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  • Relative validity effects with either one or two more valid cues in Pavlovian and instrumental conditioning.

    12 December 2017

    Two experiments investigated the relative validity effect with either 1 or 2 continuously reinforced cues in Wistar rats using appetitive Pavlovian and instrumental preparations. Discrimination training involved 3 compound cues containing a common element (1AX: 1BX: 2CX). In the first true-discrimination group (TD-1), CX was followed by food, but AX and BX were not. In the second true-discrimination group (TD-2), AX and BX but not CX were followed by food. In the third, pseudodiscrimination group (PD), food followed 50% of each compound. Compared with the PD group, there were lower levels of responding to X in Groups TD-1 and TD-2, which did not differ. That is, both TD treatments showed equivalent relative validity effects. There was evidence for a relative validity effect on the context. The Rescorla-Wagner model incorrectly predicts a smaller relative validity effect after the TD-2 than the TD-1 treatment. Comparator theory predicts these results.

  • Rule learning by rats.

    14 December 2017

    Using rules extracted from experience to solve problems in novel situations involves cognitions such as analogical reasoning and language learning and is considered a keystone of humans' unique abilities. Nonprimates, it has been argued, lack such rule transfer. We report that Rattus norvegicus can learn simple rules and apply them to new situations. Rats learned that sequences of stimuli consistent with a rule (such as XYX) were different from other sequences (such as XXY or YXX). When novel stimuli were used to construct sequences that did or did not obey the previously learned rule, rats transferred their learning. Therefore, rats, like humans, can transfer structural knowledge from sequential experiences.

  • Negative Interpretation Bias and the Experience of Pain in Adolescents.

    15 December 2017

    UNLABELLED: Negative interpretation bias, the tendency to appraise ambiguous situations in a negative or threatening way, has been suggested to be important for the development of adult chronic pain. To our knowledge, this is the first study to examine the role of a negative interpretation bias in adolescent pain. We first developed and piloted a novel task that measures the tendency for adolescents to interpret ambiguous situations as indicative of pain and bodily threat. Using this task in a separate community sample of adolescents (N = 115), we then found that adolescents who catastrophize about pain, as well as those who reported more pain issues in the preceding 3 months, were more likely to endorse negative interpretations, and less likely to endorse benign interpretations, of ambiguous situations. This interpretation pattern was not, however, specific for situations regarding pain and bodily threat, but generalized across social situations as well. We also found that a negative interpretation bias, specifically in ambiguous situations that could indicate pain and bodily threat, mediated the association between pain catastrophizing and recent pain experiences. Findings may support one potential cognitive mechanism explaining why adolescents who catastrophize about pain often report more pain. PERSPECTIVE: This article presents a new adolescent measure of interpretation bias. We found that the tendency to interpret ambiguous situations as indicative of pain and bodily threat may be one potential cognitive mechanism explaining why adolescents who catastrophize about pain report more pain, thus indicating a potential novel intervention target.

  • Reply to Falcon.

    13 December 2017

  • Resource allocation and prioritization in auditory working memory.

    15 December 2017

    A prevalent view of working memory (WM) considers it to be capacity-limited, fixed to a set number of items. However, recent shared resource models of WM have challenged this “quantized” account using measures of recall precision. Although this conceptual framework can account for several features of visual WM, it remains to be established whether it also applies to auditory WM. We used a novel pitch-matching paradigm to probe participants' memory of pure tones in sequences of varying length, and measured their precision of recall. Crucially, this provides an index of the variability of memory representation around its true value, rather than a binary "yes/no" recall measure typically used in change detection paradigms. We show that precision of auditory WM varies with both memory load and serial order. Moreover, auditory WM resources can be prioritized to cued items, improving precision of recall, but with a concomitant cost to other items, consistent with a resource model account.

  • Motor phenotype and magnetic resonance measures of basal ganglia iron levels in Parkinson's disease.

    12 December 2017

    BACKGROUND: In Parkinson's disease the degree of motor impairment can be classified with respect to tremor dominant and akinetic rigid features. While tremor dominance and akinetic rigidity might represent two ends of a continuum rather than discrete entities, it would be important to have non-invasive markers of any biological differences between them in vivo, to assess disease trajectories and response to treatment, as well as providing insights into the underlying mechanisms contributing to heterogeneity within the Parkinson's disease population. METHODS: Here, we used magnetic resonance imaging to examine whether Parkinson's disease patients exhibit structural changes within the basal ganglia that might relate to motor phenotype. Specifically, we examined volumes of basal ganglia regions, as well as transverse relaxation rate (a putative marker of iron load) and magnetization transfer saturation (considered to index structural integrity) within these regions in 40 individuals. RESULTS: We found decreased volume and reduced magnetization transfer within the substantia nigra in Parkinson's disease patients compared to healthy controls. Importantly, there was a positive correlation between tremulous motor phenotype and transverse relaxation rate (reflecting iron load) within the putamen, caudate and thalamus. CONCLUSIONS: Our findings suggest that akinetic rigid and tremor dominant symptoms of Parkinson's disease might be differentiated on the basis of the transverse relaxation rate within specific basal ganglia structures. Moreover, they suggest that iron load within the basal ganglia makes an important contribution to motor phenotype, a key prognostic indicator of disease progression in Parkinson's disease.

  • At the edge of consciousness: automatic motor activation and voluntary control.

    12 December 2017

    Conventionally, voluntary conscious acts and automatic behavior have been considered to be mediated by separate processes-and by separate brain structures. In this review, the authors consider the evidence that this might not be the case. First, they draw together disparate lines of evidence showing that visual stimuli cause automatic and unconscious motor activation. They briefly discuss the visual grasp reflex (automatic orienting of gaze to a salient visual stimulus), subliminal priming, and object affordances in healthy individuals. They also consider cases where inhibition of such reflexive behavior may be disrupted following brain lesions, as in patients demonstrating alien limb syndrome and utilization behavior. The authors argue that automatic motor activation forms an intrinsic part of all behavior, rather than being categorically different from voluntary actions. A crucial issue is how such automatic mechanisms are controlled so that the most appropriate responses are made and unwanted responses inhibited. The authors discuss some of the brain areas involved, including the supplementary motor area and the parietal cortex. Last, they review evidence that some control may actually be achieved by automatically triggered inhibition as well as modulation of unconscious processes by attention and task goals.

  • Short test of semantic and phonological fluency: normal performance, validity and test-retest reliability.

    12 December 2017

    Tests of verbal fluency, whether of Semantic Fluency (SF) or Phonological Fluency (PF), are often used as a standard method of neuropsychological assessment. However, very little normative data, standardized on a UK sample, is available, and little is known about the utility of popularly used 'short-forms' of these tasks. Additionally, very little is known about verbal fluency test-retest reliability. In this report we describe the performance of N = 365 normal participants on a version of SF requiring the generation of exemplars of the category 'animals' and a version of the PF task requiring participants to generate words beginning with the letter 'B'. From this data we have derived a percentile distribution for both tasks. We also addressed the impact of sex, age, years of education and IQ upon both SF and PF performance. No sex differences were found on either the PF or the SF tasks. A significant but small correlation between age and SF, but not PF, was observed. Modest correlations between both years of education and IQ and PF and SF performance were also seen. We also report test-retest reliability scores for performance on both SF and PF tasks. Performance on the longer 'FAS' version was found to correlate highly with scores obtained using just the letter 'B'. This suggests that little additional advantage obtains from administering three-letter versions of PF. An extremely high degree of correlation between SF tasks in which participants are given 1 minute and scores obtained when participants are given 1 minute 30 seconds was also observed. Finally, in order to assist users in deciding whether a changed retest score is due to error measurement or a real effect, we calculated Standard Error of Prediction (SEP) scores.