Memory,past and self

The purpose of this essay is to determine how we should construe the content of memories. First, I distinguish two features of memory that a construal of mnemic content should respect. These are the ‘attribution of pastness’ feature (a subject is inclined to believe of those events that she remembers that they happened in the past) and the ‘attribution of existence’ feature (a subject is inclined to believe that she existed at the time that those events that she remembers took place). Next, I distinguish two kinds of theories of memory, which I call ‘perceptual’ and ‘self-based’ theories. I argue that those theories that belong to the first kind but not the second one have trouble accommodating the attribution of existence. And theories that belong to the second kind but not the first one leave the attribution of pastness unexplained. I then discuss two different theories that are both perceptual and self-based, which I eventually reject. Finally, I propose a perceptual, self-based theory that can account for both the attribution of pastness and the attribution of past existence.     

Effects of the iodine deficiency on intellectual variables among children

An association between severe iodine deficiency and poor mental development has been found in many studies. We examined the relationship between moderate or mild iodine deficiency and intellectual capacity in order to determine whether problems common to severe iodine deficiency (including mental retardation) also emerge in a more subtle form. We also wished to know whether the classic methodology (comparing iodine-deficient zones with nondeficient zones) is the most adequate, and propose to combine this grouping by zones with urinary iodine presented by individuals in each zone. We measured IQ, manipulative and verbal capacity, attention, visual motor ability and disruptive behaviour, variables that have barely been studied in this kind of investigations. The sample comprised 760 schoolchildren from the province of Jaén (southern Spain). Our results show that children with low levels of iodine intake and with urinary iodine concentration lower than 100 microg/litre had a lower IQ and displayed more disruptive behaviour than children with high levels of the criteria. The other variables were not associated with iodine deficiency.     

The Relationship Between the Fear-Avoidance Model of Pain and Personality Traits in Fibromyalgia Patients

This study examined the relationship between several cognitive-affective factors of the fear-avoidance model of pain, the big five model of personality, and functional impairment in fibromyalgia (FM). Seventy-four FM patients completed the NEO Five-Factor Inventory, the Pain Catastrophizing Scale, the Pain Anxiety Symptoms Scale-20, the Pain Vigilance and Awareness Questionnaire, and the Impairment and Functioning Inventory. Results indicated that the cognitive-affective factors of pain are differentially associated with personality traits. Neuroticism and conscientiousness were significant predictors of pain catastrophizing, and neuroticism, openness, and agreeableness were significant predictors of pain anxiety. Personality traits did not contribute significantly to vigilance to pain. The effect of neuroticism upon pain anxiety was mediated by pain catastrophizing, and neuroticism showed a trend to moderate the relationship between impairment and pain anxiety. Results support the fear-avoidance model of pain. Implications of the findings for the understanding and management of FM are discussed.     

Conditioned taste aversion modifies persistently the subsequent induction of neocortical long-term potentiation in vivo

The ability of neurons to modify their synaptic strength in an activity-dependent manner has a crucial role in learning and memory processes. It has been proposed that homeostatic forms of plasticity might provide the global regulation necessary to maintain synaptic strength and plasticity within a functional dynamic range. Similarly, it is considered that the capacity of synapses to express plastic changes is itself subject to variation dependent on previous experience. In particular, training in several behavioral tasks modifies the possibility to induce long-term potentiation (LTP). Our previous studies in the insular cortex (IC) have shown that induction of LTP in the basolateral amygdaloid nucleus (Bla)-IC projection previous to conditioned taste aversion (CTA) training enhances the retention of this task. The aim of the present study was to analyze whether CTA training modifies the ability to induce subsequent LTP in the Bla-IC projection in vivo. Thus, CTA trained rats received high frequency stimulation in the Bla-IC projection in order to induce LTP 48, 72, 96 and 120 h after the aversion test. Our results show that CTA training prevents the subsequent induction of LTP in the Bla-IC projection, for at least 120 h after CTA training. We also showed that pharmacological inhibition of CTA consolidation with anisomycin (1 μl/side; 100 μg/μl) prevents the CTA effect on IC-LTP. These findings reveal that CTA training produces a persistent change in the ability to induce subsequent LTP in the Bla-IC projection in a protein-synthesis dependent manner, suggesting that changes in the ability to induce subsequent synaptic plasticity contribute to the formation and persistence of aversive memories.     

Reducing latency of a child's responding to instructions by means of a token system

The response latency of following directions by an 8-yr-old boy from a class for emotionally disturbed children was modified by the contingent application of a token system. To demonstrate reinforcer effectiveness, a multiple baseline approach was used. Measures were obtained for the time elapsed between the presentation of verbal directions and five performances: (1) entering the experimental room, (2) putting toys away, (3) beginning academic work, (4) putting toys away again, and (5) returning to the classroom and completing preparations for leaving school. These five measures were placed on the token system at three different times. The results demonstrated that four of the five performances were clearly affected by the token system as their response latency for following directions decreased substantially.     

Dispossessing Defeat

Higher-order evidence can make an agent doubt the reliability of her reasoning. When this happens, it seems rational for the agent to adopt a cautious attitude towards her original conclusion, even in cases where the higher-order evidence is misleading and the agent's original reasons were actually perfectly good. One may think that recoiling to a cautious attitude in the face of misleading self-doubt involves a failure to properly respond to one's reasons. My aim is to show that this is not so. My proposal is that (misleading) higher-order evidence can undermine the agent's possession of her first-order reasons, constituting what I call a dispossessing defeater. After acquiring the higher-order evidence, the agent is no longer in a position to rely competently on the relevant first-order considerations as reasons for her original conclusion, so that such reasons stop being available to her (even if they remain as strong as in the absence of the higher-order evidence). In this way, an agent with misleading higher-order evidence can adopt a cautious stance towards her original conclusion, while properly responding to the set of reasons that she possesses–a set that is reduced due to the acquisition of higher-order dispossessing defeaters.     

The role of parametric assumptions in adaptive Bayesian estimation

Variants of adaptive Bayesian procedures for estimating the 5% point on a psychometric function were studied by simulation. Bias and standard error were the criteria to evaluate performance. The results indicated a superiority of (a) uniform priors, (b) model likelihood functions that are odd symmetric about threshold and that have parameter values larger than their counterparts in the psychometric function, (c) stimulus placement at the prior mean, and (d) estimates defined as the posterior mean. Unbiasedness arises in only 10 trials, and 20 trials ensure constant standard errors. The standard error of the estimates equals 0.617 times the inverse of the square root of the number of trials. Other variants yielded bias and larger standard errors.     

Effects of working memory load on long-term word priming

Three experiments assessed the role of verbal and visuo-spatial working memory in supporting long-term repetition priming for written words. In Experiment 1, two priming tasks (word stem completion and category-exemplar production) were included with three levels of load on working memory: (1) without memory load, (2) memory load that involved storing a string of six digits, and (3) memory load that involved storing a graphic shape. Experiments 2 and 3 compared the effects of a verbal (Experiment 2) or a visual (Experiment 3) working memory load at encoding on both an implicit (word stem completion) and an explicit test (cued recall). The results show no effect of memory load in any of the implicit memory tests, suggesting that priming does not rely on working memory resources. By contrast, loading working memory at encoding causes a significant disruptive effect on the explicit memory test for words when the load is verbal but not visual.     

Variational solution of the one-dimensional t–J model

A new variational scheme based on a modified Bethe–Peierls method is used to study the ground state properties of the one-dimensional t–J model. Expectation values are evaluated by cutting out a four-site cluster from a correlated Fermi sea, the ground state of which is described by a variational trial wave function. We study a generalized Gutzwiller state where nearest-neighbour hole–hole correlations are controlled variationally. From the electron concentration dependence of the ground state energy, we determine the true thermodynamic boundary where segregation into an electron-rich, and purely hole phase sets in. We also determine the spinodal line and pair susceptibilities. The variational method is applied also to an extended t–J–V model, where V is the coupling constant of the charge interaction term.