Retrieval induces hippocampal-dependent reconsolidation of spatial memory

Nonreinforced retrieval can cause extinction and/or reconsolidation, two processes that affect subsequent retrieval in opposite ways. Using the Morris water maze task we show that, in the rat, repeated nonreinforced expression of spatial memory causes extinction, which is unaffected by inhibition of protein synthesis within the CA1 region of the dorsal hippocampus. However, if the number of nonreinforced retrieval trials is insufficient to induce long-lasting extinction, then a hippocampal protein synthesis-dependent reconsolidation process recovers the original memory. Inhibition of hippocampal protein synthesis after reversal learning sessions impairs retention of the reversed preference and blocks persistence of the original one, suggesting that reversal learning involves reconsolidation rather than extinction of the original memory. Our results suggest the existence of a hippocampal protein synthesis-dependent reconsolidation process that operates to recover or update retrieval-weakened memories from incomplete extinction.     

Reasoning from unfamiliar premises: a study with unschooled adults

A long tradition of research initiated by Luria in the 1930s has established that unschooled adults perform poorly on reasoning tasks. Particularly when the premises are unfamiliar, they adopt an inappropriate empirical bias. However, recent findings show that young children with little or no schooling reason competently if prompted to think of the unfamiliar premises as pertaining to a distant planet. We tested two groups of adults: illiterate, unschooled adults and adults with limited schooling. Both groups received problems that included either a premise with unknown content or a premise contradicting their everyday experience. When given a minimal prompt, both groups manifested the customary empirical bias. By contrast, when explicitly prompted to think of the unfamiliar premises as pertaining to a distant planet, they reasoned accurately and appropriately justified their conclusions in terms of the supplied premises.     

Amnestic effect of intrahippocampal AM251, a CB1-selective blocker, in the inhibitory avoidance, but not in the open field habituation task, in rats

CB1 is the most abundant metabotropic receptor of the brain, being found in areas classically involved in learning and memory and present at higher density at presynaptic terminals. Different sets of evidence support the idea that endogenous ligands (endocannabinoids) to the CB1 receptors act as modulators of neurotransmission. In hippocampus, endocannabinoids seem to act as retrograde messengers mediating down-regulation of GABA release. Previous reports have described a cognitive impairment effect of cannabinoid agonists, or facilitation by antagonists. The scope of the present study is to investigate the effect of intrahippocampal administration of the CB1-selective antagonist, AM251, in two behavioral tasks. One hundred and twelve male Wistar rats with bilateral cannulae implanted in the CA1 region of the dorsal hippocampus were trained in a step-down inhibitory avoidance task (IA, footshock, 0.5 mA) or an open field habituation task (OF). Immediately, after training, animals received an infusion of 0.55, 5.5, and 55.5 ng/side of AM251 (Tocris), or its vehicle (DMSO/saline), via these cannulae. Our results show that AM251 disrupted memory consolidation of the IA task, but not the OF task, an effect that seems to be purely mnemonic since the drug showed no motor performance effects. Only the intermediate dose (5.5 ng/side) of AM251 was effective in IA and the absence of effect with the larger dose may be the consequence of non-specific binding. The fact that OF was not affected raises the possibility that this endogenous system requires some degree of aversiveness to be recruited. We propose that increased levels of endogenous cannabinoids in the hippocampus, following a training session, contribute to facilitate memory consolidation, a process that may have been disrupted with AM251.     

Why do we share aggressive online content? Testing a short cycle model

The present study aimed to observe the impacts of aggressive online content exposure and personality on aggressive content sharing, considering the mediating role of positive and negative affects. A total of 302 Brazilians, equally divided into two groups, participated in a social network simulation, being exposed to aggressive (experimental group) or neutral (control group) posts and choosing what they would like to share on this site (among aggressive or nonaggressive material). A factorial MANOVA showed a significant difference for positive and negative affects and aggressive content sharing (Wilks' Λ = 0.936; F[3, 298] = 6.812; p = .001; η² = 0.064). Through structural equation modeling, an explanatory model was also tested, in which this behavior was directly predicted by aggressive online content exposure and suffered indirect effects from openness, conscientiousness, and extroversion, mediated by positive affects (goodness-of-fit index = 0.997, comparative fit-index = 0.998, Tucker-Lewis index = 0.996, SRMR = 0.028, root-mean-square error of approximation = 0.035, CI = 0.003−0.054). It is possible to conclude that the objectives are met, highlighting the contribution to understanding aggressive online behavior through the proximal processes described in the general aggression model.     

Suárez and the doctrine of the transcendentals

This article discusses Suárez's views concerning the transcendentals, that is, being and those attributes of it that extend to everything. In particular it explores Suárez's notion of transcendentality and the way in which he conceived the transcendental attributes of being are related to it. It makes two claims: First, that Suárez has an intensional, rather than an extensional understanding of transcendentality; and, second, that Suárez's understanding of truth and goodness, as expressing real extrinsic denominations based on real relations, appears to contain an inconsistency.I am grateful to Jane Bristol, John Doyle, and Scott MacDonald for their comments on an early draft of this paper.     

Concurrent measurement of heart rate and instrumental avoidance behavior in the Rhesus monkey

A graphical method has been developed for the concurrent recording of heart beats and lever responses during behavioral experiments. The EKG signal fed into any DC amplifier goes to a fixed level trigger circuit and relay driver with its own power supply. The signal from this drives any standard cumulative recorder. Lever response rates are recorded concurrently on an additional cumulative recorder using the same paper speed.     

Ideology,modernization and politico-economic development in Latin America

The authors state that social and political processes are continuously interrelated and modify each other in a circular fashion. The economic variable seems to be the most independent and strategic one in the complex and circular causal process of contemporary history. Its importance is due to the fact that economic forces have become the means that contribute the most to the attainment of varied social and political goals. holding appointments in the Department of International Relations, Economics, Political Science and Sociology/Anthropology. He is also a Senior Research Scholar at the University of Miami’s Graduate School of International Studies. He has been a Senior Fellow at Brookings Institution and is presently a staff member there. He has published more than thirty books and over one hundred articles.     

Interaction between consecutive learnings: inhibitory avoidance and habituation

Rats were submitted to step-down inhibitory avoidance training and to habituation of a rearing response to a tone with a 2-h interval between the two tasks, and were tested for retention of both tasks on the next day. When animals were trained first in inhibitory avoidance and then in habituation, retention of the avoidance behavior was impaired. When the animals were trained first in the habituation task and then in the avoidance task, retention of the two tasks was normal. The same results were obtained regardless of the order in which the two tasks were presented on the day of testing. This asymmetrical influence of habituation training on inhibitory avoidance retention could be due either to cognitive or, more likely, to task-specific neurochemical interactions.