of the conditioned stimulus (CS) resulted in a decrease in responding (extinction); the introduction of a delay between the extinction of a CS and its test produced an increase in responding (spontaneous recovery); and re-exposure to the unconditioned stimulus after extinction also led to an increase in responding (reinstatement). The results are discussed in relation to current interference theories of extinction.Animal Behaviour 01/2014; 92:75–83. · 3.07 Impact Factor
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ABSTRACT: Background: Fatigue is a common term used to describe feelings of tiredness along with observations of reduced physical effort in both health and disease. The study of fatigue has centered mainly on understanding its putative causes. Recently (1990s), fatigue has been researched with an expanded view encompassing its potential origins and purposes in human physiology. Purpose: This review will explore and consider different fatigue models which could assist in the evolving understanding of this human condition. Methods: In this narrative review, Medline and Google Scholar were initially utilized to identify studies and texts documenting the developing understanding of fatigue. Following this, key words were used to locate investigations describing reactions to external stimuli in basic and complex organisms. The term anticipatory regulation was entered to locate studies which evaluated this construct in both health and disease. Results: This review shifts the focus of the fatigue paradigm from the catastrophe model, which emphasizes peripheral energy supply and demand, to the anticipatory regulation model, which focuses on a central regulatory process that anticipates energy demands and makes adjustments to accommodate future demand. The potential for this model to be used to explain the fatigue process in both health and disease is also discussed with respect to specific pathologies. Conclusion: There is now a body of evidence indicating that fatigue may represent a process of anticipatory regulation for maintaining homeostasis.Fatigue: Biomedicine, Health & Behavior. 01/2014;