EXPRESS: The effect of spatial distance on numerical distance processing.

The close relationship between numerical and spatial representation has been widely studied. However, little is known regarding the influence of spatial distance on the processing of numerical distance. The purpose of the current study was to examine this relationship by employing a modified numerical Stroop task, in which the spatial distance was either congruent or incongruent with the numerical distance. That is, numerical and spatial distances were either compatible with each other or incompatible. Experiment 1 demonstrated that when participants were directly requested to assess the numerical distance, spatial distance influenced task performance, thereby revealing a novel effect - the spatial-numerical distance congruency effect. Experiment 2 demonstrated that these relations are asymmetrical and revealed that numerical distance did not influence spatial distance when the numerical distance was task-irrelevant. Experiment 3 revealed that the spatial-numerical distance congruency effect can also be obtained automatically by employing a numerical comparison task, which is considered a marker for indirect distance processing. In addition, also tested across the three experiments was whether spatial alignment on the screen (i.e., left, center, and right) can influence the spatial-numerical distance congruency effect. Results revealed that when numbers were presented more naturally (on the left and center of the screen), a larger effect was obtained compared to when stimuli were presented on the right side. Together, these findings shed new light regarding the relationship between numerical distance and spatial distance and whether and how these aspects influence each other.

The effect of proportion manipulation on the size-congruency and distance effects in the numerical Stroop task.

In the numerical Stroop task, participants are presented with two digits that differ in their numerical and physical size and are requested to respond to which digit is numerically larger. Commonly, slower responses are observed when the numerical distance between the digits is small (the distance effect) and when the numerical and physical size are incongruent (the size-congruency effect). The current study will use proportion manipulation, which consists of two experimental lists with high versus low frequency of trials belonging to different conditions, as a tool to reduce these effects. Specifically, it will be used to examine how these two interference effects depend on each other, and how a reduction of one effect will affect the other. In Experiment 1, the size-congruency proportions were manipulated; in Experiment 2, the distance proportions were manipulated. The results show that manipulating size-congruency proportions modulates the size-congruency effect but not the distance effect, while manipulating the distance proportions modulates the distance effect but not the size-congruency effect. These results demonstrate for the first time that the distance effect can be modulated by the distance proportions. Furthermore, these results indicate that proportion manipulation is specific and only modulates the variable being manipulated. Together, these results shed new light on the specificity of proportion manipulation in the context of numerical information processing. These results are further discussed in the context of various numerical models that suggest a different relationship between these effects and demonstrate how proportion manipulation can aid to investigate numerical processes.

Effect of ingesting a meal and orthostasis on the regulation of splanchnic and systemic hemodynamics and the responsiveness of cardiovascular α1-adrenoceptors.

Postprandial orthostasis activates mechanisms of cardiovascular homeostasis to maintain normal blood pressure (BP) and adequate blood flow to vital organs. The underlying mechanisms of cardiovascular homeostasis in postprandial orthostasis still require elucidation. Fourteen healthy volunteers were recruited to investigate the effect of an orthostatic challenge (60°-head-up-tilt for 20 min) on splanchnic and systemic hemodynamics before and after ingesting an 800-kcal composite meal. The splanchnic circulation was assessed by ultrasonography of the superior mesenteric and hepatic arteries and portal vein. Systemic hemodynamics were assessed noninvasively by continuous monitoring of BP, heart rate (HR), cardiac output (CO), and the pressor response to an intravenous infusion on increasing doses of phenylephrine, an α1-adrenoceptor agonist. Neurohumoral regulation was assessed by spectral analysis of HR and BP, plasma catecholamine and aldosterone levels and plasma renin activity. Postprandial mesenteric hyperemia was associated with an increase in CO, a decrease in SVR and cardiac vagal tone, and reduction in baroreflex sensitivity with no change in sympathetic tone. Arterial α1-adrenoceptor responsiveness was preserved and reduced in hepatic sinusoids. Postprandial orthostasis was associated with a shift of 500 mL of blood from mesenteric to systemic circulation with preserved sympathetic-mediated vasoconstriction. Meal ingestion provokes cardiovascular hyperdynamism, cardiac vagolysis, and resetting of the baroreflex without activation of the sympathetic nervous system. Meal ingestion also alters α1-adrenoceptor responsiveness in the hepatic sinusoids and participates in the redistribution of blood volume from the mesenteric to the systemic circulation to maintain a normal BP during orthostasis.NEW & NOTEWORTHY A unique integrated investigation on the effect of meal on neurohumoral mechanisms and blood flow redistribution of the mesenteric circulation during orthostasis was investigated. Food ingestion results in cardiovascular hyperdynamism, reduction in cardiac vagal tone, and baroreflex sensitivity and causes a decrease in α1-adrenoceptor responsiveness only in the venous intrahepatic sinusoids. About 500-mL blood shifts from the mesenteric to the systemic circulation during orthostasis. Accordingly, the orthostatic homeostatic mechanisms are better understood.

Modulation of conflicts in the Stroop effect.

The purpose of the current study was to evaluate the unique contribution of task conflict, semantic conflict and response conflict to the Stroop effect and to test how these conflicts are modulated by manipulating the proportion of neutral trials, known to affect the magnitude of the Stroop effect. In the first experiment, we employed the two-to-one paradigm (De Houwer, 2003) while adding neutral illegible stimuli, and in the second experiment, we employed two colors and four word colors. In both experiments, we created four congruency conditions (neutral, congruent and two kind of incongruent conditions-those that include response conflict and those that do not), which allowed decomposing the Stroop effect into three orthogonal conflicts. In both experiments, we also manipulated the proportion of neutral trials. Task conflict was defined by the contrast between illegible neutrals and color words, semantic conflict by the contrast between congruent and incongruent stimuli, and response conflict by contrasting the two kinds of incongruent stimuli. Our results showed that all conflicts contributed to the Stroop effect. Task conflict and semantic conflict were modulated by the proportion of neutrals but response conflict was not. These findings imply that task conflict and semantic conflict are part of the control loop of the Stroop effect, as conceptualized by Botvinick et al.'s (2001) conflict monitoring model. There is no clear evidence of the response conflict being part of the loop. To complete the picture, we also analyzed the conflicts in the Stroop task using the traditional dependent contrasts approach and found the basic pattern of results was similar. Thus, the main advantage of the orthogonal comparisons approach is the possibility to estimate the unique contribution of the conflicts contributing to the Stroop effect and their modulation of the Stroop phenomenon.