Positivity effect in healthy aging in observational but not active feedback-learning

The present study investigated the impact of healthy aging on the bias to learn from positive or negative performance feedback in observational and active feedback learning. In active learning, a previous study had already shown a negative learning bias in healthy seniors older than 75 years, while no bias was found for younger seniors. However, healthy aging is accompanied by a 'positivity effect', a tendency to primarily attend to stimuli with positive valence. Based on recent findings of dissociable neural mechanisms in active and observational feedback learning, the positivity effect was hypothesized to influence older participants' observational feedback learning in particular. In two separate experiments, groups of young (mean age 27) and older participants (mean age 60 years) completed an observational or active learning task designed to differentially assess positive and negative learning. Older but not younger observational learners showed a significant bias to learn better from positive than negative feedback. In accordance with previous findings, no bias was found for active learning. This pattern of results is discussed in terms of differences in the neural underpinnings of active and observational learning from performance feedback.     

Small and large number discrimination in guppies

Non-verbal numerical behavior in human infants, human adults, and non-human primates appears to be rooted in two distinct mechanisms: a precise system for tracking and comparing small numbers of items simultaneously (up to 3 or 4 items) and an approximate system for estimating numerical magnitude of a group of objects. The most striking evidence that these two mechanisms are distinct comes from the apparent inability of young human infants and non-human primates to compare quantites across the small (<3 or 4)/large (>4) number boundary. We ask whether this distinction is present in lower animal species more distantly related to humans, guppies (Poecilia reticulata). We found that, like human infants and non-human primates, fish succeed at comparisons between large numbers only (5 vs. 10), succeed at comparisons between small numbers only (3 vs. 4), but systematically fail at comparisons that closely span the small/large boundary (3 vs. 5). Furthermore, increasing the distance between the small and large number resulted in successful discriminations (3 vs. 6, 3 vs. 7, and 3 vs. 9). This pattern of successes and failures is similar to those observed in human infants and non-human primates to suggest that the two systems are present and functionally distinct across a wide variety of animal species.     

Decrease of prefrontal-posterior EEG coherence: loose control during social-emotional stimulation

In two experiments we aimed to investigate if individual differences in state-dependent decreases or increases of EEG coherence between prefrontal and posterior cortical regions may be indicative of a mechanism modulating the impact social-emotional information has on an individual. Two independent samples were exposed to an emotional stimulation paradigm in which the participants were invited to get involved and sympathize with the persons they were watching (study 1) or listening to (study 2), and who were expressing sadness or anxiety. The two studies yielded consistent results. Higher scores in trait absorption and in the propensity to ruminate were associated with decreased EEG beta coherence during the stimulation, whereas coherence increased in individuals low in absorption or rumination. Coherence changes did not predict to which degree the participants felt infected by the displayed emotions, but in individuals showing decreased prefrontal-posterior coupling during the stimulation, feelings of sadness and anxiety had a greater tendency to persist. The findings suggest that more loose prefrontal-posterior coupling may be related to loosening of control of the prefrontal cortex over incoming social-emotional information and, consequently, to deeper emotional involvement and absorption, whereas increased prefrontal-posterior coupling may be related to strong control, dampening of emotional experience, and not letting oneself become emotionally affected.     

Hemispheric asymmetries and cognitive flexibility: an ERP and sLORETA study

Although functional cerebral asymmetries (FCAs) affect all cognitive domains, their modulation of the efficacy of specific executive functions is largely unexplored. In the present study, we used a lateralized version of the task switching paradigm to investigate the relevance of hemispheric asymmetries for cognitive control processes. Words were tachistoscopically presented in the left (LVF) and right visual half field (RVF). Participants had to categorise the words either based on their initial letters, or according to their word type. On half of the trials the task changed (switch trials) whereas on the other half it stayed the same (repeat trials). ERPs were recorded and the neural sources of the ERPs were reconstructed using standardised low resolution brain electromagnetic tomography (sLORETA). In the word type task, participants were faster on repeat trials when stimuli were presented in the RVF. In contrast, in the initial letter task participants were faster on repeat trials and in general more accurate after stimulus presentation in the LVF. In both tasks, no hemispheric asymmetries in reaction times were observed on switch trials. On the electrophysiological level, we observed a left lateralization of the N1 that was mediated by activation in the left extrastriate cortex as well as a greater positivity of the P3b after stimulus presentation in the RVF compared to the LVF that was mediated by activation in the superior parietal cortex. These results show that FCAs affect the neurophysiological correlates of executive functions related to task switching. The relation of neurophysiological and behavioural asymmetries is mediated by task complexity, with more complex tasks leading to more interhemispheric interaction and smaller left-right differences in behavioural measures. These findings reveal that FCAs are an important modulator of executive functions related to cognitive flexibility.     

When, what, and how much to reward in reinforcement learning-based models of cognition

Reinforcement learning approaches to cognitive modeling represent task acquisition as learning to choose the sequence of steps that accomplishes the task while maximizing a reward. However, an apparently unrecognized problem for modelers is choosing when, what, and how much to reward; that is, when (the moment: end of trial, subtask, or some other interval of task performance), what (the objective function: e.g., performance time or performance accuracy), and how much (the magnitude: with binary, categorical, or continuous values). In this article, we explore the problem space of these three parameters in the context of a task whose completion entails some combination of 36 state-action pairs, where all intermediate states (i.e., after the initial state and prior to the end state) represent progressive but partial completion of the task. Different choices produce profoundly different learning paths and outcomes, with the strongest effect for moment. Unfortunately, there is little discussion in the literature of the effect of such choices. This absence is disappointing, as the choice of when, what, and how much needs to be made by a modeler for every learning model.     

Performance Benefits of Spatially Distributed Versus Stacked Information on Integration Tasks

Understanding the best way to present information has been an issue of interest to many researchers. Regardless of the content of the information, purely physical elements such as spatial organization may also influence performance. Across two studies with 111 undergraduates (78 in Study 1 and 33 in Study 2), we compared spatially distributed (i.e. when information sources are presented side‐by‐side) against stacked displays (i.e. when information sources are sitting on top of one another with only the top source fully visible). A distributed display time advantage was consistently observed. As potential explanations, a memory strategy selection hypothesis was examined along with other procedural alternative explanations. Copyright © 2011 John Wiley & Sons, Ltd.     

Role of the sympathetic nervous system in cerebrovascular responses to air-jet stress in rats

This study examined the role of sympathetic nerves in the control of cerebral hemodynamics during air-jet stress. In adult male Sprague-Dawley rats, blood flow velocity (pulsed Doppler) was measured in both internal carotid arteries 1 week after excision of one superior cervical ganglion. Blood pressure (BP) and carotid blood flows (CBFs) were simultaneously recorded during exposure to air-jet stress. In 5 out of 13 rats, stress was applied after β(2)-adrenoceptor blockade with ICI 118551 (0.4 mg/kg, then 0.2 mg/kg/h, i.v). Stress evoked an immediate rise in BP, CBFs, and vascular conductances. Vasodilatation was much larger on the denervated side than on the intact side (mean ± SEM: 78 ± 7 versus 19 ± 4%; P < 0.02) and lasted about 10 s. Thereafter, blood flows returned to or near normal and showed parallel variations while BP remained elevated. There was, therefore, a net vasoconstriction on both sides. In ICI 118551-treated rats, the initial vasodilatation was not significantly reduced on the denervated side (64 ± 4%), but the subsequent vasoconstriction was enhanced (P < 0.05) on both sides. In conclusion, air-jet stress evokes an immediate, short-lasting vasodilatation through a mechanism unrelated to β(2)-adrenoceptor stimulation. Sympathetic nerves powerfully limit this phenomenon, and thus contribute to protect the cerebral circulation from stress-induced BP surges.     

Buddhism and Quantum Physics

Rudyard Kipling, the famous English author of The Jungle Book, born in India, wrote one day these words: ‘Oh, East is East and West is West, and never the twain shall meet’. In my paper I show that Kipling was not completely right. I try to show the common ground between Buddhist philosophy and quantum physics. There is a surprising parallelism between the philosophical concept of reality articulated by Nāgārjuna and the physical concept of reality implied by quantum physics. For neither is there a fundamental core to reality; rather, reality consists of systems of interacting objects. Such concepts of reality cannot be reconciled with the substantial, subjective, holistic or instrumentalistic concepts of reality that underlie modern modes of thought.     

Are free testosterone and cortisol concentrations associated with training motivation in elite male athletes?

ObjectivesTo examine correlative associations between salivary free testosterone (T) and cortisol (C) concentrations and training motivation in elite male athletes.DesignSingle group, longitudinal design with repeated measures.MethodsParticipants (n = 15) completed a 5-week progressive resistance training programme. Across 2 weekly workouts, pre and post measures of salivary free T and C concentrations were taken along with voluntary chosen workload, as a proxy for training motivation. Strength and body mass were assessed pre and post training.ResultsIndividual changes in pre-workout free T concentrations correlated strongly to voluntary workloads (pooled r = 0.81, p < 0.001). Pre-workout free C concentrations was weakly correlated to voluntary workload (pooled r = 0.35). Pre-workout hormones (r = 0.57–0.89) and the strength gains were also related.ConclusionsThe salivary free T concentrations of male athletes presented before training were strongly associated with subsequent voluntary workloads, indicating a potential link to training motivation.