Synaptic Reliability Correlates with Reduced Susceptibility to Synaptic Potentiation by Brain-Derived Neurotrophic Factor

Recent studies have implicated brain-derived neurotrophic factor (BDNF) in use-dependent modification of hippocampal synapses. BDNF can rapidly potentiate synaptic transmission at glutamatergic synapses by enhancing transmitter release. Using simultaneous perforated patch recording from pairs and triplets of glutamatergic hippocampal neurons, we have examined how the initial state of the glutamatergic synapse determines its susceptibility to synaptic modification by BDNF. We found that the degree of synaptic potentiation by BDNF depends on the initial reliability and strength of the synapse: Relatively weak connections were strongly potentiated, whereas the effect was markedly reduced at stronger synapses. The degree of BDNF-induced potentiation strongly correlated with the initial coefficient of variation (CV) of the amplitude of excitatory postsynaptic currents (EPSCs) and inversely correlated with the initial paired–pulse facilitation, suggesting that synapses with lower release probability (P_r) are more susceptible to the action of BDNF. To determine whether saturation of P_r could have masked the potentiation effect of BDNF in the stronger synapses, we lowered the initial P_r either by reducing the extracellular Ca²⁺ concentration ([Ca²⁺]_o) or by bath application of adenosine. Synapses that were initially strong remained unaffected by BDNF under these conditions of reduced P_r. Thus, the lack of BDNF effect on synaptic efficacy cannot simply be accounted for by saturation of P_r, but rather may be due to intrinsic changes associated with synaptic maturation that might covary with P_r. Finally, the dependence on initial synaptic strength was also found for divergent outputs of the same presynaptic neuron, suggesting that synaptic terminals with different degrees of responsiveness to BDNF can coexist within in the same neuron.     

Towards a unified theory of reciprocity

In a unified theory of human reciprocity, the strong and weak forms are similar because neither is biologically altruistic and both require normative motivation to support cooperation. However, strong reciprocity is necessary to support cooperation in public goods games. It involves inflicting costs on defectors; and though the costs for punishers are recouped, recouping costs requires complex institutions that would not have emerged if weak reciprocity had been enough.     

Minimizing sleep deprivation effects in healthy adults by differential outcomes

Sleep deprivation reduces vigilance or arousal levels, affecting the efficiency of certain cognitive functions such as learning and memory. Here we assessed whether the differential outcomes procedure (DOP), a learning procedure that has proved useful to ameliorate episodic memory deficits, can also improve memory performance in sleep-deprived participants. Photographs were presented as sample faces. A probe face was then presented for recognition after either short or long delays. In the differential outcomes condition a unique reinforcer followed correct responses. In the non-differential outcomes condition reinforcers were provided in a random manner. The results indicated that the DOP prevented the recognition memory to decrement during the long delay in the control group, replicating previous findings. The sleep-deprived group showed DOP benefits mainly with the short delay, when working memory could be affected by low arousal. These findings confirm that the DOP can overcome impaired recognition memory due to sleep deprivation conditions.     

Substructural logics,pluralism and collapse

When discussing Logical Pluralism several critics argue that such an open-minded position is untenable. The key to this conclusion is that, given a number of widely accepted assumptions, the pluralist view collapses into Logical Monism. In this paper we show that the arguments usually employed to arrive at this conclusion do not work. The main reason for this is the existence of certain substructural logics which have the same set of valid inferences as Classical Logic—although they are, in a clear sense, non-identical to it. We argue that this phenomenon can be generalized, given the existence of logics which coincide with Classical Logic regarding a number of metainferential levels—although they are, again, clearly different systems. We claim this highlights the need to arrive at a more refined version of the Collapse Argument, which we discuss at the end of the paper.

     

Theories of Truth without Standard Models and Yablo’s Sequences

The aim of this paper is to show that it’s not a good idea to have a theory of truth that is consistent but ω-inconsistent. In order to bring out this point, it is useful to consider a particular case: Yablo’s Paradox. In theories of truth without standard models, the introduction of the truth-predicate to a first order theory does not maintain the standard ontology. Firstly, I exhibit some conceptual problems that follow from so introducing it. Secondly, I show that in second order theories with standard semantics the same procedure yields a theory that doesn’t have models. So, while having an ω- inconsistent theory is a bad thing, having an unsatisfiable theory of truth is actually worse. This casts doubts on whether the predicate in question is, after all, a truthpredicate for that language. Finally, I present some alternatives to prove an inconsistency adding plausible principles to certain theories of truth.     

Han Fei's Enlightened Ruler

In this essay I will revise, based on the notion of the ‘enlightened ruler’ or mingzhu and his critique of the literati of his time, the common belief that Han Fei was an amoralist and an advocate of tyranny. Instead, I will argue that his writings are dedicated to advising those who ought to rule in order to achieve the goal of a peaceful and stable society framed by laws in accordance with the dao.     

Feelings of control restore distorted time perception of emotionally charged events

Humans perceive time with millisecond precision. However, when experiencing negative or fearful events, time appears to slow down and aversive events are judged to last longer than neutral or positive events of equal duration. Feelings of control have been shown to attenuate increases in arousal triggered by anxiety-provoking events. Here, we tested whether feelings of control can go as far as influencing people’s perception of the world, by modulating the perceived duration of aversive events. Observers judged the duration of images depicting positive or negative content, and we manipulated the amount of control experienced by participants. Crucially, participants never had any real control over events. All control was illusory. Results showed that when participants experienced low levels of control, negative images were judged as lasting longer than positive images. However, when participants illusorily experienced high levels of control, they no longer experienced aversive negative images as lasting longer than positive images.     

Psychological consequences of collective violence in childhood: the case of Monterrey,Mexico / Consecuencias psicológicas de la violencia colectiva en la niñez: el caso de Monterrey,México

Abstract

During the last years, different types of violence have severely damaged Mexico. In this paper we examine the consequences that violence could have in children, one of the most vulnerable segments of society. In short, we predict that exposure to any type of violence will lead to higher depression and that this could be explained through the effects of violence on childhood well-being. Our hypothesis was supported in two studies, showing that exposure to street violence (Study 1, N = 607) and exposure to collective violence (Study 2, N = 172) can increase childhood depression. Moreover, in both studies, this effect was explained by the decrease of childhood well-being caused by violence exposure. The implications of these results are discussed.