Neurobiology of expectancy effects and omission of reinforcement on behavior

The reinforcement omission effects have been traditionally interpreted in terms of: behavioral facilitation after reinforcement omission induced by primary frustration or behavioral suppression after reinforcement delivery induced by postconsummatory states. The studies reviewed here indicate that amygdala is involved in modulation of these effects. However, the fact that amygdala lesions, extensive or selective, can eliminate, reduce and enhance the omission effects makes it difficult to understand how it is the exact nature of their involvement. The amygdala is related to several functions that depend on its connections with other brain systems. Thus, it is necessary to consider the involvement of a more complex neural network in the modulation of the reinforcement omission effects. The connection of amygdala subareas to cortical and subcortical structures may be involved in this modulation since they also are linked to processes related to reward and expectancy.

Exercise and Training at Altitudes: Physiological Effects and Protocols

An increase in altitude leads to a proportional fall in the barometric pressure, and a decrease in atmospheric oxygen pressure, producing hypobaric hypoxia that affects, in different degrees, all body organs, systems and functions. The chronically reduced partial pressure of oxygen causes that individuals adapt and adjust to physiological stress. These adaptations are modulated by many factors, including the degree of hypoxia related to altitude, time of exposure, exercise intensity and individual conditions. It has been established that exposure to high altitude is an environmental stressor that elicits a response that contributes to many adjustments and adaptations that influence exercise capacity and endurance performance. These adaptations include in crease in hemoglobin concentration, ventilation, capillary density and tissue myoglobin concentration. However, a negative effect in strength and power is related to a decrease in muscle fiber size and body mass due to the decrease in the training intensity. Many researches aim at establishing how training or living at high altitudes affects performance in athletes. Training methods, such as living in high altitudes training low, and training high-living in low altitudes have been used to research the changes in the physical condition in athletes and how the physiological adaptations to hypoxia can enhanceperformance at sea level. This review analyzes the literature related to altitude training focused on how physiological adaptations to hypoxic environments influence performance, and which protocols are most frequently used to train in high altitudes.

The impact of a minimum pension on old age poverty and its budgetary cost. Evidence from Latin America

This paper examines the impact on old age poverty and the fiscal cost of universal minimum oldage pensions in Latin America using recent household survey data for 18 countries. Alleviatingold age poverty requires different approach from other age groups and a minimum pension islikely to be the only alternative available. First we measure old age poverty rates for all countries.Second we discuss the design of minimum pensions schemes, means-tested or not, as wellas the disincentive effects that they are expected to have on the economic and social behavior ofhouseholds including labor supply, saving and family solidarity. Third we use the household surveysto simulate the fiscal cost and the impact on poverty rates of alternative minimum pensionschemes in the 18 countries. We show that a universal minimum pension would substantiallyreduce poverty among the elderly except in Argentina, Brazil, Chile and Uruguay where minimumpension systems already exist and poverty rates are low. Such schemes have much tobe commended in terms of incentives, spillover effects and administrative simplicity but have ahigh fiscal cost. The latter is a function of the age at which benefits are awarded, the prevailinglongevity, the generosity of benefits, the efficacy of means testing, and naturally the fiscal capacityof the country.

Racial and spatial interaction for neighborhood dynamics in Chicago

We look at at the empirical validity of Schelling’s models for racial residential segregation applied to the case of Chicago. Most of the empirical literature has focused exclusively the single neighborhood model, also known as the tipping point model and neglected a multineighborhood approach or a unified approach. The multi-neighborhood approach introduced spatial interaction across the neighborhoods, in particular we look at spatial interaction across neighborhoods sharing a border. An initial exploration of the data indicates that spatial contiguity might be relevant to properly analyse the so call tipping phenomena of predominately non-Hispanic white neighborhoods to predominantly minority neighborhoods within a decade. We introduce an econometric model that combines an approach to estimate tipping point using threshold effects and a spatial autoregressive model. The estimation results from the model disputes the existence of a tipping point, that is a discontinuous change in the rate of growth of the non-Hispanic white population due to a small increase in the minority share of the neighborhood. In addition we find that racial distance between the neighborhood of interest and it surrounding neighborhoods has an important effect on the dynamics of racial segregation in Chicago.

Natural resource windfalls and efficiency of local government expenditures: evidence from Peru

We study the role of natural resource windfalls in explaining the efficiency of public expenditures. Using a rich dataset of expenditures and public good provision for 1,836 municipalities in Peru for period 2001-2010, we estimate a non-monotonic relationship between the efficiency of public good provision and the level of natural resource transfers. Local governments that were extremely favored by the boom of mineral prices were more efficient in using fiscal windfalls whereas those benefited with modest transfers were more inefficient. These results can be explained by the increase in political competition associated with the boom. However, the fact that increases in efficiency were related to reductions in public good provision casts doubts about the beneficial effects of political competition in promoting efficiency.