Variability in the affective and cognitive symptom response to antidepressant treatment has been observed in geriatric depression. The underlying neural circuitry is poorly understood. This study evaluated the cerebral glucose metabolic effects of citalopram treatment and applied multivariate, functional connectivity analyses to identify brain networks associated with improvements in affective symptoms and cognitive function. Sixteen geriatric depressed patients underwent resting positron emission tomography (PET) studies of cerebral glucose metabolism and assessment of affective symptoms and cognitive function before and after 8 weeks of selective serotonin reuptake inhibitor treatment (citalopram). Voxel-wise analyses of the normalized glucose metabolic data showed decreased cerebral metabolism during citalopram treatment in the anterior cingulate gyrus, middle temporal gyrus, precuneus, amygdala, and parahippocampal gyrus. Increased metabolism was observed in the putamen, occipital cortex, and cerebellum. Functional connectivity analyses revealed two networks which were uniquely associated with improvement of affective symptoms and cognitive function during treatment. A subcortical-limbic-frontal network was associated with improvement in affect (depression and anxiety), while a medial temporal-parietal-frontal network was associated with improvement in cognition (immediate verbal learning/memory and verbal fluency). The regions that comprise the cognitive network overlap with the regions that are affected in Alzheimer's dementia. Thus, alterations in specific brain networks associated with improvement of affective symptoms and cognitive function are observed during citalopram treatment in geriatric depression
The present study examined the modality specificity and spatio-temporal dynamics of "what" and "where" preparatory processes in anticipation of auditory and visual targets using ERPs and a cue-target paradigm. Participants were presented with an auditory (Experiment 1) or a visual (Experiment 2) cue that signaled them to attend to the identity or location of an upcoming auditory or visual target. In both experiments, participants responded faster to the location compared to the identity conditions. Multivariate spatio-temporal partial least square (ST-PLS) analysis of the scalp-recorded data revealed supramodal "where" preparatory processes between 300-600 msec and 600-1200 msec at central and posterior parietal electrode sites in anticipation of both auditory and visual targets. Furthermore, preparation for pitch processing was captured at modality-specific temporal regions between 300 and 700 msec, and preparation for shape processing was detected at occipital electrode sites between 700 and 1150 msec. The spatio-temporal patterns noted above were replicated when a visual cue signaled the upcoming response (Experiment 2). Pitch or shape preparation exhibited modality-dependent spatio-temporal patterns, whereas preparation for target localization was associated with larger amplitude deflections at multimodal, centro-parietal sites preceding both auditory and visual targets. Using a novel paradigm, the study supports the notion of a division of labor in the auditory and visual pathways following both auditory and visual cues that signal identity or location response preparation to upcoming auditory or visual targets.
Hart and John Moore (2008) introduce new behavioral assumptions that can explain long-term contracts and the employment relation. We examine experimentally their idea that contracts serve as reference points. The evidence confirms the prediction that there is a trade-off between rigidity and flexibility. Flexible contracts--which would dominate rigid contracts under standard assumptions--cause significant shading in ex post performance, while under rigid contracts much less shading occurs. The experiment appears to reveal a new behavioral force: ex ante competition legitimizes the terms of a contract, and aggrievement and shading occur mainly about outcomes within the contract
Higher-dimensional symmetric games become of more and more importance for applied micro- and macroeconomic research. Standard approaches to uniqueness of equilibria have the drawback that they are restrictive or not easy to evaluate analytically. In this paper I provide some general but comparably simple tools to verify whether a symmetric game has a unique symmetric equilibrium or not. I distinguish between the possibility of multiple symmetric equilibria and asymmetric equilibria which may be economically interesting and is useful to gain further insights into the causes of asymmetric equilibria in symmetric games with higher-dimensional strategy spaces. Moreover, symmetric games may be used to derive some properties of the equilibrium set of certain asymmetric versions of the symmetric game. I further use my approach to discuss the relationship between stability and (in)existence of multiple symmetric equilibria. While there is an equivalence between stability, inexistence of multiple symmetric equilibria and the unimportance of strategic effects for the comparative statics, this relationship breaks down in higher dimensions. Stability under symmetric adjustments is a minimum requirement of a symmetric equilibrium for reasonable comparative statics of symmetric changes. Finally, I present an alternative condition for a symmetric equilibrium to be a local contraction which is more general than the conventional approach of diagonal dominance and yet simpler to evaluate than the eigenvalue condition of continuous adjustment processes.
Nous proposons une synthèse des recherches sur l'énigme de la baisse de la productivité totale
des facteurs durant la Grande Dépression des années 1930. Cette nouvelle littérature met
l'accent sur l'apport des modèles d'équilibre général dynamique et stochastique pour la
compréhension de cette énigme.
The core difficulty in developmental dyslexia across languages is a “phonological deficit”, a specific difficulty with the neural representation of the sound structure of words. Recent data across languages suggest that this phonological deficit arises in part from inefficient auditory processing of the rate of change of the amplitude envelope at syllable onset (inefficient sensory processing of rise time). Rise time is a complex percept that also involves changes in duration and perceived intensity. Understanding the neural mechanisms that give rise to the phonological deficit in dyslexia is important for optimising educational interventions. In a three-deviant passive ‘oddball’ paradigm and a corresponding blocked ‘deviant-alone’ control condition we recorded ERPs to tones varying in rise time, duration and intensity in children with dyslexia and typically developing children longitudinally. We report here results from test Phases 1 and 2, when participants were aged 8–10 years. We found an MMN to duration, but not to rise time nor intensity deviants, at both time points for both groups. For rise time, duration and intensity we found group effects in both the Oddball and Blocked conditions. There was a slower fronto-central P1 response in the dyslexic group compared to controls. The amplitude of the P1 fronto-centrally to tones with slower rise times and lower intensity was smaller compared to tones with sharper rise times and higher intensity in the Oddball condition, for children with dyslexia only. The latency of this ERP component for all three stimuli was shorter on the right compared to the left hemisphere, only for the dyslexic group in the Blocked condition. Furthermore, we found decreased N1c amplitude to tones with slower rise times compared to tones with sharper rise times for children with dyslexia, only in the Oddball condition. Several other effects of stimulus type, age and laterality were also observed. Our data suggest that neuronal responses underlying some aspects of auditory sensory processing may be impaired in dyslexia.
This study applies financial portfolio theory to determine efficient frontiers in the provision of electricity for the United States and Switzerland. Expected returns are defined by the rate of productivity increase of power generation (adjusted for external costs), volatility, by its standard deviation. Since unobserved productivity shocks are found to be correlated, Seemingly Unrelated Regression Estimation (SURE) is used to filter out the systematic component of the covariance matrix of the productivity changes. Results suggest that as of 2003, the feasible maximum expected return (MER) electricity portfolio for the United States contains more Coal, Nuclear, and Wind than actual but markedly less Gas and Oil. The minimum variance (MV) portfolio contains markedly more Oil, again more Coal, Nuclear, and Wind but almost no Gas. Regardless of the choice between MER and MV, U.S. utilities are found to lie substantially inside the efficient frontier. This is even more true of their Swiss counterparts, likely due to continuing regulation of electricity markets.
This paper reconsiders the role of monetary policy in Sweden’s strong recovery from the Great Depression. The Riksbank in the 1930s is sometimes seen as an example of a central bank that was relatively innovative in terms of the conduct of monetary policy. To consider this analytically, we estimate a small-scale, structural general equilibrium model of a small open economy using Bayesian methods. We find that the model captures the key dynamics of the period surprisingly well. Importantly, our findings suggest that Sweden avoided the worst excesses of the depression by conducting conservative rather than innovative monetary policy. We find that, by keeping the Swedish krona undervalued to replenish foreign reserves, Sweden’s exchange rate policy unintentionally contributed to the Swedish growth miracle of the 1930s, avoiding a major slump in 1932 and enabling the country to benefit quickly from the eventual recovery of world demand.
Recent developments on international financial markets have called the benefits of
bank globalization into question. Large, internationally active banks have
acquired substantial market power, and international activities have not
necessarily made banks less risky. Yet, surprisingly little is known about the
actual link between bank internationalization, bank risk, and market power.
Analyzing this link is the purpose of this paper. We jointly estimate the
determinants of risk and market power of banks, and we analyze the effects of
changes in terms of the number of foreign countries (the extensive margin) and
the volume of foreign assets (the intensive margin). Our paper has four main
findings. First, there is a strong negative feedback effect between risk and market
power. Second, banks with higher shares of foreign assets, in particular those held
through foreign branches, have higher market power at home. Third, holding
assets in a large number of foreign countries tends to increase bank risk. Fourth,
the impact of internationalization differs across banks from different banking
groups and of different size.
Modern trade theory emphasizes firm-level productivity differentials to explain
the cross-border activities of non-financial firms. This study tests whether a
productivity pecking order also determines international banking activities. Using
a novel dataset that contains all German banks’ international activities, we
estimate the ordered probability of a presence abroad (extensive margin) and the
volume of international assets (intensive margin). Methodologically, we enrich the
conventional Heckman selection model to account for the self-selection of banks
into different modes of foreign activities using an ordered probit. Four main
findings emerge. First, similar to results for non-financial firms, a productivity
pecking order drives bank internationalization. Second, only a few non-financial
firms engage in international trade, but many banks hold international assets, and
only a few large banks engage in foreign direct investment. Third, in addition to
productivity, risk factors matter for international banking. Fourth, gravity-type
variables have an important impact on international banking activities.
