Which digit is larger? Brain responses to number and size interactions in a numerical Stroop task.

When comparing the digits of different physical sizes, the processing of numerical value interacts with the processing of physical size. Given the universal use of Arabic numbers in mathematics and daily life, this study aims to elucidate the cognitive processes involved in the interactions of task-relevant and task-irrelevant features during information processing. We investigated this question by examining event-related potential (ERP) using a modified version of the size congruity comparison, which is a Stroop-like task. Numerical value and physical size were varied independently under task-relevant and task-irrelevant conditions. To better examine how the task-irrelevant features modulated the processing of the task-relevant attributes, a neutral condition was included in both tasks. For the physical task, congruent trials showed a less negative N200 response than neutral trials (indicating a facilitation effect), and incongruent trials elicited a larger N450 and smaller late positive complex (LPC) response than neutral trials (indicating an interference effect). For the numerical task, congruent trials showed a larger LPC response than neutral trials (indicating a facilitation effect). These ERP findings indicate that the sources of the facilitation and interference effects appear in different cognitive processes for each task. We further suggest that language characteristics may be a factor in the superior numerical processing exhibited in this study.

Antecedent acute cycling exercise affects attention control: an ERP study using attention network test.

The purpose of this study was to investigate the after-effects of an acute bout of moderate intensity aerobic cycling exercise on neuroelectric and behavioral indices of efficiency of three attentional networks: alerting, orienting, and executive (conflict) control. Thirty young, highly fit amateur basketball players performed a multifunctional attentional reaction time task, the attention network test (ANT), with a two-group randomized experimental design after an acute bout of moderate intensity spinning wheel exercise or without antecedent exercise. The ANT combined warning signals prior to targets, spatial cueing of potential target locations and target stimuli surrounded by congruent or incongruent flankers, which were provided to assess three attentional networks. Event-related brain potentials and task performance were measured during the ANT. Exercise resulted in a larger P3 amplitude in the alerting and executive control subtasks across frontal, central and parietal midline sites that was paralleled by an enhanced reaction speed only on trials with incongruent flankers of the executive control network. The P3 latency and response accuracy were not affected by exercise. These findings suggest that after spinning, more resources are allocated to task-relevant stimuli in tasks that rely on the alerting and executive control networks. However, the improvement in performance was observed in only the executively challenging conflict condition, suggesting that whether the brain resources that are rendered available immediately after acute exercise translate into better attention performance depends on the cognitive task complexity.

The benefits of endurance exercise and Tai Chi Chuan for the task-switching aspect of executive function in older adults: an ERP study.

This study was designed to determine the relationship between physical activity and the task-switching aspect of executive function by investigating the modulating roles of age, modality of physical activity, and type of cognitive function using behavioral and event-related potential (ERP) assessments. Sixty-four participants were assigned to one of four groups based on age and history of physical activity: older adults performing endurance exercise (OEE), older adults practicing Tai Chi Chuan (OTC), older adults with a sedentary lifestyle (OSL), and young adults (YA). Study participants completed a task-switching task under homogeneous and heterogeneous conditions while ERPs were recorded. The results revealed that YA had shortest reaction times compared with the three older adults groups, with OSL exhibiting the longest reaction time. YA also exhibited shorter P3 latency than OSL. No differences were observed in P3 amplitude between YA, OEE, and OTC; however, all three groups had significantly larger P3 amplitude compared with OSL in both task conditions. In conclusion, age and participation in physical activity influence the relationship between physical activity and task-switching, and a positive relationship was observed regardless of the modality of physical activity and type of cognitive function. Our ERP findings support the model of the scaffolding theory of aging and cognition (STAC) and suggest that regular participation in endurance exercise and Tai Chi Chuan may have equivalent beneficial effects on cognition at the behavioral and neuroelectric levels.

Erythropoietin activates the phosphoinositide 3-kinase/Akt pathway in human melanoma cells.

Erythropoietin (Epo) is used commonly to treat cancer and/or therapy-related anemia. Until recently, Epo was considered to be a specific stimulator of erythropoiesis, acting via its receptor, EpoR. It becomes clear, however, that EpoR is expressed in a variety of cell types other than hematopoietic cells, and that Epo is a potent cytoprotective cytokine increasing cell survival under hypoxic conditions. Epo and EpoR are also expressed in various malignant tumors, and EpoR expression shows association with tumor invasion and progression. Recently, a functional Epo autocrine signaling mechanism was also detected in human melanoma cells. In this study, we examined the hypothesis that Epo activates the Akt signaling pathway in human melanoma cells and thus promotes the survival of tumor cells. The Akt signaling pathway in response to Epo was examined in melanoma. Similar to Epo, the expression of EpoR was up-regulated in response to hypoxia and Epo stimulation in melanoma cells. Melanoma cells constitutively expressed Akt with variable expression of mammalian target of rapamycin, and Epo dose-dependently induced their activity. Epo increased Akt kinase activity, which was abrogated by co-treatment with LY294002, a specific blocker of phosphoinositide 3-kinase. LY294002 also inhibited the cytoprotective effects of Epo in melanoma cells under both normoxic and hypoxic conditions. Our results suggest that Epo promotes melanoma cell survival by activating an Akt-dependent signaling pathway.