Hedging and Financial Fragilities in Fixed Exchange Rate Regimes.

Currency crises that coincide with banking crises tend to share four elements. First, governments provide guarantees to domestic and foreign bank creditors. Second, banks do not hedge their exchange rate risk. Third, there is a lending boom before the crises. Finally, when the currency/banking collapse occurs interest rates rise and there is a persistent decline in output. This paper proposes an explanation for these regularities.BANKS ; EXCHANGE RATE ; FINANCIAL MARKET

Dynamical model of sequential spatial memory: winnerless competition of patterns

We introduce a new biologically-motivated model of sequential spatial memory which is based on the principle of winnerless competition (WLC). We implement this mechanism in a two-layer neural network structure and present the learning dynamics which leads to the formation of a WLC network. After learning, the system is capable of associative retrieval of pre-recorded sequences of spatial patterns.Comment: 4 pages, submitted to PR

Prioritized Sweeping Neural DynaQ with Multiple Predecessors, and Hippocampal Replays

During sleep and awake rest, the hippocampus replays sequences of place cells that have been activated during prior experiences. These have been interpreted as a memory consolidation process, but recent results suggest a possible interpretation in terms of reinforcement learning. The Dyna reinforcement learning algorithms use off-line replays to improve learning. Under limited replay budget, a prioritized sweeping approach, which requires a model of the transitions to the predecessors, can be used to improve performance. We investigate whether such algorithms can explain the experimentally observed replays. We propose a neural network version of prioritized sweeping Q-learning, for which we developed a growing multiple expert algorithm, able to cope with multiple predecessors. The resulting architecture is able to improve the learning of simulated agents confronted to a navigation task. We predict that, in animals, learning the world model should occur during rest periods, and that the corresponding replays should be shuffled.Comment: Living Machines 2018 (Paris, France

The role of frontal cortex-reticular interactions in performance and extinction of the classically conditioned nictitating membrane response in the rabbit

In order to investigate the behavioral role of interactions between frontal cortex and reticular nuclei, we examined the effects of single and combined lesions of these structures on the classically conditioned nictitating membrane response (NMR) of rabbits. Lesions of frontal cortex decreased latencies of the conditioned NMRs in reacquisition and retarded extinction of the conditioned response. Lesions of nucleus reticularis pontis oralis (NRPO) produced similar effects. In contrast, lesions of nucleus reticularis tegmenti (NRT) increased NMR latencies during reacquisition. The opposite effects of frontal cortex and NRT lesions were abolished when the two lesions were combined, indicating that the two lesion effects summed. In contrast, the deficits due to frontal and NRPO lesions did not sum; combined frontal--NRPO lesions produced deficits very similar in magnitude and time course to those of the NRPO lesions alone. These findings suggest that frontal cortex may exert its inhibitory effects on behavior not by directly interacting with NRT, but by facilitating NRPO, which in turn may inhibit the nucleus of the VIth nerve, the final common pathway to the NMR. NRT may facilitate the motor pathway by modulating the inhibitory effect of NRPO on the VIth nerve nucleus.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/23959/1/0000208.pd

Radioautographic localization of inhibition of protein synthesis in specific regions of monkey brain

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/33800/1/0000055.pd

Elemental spatial and temporal association formation in left temporal lobe epilepsy

The mesial temporal lobe (MTL) is typically understood as a memory structure in clinical settings, with the sine qua non of MTL damage in epilepsy being memory impairment. Recent models, however, understand memory as one of a number of higher cognitive functions that recruit the MTL through their reliance on more fundamental processes, such as “self-projection” or “association formation”. We examined how damage to the left MTL influences these fundamental processes through the encoding of elemental spatial and temporal associations. We used a novel fMRI task to image the encoding of simple visual stimuli, either rich or impoverished, in spatial or spatial plus temporal information. Participants included 14 typical adults (36.4 years, sd. 10.5 years) and 14 patients with left mesial temporal lobe damage as evidenced by a clinical diagnosis of left temporal lobe epilepsy (TLE) and left MTL impairment on imaging (34.3 years, sd. 6.6 years). In-scanner behavioral performance was equivalent across groups. In the typical group whole-brain analysis revealed highly significant bilateral parahippocampal activation (right > left) during spatial associative processing and left hippocampal/parahippocampal deactivation in joint spatial-temporal associative processing. In the left TLE group identical analyses indicated patients used MTL structures contralateral to the seizure focus differently and relied on extra-MTL regions to a greater extent. These results are consistent with the notion that epileptogenic MTL damage is followed by reorganization of networks underlying elemental associative processes. In addition, they provide further evidence that task-related fMRI deactivation can meaningfully index brain function. The implications of these findings for clinical and cognitive neuropsychological models of MTL function in TLE are discussed

Cognitive decline associated with normal aging in rats: a neuropsychological approach.

The effects of aging on cognitive capacities were examined by comparing the performance of young and old rats on tasks characterized as dependent on different brain systems. This neuropsychological approach was employed to determine the extent to which multiple neural systems are compromised in aging and whether deterioration of one system correlates with that of another. The two tasks used in the present study were an odor-guided recognition memory task, for which different aspects of performance have been shown to be dependent on the integrity of the orbital prefrontal and perirhinal-entorhinal cortex, and the Morris water maze, for which performance depends on the medial prefrontal cortex and hippocampus. Rats were trained on the recognition memory task under minimal memory load and then challenged with longer memory delays and higher levels of inter-item interference. Considerable variation was observed in the performance of aged rats on acquisition of the recognition memory task, and unlike young rats, some aged rats could not acquire the task. Nevertheless, those aged rats who did acquire the cDNM task performed as well as young animals when the memory delay was extended and interference was elevated. In addition, consistent with previous findings, the performance of the same aged rats was highly variable in the Morris water maze task. Furthermore, although correlations between scores on the two tasks for individual aged rats were not reliable, only those aged rats that performed outside the performance range of young rats in the water maze were impaired on acquisition of the recognition memory task. This pattern of findings is consistent with age-related dysfunction in multiple subdivisions of the prefrontal cortex as well as the hippocampus and suggests that these brain regions may deteriorate in the same subgroup of aged rats

Why are Prices Sticky? Evidence from Business Survey Data

This paper offers new insights on the price setting behaviour of German retail firms using a novel dataset that consists of a large panel of monthly business surveys from 1991-2006. The firm-level data allows matching changes in firms' prices to several other firm-characteristics. Moreover, information on price expectations allow analyzing the determinants of price updating. Using univariate and bivariate ordered probit specifications, empirical menu cost models are estimated relating the probability of price adjustment and price updating, respectively, to both time- and state- dependent variables. First, results suggest an important role for state-dependence; changes in the macroeconomic and institutional environment as well as firm-specific factors are significantly related to the timing of price adjustment. These findings imply that price setting models should endogenize the timing of price adjustment in order to generate realistic predictions concerning the transmission of monetary policy. Second, an analysis of price expectations yields similar results providing evidence in favour of state-dependent sticky plan models. Third, intermediate input cost changes are among the most important determinants of price adjustment suggesting that pricing models should explicitly incorporate price setting at different production stages. However, the results show that adjustment to input cost changes takes time indicating "additional stickiness" at the last stage of processing