Qualitatively varied reinforcement does not increase rates of schedule-induced behaviour

Qualitatively varied reinforcement (QVR) refers to the delivery of two or more consequences for the same operant response. It has been suggested that QVR ought to elicit higher response rates than a single reinforcer. Schedule-induced behaviours, like wheel running, have been compared to operant behaviours, thus they could be thought to be controlled by the same variables. The aim of this study was to compare the rates of lever pressing and wheel running during a component in which QVR was available to those in which a single reinforcer was available. Subjects were 8 experimentally naïve male Wistar rats deprived of food and water. Subjects were exposed to a multiple schedule with 3 components in which different consequences were available: food, water, or either food or water, according to a variable interval 120-s schedule for lever pressing. Each component lasted 30 minutes. During experimental sessions subjects also had access to a running wheel. Higher, albeit not significant, lever-pressing rates were recorded during the food component than during the water component or the qualitatively-varied one, and no systematic differences were found between components in wheel-running rates. A second experiment with a similar procedure but in which rats received double amount of reinforcer (food, water, and food and water) yielded similar results, but with slightly higher response rates during the qualitatively varied component than in Experiment 1. Results are consistent with the findings that schedule-induced behaviours are affected by the same variables than operant behaviours. There was no significant effect of QVR to produce higher response rates than single reinforcers.N

Activity-based anorexia alters hypothalamic POMC and orexin populations in male rats

The objective of this study was to investigate the orexin and POMC populations in the hypothalamic nuclei of male Wistar rats after the activity-based anorexia (ABA) procedure. Four groups were established based on food restriction and activity: activity (A), ABA, diet (D) and control (C). The ABA protocol consisted of free access to a running wheel for a period of 22 h and access to food for 1 h. When the animals in the ABA group reached the ABA criterion, were sacrificed, and their brains were collected and serially sectioned. The free-floating sections were processed for orexin and POMC immunostaining. The number of orexin A-ir cells in the perifornical-dorsomedial-hypothalamus continuum (PFD) and lateral hypothalamus (LH) and the number of POMC-ir cells in the arcuate nucleus (Arc) were estimated. Data on food intake, body weight and wheel turns were also analyzed. The ABA procedure caused a significant decrease in body weight along with a significant increase in activity. Moreover, at the end of the ABA procedure, the number of POMC-ir cells decreased in the Arc in the A group, and significantly more in the ABA group, and the number of orexin A-ir positive cells decreased in the LH in D and ABA groups. The differential decrease in POMC in the ABA group emphasizes the importance of the melanocortin system in the maintenance of ABA, but more research is needed to elucidate the involvement of this peptide in the mechanism that promotes and maintains anorexia nervosa and how increased activity may interact with all these processes.The present work was supported by grants PSI2017-86396-P and IMIENS (PC/HP) and PSI2016-80082-P (RP), both from Ministerio de Economía, Industria y Competitividad (MINECO, Spanish Government), and from Banco de Santander 2015 collaborative research (UNED).S

Static internal representation of dynamic situations reveals time compaction in human cognition

Introduction: The human brain has evolved under the constraint of survival in complex dynamic situations. It makes fast and reliable decisions based on internal representations of the environment. Whereas neural mechanisms involved in the internal representation of space are becoming known, entire spatiotemporal cognition remains a challenge. Growing experimental evidence suggests that brain mechanisms devoted to spatial cognition may also participate in spatiotemporal information processing. Objectives: The time compaction hypothesis postulates that the brain represents both static and dynamic situations as purely static maps. Such an internal reduction of the external complexity allows humans to process time-changing situations in real-time efficiently. According to time compaction, there may be a deep inner similarity between the representation of conventional static and dynamic visual stimuli. Here, we test the hypothesis and report the first experimental evidence of time compaction in humans. Methods: We engaged human subjects in a discrimination-learning task consisting in the classification of static and dynamic visual stimuli. When there was a hidden correspondence between static and dynamic stimuli due to time compaction, the learning performance was expected to be modulated. We studied such a modulation experimentally and by a computational model. Results: The collected data validated the predicted learning modulation and confirmed that time compaction is a salient cognitive strategy adopted by the human brain to process time-changing situations. Mathematical modelling supported the finding. We also revealed that men are more prone to exploit time compaction in accordance with the context of the hypothesis as a cognitive basis for survival. Conclusions: The static internal representation of dynamic situations is a human cognitive mechanism involved in decision-making and strategy planning to cope with time-changing environments. The finding opens a new venue to understand how humans efficiently interact with our dynamic world and thrive in nature