Extinction and renewal of Pavlovian modulation in human sequential Feature Positive discrimination learning

Using a conditioned suppression task, we investigated extinction and renewal of Pavlovian modulation in human sequential Feature Positive (FP) discrimination learning. In Experiment 1, in context a participants were first trained on two FP discriminations, X-->A+/A- and Y-->B+/B-. Extinction treatment was administered in the acquisition context a (aaa group) or in a new context b (aba group), and comprised X-->A- extinction and Y- control trials. Discriminative X-->A/A responding was lost in both groups when tested in the extinction context, but partially recovered in the aba and not in the aaa group when tested in the acquisition context, suggesting extinction and renewal of extinguished modulation. The same was observed for the Y-->B/B control pair, however, questioning whether the loss of discriminative X-->A/A responding represented genuine extinction of modulation. In Experiment 2, including only aba groups, participants were trained in context a on two FP discriminations, X-->A+/A- and Y-->B+/B-, after which the group "Extinction" was exposed to X-->A- extinction trials in context b, whereas the group "Control" was exposed to X- control trials; concurrently, both groups received further Y-->B+/B- training. In the group Control, differential Y-->B/B and X-->A/A responding were acquired and maintained throughout the experiment. In the group Extinction, while Y-->B/B responding was also maintained throughout, differential X-->A/A responding disappeared because of X-->A- extinction treatment when tested in the extinction context b, but partially reappeared when tested in the acquisition context a. This evidences aba-renewal of extinguished modulation.     

Return of fear in a human differential conditioning paradigm caused by a return to the original acquistion context

In a differential human fear conditioning paradigm evidence for ABA-renewal was obtained manipulating the lighting in the experimental room. During acquisition in either a dark or illuminated room, one neutral slide was sometimes paired with a loud aversive noise whereas another slide was not. Subsequently, extinction took place in the opposite lighting context. When afterwards the participants were tested again in the original acquisition context, measurements revealed a recovery of the conditioned electrodermal response and an increase in the retrospective verbal US-expectancy ratings. No response recovery was obtained in an AAA-group that received acquisition, extinction and test trials in one and the same context. Several theoretical explanations for this type of return of fear as well as implications for clinical practice are discussed.     

The emerging fragile X premutation phenotype: evidence from the domain of social cognition

Fragile X syndrome is a neurodevelopmental disorder that is caused by large methylated expansions of a CGG repeat (>200) region upstream of the FMR1 gene that results in the lack of expression of the fragile X mental retardation protein (FMRP). Affected individuals display a neurobehavioral phenotype that includes a significant impairment in social cognition alongside deficits in attentional control, inhibition and working memory. In contrast, relatively little is known about the trajectory and specificity of any cognitive impairment associated with the fragile X premutation ("carrier-status") (approximately 55-200 repeats). Here, we focus on one aspect of cognition that has been well documented in the fragile X full mutation, namely social cognition. The results suggest that premutation males display a pattern of deficit similar in profile, albeit milder in presentation, to that of the full mutation. However, little evidence emerged for a correlation between CGG repeat length and severity of phenotypic outcomes. The findings are discussed in the context of functional neuroimaging and brain-behaviour-molecular correlates. We speculate that the deficiencies in social cognition are attributable to impairment of neural pathways modulated by the cerebellum.     

A Dynamic Model for Rule Induction Tasks

In this paper, a model for performance on rule induction tasks (e.g., items on intelligence tests) is developed. The model simultaneously specifies distributions for response times and response accuracies on an item-by-item basis. It is dynamic in the sense that it can be used to specify and test different ways of learning throughout a test. Three versions of the general model (i.e., with three different learning rules) are described and the fit of these versions is investigated in two datasets on solving number series. The results indicate that one of these versions (one of the learning rules) is better at accounting for the data.     

Automatic stride interval extraction from long,highly variable and noisy gait timing signals

This paper presents a probabilistic algorithm for automatically extracting the stride interval time series from long, highly variable and noisy two-state timing signals. Long interstride temporal records are of particular interest in nonlinear dynamical analysis of gait. The proposed method consists of probabilistic estimation and extraction followed by post-extraction filtering. With noisy timing signals from 10 children with Spastic Diplegia, no statistical differences in the numbers of extracted strides (p=0.94), the mean stride intervals (p=0.55) and the scaling exponents (p=0.94) (a measure of temporal heterogeneity) were found between series extracted by hand and by the probabilistic algorithm. The method is robust to noise and violations of normality. Results support the use of probabilistic extraction as an alternative to laborious manual extraction.     

Not all triads are created equal: further support for the importance of visual and semantic proximity in object identification

Identification deficits were investigated in ELM, a temporal lobe stroke patient with category-specific deficits. We replicated previous work done on FS, a patient with category specific deficits as a result of herpes viral encephalitis. ELM was tested using novel, computer generated shapes that were paired with artifact labels. We paired semantically close or disparate labels to shapes and ELM attempted to learn these pairings. Overall, ELM's shape-label confusions were most detrimentally affected when we used labels that referred to objects that were visually and semantically close. However, as with FS, ELM had as many errors when shapes were paired with the labels "donut," "tire," and "washer" as he did when they were paired with visually and semantically close artifact labels. Two explanations are put forth to account for the anomalous performance by both patients on the triad of donut-tire-washer.     

Automatic integration of non-perceptual action effect features: the case of the associative affective Simon effect

In the first phase of Experiment 1, participants were instructed to move a response key up or down in response to a go signal. One of both responses was consistently followed by an aversive stimulus, whereas the other response was never followed by the aversive stimulus. In a subsequent test phase, the same responses had to be emitted according to the grammatical category (noun or adjective) of positive and negative target words. Results showed that the level of affective correspondence between the task-irrelevant positive or negative connotation of the target and the motivational significance of the effect of the correct response influenced performance. The results of Experiment 2 replicated those of Experiment 1, using alternating target-response assignment. These findings point to the integration of affective action effect feature codes in the cognitive representation of actions.